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G, va Care Late ae parte I \i // ») > AG Lever ee he F Cte nae / Ye - a ELA, ( is Uaterte. i \" Cy. 2s )) Le Ur , 0 Die one . - Hes oy oe althny 5 a Vp age als l ay . ea LE fe bea (le \ i letavt iLL OL ! he Y fi \ f 5 f » Ney 3 Cyt | ee ONL Vie see . i i ; : i es Tu ewe Aue wt gvar - A “it Z MCL Chet At LY tte J oe ¢ ji GRRE ere ead ee oe A es a ee yb p ? at hirti 6 , » '@ ee 9 9 x : ~ )4 d— Denes TENS S / 2 se ber Ltn hive fh S ( > ie c Ol is beam ee ee da i fi / é a3) a es Sra ; ACA - QL \ fens . , y acd C boa ( j MAA Cees SS a = CA WIE0S MAILILS OF IWMAGAIRA, — FROM A RECENT PHOTOGRAPH Ee MENS ee AL OF PEVSICAL GHOGRA PENG FOR THE USE OF SCHOOLS, ACADEMIES, AND COLLEGES. BY EDWIN J. HOUSTON, A.M. PxD,, EMERITUS PROFESSOR OF PHYSICAL GEOGRAPHY AND NATURAL PHILOSOPHY IN THE CENTRAL HIGH SCHOOL OF. PHILADELPHIA; PROFESSOR OF PHYSICS IN THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA, REVISED EDITION. PHILADELPHIA: PuBLISHED BY ELDREDGE & BROTHER, No. 17 North Seventh Street. A896. > bo" #2000" Entered, according to Act of Congress, in the year 1891, by ELDREDGE & BROTHER, in the Office of the Librarian of Congress, at Washington. ee 28 Copyright, 1895. ¢G aA Westcott & THOMSON, THe GEORGE S. FERGUSON CO., Electrotypers, Philada. Printers, Philada, PREFACE TO THE ORIGINAL EDITION. ——+02e300—_ ie the preparation of this work, an endeavor has been made to supply a concise yet comprehensive text-book, suited to the wants of a majority of our schools. The Author, in the course of his teaching, has experienced the need of a work in which unneces- sary details should be suppressed, and certain subjects added, which, though usually omitted in works on Physical Geography, seem, in his judgment, to belong properly to the science. The variety of topics necessarily included under the head of Physical Geography renders it almost impossible to cover the entire ground of the ordinary text-books during the time which most schoals are able to devote to the study, and the feeling of incompleted work thus impressed on the mind of both teacher and scholar is of the most discouraging nature. To remove these difficulties, the Author, during the past few years, has arranged for his own students a course of study, which, with a few modifications, he has at last put into book form, thinking that it may prove beneficial to others. The division of the text into large and small print has been made with a view of meeting the wants of different grades of schools, the large type containing only the more important statements, and the small type being especially designed for the use of the teacher and the advanced student, The maps have been carefully drawn by the Author according to the standard works and the latest authorities. Neither time nor expense has been spared to insure accuracy of detail and clearness of delineation. : Throughout the work no pains have been spared to insure strict accuracy of statement. Clearness and conciseness have been particularly aimed at; for which reason the names of authorities for state- ments which are now generally credited have been purposely omitted. The Author has not hesitated to draw information from all the standard works on Geonaehy, Physics, Geology, Astronomy, and other allied sciences; and in the compilation of the Pronouncing Vocabulary he acknowledges his indebtedness to Lippincott’s Gazetteer of the World. Acknowledgments are due to Mr. William M. Spackman, of Philadelphia, and Prof. Elihu Thomson, of the Central High School, for critical review of the manuscript. Also to Mr. M. Benja- min Snyder, of the Central High School, for revision of the proof-sheets of the chapter on Mathe- matical Geography. E. J. H. CENTRAL Hi@H ScHOOL, Philadelphia, Pa. { \Eeet WW PREFACE TO THE REVISED EDITION. J\HE marked progress which has been made in most of the departments of science embraced in the study of Physical Geography since the issue of the original edition of “The Elements of Physical Geography” has rendered the preparation of a revised edition a matter of necessity. The study of Physical Geography, including as it does not only the crust of the earth and 2 heated interior, but also the distribution of its land, water, air, plants, and animals, includes, in its range, a great variety of topics, and necessitates for its proper elucidation many branches of science. Some knowledge of the elementary principles of these sciences is necessary to the proper study of Physical Geography. The number of such principles is great, and the temptation naturally exists to encumber even an elementary text-book with such an abundance of leading principles as to render it either incomprehensible, or too extended for actual use in the school- room. The author has endeavored in the revised edition to avoid undue multiplicity either of ele- mentary principles or unimportant details. His object has been to develop forcibly the close inter- dependence of the inanimate features of the earth’s surface, the land, water, and air, with its animate features, its flora, and fauna, and to show the marked influence which all of these exert on the development of the human race, and, therefore, on history itself. Recognizing, from his standpoint of a teacher, the inadvisability of crowding a book with new matter simply because it is new, the author has carefully avoided the introduction of new theories unless they have been generally accepted by the best authorities. Old theories are in all cases given the preference of new ones, unless the latter bear the stamp of general approval. At the same time the results of recent investigations have been freely given in all cases where they have been considered sufficiently authoritative. iv PREFACE. Vv In order to avoid confusing the mind of the student, controversial matters have been carefully avoided. When, however, opinion on any subject is fairly divided, a brief statement is made of the differing views. ; The favorable reception accorded by the teaching profession to the earlier editions of the book, and the flattering increase in the number of schools using it, have satisfied the author of the inadvisability of changing, to any considerable extent, the order of sequence of topics discussed, or the general manner of explanation therein adopted. In the preparation of the revised edition the author has freely consulted the latest standard authorities in the many sciences represented. The maps have all been re-drawn according to the best authorities, and are printed and colored by processes that in point of clearness and beauty leave little room for improvement. EDWIN J. HOUSTON. Centrat Hien Scuoot, PHILADELPHIA, PA. NOTE. The first chapter of this book is intended mainly for reference, containing as it does, an abstract. of the elementary principles of Mathematical Geography, with which most pupils beginning the study of Physical Geography are familiar. In many schools in which the book is used, it is customary to begin the formal study of the book with the Syllabus, page 21, which presents a comprehensive review of the chapter, and in practice and results this plan has proved satisfactory. CONTENTS. Sia PAGE CHAPTER PAGE INTRODUCTORY ..... 5 AR 9 ETS AR VRS (seers = sere eiete sirreutewcsoaa ae ene wise 208 IV. TRANSPORTING POWER OF RIVERS ... 65 V. DRAINAGE SYSTEMS .......... 67 PART I. AVA lia By Grantee em at oe See eee eyeawOO THE EARTH AS A PLANET. SYUGABUS: can cattcey apenas cue seat Seer 71 CHAPTER REVIEW AND MAP QUESTIONS ....... 72 I, MATHEMATICAL GEOGRAPHY ...... 10 SYLLABUS aries ten ielemev earetemreurs ye cces seo z REVIEW QUESTIONS .......... aol Section II. OCEANIC WATERS. PART II. Te THE OGRAN: ai.) sis ai ee eis sis alb laden 118 II. OckaAnic MovEMENTS ....... See LO THE LAND. ELE OCEANS ©CURRENTSHits scree nee teste 79 Section I. SMA TABUS petaeseree carseat asa ator ye 83 THE INSIDE OF THE EARTH. REVIEW AND MAp QUESTIONS. ....... 84 I. Tot HEATED INTERIOR .........22 II. VOLCANOES ..... ace cunsoe em ae aieae esto AR THO WAKES Hore: ies ds et fed acorn es rey ae 28 PAS ry: SWEPABUS ie recs ce cee te mecn ten te te mrut uae 81 REVIEW AND Map QUESTIONS ....... - 82 Oe ee Section II. THE OUTSIDE OF THE EARTH, I, THe Crust oF THE EARTH ...... .33 II. DisTRIBUTION OF THE LAND AREAS... . 87 GA SUAN DS cause ciesiese cu sauce ele ican etic - 39 IV. Revier Forms of THE LAND ..... .42 V. RELIEF FoRMS OF THE CONTINENTS .. .45 SYUMABUS 8) cis +3. 6 ir saeercne aoe oeacer: 54 REVIEW QUESTIONS ...... Ceaiebicie one 55 Map QUESTIONS ....... sure ones O0, PART ITI. THE WATER. Section I. CONTINENTAL WATERS. I. PaysicAL PROPERTIES OF WATER... .57 Po DRATNAGES) stce ret ee oes eek Seer NSS 59 vi ‘Section I. THE ATMOSPHERE. I. GENERAL PROPERTIES OF THE ATMOSPHERE 85 A © MAE eres lla, cp lace les arnt neuer Maremma ain 87 De BWalINIDS: 37s) clsers: Tours crs need ee tears 90 MVEESTORMS Siesaa sce ce eee eee - 96 SNAG ABU So eetienae ee aiee sr eects See es sar aaa ese 98 REVIEW QUESTIONS ss ccers Sole wees a ane ys Peo) MUAPEO@) UESTIONSS voptenysaccetsnt nest yeoman eee ees 100 Section ILI. MOISTURE OF THE ATMOSPHERE. I, PRECIPITATION OF MOISTURE ...... 101 IJ. Hart, Snow, AND GLACIERS ...... 107 III. ELEcTRICAL AND OPTICAL PHENOMENA . 110 DSWLEABUS we esanss tue ce eres tenon piece miei eae te 115 REVIEW QUESTIONS ........2. Rea eerelelG MEAPS @UESTIONSiigee suaeiacgees Pollan ts Went wercins eae ae 117 i Wh We CG piel fl a mun 1 el Sa Ns Aa SENS BSA 1, a CELE CARTAN CTT TAT SR aa fui Hk SSS ae Ae ( it ne Ml Sty f aa | i i) Ws eb NS i PHYSICAL iy nv I sk ay) ut Geography is a description of the earth. The earth may be considered in three different ways: (1.) In its relations to the solar system ; (2.) In its relations to government and society ; (3.) In its relations to nature. Hence arise three distinct branches of geog- raphy—Mathematical, Political, and Physical. 2. Mathematical Geography treats of the earth in its relations to the solar system. Mathematical Geography forms the true basis for accurate geographical study, since by the view we thus obtain of the earth in its relations to the other members of the solar system, we are enabled to form clearer concep- tions of the laws which govern terrestrial phenomena, Here we learn the location of the earth in space, its size, form, and movements, its division by imaginary lines, and the methods of representing portions of its surface on maps. 3. Political Geography treats of the earth in its relations to the governments and societies of 2 [ a is (F¥EOGRA PHY. INTRODUCTORY. men, of the manner of life of a people, and of their civilization and government. 4, Physical Geography treats of the earth in its relations to nature and to the natural laws by which it is governed. It treats especially of the - systematic distribution of all animate and inani- mate objects found on the earth’s surface. It not only tells of their presence in a given locality, but it also endeavors to discover the causes and results of their existence. Physical Geography, therefore, treats of, the distribution of six classes of objects—Land, Water, Air, Plants, Animals, and Minerals. Geography deals with the inside as well as with the out- side of the earth. It encroaches here on the province of geology. Both treat of the earth: geography mainly with the earth’s present condition ; geology with its condition both in the past and present, though mainly during the past. _ Some authors make physical geography a branch of geol- ogy, and call it physiographic geology, but we prefer the word “physical,’”’ or as the etymology would make it, “natural” geography. 4 9: ie Awan 1D THE EARTH. AS A. PLANET. Fig, 1, The Earth in Space, CHAPTER lL Mathematical Geography. 5. The Earth moves through empty space around the sun. The old idea of the earth resting on, or being supported by something, is erroneous. The earth rests on nothing. A book or other inanimate object placed on a support will remain at rest until something or somebody moves it, because it has no power of self-motion. This property. is called iertia. Inertia is not confined to bodies at rest. If the book be thrown up through the air, it ought to keep on moving upward for ever, because it has no more power to stop moving than to begin to move. We know, however, that in reality it stops very soon, and falls to the earth; because— (1.) The earth draws or attracts it; + (2.) The falling body gives some of its motion to the air through which it moves. Were the book thrown in any direction through the empty space in which the stars move, it would continue moving in that direction for ever, unless it came near enough to some other body which would attract it and cause it to change its motion. Our earth moves through empty space on ac- count of its inertia, and must continue so moving for eternities. There are ample reasons for believ- 10 ing that all heavenly bodies continue their mo- tion solely on account of their inertia. The curved paths in which the earth and the other planets move are resultant paths produced in a-manner that will be explained hereafter. Space is not absolutely empty, but is everywhere filled with a very tenuous substance called ether, which trans- mits to us the light and heat of the heavenly bodies. Wherever the telescope reveals the presence of stars we must believe the ether also extends. _ 6, The Stars.—The innumerable points of light that dot the skies are immense balls of matter which, like our earth, are moving through empty space. Most of them are heated so intensely that they give off heat and light in all directions. They are so far from the earth that they would not be visible but for their/immense size. Beyond them are other balls, also self-luminous, but too far off to be visible except through a telescope. Beyond these, again, we have reason to believe that there are still others. These balls of matter are called stars. All the heavenly bodies, however, do not shine by their own light. A few—those nearest the earth—shine by reflecting the light of the sun. These are called planets, and move with the earth around the sun. 7. The Solar System comprises the sun, eight large bodies called planets, and, as far as now known, three hundred .and eighty-four smaller bodies called planetoids or asteroids, besides nu- merous comets and meteors. Some of the planets have bodies called moons or satellites moving around them. These also belong to the solar system. s Fig. 2 represents the solar system. In the centre is the sun. The circles drawn around the sun show the paths or orbits of the planets. These orbits are represented as circular, but in. reality they are slightly flattened or elliptical. The elongated orbits mark the paths of the comets. MATHEMATICAL GEOGRAPHY. Mi . . 2 Ye ui ae The drawing shows the order of the planets from the sun their common centre, together with the satellites or moons of some of the planets, and the rings of Saturn. 8. Names of the Planets.—The planets, named in their regular order from the sun, beginning with the nearest, are as follows—viz.: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four—Mereury, Venus, Earth, and Mars—are comparatively small; the second _four—Jupiter, Saturn, Uranus, and Neptune—are very large, Jupiter being nearly fourteen hun- — dred times larger than the earth. The initial letters of the last three planets, Saturn, Uranus, and Neptune, taken in their order from the sun: s, u, and n—spell the name of their common centre. * Mercury has a mean or average distance of 36,000,000 of miles from the sun; Venus, 67,200,000; Earth, 92,900,000 ; and Mars, 141,500,000. Jupiter is 483,000,000; Saturn, 886,000,000; Uranus, 1,781,900,000; Neptune, 2,791,600,000. The asteroids move around the sun in the space between the orbits of Mars and Jupiter. * Calculated in round numbers for the mean svlar distance of 92,897,000 miles, : 12 PHYSICAL GEOGRAPHY. It is difficult to obtain clear conceptions of distances that are represented by millions of miles. We may learn the numbers, but in general they convey no definite ideas. Should a man travel forty times around the earth at the equator, he would only have gone over about 1,000,000 miles. Now, Mercury, the nearest of the planets, is thirty- six times farther from the sun than the entire distance the man would have travelled, while Neptune is nearly three thousand times the distance he would have travelled. 9. The Satellites—A satellite is a body that revolves around another body: the planets are satellites of the sun; the moon is a satellite of the earth. Mars has two moons. So far as is known, neither Mercury nor Venus has a satel- lite. All the planets whose orbits are beyond the orbit of the earth have moons: Jupiter has five, Uranus six, Saturn eight, and Neptune one. Be- sides its moons, Saturn has a number of curious ring-like accumulations of separate solid or liquid particles revolving around it. The earth’s moon is about 240,000 miles from the earth. Its vol- ume is about one-forty-ninth that of the earth’s. 10. The Sun is the great central body of the solar system. Around it move the planets with their satellites, receiving their light and heat from it. The sun is a huge heated mass about 1,300,000 times the size of the earth. Its diam- eter is about 866,500 miles. It appears the largest self-luminous body in the heavens because it is comparatively near the earth. Many stars which appear as mere dots of light are much larger than the sun. The sun is a body heated to luminosity, and gives out or emits light and heat like any other highly-heated body. If no causes exist to maintain its heat, it will eventu- ally cool and fail to emit light. The sun’s heat is partly kept up by a variety of causes, the principal of which is the heat developed by meteoric showers that fall on its surface. If a meteor fall toward the sun from inter- planetary space, it will reach the surface with enormous velocity, and its motion will there be converted into heat. Since, however, the increase of the sun’s mass so necessitated’ is not confirmed by astronomical observa- tions, itis believed that the sun’s heat is not being main- tained in this way, and that the sun must eventually cool —an event, however, so remote in time that the life of the solar system may be regarded as practically infinite. Size of the Sun.—Were the sun hollow and the earth placed at its centre, there would not only be sufficient room to enable the moon to revolve at its present actual distance around the earth, but it would still, in all parts of its orbit, be nearly 200,000 miles below the surface of the sun. All the fixed stars are distant suns, and probably have worlds like our own moving around them. From the enormous distances of the fixed stars, we are obliged, in estimating their distances, to use for our unit of measurement the velocity of light. Any other common unit would be too small. Light moves through space at the rate of about 186,000 miles a second, which is over 11,000,000 miles a minute. Notwithstanding this prodig- ious velocity, it would take over three thousand years for light to reach the earth from some of the stars that are visible to the naked eye. But beyond these stars the tele- scope reveals myriads of others, whose number is limited only by the power of the instrument. We may conclude that the universe is as boundless as space; that is, light can never reach its extreme limits. 11. Cause of the Harth’s Revolution.—The earth continues its motion through space solely on account of its inertia. Its curved path around the sun is a resultant caused by the constant action of two forces: one, a pro- jectile force probably imparted to it when it began its separate existence; the other, the sun’s attraction, which causes the earth to fall toward the sun. Under the infiu- ence of the projectile force alone the earth would, in a given time, move from a to d (Fig. 3); but during this time Fig. 3, Cause of the Curved Shape of the Barth's Orbit, it has been continually changing its direction by an amount equivalent to a direct fall from 6 to ¢ along bd; hence its real orbit, during this time, is along the curved line ac. 12. Position of the Solar System in Space— The sun, with all the bodies which move around it, is in that portion of the heavens called the Milky Way. The sun is an insignificant star among the millions of other stars the telescope has revealed to us. It was formerly believed that the sun was stationary, for it was not then known that the positions of the fixed stars were undergoing slight variations as regards the earth. It is now generally conceded that the sun, with all the planets, is moving through space with tremendous veloc- ity, the direction at present being toward the constella- tion Hercules. The astronomer Maedler, however, believes that the grand centre around which the solar system is moving is Aleyone, the brightest star in the constellation of the Pleiades. The estimated velocity of the sun in its immense orbit is 1,382,000,000 miles per year. As the earth is carried along with the sun in its orbit, it is continually entering new realms of space. 13. The Earth.—The-shape of the earth is that of a round ball or sphere slightly flattened at two opposite sides. Such a body is termed a spheroid. There are two kinds of spheroids—oblate and pro- late; the former has the shape of an orange, the latter that of a lemon. MATHEMATICAL GEOGRAPHY. 18 The straight line that runs through the centre of a sphere or spheroid and terminates at the cir- cumference is called the diameter. If the sphere rotates—that is, moves around like a top—the Fig. 4, Oblate Spheroid, diameter on which it turns is called its awis. In the oblate spheroid the axis is the shorter diam- eter ; in the prolate spheroid the axis is the longer diameter. Fig, 6, Curvature of the Harth’s Surface. The shape of our earth is that of an oblate spheroid. The polar diameter is 26.47 miles shorter than the equatorial diameter. 14. Proofs of the Rotundity of the Earth— The earth is so large a sphere that its surface everywhere appears flat. The following simple considerations will prove, however, that its form is nearly spherical: (1.) Appearance of Approaching Objects —If the earth were flat, as soon as an object appeared on the horizon we would see the upper and lower parts at the same time; but if it were curved, the top parts would first be seen. Now, when a ship is coming into port we see first the topmasts, then the sails, and finally the hull; hence the earth must be curved; and, since the appearance is the same no matter from what direction the ship is approaching, we infer that the earth is evenly curved, or spherical. (2.) Circular Shape of the Horizon.—The hori- zon—or, as the word means, the boundary—is the line which limits our view when nothing inter- venes. The fact that this is always a circle fur- nishes another proof that the earth is spherical. The horizon would still be a circle if the earth were perfectly flat, for we would still see equally far in all di- rections; but it would not everywhere be so, since to an observer near the edges some other shape would appear. It is on account of the spherical form of the earth that our field of view on a plain is so soon limited by the apparent meeting of the earth and sky. As we can see only in straight lines, objects continue visible until they reach such a distance as to sink below the horizon, so that a straight line from the eye will pass above them, meeting the sky far beyond, on which, as a background, the objects on the horizon are projected. (8.) Shape of the Earth’s Shadow.—We can obtain correct ideas of the shape of a body by the shape of the shadow it casts. Now, the shadow which the earth casts on the moon dur- ing an eclipse of the moon is always circular, and as only spherical bodies cast circular shad- ows in all positions, we infer that the earth is spherical. (4.) Measurement.—The shape of the earth has been accurately ascertained by calculations based on the measurement of an arc of a meridian. We therefore not only know that the earth is oblately spheroidal, but also approximately the amount of its oblateness. (5.) The Shape of the Great Circle of Ilumi- nation, or the line separating the portions of the earth’s surface lighted by the sun’s rays from those in the shadow, is another evidence of the rotundity of the earth. rs \ 15. The Dimensions of the Earth.—The equa- torial diameter of the earth, or the distance through at the equator, is, approximately, 7926 14 PHYSICAL GEOGRAPHY. miles; its polar diameter, or the length of its axis, is 7899 miles. The circumference is 24,899 miles. The entire surface is equal to nearly 197,000,000 square miles. The specific gravity of the earth is about 53; that is, the average weight of all its matter is five and two-third times heavier than an equal volume of water. 16. Imaginary Circles—In order to locate places on the earth, as well as to represent por- tions of its surface on maps, we imagine the earth to be encircled by a number of curved lines called great and small circles. A great circle is one which would be formed on the earth’s surface by a plane passing through the earth’s centre, hence dividing it into two equal parts. All great circles, therefore, divide the earth into hemispheres. The formation of a great circle on a sphere by cutting it into two equal parts is shown in Fig. 7. The shortest distance between any two places on the earth is along the arc of a great circle. All planes passing through the earth’s centre form ap- proximately great circles on its surface. A small circle is one formed by a plane which does not cut the earth into two equal parts. The formation of a small circle by cutting a sphere into unequal parts is shown in Fig. 8. Fig, 8. Small Circle. The great circles employed most frequently in geography are the equator and the meridian circles. The small circles are the parallels, ——, If we divide the circumference of any circle, whether great or small, into three hundred and sixty equal parts, each part is called a degree. The one-sixtieth part of a degree is a minute; the one-sixtieth part of a minute is a second. These divisions are represented as follows: 34°, 12!, 38’°; which reads, thirty-four degrees twelve minutes and thirty-eight seconds. The Equator is that great circle of the earth which is equidistant from the poles. Meridian Circles are great circles of the earth which pass through both poles. The Meridian of any given place is that half of the meridian circle which passes through that place and both poles. A meridian of any place reaches from that place to both poles, and there- fore is equal to one-half of a great circle, and, with the meridian directly opposite to it, forms a great circle called a meridian circle. There are as many meridian circles as there are places on the equator or on any parallel. In large cities the meridian is generally assumed to pass through the principal observatory. Fig. 9, Meridians and Parallels, Parallels are small circles which pass around the earth parallel to the equator. The meridians extend due north and@ south, and are everywhere of the same length; the parallels extend due east and west, and decrease in length as they approach the poles. The Tropics are parallels which lie 23° 27’ porth and south of the equator: the northern tropic is called the Tropic of Cancer, the south- ern tropic is called the Tropic of Capricorn. The Polar Circles are parallels which lie 23° 27’ from each pole. The circle in the Northern Hemisphere is called the Arctic Circle; that in the Southern Hemisphere, the Antarctic Cirele. 17. Latitude is distance north or south from "the equator toward the poles, measured ‘along the meridians. It is reckoned in degrees. . The meridian circles are divided into nearly equal parts by the parallels, and it is the number of these parts that occur on the meridian of any place between it and the equator which deter- MATHEMATICAL GEOGRAPHY. 15 mines the value of its latitude. If we conceive eighty-nine equidistant parallels drawn between the equator and either pole, they will divide all the meridians into ninety nearly equal parts; the value of each of these parts will be one degree of latitude. Therefore, if the parallel running through a place is distant from the equator forty- five of these parts, its latitude is 45°. If more than eighty-nine parallels be drawn, the value of each part will be less than one degree. Places north of the equator are in north lati- tude; those south of it are in south latitude. Since the distance from the equator to the poles is one-fourth of an entire circle, and there are only 360° in any circle, 90° is the greatest value — of latitude a place can have. Latitude 90° N. therefore corresponds to the north pole. To recapitulate: Latitude is measured on the | meridians by the parallels. : 18. Longitude is distance east or west of any given meridian. Places on the equator have their longitude measured along it; everywhere else longitude is measured along the parallels. The meridian from which longitude is reckoned is called the Prime Meridian. Most nations take the meridians of their own capitals for their prime meridian. The English reckon from the me- ridian which runs through the observatory at Greenwich; the French from Paris. In the United States we reckon from Washington. Any prime meridian circle divides all the par- allels into two equal parts. A place situated east of the prime meridian is in east longitude; west of it is in west longitude. Since there are only 180° in half a circle, the greatest value the longitude can have is 180°; for a place 181° east of any meridian would not fall within the eastern half of the parallel on which it is situated, but in the western half; and its distance, computed from the prime meridian, would be 179° west. . 3 ¢ It is the meridians that divide the parallels into degrees; therefore longitude is measured on the parallels by the meridians. — 19. Value of Degrees of Latitude and Longi- tude——As latitude is distance measured on the are of a meridian, the value of one degree must be the 345th part of the circumference along that meridian, since there are only 360° in all. This makes the value of a single degree approximately equal to 694 miles. Near the poles the flattening of the earth causes the value of a degree slightly to exceed that of one near the equator. The value of a degree of longitude is subject to great variation. It is equal to the g{oth part of the earth’s circumference, provided the place be situated on the equator; otherwise, it is the gigth part of the parallel passing through the place that is taken; and as the parallels decrease in size as we approach the poles, the value of a degree of longitude must likewise decrease as the latitude increases, until at either pole the longi- tude becomes equal to zero. The value of a single degree of longitude on the equator, or at lat. 0°, is equal to about 694 miles. At latitude 45° it is equal to about 49 miles. “ 60° “ “c 35 “ “ce 80° “ , “c 12 coe “ 90° 73 “ 0 “ Geographical Mile.—The sztypth of the equatorial circumference, or the one-siatieth of a degree of longitude at the equator, is called a nautical or geographical mile. The statute mile contains 1760 yards; the geographical or nautical mile, 2028 yards. The nautical mile is sometimes called a knat. 20. Map Projections—The term projection as applied to map-drawing means the various methods adopted for representing portions of the earth’s surface on the plane of a sheet of paper. The projections in most common use are Merca- tor’s, the orthographic, the stereographic, and the conical projections. Of these the stereographic is best adapted to ordinary geographical maps, and Mercator’s to physical maps. All -projections must be regarded as but approximations. 1. The Orthographic Projection is that by which the earth’s surface is represented as it would appear to an observer viewing it from a great distance. 2. The Stereographic Projection is that by which the earth’s surface is represented as it would appear to an observer whose eye is directly on the surface, if he looked through the earth as through a globe of clear glass, and drew the details of the surface as they appeared projected on a transparent sheet of paper stretched in front of his eye across the middle of the earth. There may be an almost infinite number of such projections, according to the position of the observer. The two stereographic pro- jections in most common use are the Equatorial and the Polar. Mercator’s Projection represents the earth on a map in which all the parallels and meridians are straight lines. Mercator’s charts are drawn by conceiving the earth to have the shape of a cylinder instead of that of a sphere, and to be unrolled from this cylinder so as to form a flat surface. The me- ridians, instead of meeting in points at the north and south poles, are drawn parallel to each other. This makes them as far apart in the polar regions 16 PHYSICAL GEOGRAPHY. as at the equator, and consequently any portion of the earth’s surface represented on such a chart, if situated toward the poles, will be dispropor- Fig. 10, The Earth on Mercator's Projection. tionally large. In order to avoid the distortion in the shape of the land and water areas, the dis- tance between successive parallels is increased as they approach the poles. The dimensions of the land or water, however, are greatly exaggerated in these regions. The immediate polar regions are never represented on such charts, the poles being supposed to be at an infinite distance. Mercator’s charts are generally employed for physical maps, on account of the facility they afford for showing direction. The distortion they produce in the relative size of land or water areas must be carefully borne in mind, or wrong ideas of the relative size of various parts of the world will be obtained. Mercator’s charts make bodies of land and water situated near the poles appear much larger than they really are. In an Equatorial Projection of the entire earth the equator passes through the middle of each hemisphere, and a meridian circle forms the borders. In a Polar Projection of the entire earth the RE See poles occupy the centres of each hemisphere, and the equator forms the borders. In a Conical Projection the earth’s surface is QW Fig. 11, The Earth on an Equatorial Projection. represented as if drawn on the frustum of a cone and afterward unrolled. This projection is. suit- able where only portions of the earth’s surface, Fig. 12, The Earth on a Polar Projection. and not hemispheres, are to be represented. The cone is supposed to be placed so as to touch the earth at the central parallel of the country to be represented. In maps as ordinarily constructed it is not true that the upper part is north, the lower part south, the right hand east, and the left hand west, except in those on Merca- tor’s projection. Jn all maps due north and south lie along the meridians, and due east and west along the parallels, since MATHEMATICAL GEOGRAPHY. 17 Fig. 18, The Conical Projection. in most maps both parallels and meridians are curved lines. Therefore, in most maps due north and south and due east and west will lie along the meridians and parallels, and not directly toward the top and bottom, or the right- and left-hand side. . 21, The Hemispheres.—The equator divides the earth into a Northern and a Southern Hemisphere. The meridian of long. 20° W. from Greenwich is generally taken as the dividing-line between the Eastern and Western Hemispheres. 22. The Movements of the Earth; Rotation.— The earth turns around from west to east on its diameter or axis. This motion is called its ro- tation. That the earth rotates from west to east the following consideration will show: To a person in a steam-car mov- ing rapidly in any direction, the fences and other objects along the road will appear to be moving in the opposite direction: their motion is of course apparent, and is caused by the real motion of the car. Now, the motion of the sun and the other heavenly bodies, by which they appear to rise in the east and set in the west, is apparent, and is caused by the real motion of the earth on its axis; this motion must therefore be from west to east. The sun, the planets, and their satellites, so far as is known, also turn on their axes from west to east. The earth makes one complete rotation in about every twenty-four howrs—accurately, 23 hours 56 minutes 4.09 seconds. The velocity of its rota- tion is such that any point on the equator will travel about 1042 miles every hour. The veloci- ty of course diminishes at points distant from the equator, until at the poles it becomes nothing. 23. Change of Day and Night—tThe earth re- ceives its light and heat from the sun, and, being an opaque sphere, only one-half of its surface can be lighted at one time. The other half is in dark- ness, since it is turned from the sun toward por- tions of space where it only receives:the dim light ° of the fixed stars. The boundary-line between the light and dark parts forms approximately a great circle called the Great Circle of Illumination. Had 3 the earth no motion either on its axis or in its orbit, that part of its surface turned toward the sun would have perpetual day, and the other part perpetual night ; but by rotation different portions of the surface are turned successively toward and away from the sun, and thus is occasioned the change of day and night. 24, The Revolution of the Earth —The earth has also a motion around the sun, called its revolution. The revolution of the earth is from west to east; this is also true of all the planets and asteroids, and of all their satellites, except those of Uranus, and probably of Neptune. The phrases “rotation of the earth on its axis” and “yevolution in its orbit” are often used in reference to the earth’s motion; but the simple words “rotation” and “yvevolution” are sufficient, since the first refers only to the motion on its axis, and the second only to the motion in its orbit. The earth makes a complete revolution in 365 days 6 hours 9 minutes 9.6 seconds.. This time forms what is called a sidereal year. The tropical year, or the time from one March equinox to the next, is somewhat shorter, or 865 days 5 hours 48 minutes 49.7 seconds. The latter value is the one generally given for the length of the year. It is nearly 3653 days. It will be found that the sum of the days in all the months of an ordinary year is only equal to 365, while the true length is approximately one-quarter of a day greater. This deficiency, which in every four years amounts to an entire day, is met by adding one day to February in every fourth or leap year. The exact time of one revolution, however, is some 11 minutes less than 6 hours. These eleven extra minutes are taken from the future, and are paid by omitting leap year every hundredth year, except that every 400 years leap year is counted. In other words, 1900 will not be a leap year, since it is not divisible by 400, but the year 2000 will be a leap year. The length of the orbit of the earth is about 577,000,000 miles. Its shape is that of an el- lipse which differs but little from a circle. The sun is placed at one focus of the ellipse, and, as this. is not in the centre of the orbit, the earth must be nearer the sun at some parts of its revo- lution than at others. When the earth is in that part of its orbit which is near- est to the sun, it is said to be at its perihelion; when in that part farthest from the sun, at its aphelion. The peri- helion distance is about 90,259,000 miles; the aphelion dis- tance, 93,750,000 miles. The earth reaches its perihelion about January Ist. The earth does not move with the same rapidity through all parts of its orbit, but travels more rapidly in perihelion than in aphelion. Its mean velocity is about 19 miles a second, which is nearly sixty times faster than the speed of a cannon-ball. 18 PHYSICAL GEOGRAPHY. 25, Laplace’s Nebular Hyp othesis.—The uniformity in the direction of rotation and revolution of the planets has led to a very plausible supposition as to the origin of the solar system, by the celebrated French astronomer La- place. This supposition, known as Laplace’s nebular hy- pothesis, assumes that, originally, all the materials of which the solar system is composed were scattered throughout space in the form of very tenuous or nebulous matter. It being granted that this matter began to accumulate around a centre, and that a motion of rotation was thereby’ ac- quired, it can be shown, on strict mechanical principles, that asystem resembling the solar system might be evolved. As the mass contracted on cooling, the rapidity of its rotation increased. The equatorial portions bulged out through the centrifugal force, until ring-like portions separated, and, collecting in spherical masses, formed the planets. The planets in a similar manner detached their satellites. At the time of the separation of Neptune the nebulous sun must have extended beyond the orbit of this planet. The temperature requisite for so great an expan- sion must have been enormous. Although a mere hypothesis, there are many facts which tend to sustain it, and it is now generally accepted. 26. The Plane of the Earth’s Orbit is a per- fectly flat surface so placed as to touch the earth’s orbit at every point. It may be regarded as an imaginary plane of enormous extent on which the earth moves in its journey around the sun. ~~ 27. Causes of the Change of Seasons.—The change of the earth’s seasons is caused by the revolution of the earth, together with -the fol- lowing circumstances: Fig, 14, Inclination of Axis-to Orbit and Ecliptic. (1.) The inclination of the earth’s axis to the plane of its orbit. The inclination is equal to 66° 33’. The ecliptic is the name given to a great circle whose plane coincides with the plane of the earth’s orbit. Since the earth’s axis is 90° distant from the equator, the piane of the ecliptic must be inclined to the plane of the equator 90° minus 66° 33’, or 23° 27’. The mere revolution of the earth would be unable to produce a change of seasons, unless the earth’s axis were inclined to the plane of its orbit. If, for example, the axis of the earth stood perpendicularly on the plane of its orbit, the sun’s rays would so illumine the earth that the great circle of illumination would always be bounded by some meridian circle. The days and nights would then be of equal length, and the distribution of heat the same throughout the year. Under these circumstances there could be no change of seasons, since the sun’s rays would always fall perpendicularly onthe same part of the earth: on the equator. (2.) The Constant Parallelism of the Earth’s Axis.—During the earth’s revolution its axis always points nearly to the same place in the heavens, viz. to the north star. It is therefore always approximately parallel to any former position. Unless the axis were constantly parallel to any former position, the present change of seasons would not occur. On account of the spherical form of the earth, only a small part of its surface can receive the vertical rays of the sun at the same time. This part can be regarded as nearly a point; and since only one-half of the earth is lighted at any one time, the great circle of illumination must extend 90° in all directions from the point which receives the vertical rays. By rotation all portions of the surface situated anywhere within the tropics in the same latitude, at some time or another during the day, are turned: so as to receive the vertical rays of the sun, and consequently, the portion so illumined has the form of a ring or zone. Other things being equal, this zone con- tains the hottest portions of the surface, the heat gradually diminishing as we pass toward either pole. On account of the inclination of its axis, the earth receives the vertical rays of the sun on new portions of its surface every day during its revo- lution; and it is because different portions of the ‘surface are constantly being turned toward the sun that the change of seasons is to be attributed. As the earth changes its position in its orbit, the sun’s rays fall vertically on different parts of the surface, so that during the year one part or an- other of the surface within 23° 27’ on either side of the equator receives the vertical rays. The astronomical year begins on the 20th of March, and we shall therefore first consider the position of the earth in its orbit at that time. An inspection of Fig. 15 will show that at this time the earth is so turned toward the sun that the vertical rays fall exactly on the equator. The great circle of illumination, therefore, reaches to the poles, and the days and nights are of an equal length all over the earth. This time is called the March equinox. Spring then begins in the North- ern Hemisvhere, and autumn in the Southern. This is shown more clearly in Fig. 16, which represents the relative positions of the illumined and non-illumined portions at that time. = MATHEMATICAL GEOGRAPHY. 19 SEPTEMBER © EQUINOX > Zi ( ZZ “E_nm')=é : AN \ Mt | So 2 ‘ ncn lilt ae °MARCH — EQUINOX \ OB peo \ vv 4 HA . - Fig. 15. The Orbit of the Earth, showing the Change of Seasons, As the earth proceeds in its orbit, the inclina- tion of the axis causes it to turn the Northern . Hemisphere more and more toward the sun. The vertical rays, therefore, fall on portions farther and farther north until, on the 2Zst of June, the Fig. 16, The Earth at an Equinox. vertical rays reach their farthest northern limit, and fall directly on the Tropic of Cancer, 28° 27' N., when the sun is said to be ‘at its summer sol- stice. Since the portions receiv'ag the vertical rays of the sun are now onthe Tropic of Cancer, the light and heat must extend in the Northern Hemisphere to 23° 27’ beyond the north pole, or | to the Arctic Circle; while in the Southern Hemi- sphere they must fall short of the south pole by the same number of degrees, or reach to the Ant- Fig. 17, The Earth at the Summer Solstice, arctic Circle. The Northern Hemisphere then be- gins its summer, and the Southern tts winter. The relative positions of the illumined and non-illumined portions of the earth at the sum- mer solstice are more clearly shown in Fig. 17. Here, as is shown, the great circle of illumination \20 PHYSICAL GEOGRAPHY. extends in the Northern Hemisphere as far over the pole as the Arctic Circle. After the 21st of June the Northern Hemi- sphere is turned less toward the sun, and the vertical rays continually approach the equator, all the movements of the preceding season being reversed, until on the 22d of September, the time of the September equinox, the equator again receives the vertical rays, the great circle of illumination again coinciding with the meridian circles. The earth has now moved from one equinox to an- other, and has traversed one-half of its orbit. The Southern Hemisphere then begins its spring, the Northern its autumn. From the 22d of September until the 20th of March, while the earth moves through the other half of its orbit, the same phenomena occur in the Southern Hemisphere that’ have already. been noticed in the Northern. Immediately after the 22d of September the inclination of the axis causes the earth to be so turned toward the sun _ that its rays begin to fall south of the equator ; and, as the earth proceeds in its orbit, the South- ern Hemisphere is turned more and more toward | the sun, and the vertical rays fall farther and farther toward. the pole. This continues until the 21st of December, when the rays fall vertically on the Tropic of Capricorn, and the December sol- stice is reached. The great circle of illumination now extends beyond the south pole as far as the Antarctic Circle, but falls short of the north pole 93° 27’, reaching only the Arctic Circle. Sum- mer then commences in the Southern Hemisphere, and winter in the Northern. After the 21st of December the Southern Hemisphere is turned less and less toward the —'S.FRIGID Fig. 18, Mathematical Climatic Zones, gun, and the part receiving the vertical rays approaches the equator, until on the 20th of March the equator again receives the vertical rays, and, with the March equinox, spring com- mences in the Northern Hemisphere, and with it a new astronomical year. The equinoxes and solstices as a rule occur on the dates named. Occasionally. they occur immediately before or after said dates. s 28. Mathematical Zones.—The Torrid Zone.— That belt of the earth’s surface which lies be- tween the tropics is called the Torrid Zone. During one time or another throughout the year every part of its surface receives the ver- tical rays of the sun. The Temperate Zones are included between the tropics and the polar circles. The northern zone is called the North Temperate Zone, and the south- ern zone, the South Temperate Zone. The Polar Zones are included’ between the polar circles and the poles. The northern zone is called the North Frigid Zone, and the southern . ’ gone, the South Frigid Zone. These zones, which are separated by the parallels of lati- tude, are generally termed the astronomical or mathematical zones to distinguish them from others called physical zones, which are bounded by the lines of mean annual temper- - ature. It will be noticed that the distance of the tropics from the equator and of the polar circles from the poles is 23° 27’, or the value of the’inclination of the plane of the ecliptic to the plane of the equator. 29, Length of Day and Night.— Whenever more than half of either the Northern or South- ern Hemisphere is illumined, the great circle of illumination will divide the parallels unequally, and the length of the daylight in that hemisphere will exceed that of the night in proportion as the length of the illumined part, measured along any of the parallels, exceeds that of the dark part. The length of daylight or darkness may exceed that of one complete rotation of the earth. The great circle of illumination may at times pass over the poles as far beyond them as 23° 27’; and places situated within this limit may remain during many rotations exposed to the rays of the sun. A little consideration will show that the longest day must occur at the poles, since the poles must continue to receive the sun’s rays from the time they are first illu. mined at one equinox until the sun passes through a sol- stice and returns to the other equinox. Nowhere, outside the polar circles, will the length of daylight exceed one entire rotation of the earth. The length of the longest day at the equator, latitude 0°, is 12 hours. ; Of the longest day a3; the poles, latitude 90°, is six months. . MATHEMATICAL GEOGRAPHY. 21 y ‘G SYLLABUS. —— 00300 — There are three kinds of geography—Mathematical, Po- litical, and Physical. Physical Geography treats of Land, Water, Air, Plants, Animals, and Minerals. Geography deals mainly with the earth as it is; geology mainly with the earth as it was. The earth continues its motion around the sun in conse- quence of its inertia. The distant stars are balls of fire like our sun, and prob- ably-have worlds resembling ours revolving around them. The sun and the bodies that revolve around it consti- tute the solar system. The sun is about 1,300,000 times larger than the earth. The sun is a body heated to luminosity, and gives out or > emits light and heat like any other highly-heated body. The shape of the earth is that of an oblate spheroid whose equatorial diameter is about 26 miles longer than its polar. That the earth is round and not flat is proved —Ilst, by the appearance of approaching or receding ob- jects; 2d, by the circular shape of the horizon; 3d, by the circular shape of the earth’s shadow; 4th, by actual nieas- urement; and 5th, by the shape of the great circle of illumination. The earth’s diameter is nearly 8000 miles, its circumfer- ence not quite 25,000 miles, and its area about 197,000,000 square miles, The imaginary circles used in geography are the Equa- tor, the Meridian Circles, and the Parallels. Latitude is measured on the meridians by the parallels. The greatest number of degrees of latitude a place can have is 90°; the greatest of longitude, 180°. The latitude at the equator is 0° N.orS. The longitude at the poles or on the prime meridian is 0° E. or W. Longitude is measured on the equator, or on the parallels, by the meridians. Maps are drawn on different projections : the Equatorial, the Polar, and Mercator’s projections are in most general use. A Mercator’s projection causes places near the poles to appear larger than they really are. On all maps due north and south lies along the merid- ians; due east and west, along the parallels: when these are curved lines, the top and bottom of the map will not always represent north and south, nor the right and left hand east and west. The inclination of the earth’s axis to the plane of its orbit, and the constant parallelism of the axis with any former position, together with the revolution around the sun, cause the change of seasons. The astronomical year begins March 20th. On the 20th of March and on the 22d of September the days and nights are of equal length all over the earth. From the 20th of March the days increase in length in the Northern Hemisphere until the 21st of June, when they attain their greatest length; they then decrease until the 22d of September, when they again become equal. x The Torrid Zone is the hottest part of the earth, because, during one time or another throughout the year, every part of its surface receives the vertical rays of the sun. REVIEW QUESTIONS. ———0503 00 ——_. ; The Solar System. How does the principle of inertia apply to the earth’s motion around the sun? What do you understand by the solar system ? Describe the earth’s position in the solar system. Which of the planets are between the earth and the sun? Which are beyond the orbit of the earth? How does the size of the sun compare with that of the earth ? Are any of the distant stars larger than our sun ? Whatisasatellite? Which of the planets have satellites ? Explain the cause of the circular shape of the earth’s orbit. In what part of space is the solar system ? Has our sun any motion through space? Enumerate the proofs of the rotundity of the earth. State accurately the length of the equatorial diameter of the earth; of its polar diameter; of its circumference. What is its area? How many times heavier is the earth than an equally large. globe of water? Ra by Imaginary Circles. Define great and small circles. Name the circles most commonly used in geography. What do you understand by latitude? How is latitude reckoned? Of what use is latitude in geography? Why can the value of the latitude never exceed 90°? Of what use are meridians and parallels in measuring latitude? What do you understand by longitude? How is longi- tude reckoned? Of what use is longitude in geography ? Why can its value never exceed 180°? Of what use are meridians and parallels in measuring longitude? Where is the value of a degree of latitude the greatest ?. Of a degree of longitude? Why? What effect has a Mercator’s chart on the appearance of bodies of land or water in high northern or southern lati- tudes ? What is an equatorial projection? A polar projection? A conical projection? What is the position of the poles in an equatorial projection? In a polar projection ? Movements of the Earth. Prove that the earth turns on its axis from west to east. Explain the cause of the change of day and night. Define a sidereal year; a tropical year. Which value is generally taken for the length of the civil year? Describe Laplace’s nebular hypothesis. Enumerate the causes which produce the change of seasons. On what days of the year will the sun’s rays fall verti- cally on the equator? On what days will its rays fall ver- tically on the Tropic of Cancer? On the Tropic of Capri- corn? PART II. PAE AND, 020300 ALTHOUGH water occupies much the larger portion of the earth’s surface, yet, when compared with the entire volume of the globe, its quantity is comparatively insignificant ; for the mean depth of the ocean probably does not exceed two and one-third miles, and underneath this lies the solid crust, with its heated interior. The crust and heated interior are composed of a variety of simple and compound substances. Simple or elementary substances are those which have never been separated into components. Compound substances are those which are composed of two or more simple or elementary substances combined under the influence of the chemical force. — S. £8 KGW RB $$ SEC rtowe THE INSIDE OF THE EARTH. ——+070300— CHAPTER I. The Heated Interior. 30. The Proofs of the Earth’s Original Fluidity or fused condition through heat are— 1.) Its Spherical Shape, which is the shape the earth would have taken had it been placed in space when in a melted condition. This is the shape of nearly all the heavenly bodies. 22 . (2.) The fact that the rocks which were first formed give evidence by their appearance of having been greatly heated. These rocks are generally highly crystalline. (3.) The general climate of the earth during the geological past was much warmer than at present. Very little of the internal heat now reaches the surface. According to Poisson, all that escapes would raise the mean annual temperature only #,th of a degree Fahr. VOLCANOES. 31, Laplace’s Nebular Hypothesis agrees very well with the idea of a former igneous fluidity, since, at the time of its separation from the nebulous sun, the earth . must have had a temperature sufficient not only to fuse, but even to volatilize, most of its constituents. 32. Proofs of a Present Heated Interior—The following considerations show that the inside of the earth is still highly heated: (1.) The deeper we penetrate the crust, the higher the temperature becomes. Moreover, the rate of increase, though varying in different lo- calities with the character of the materials of the crust, is nearly uniform over all parts of the sur- face, the average value of the inerease being 1° Fahr. for every 55 feet of descent. This would seem to indicate that the entire inside of the earth is heated, and that the heat increases as we go toward the centre. We cannot, however, estimate the thickness of the crust from this fact— 1. Because we have never penetrated the crust more than a few thousand feet below the level of the sea, and therefore we do not know that this rate of increase of temperature continues the same; 2. Even if it did continue uniform, since the melting- point of solids increases with the pressure, we do not know what allowance should be made for this increase. (2.) In all latitudes: prodigious quantities of melted rock escape from the interior through the craters of volcanoes. The interior, there- fore; must be hot enough to melt rock. 83. Condition. of the Interior—We do not know the condition of the material which fills the interior of the earth. It might be supposed, since rock escapes from the craters of volca- noes in a fluid or molten condition, that the in- terior is filled with molten matter; but this is not necessarily so, since the enormous pressure to which the interior is subjected would prob- | ably be sufficient to compress it into .a viscous . or pasty mass, or, possibly, even to render it solid. The lava which issues from the crater of a vol- cano is necessarily more mobile than the interior of the earth; for, coming, as it does, from great depths, it must grow more and more liquid as it approaches the surface and is thus relieved of its pressure. Indeed, the most viscous rock conceiv- able, if highly heated when ejected from pro- found depths, would become comparatively fluid on reaching the surface. 34, Views Concerning the Condition of the Interior —Considerable difference of opinion ex- ists as to the exact condition of the interior of the earth. The following opinions may be men- tioned ; (1.) That the earth has a solid centre and crust, with a heated or pasty layer between. (2.) That the crust is solid, but the interior highly heated, so as to be in a fused or pasty condition. (8.) That the earth is solid throughout, but highly heated in the interior. Of the above views, the second is perhaps the most tenable, and will be adopted as serving in the simplest manner to explain the phenomena of the earth arising from the presence of a highly heated interior. Admitting the crust to be suf- ficiently thin, and in such a condition as to per- mit of but a small degree of warping, then all the phenomena can be satisfactorily explained. 35. Thickness of the Crust—We cannot as- sign a definite limit to the thickness of the crust, since the portions that are solid from having cooled, most probably pass insensibly into those that are nearly solid from the combined influence of loss of heat and increasing pressure. It seems probable that the portion solidified by cooling is thin, when compared with the whole bulk of the earth; in other words, the heated interior lies comparatively near the surface. 36. Effects of the Heated Interior—As the crust loses its heat it shrinks or contracts, and, growing smaller, the materials of the interior are crowded into a smaller space, and an enormous force is thus exerted, both on the interior and on the crust itself, tending either to change the shape of the crust, to break it, or to force out some of the interior. The following phenomena are there- fore caused by the contraction of the crust: (1.) Volcanoes ; (2.) Earthquakes ; (3.) Non-voleanic igneous eruptions ; (4.) Gradual elevations or subsidences of the crust. —0594 00 —_ CHAP DER «Ji V oleanoes. 37. Voleanoes.—One of the most striking proofs of the existence of a heated interior is the ejection of enormous quantities of melted rock through openings in the crust. A volcano is a mountain, or other elevation, through which the materials of the interior escape to the surface. The opening is called the crater, and may he either on the top or on the sides of the mountain. PHYSICAL GEOGRAPHY. ey, Fig, 19, An Eruption of Mount Vesuvius, 38. Peculiarities of Craters.—The crater, as its name indicates, is cup-shaped. The rim, though generally entire, is sometimes broken by the force of the eruption, as in Mount Vesuvius, where the eruption in 79 A. D.—the first" on record—blew off the northern half of the crater. The material thus detached, together with the showers of ashes and streams of lava, completely buried the cities of Her- culaneum and Pompeii, situated near its base. The crater is often of immense size. Mauna Loa, on the island of Hawaii, has two craters—one on the summit, and the other on the mountain-side, about 4000 feet above the sea. The latter—Kilauea—is elliptical in shape, and about 73 miles in circumference ; its areais nearly 4 square miles, and its depth, from 600 to 1000 feet. Volcanic mountains are of somewhat different shapes, but near the crater the conical form pre- dominates, and serves to distinguish these moun- tains as a class. The shape of the volcanic cone is caused by the ejected materials accumulating around the mouth of the crater in more or less concentric layers. 39. The ejected materials are mainly as fol- lows: (1.) Melted Rock, or Lava.—Lava varies, not only with the nature of the materials from which it was formed, but also with the conditions under which it has cooled, and the quantity of air or vapor entangled in it. Though generally of a dark gray, it occurs of all colors; and its texture varies from hard, compact rock to porous, spongy material that will float on water. : When just emitted from the crater, ordinary lava flows about as fast as molten iron would on the same slope. On steep mountains, near the crater, the lava, when very hot, may flow faster than a horse can gallop; but it soon cools, and becomes covered with a crust that greatly re- tards the rapidity of its flow, until its motion can only be ' determined by repeated observations. At Kilauea, jets of very liquid lava are sometimes thrown out, which, falling back into the crater, are drawn out by the wind into fine threads, thus producing what the natives call Pélé’s hair, after their mythical goddess. The volume of the ejected lava is often very great. Vol- canic islands are generally formed entirely by lava streams. Hawaii and Iceland were probably formed entirely of lava emitted from numerous volcanic cones. (2.) Ashes or Cinders.—These consist of minute fragments of lava that are ejected violently from the crater; at night they appear as showers of brilliant sparks. When they fall directly back on the mountain, they aid in rearing the cone. More frequently, they are carried by the wind to points far distant. The destructive effects of volcanic eruptions are caused mainly by heavy showers of ashes. The ashes, when exceedingly fine, form what is called volcanic dust. At the beginning of an eruption large frag- ments of rock are sometimes violently thrown out of the crater. (3.) Vapors, or Gases—The vapor of water often escapes in great quantities from the crater, especially at the beginning of the eruption. On cooling, it condenses and forms dense clouds, from which torrents of rain fall. These clouds, lighted by the glowing fires beneath, appear to be actually burning, and thus give rise to the erroneous belief that a volcano is a burning mountain. To the condensation of this vapor is probably to be as-. cribed the lightning which often plays around the summit of the voleano during an eruption. Be- sides the vapor of water, various gases éscape, of which sulphurous acid is the most common. When a large quantity of rain mingles with the ashes, torrents of mud are formed, which move with frightful velocity down the slopes of the mountain, occasioning con- siderable damage. During the eruption of Galungung, in Java, more than one hundred villages were thus destroyed. The rock that is formed by the hardening of volcanic mud is called tufa. 40. The Inclination of the Slopes of the vol- canic cones depends on the nature of the material of which they are formed. Where lava is the main ingredient, the cone is broad and flat. The inclination of a lava cone ranges from 8° to 10°, Fig, 20, Lava Cone, Inclination from 3° to 10° according to the liquidity of the lava. A very stiff lava will form a much steeper cone. Pages 20-26 Missing From Original VOLCANOES. 27 45. The number of volcanoes is not accurately known. The best authorities estimate it at about 672, of which 270 are active. Of the latter, 175 are on islands, and 95 are on the coasts of the con- tinents. 46. Regions of Voleanoes.—The principal vol- canic regions of the earth are—* (1.) Along the Shores of the Pacific, where an immense chain of volcanoes, with but few breaks, encircles it in a huge “Sea of Fire.” On the Eastern Borders, in the Andean range, are the volcanic series of Chili, Bolivia, and Ecua- dor; those of Central America and Mexico; in the United States are the series of the Sierra Nevada and Cascade ranges and of Alaska; and finally, connecting the system with Asia, the vol- canic group of the Aleutian Islands. On the Western Borders volcanoes occur in the following districts: the Kamtchatkan Peninsula, with its submerged ranges of the Kurile Islands; the Japan, the Loo Choo, and the Philippine Islands; the Moluccas; the Australasian Island Chain, terminating in New Zealand ; and finally, nearly in a line with these, the volcanoes of Ere-’ bus and Terror on the Antarctic continent. (2.) In the Islands of the Pacifie—Volcanic activity is not wanting over the bed of the Pa- cific. The Sandwich Islands, the Society Group, the Marquesas, Friendly Islands, New Hebrides, Ladrones, and many others, are volcanic. (3.) Scattered over the Seas that divide the Northern and Southern Continents, or in their Vicinity, viz.: in the neighborhood of the Carib- bean Sea, in the Mediterranean and Red Seas, and in the Pacific and Indian Oceans between Asia and Australia. In the neighborhood of the Caribbean Sea.—This region includes the two groups of the Antilles in the Caribbean Sea, and the Gallapagos Islands in the Pacific Ocean. In the neighborhood of the Mediterranean and Red Seas.—This region includes the voleanoes of the Mediterranean and its borders, those of Italy, Sicily, the Grecian Archipelago, of Spain, Central France, and Germany, together with those near the Caspian and Red Seas. Between Asia and Australia.—This region in- cludes the Sunda Islands, Sumatra, J ava, Sum- bawa, Flores, and Timor, which contain numerous craters. In Java there are nearly 50 volcanoes, 28 of which are active, and there are nearly as * We follow mainly the classification of Dana. 4 many in Sumatra. There ate 169 volcanoes in the small islands near Borneo. (4.) In the Northern and Central Parts of the Atlantic Ocean. All the islands in the deep ocean which do not form. a part of the continent are volcanic; as, for example, the island of St. Helena, Ascension Island, the Cape Verdes, the Canaries, the Azores, and Iceland. The Cameroons Mountains, on the African coast near the Gulf of Guinea, together with some of the islands in the gulf, are volcanic. (5.) In the Western and Central Parts of the Indian Ocean. Volcanoes are found in Madagascar and in the adjacent islands. They also occur farther south, in the island of St. Paul and in Kerguelen Land, and in Kilimandjaro, near the eastern coast of Africa. ~ 47, Submarine Volcanoes.—From the difficulty in ob- serving them, submarine volcanoes are not so well known as the others. The following regions are well marked: In the Mediterranean Sea, near Sicily and Greece. Near the island of Santorin the submarine volcanic en- ergy is intense. It has been aptly described as a’ region “Where isles seem to spring up like fungi in a wood.” In the Atlantic Ocean; off the coast of Iceland; near St. Michael, in the Azores; and over a region in the nar- rowest part of the ocean between Guinea and Brazil. In the Pacific Ocean; near the Aleutian Islands, where two large mountain-masses have risen from the water within recent time. Near the Japan Islands, where, about twenty-one centuries ago, according to native his- torians, Fusi Yama, the highest mountain in J. apan, rose from the sea in a single night. In the Indian Ocean, the island of St. Paul, in the deep ocean between Africa and Australia, exhibits signs of submarine activity. 48. Peculiarities of Distribution—Nearly all volcanoes are found near the shores of continents or on islands. The only exceptions are found in the region south of the Caspian Sea, and in that of the Thian Shan Mountains. As volcanoes are but openings in the earth’s crust which permit an es- cape of materials from the pasty interior, they will occur only where the crust is weakest. This will be on the borders of sinking oceans, in the lines of fracture formed by the gradual separa- tion of the ocean’s bed from the coasts of the continent. The floor of the ocean in all latitudes is covered with a layer of quite cold water, so that the difference in the amount of the contrac- tion will in general be most marked on the bor- ders of the oceans or on the edges of the conti- nents. In most regions the volcanoes lie along lines 28 PHYSICAL GEOGRAPHY. more or less straight. Lines joining such a series may be considered as huge cracks in the crust, the volcanic phenomena occurring in their weak- est places. The frequent occurrence of volcanoes in moun- tainous districts is caused by the crust being broken and flexed, so as to admit of an easy passage for the molten rock. Where one system of fissures crosses another the crust becomes weak, the openings numerous, and the volcanic activity great. The two antipodal points of the Antilles and the Sunda Islands are excel- lent examples, and are the most active volcanic regions on the earth. Efforts have been made to show some connection be- tween certain states of the weather and periods of vol- canic activity; but, so far, these have amounted to mere predictions of coming changes, based on observations of the direction of upper currents of air from the clouds of ashes or smoke ejected by the volcano. No law of periodicity of eruption has, as yet, been discovered. 49. Other Volcanic Phenomena: Mud Volcanoes are small hillocks that emit streams of hot mud and water from their craters, but never molten rock. They are found in vol- canic regions. Solfataras are places where sulphur vapors es- cape and form incrustations. They occur in vol- | canic regions. Geysers are sometimes ranked with volcanic phe- nomena. They are described under Hot Springs. 09300 — CLAP PER: Wir Earthquakes. 50. Earthquakes are shakings of the earth’s crust, of degrees varying in intensity from scarcely perceptible tremors to violent agita- tions that overthrow buildings and open huge fissures in the ground. They may therefore be divided into two classes: (1.) A shaking movement without any perma- nent change in the surface ; '(2.) A shaking movement accompanying an uplift or subsidence. An earthquake is sometimes called a seismic shock. 51. Facts concerning Earthquakes—A careful study of earthquakes appears to establish the fol- lowing facts: (1.) The place or origin of the shock is not deep-seated or far below the earth’s surface, but Fig, 23, Fissures produced by the Charleston Earthquake of 1886. is near the surface, probably never deeper than thirty miles, and often much less. (2.) ‘The area of disturbance depends not only on the energy of the shock, but also on the depth of its origin below the surface: the deeper the origin, the greater the area. (3.) The shape of the origin is generally that of a line, often many miles in length. (4.) The direction of the motion at the surface is nearly upward over the origin, and more in- clined as the distance from the origin increases. (5.) The shape of the area of disturbance de- pends on the nature of the materials through which the wave is moving. If these are of nearly uniform elasticity in all directions, the area is nearly circular; if more elastic in one direction than in another, the area is irregular in shape. 52. The Varieties of Earthquake Motion at the Earth’s Surface are— (1.) A wave-like motion, in which the ground rises and falls like waves in water. (2.) An upward motion, somewhat similar to that which follows an explosion of powder below the surface. This has been known to occur with sufficient force to throw heavy bodies considerable distances up into the air. : (8.) A rotary motion, which, from its destruc- tive effects, is fortunately of rare occurrence. Humboldt mentions an earthquake that happened in Chili where the ground was so shifted that three great SS .- sss 0.0 EARTHQUAKES. 29 palm trees were twisted around one another like willow wands. There are two kinds of movement transmitted through the crust during earthquakes: these are the earthquake motion proper, and the motion that produces the accompanying sounds. 58. The Velocity of Earthquake Motion varies according to the intensity of the shock and the na- ture of the material through which it is trans- mitted. No average’ result can therefore be given. Various observers have estimated it at from 8 to 30 miles per minute. 54. The Sounds Accompanying Earthquakes vary both in.kind and intensity. Sometimes they resemble the hissing noises heard when red- hot coals are thrown into water; sometimes they are rumbling, but more frequently they are of greater intensity, and are then comparable to discharges of artillery or peals of thunder. The confused roaring and rattling are probably caused by the different rates of transmission of the sound through the air and rocks. 55. Duration of the Shocks—When the area of disturbance is large, shocks of varying intensity generally follow each other at irregular intervals. Though, in general, the violence of the shock is soon. passed, disturbances may occur at intervals of days, weeks, or even years. During the earthquake in Calabria in 1783, when nearly 100,000 persons perished, the destructive vibrations lasted scarcely two minutes, but the tremblings of the crust con- tinued long afterward. During the earthquake at Lisbon in 1755, when about the same number perished, the shock which caused the greatest damage continued but five or six seconds, while a series of terrible movements followed one another at intervals during the space of five minutes. 56. Cause of Earthquakes.—It is generally be- lieved that the principal cause of earthquakes is the force produced by the contraction of a cooling crust. During the cooling of the earth the crust con- tinually contracts, and the pressure so produced, slowly accumulating for years, at last rends it in vast fissures, thus producing those violent movements of its crust called earthquakes. If this theory be admitted—and it is a probable one —the earth’s crust must every now and then be in such a strained condition that the slightest increase of force from within, or of diminished resistance from without, would disturb the con- ditions of equilibrium, and thus result in an earthquake. 57. Strain Caused by Contraction consequent on cooling is well exhibited in the so-called “ Prince Ru- pert’s Drops,” which are made by allowing melted glass to fall in drops through cold water. The sudden cooling of the outside produces powerful forces, which tend to compress the drop; but, since these forces balance one another, no movement occurs until, by breaking off the long end of the drop, one set of forces is removed, when the others, no longer neutralized, tear the drop into almost countless pieces, Similar effects are produced by unequal contraction and expansion. Hot water poured into a tumbler will often crack it. The crackling sound of a stovepipe when sud- denly heated or cooled is a similar effect, 58. Other Causes of Earthquakes. — Earth- quakes may also be occasioned by— (1.) The sudden evolution of gases or vapors -from the pasty interior. This is probably the cause of many of the slight shocks that occur in the neighborhood of active volcanic regions. (2.) Shocks caused by falling masses. Those who deny ‘the existence of a pasty interior, en- deavor to explain the production of earthquakes by the shock caused by the occasional caving in of huge masses of rocks, in caverns hollowed out by the action of subter- ranean waters; or by the’gradual settling of the upturned strata in mountainous districts. There can be no doubt that even moderately severe shocks are caused by falling masses; but such a force is utterly inadequate to produce a shock like that which destroyed Lisbon, when an area of nearly 7,500,000 square miles was shaken. 59. Periodicity of Earthquakes—It was for- merly believed that earthquakes occurred with- out any regularity, but by a comparison of the times of occurrence of a great number it has been discovered that they occur more frequently— (1.) In winter than in summer; (2.) At night than during the day ; (3.) During the new and full moon, when the attractive force of the sun and moon acts simul- taneously on the same parts of the earth. Earthquake shocks are more frequent in winter, and during the night, because the cooling, and consequent contraction, occur more rapidly at these times, and therefore the gradually accumu- lating force is more apt to acquire sufficient inten- sity to rend the solid crust. Earthquakes are more frequent during new and full moon, because the increased force on the earth’s crust caused by the position of the sun and moon at these times, is then added to the accumulated force produced by cooling. It has been asserted that in the equatorial regions earth- quakes are especially frequent during the setting in of periodical winds called the monsoons, at the change of the rainy season or during the prevalence of hurricanes, These facts, however, are not well established. 60. Distribution of Earthquakes. — Earth- quakes may occur in any part of the world, but 30 PHYSICAL GEOGRAPHY. are most frequent in volcanic districts. They are more frequent in mountainous than in flat coun- tries. They are especially frequent in the high- est mountains. According to Huxley, fairly pro- nounced earthquake shocks occur in some part of ’ the earth at least three times a week. There is, in many instances, an undoubted connection between volcanic eruptions and earthquakes. Humboldt relates that during the earthquake at Riobamba, when some 40,000 persons perished, the volcano of Pasto ceased to emit its vapor at the exact time the earthquake began. The same is related of Vesuvius at the time of the earth- \ quake at Lisbon. — 61, Phenomena of Earthquakes.—In order to give some idea of the phenomena by which severe earthquake shocks are attended, we append a brief description of the earthquake which destroyed the city of Lisbon, on the 1st of November, 1755. The loss of life on this occasion was the more severe, since the shock occurred on a holy day, when nearly the whole population was assembled in the churches. A sound like thunder was heard, and, almost immediately afterward, a series of violent shocks threw down nearly every building in the city. Many who es- caped the falling buildings perished in the fires that soon kindled, or were murdered by lawless bands that after- ward’ pillaged the city. The ground rose and fell like the waves of the sea; huge chasms were opened, into which many of the buildings were precipitated. In the ocean a huge wave, over 50 feet high, was formed, which, retreating for a moment, left the bar dry, and then rushed toward the land with frightful force. This was repeated several times, and thousands perished from this cause alone. The neighboring moun- tains, though quite large, were shaken like reeds, and were rent and split in a wonderful manner. This earthquake was especially remarkable for the im- mense area over which the shock extended. It reached as far north as Sweden. Solid mountain-ranges—as, for example, the Pyrenees and the Alps—were severely shaken. A deep fissure was opened in France. On the south, the earthquake waves crossed the Mediterranean and destroyed a number of villages in the Barbary States. On the west, the waves traversed the bed of the Atlantic, and caused unusually high tides in the West Indies. In North Amer- ica the movements were felt as far west as the Great Lakes. Feebler oscillations of the ground occurred at intervals for several weeks after the main shock. 62. Non-voleanic Igneous Eruptions.—In re- gions remote from volcanoes, melted rock has been forced up from the interior through fissures in the rocks of nearly all geological formations. On cooling, the mass forms what is called a dyke. Dykes vary in width from a few inches to several yards. They are generally much harder than the rocks through which they were forced, and, being less subject to erosion, often project considerably above the general surface. From their mode of formation, dykes are gen- erally without traces of stratification, but by cool- ing a series of transverse fractures are sometimes produced. The dykes thus obtain the appearance of aseries of columns, called basaltic columns. Igneous rocks of this description are found in all parts of the continents, but are especially com- mon near the borders of mountainous districts. Fingal’s Cave, in Scotland, is a noted example of basaltic columns. Fig. 24, Basaltic Columns, Fingal’s Cave, Scotland. 68. Gradual Elevations and Subsidences——Be- sides the sudden changes of level produced by earthquakes, there are others that take place slowly, but continuously, by which large portions of the surface are raised or lowered from their former positions. The rate of movement is very slow—probably never exceeding a few feet in a century. The following examples are the most noted : ‘ The Scandinavian peninsula (Norway and Swe- den) is slowly rising in the north and sinking in the south. The southern part of the coast of Greenland is sinking. The North American coast, from Labrador to New Jersey, is rising. The Andes Mountains, especially near Chili, are gradually rising. The Pacific Ocean, near the centre, is sinking over an area of more than 6000 miles. The cause of these movements is to be traced to the warping action caused by gradual contrac- tion of a cooling crust. SYLLABDS. . 31 SYLLABUS. ——0r9300—_ The earth was originally melted throughout. It after- ward cooled on the surface and formed a crust. The earth’s original fluidity is rendered probable— (1.) By the spherical shape of the earth; (2.) By the crystalline rocks underlying all others; and (3.) By the greater heat of the earth during geological time. The interior is still in a highly-heated condition. This is proved—Ist. By the increased heat of the crust as we go below the surface; 2d. By the escape of lava from volca- noes in all latitudes. The following opinions are held concerning the condi- tion of the interior of the earth: (1.) That the earth has a solid centre and crust, with a heated layer between. (2.) That the earth has a solid crust only, and an inte- rior sufficiently heated to be in a fused or in a pasty con- dition. (3.) That the earth is solid throughout, but highly heated in the interior. The thickness of the crust is not known. It is probable that the portions solidified by cooling pass insensibly into those that are nearly solid from the combined influence of loss of heat and increasing pressure. The heated interior, however, must lie comparatively near the sur- face. The effects produced by the heated interior on the crust are—Ist. Volcanoes; 2d. Earthquakes; 3d. Non-volcanic igneous eruptions ; and 4th. Gradual elevations or subsi- dences. Volcanic mountains are of a variety of shapes. Near their craters the cone shape predominates, and serves to distinguish these mountains as a class. The ejected materials of volcanoes are—Ist. Melted rock _ or lava; 2d. Ashes or cinders; 3d. Vapors or gases. These materials are brought up from great depths into the volcanic mountain by the force produced by a contract- ing globe. They may escape from the crater—lst. By the pressure of highly-heated vapors; or, 2d. By the pressure of a column of melted lava. The inclination of the slopes of the volcanic cone de- pends on the materials of which it is composed. Ash- cones are steeper than those formed of lava. Eruptions are of two kinds, ae and non-explo- sive. High volcanic mountains are, as a rule, characterized by non-explosive eruptions. Volcanoes occur both on the surface of the land and on the bed of the ocean. Those on the land occur mainly near the borders of sinking oceans, where the crust is weakest. The principal volcanic districts of the world are—1. Along the shores of the Pacific; 2. On the islands which are scattered over the Pacific; 3. Scattered over the seas which divide the northern and southern continents; 4. In the northern and central parts of the Atlantic Ocean; 5. In the western and central parts of the Indian Ocean. The centres of volcanic activity’ are found in the An- tilles and in the Sunda Islands, where several lines of fracture cross each other. Subordinate volcanic phenomena are seen in—1. Mud volcanoes; 2. Solfataras; 3. Geysers. Earthquakes are snes of the earth’s crust; they may occur with or without a permanent displacement. The following facts have been discovered as to earth- quakes: (1.) Their place of origin is not very deep-seated. (2.) The area of disturbance increases with the energy of the shock and the depth of the origin. (3.) The shape of the origin is that of a line, and not that of a point. (4.) The shape of the area of disturbance depends on the elasticity of the materials through which the shock moves. (5.) The earthquake motion travels through the earth as spherical waves which move outward in all directions from the origin of the disturbance. The movement at the earth’s surface may be—Ist. In the form of a gentle wave; 2d. An upward motion; 3d. A rotary motion. The velocity with which the earthquake motion is trans- mitted varies with the intensity of the shock and the nature of the materials through which it is propagated. There are two distinct kinds of motion accompanying earthquake waves: the earthquake motion proper, and the motion producing the accompanying sounds. As a rule, the earthquake shocks which ‘produce the greatest damage are of but short duration, generally but a few seconds or minutes. Slighter disturbances may fol- low the main shock at intervals of days, weeks, or even years. Earthquake shocks are more frequent—lst. In winter than in summer; 2d. At night than during the day; 3d. During the time of new and full moon than at any other phase. Earthquakes are. mainly caused by the gradually in- creasing force produced by the contraction of the crust. Earthquakes are also to be attributed to the forces which eject the molten matter from the craters of volcanoes.. | Slight earthquake shocks may be occasioned by the fall- ing in of masses of rock from the roofs of subterranean. caverns, or by the settling of upturned strata. Earthquakes may occur in any part of the earth, but are most frequent in volcanic and in mountainous regions. Dykes are masses of rock formed by the gradual cooling of melted matter which has been forced up through fis- sures from. the interior. Basaltic columns are formed by dykes. They owe their columnar structure to fractures produced on cooling. The crust of the earth is subject to gradual as well as to sudden changes of level. The Scandinavian peninsula is rising on the north and sinking on the south. The southern coast of Geeenland is sinking. The North American coast, from Labrador to New Jer- sey, is rising. The range of the Andes near Chili is rising. The bed of the Pacific in the neighborhood of the Poly- nesian island chain is sinking. These movements are caused by the contraction of a cooling crust. 32 PHYSICAL GEOGRAPHY. REVIEW QUESTIONS. ——-0£0400—_. The Heated Interior. Enumerate the proofs that the interior of the earth is still in a highly-heated condition. Name some circumstances which render it probable that the earth was originally melted throughout. What is the average rate of increase of temperature with descent below the surface ? How can it be shown that the whole interior of the earth is filled with highly-heated matter? Why is it so difficult to assign a definite limit to the thickness of the earth’s crust? Is the interior of the earth supposed to be in as fluid a condition as that of the lava which escapes from a volcano? What four classes of effects are produced in the crust by the heated interior? Voleanoes. What are volcanoes? What connection have they with the interior of the earth? How do active volcanoes differ from those which are extinct? Explain the origin of the conical form of volcanic mountains, Which generally produces the more destructive effects, ashes or lava? Why? Enumerate the materials which are ejected from the in- terior of the earth through the craters of volcanoes. What is tufa? How is it formed? Which has the greater inclination, a lava-cone or an ash-cone ? Explain in full the manner in which the shrinkage, or contraction of the earth on cooling, produces a pressure both in the interior and in the crust. By what forces are volcanic eruptions produced? Into what two classes may all volcanic eruptions be di- vided? How are those of each class caused? Give an example of each of these classes. What is the highest volcano in the world? Under what five regions may all the volcanoes in the world be arranged ? In what parts of the world are volcanoes most numer- ous? Why are volcanoes more numerous here than elsewhere? Name some of the regions of submarine volcanoes. Why are all volcanoes found near the coasts of the con- tinents or on islands? i What are mud volcanoes? Solfataras? Earthquakes. What are earthquakes? Into what two classes may they be divided ? Name some facts that have been discovered about earth- quakes. ‘ n Name three kinds of earthquake motion. Which is the most dangerous ? Describe the sounds which accompany earthquakes. What is the main cause of earthquakes? To what other causes may they be attributed? What facts have been discovered respecting the pericd- icity of earthquakes ? Give a short description of the earthquake which de- stroyed the city of Lisbon. Are any portions of the earth free from earthquake shocks? In what parts of the earth are earthquake shocks most frequent ? What are dykes? How were they formed? Enumerate some of the gradual changes of level which are now occurring in the crust of the earth. By what are these changes caused ? MAP QUESTIONS. —-059300——. Trace on the map the five principal volcanic districts of the earth. Which contains the greater number of volcanoes, the Atlantic or the Pacific shores of the continents? Does the eastern or the western border of the Indian Ocean contain the greater number of volcanoes? Name the principal volcanic islands of the Atlantic. Of the Indian. Of the Pacific. Locate the following volcanoes: Hecla, Pico, Kilauea, Sarmiento, Llullayacu, Egmont, Cosiguina, » Teneriffe, Antisana, Kilimandjaro, Demavend, Peshan, Osorno, Ere- bus, and Terror. . y->Name the principal volcanic mountains of North America, In what part of the Atlantic Ocean are submarine erup- tions especially frequent ? Name three noted volcanoes of the Mediterranean Sea. Name the portions of the earth which were shaken by the earthquake of Lisbon. When did this earthquake occur? What noted volcanoes are found in the region visited by the earthquake of Lisbon? 3 In what portions of the Eastern Hemisphere are earth- quake shocks especially frequent? In what portions of the Western Hemisphere? PHEOORUS DL (OR (TEE aA TH: 33 . SECTLON lh NJ CHAPTER L The Crust of the Earth. 64. Composition of the Crust.—The elementary substances are not equally distributed throughout the earth’s crust. Many of these substances occur only in extremely small quantities, while others are found nearly everywhere. Although the deepest cutting through the earth’s crust does not extend vertically more than about two miles be- low the level of the sea, yet the upturning of the strata, or the outcropping of the different formations, enables us to study a depth of about sixteen miles of the earth’s crust. A careful study of the composition of this part of the crust shows that oxygen constitutes nearly one-half of it, by weight. Silicon, an element which, when combined with oxygen, forms silica or quartz, constitutes, either as sand, or combined with various bases as silicates, one- fourth; so that these two elements form at least three- fourths, by weight, of the entire crust. The following are also prominent ingredients of rocks—aluminium, which, when combined with oxygen, forms alumina, the basis of clay; magnesium, calcium, potassium, sodium, iron, and car- bon. These nine substances, according. to Dana, form Zoyoths, by weight, of the entire crust. Sulphur, hydrogen, chlorine, and nitrogen also occur fre- quently. The remaining elements are of comparatively rare occurrence. 65. The Origin of Rocks.——When the earth was yet a melted globe, the water which now covers the larger portion of its surface hung over it, uncondensed, either as huge clouds or as masses of vapor. After a comparatively thin crust had formed, the vapor was condensed as rain, and cov- ered the earth with a deep layer of boiling water. Occasionally the cooling crust was broken by the increasing tension, and portions of the molten in- terior were forced out: and spread over the sur- face. The muddy waters then cleared by depos- iting layers of sediment over the ocean’s bed. When, by long-continued cooling, the crust be- came thicker, the breaking out of the interior oc- curred less frequently, and contraction, wrinkling the surface in huge folds, caused portions to emerge from the ocean and form dry land. Dur- ing all this time the waters were arranging the looser materials in layers or strata wnieh were ment by water. THE OUTSIDE OF THE EARTH. Ri ~ i ——020300——_ originally more or less horizontal; but wher} ever the contraction forced the melted interior through the crust or upturned it in huge folds, the horizontal position of the deposits was de- stroyed; and even when not so disturbed, the heat of the interior, escaping through fissures, often produced such alterations as to confuse or completely to obliterate all traces of their regu- lar bedding. The almost inconceivable extent of geological time may be inferred from the calculations of Helmholtz, based on the rapidity of the cooling of lava. These calculations show that in passing from a temperature of 2000° C. to 200° C. a time equal to three hundred and fifty million years must have elapsed. Before this a still greater time must have elapsed, and after it came the exceedingly great ex- tent of geological time proper. 66. According to their Origin, rocks may be divided into three distinct classes: (1.) Igneous Rocks, or those ejected in a melted condition from the interior, and afterward cooled. (2.) Aqueous Rocks, or those deposited as sedi- When mineral matter settles in water, the coarser, heavier particles reach the bot- tom first, 80 that a sorting action occurs, which makes the different layers or strata vary in the size and density of their particles, and, to a great extent, in their composition. Aqueous rocks are sometimes called sediment- ary rocks. (3.) Metamorphic Rocks, or those originally deposited in layers, but afterward so changed by the action of heat as to lose all traces of stratifi- cation. This change, which is called metamorphism, is caused by heat acting under pressure in the presence of moisture. Under these conditions a far less intense heat is required to re- move all traces of stratification. Metamorphism appears to consist mainly in a rearrangement of the chemical con- stituents of the rocks, 67. According to their Condition, rocks may be divided into two classes: (1.) Stratified Rocks, or those arranged i regular layers. Aqueous rocks are always ian fied, and sometimes, though rarely, metamorphic ori are stratified. 84 PHYSICAL GEOGRAPHY. WRK Fig, 25. Stratified Rock, In Fig. 25 the different layers or strata are shown by the shadings. Stratified rocks are the most common form of rocks found near the earth’s surface. Stratified rocks are largely composed of fragments of older rocks; for this reason they are sometimes called fragmental rocks. (2.) Unstratified Rocks, or those destitute of any arrangement in layers. They are of two kinds: (1.) Igneous, or those which were never stratified. (2.) Metamorphic, or those which were once stratified, but have lost their stratification by the action of heat. Unstratified rocks are sometimes called crystad- line rocks, because they consist of crystalline particles. 68. Fossils are the remains of animals or plants which have been buried in the earth by natural causes. . Generally, the soft parts of the organism have disappeared, leaving only the harder parts. Sometimes the soft parts have been gradually re- moved, and replaced by mineral matter, generally lime or silica; thus producing what are called petrifactions. At times the mere impression of the animal or plant is all that remains to tell of its former existence. 4 Fig, 26, Fossil Encrinite, When the remains of an animal or plant are exposed to the air or buried in dry earth, they generally decompose and pass off almost entirely as gases; but when buried under water or in damp earth, their preservation is more probable. Therefore, the species most likely to become fossilized are those living in water or marshes, or in the ‘neighborhood of water or marshes. 69. According to the Presence or Absence of Fossil Remains, rocks may be divided into two classes : (1.) Fossiliferous Rocks, or those which con- tain fossils. They are stratified and are of aqueous origin. Metamorphic rocks, in very rare instances, are found to contain fragments of fossils. (2.) Non-fossiliferous Rocks, or those destitute of fossils. They include all igneous rocks and most of those that are metamorphic. 70. Paleeontology is the science which treats of fossils. . Paleontology enables us to ascertain the earth’s condi- tion in pre-historic times, since by a careful examination of the fossils found in any rocks we discover what animals and plants lived on the earth while such rocks were being deposited. The earth’s strata thus become the pages of a huge book; and the fossils found in them, the writings concerning the old life of the world. By their careful study geologists have been enabled to find out much of the earth’s past history. 71, Division of Geological Time.—A compari- son of the various species of fossils found in the earth’s crust discloses the following facts: (1.) The fossils found in the lowest rocks bear but. a slight resemblance to the animals and plants now living on the earth. (2.) The fossils found in the intermediate strata bear a resemblance to existing species, though this resemblance is not so strongly marked as in the upper strata. (3.) ‘The fossils found in the upper strata bear a decided resemblance to existing species. It is on such a basis that the immense extent of geological time is divided into the following shorter periods or times: (1.) Archean Time, or the time which wit- nessed the dawn of life. This time included an extremely long era, during most of which the con- ditions of temperature were such that no life could possibly have existed. Toward its close, however, the simplest forms of life were created. The lower Archean rocks resulted from the original cooling of the molten earth, and cover its entire surface, including the floor of the ocean. On these rest less ancient Archean rocks, formed as sedimentary deposits of the older rocks. The rocks of the Archean Time in North America in- clude the Laurentian, the lowest, hamed from the river St. Lawrence, near which they occur, and the Huronian, named from their occurrence near Lake Huron. (2.) Paleozoic Time, or ancient life, included the time during which the animals and plants bore but little resemblance to those now living. (3.) Mesozoic Time, or middle life, included the time during which the animals and plants began to resemble those now living. Ne / THE CRUST OF THE EARTH. 35 (4.) Cenozoic Time, or recent life, included the time during which the animals and plants bore decided resemblance to those now living. These times are divided into ages. Archean Time includes— (1.) The Azoic Age; (2.) The Eozoic Age. Paleozoic Time, or, as it is sometimes called, the Primary, includes— (1.) The Age of Invertebrates, or the Silurian ; (2.) The Age of Fishes, or the Devonian; (8.) The Age of Coal-plants, or the Carbon- iferous. Mesozoic Time, or, as it is sometimes called, the Secondary, includes the Age of Reptiles. Cenozoic Time includes— (1.) The Tertiary, or the Age of Mammals; (2.) The Quaternary, or the Age of Man. Where no disturbing causes existed, and the land remained under the seas, the rocks deposited during these periods were thrown down in regu- lar strata, one over the other. The Archean were the lowest; above them were the Paleozoic, then the Mesozoic, and finally those of the Ceno- zoic. Generally, however, frequent dislocations of the strata have disturbed the regular order of arrangement. 72. The Azoic Age included all the time from the first formation of the crust to the appearance of animal and vegetable life. The Eozoic Age is that which witnessed the dawn of life. The sedimentary rocks of this age are so highly metamorphosed that nearly all traces of life have been obliterated. Among plants, the marine alge, or sea-weeds, and among animals, the lowest forms of the protozoa, were probably the chief species. 73. The Age of Invertebrates, or the Silurian, is sometimes called the Age of Mollusks. Among plants, algw, or sea-weeds, are found; among ani- mals, protozoa, radiates, articulates, and mollusks, but no vertebrates. Hence the name, Age of In- vertebrates. Mollusks were especially numerous. The name Silurian is derived from the ancient Silures, a tribe formerly inhabiting those parts of England and Wales where the rocks abound. 74, The Age of Fishes, or the Devonian.— During this age all the sub-kingdoms of animals are found, but the vertebrates first appear, being represented by fishes, and from this fact the name has been given to the age. Land-plants are also found. Immense beds of limestone and red sand- stone were deposited. 5 The name Devonian is derived from the district of Dev- onshire, England, where the rocks abound. 75. The Age of Coal-Plants, or the Carbonif- erous.—The continents during this age consisted mainly of large, flat, marshy areas, covered with luxuriant vegetation, subject, at long intervals, to extensive inundations. The decaying vegetation, decomposing under water, retained most of its solid constituent, carbon, and formed beds of coal. All the sub-kingdoms of animals were represented and reptiles also existed. The comparatively few -land-plants of the preceding age now increased and formed a dense vegetation. To favor such a luxuriant vegetation the air must have been warm and moist. Since all the coal then deposited previously existed in the air as carbonic acid, the Carboniferous Age was nec- essarily characterized by a purification of the atmosphere. Fig, 27, Carboniferous Landscape, (A restoration.) Formation of Coal.—In every 100 parts of dry vege- table matter there are about 49 parts of carbon, 6 of hydro- gen, and 45 of oxygen. The carbon is a solid; the hydro- gen and oxygen are gases. Itis from the carbon that coal is mainly formed. When the decomposition of the vege- table matter takes place in air, the carbon passes off with the hydrogen and oxygen as various gaseous compounds; but when covered by water, most of the carbon is retained, together with part of the oxygen andhydrogen. Although every year our forests drop tons of leaves, no coal results, the deposit of one year being almost entirely removed before that of the next occurs. F It has been computed that it would require a depth of eight feet of compact vegetable matter to form one foot.of bituminous coal, and twelve feet of vegetable matter to form one foot of anthracite coal. Anthracite coal differs 36 PHYSICAL GEOGRAPHY. from bituminous mainly in the greater metamorphism to which it has been subjected; it contains a greater propor- tion of carbon and less hydrogen and oxygen. 76. The Age of Reptiles.—In this age the ani- mals and plants begin to resemble existing species. The age is characterized mainly by the prepon- derance of reptiles, many of which were very large, as, for example, the plesiosaurus, an animal with a long, snake-like neck and a huge body, or the ichthgosaurus, with a head like a crocodile and short neck and large body. Both of these ani- mals were furnished with fin-like paddles, and lived in the water. Huge pterodactyls, or bat- like saurians, flew in the air or paddled in the water. Mammals and birds also occur. Fig, 28, ‘The Age of Reptiles. (A restoration.) 77. The Age of Mammals, or the Tertiary Age. —Mammals, or animals that suckle their young, occurred in great numbers, and, being the highest == cae Fig, 29. Mastodon giganteus, An Animal of the Mammalian Age type of life, gave the name to the age. The ani- mals and plants of the Mammalian Age closely resembled existing species, though most of them were much larger; as, for example, the dinothe- rium, a huge animal, with a trunk like an ele- phant, but with downward-turned tusks; the paleotherium, and many others. 78. The Era of Man, or the Quaternary Age, witnessed the introduction of the present animals and plants and the creation of man. 79. Changes Now Occurring in the Earth's Crust.— Geological time was characterized by ex- tensive changes, both in the hind and luauriance of life, and in the nature of its distribution. The earth is still undergoing extensive changes, which are caused by the following agencies: (1.) By the Winds, which often carry sand from a desert and distribute it over fertile plains: in this manner the narrow tract of fertile land on the borders of the Nile, in Egypt, receives much sand from the Sahara. The winds are also piling up huge mounds of sand along the sea-coasts, forming what are called dunes, or sandhills, (2.) By the Moisture of the Atmosphere, soak- ing into porous rocks or running into the crevices between solid ones. This water in freezing ex- pands with force sufficient to rend the rock into fragments, which are carried away by the rivers or, when sufficiently small, by the winds. 2 (8.) By the Action of Running Water.— Rivers wash away portions of their banks or cut their i VAT ENE START Fig. 30, Curious Effect of Erosion, their channels. This action is It occurs even in the hardest way throug called erosgon. DISTRIBUTION OF THE LAND-AREAS. 37 The materials thus carried away are rocks. spread over the lowlands near the mouth of the river or thrown into the sea, where they often form large deposits. By the constant action of these causes the mean heights of the continents are decreasing and their breadths increasing. The most remarkable instance of erosion is found in the cafions of the Colorado River, where. the waters have eaten a channel through the hard limestones and granites that form the bed of the stream, until they now run through gorges whose walls ascend almost perpendicularly to the height of from 3000 to 6000 feet. A good idea of this great depth may be obtained by walking along a straight street for about a mile (5280 feet), and then imagining the street set upright in the air. On looking down toward the starting-place, we would see it as it would appear at the bottom of a hole about 6000 feet deep.’ ; The forms produced by erosion are often extremely fan- tastic. Tall, slender, needle-like columns, capped by a layer of harder rock, sometimes occur, thus showing in a marked manner an effect of erosion. (4.) By the Action of Ocean Waves, changing the outlines of coasts; as may be seen in portions of the coasts of England and Scotland. (5.) By the Agency of Man, witnessed mainly in the destruction of the forests over extended areas. (6.) By the Contraction of a Cooling Crust, resulting in—1. Earthquakes; 2. Volcanoes; 3. Gradual uplifts and subsidences. 2020300 CHAPTER II. Distribution of the Land-Areas. 80. Geographic Effects of Light, Heat, and Moisture.—The peculiarities observed in the dis- tribution of animal and vegetable life are caused by differences in the distribution of light, heat, and moisture. Since light, heat, and moisture * are influenced by the interaction of land, water, and air, we must first study the distribution and grouping of these inorganic or dead forms before we can understand those that are living. 81. The Distribution of the Land—Of the 197,000,000 square miles that make up the darth’s surface, about 144,000,000 are water and 53,000,000 land. The proportion is about as the square of 5 is to the square of 8. If, therefore, we erect a square on a side of five, its entire area will represent the relative water-area of the globe; while a square whose side is three will represent the relative land-area. Vy | VO QD === oe 82. The Distribution of the Land can be best studied when arranged under two heads: (1.) The Horizontal Forms of the Land, or the different shapes produced in the land-areas by the coast lines, or by the contact of land and water; (2.) The Vertical Forms of the Land, produced by the irregularity of the surface of the high lands and low lands. 83. The Horizontal Forms.—The land-areas are divided into continents and islands. The Eastern Hemisphere contains four conti- ‘nents: Europe, Asia, Africa, and Australia. The first three form one single mass, which is called the Eastern Continent. Though the word “continent” strictly refers to an ex- tended area of land entirely surrounded by water, usage has sanctioned the application of the term to the grand divisions of the land. It is quite correct, therefore, to speak of the North American Continent, the Asiatic Con- tinent, ete. The Western Hemisphere contains two conti- nents: North and South America; these consti- tute what is called the Western Continent. The following are the extremities of the conti: nents: In the Hastern Continent— Most northern point, Cape Chelyuskin, lat. 78° 16’ N. Most southern point, Cape Agulhas, lat. 34°51’ 8. Most eastern point, East Cape, long. 170° W. Most western point, Cape Verd, long. 17° 34’ W. In the Western Continent— Most northern point, Point Barrow, lat. 72° N. Most southern point, Cape Froward, lat. 53° 53’ 8. Most western point, Cape Prince of Wales, long. 168° W. Most eastern point, Cape St. Roque, long. 35° W. ~ 38 PHYSICAL GEOGRAPHY. 84, Peculiarities in the Distribution of the Land: (1.) The continents extend farther to the north than to the south. (2.) The land masses are crowded together near the north pole, which they surround in the shape of an irregular ring. (3.) The three main southern projections of the land—South America, Africa, and Australia —are separated from each other by extensive oceans. 85. Land and Water Hemispheres.——The ac- cumulation of the land in the north and its sepa- ration in the south lead to a curious result—nearly all the land is collected in one hemisphere. If one point of a pair of compasses be placed at the north pole of a globe, and the other stretched out to reach to any point on the equator, they will describe on the surface of the globe a great circle, and consequently will divide the globe into hemispheres. If, while they are stretched this dis- tance apart, one of the points be placed at about the city of London, a cirele swept with the other point will divide the earth into land and water hemispheres. Such a great circle would pass through the Malay Peninsula and the coast of Peru. The Land Hemisphere contains all of North America, Europe, and Africa, and the greater part of South America and Asia. The Water Hemi- sphere contains the southern portions of South America, the Malay Peninsula, and Australia. Fig. 32, Land and Water Hemispheres. 86. Double Continents.—The six grand divis- ions or continents may be divided into three pairs, called Double or Twin Continents. Each Double Continent consists of a northern and southern continent, almost separated from each other, but connected by a narrow isthmus or island chain. The three double continents are North and South America, Europe and Africa, and Asia [Seis and Australia. There are, therefore, three north- ern and three southern continents. The northern continents lie almost entirely in temperate latitudes, while the southern lie mainly %, the tropics. “87. Lines of Trend—The study of any map of the world on a Mercator’s projection will dis- close the following peculiarities in the earth’s structure : There are two great systems of courses, trends, or lines of direction, along which the shores of the con- tinents, the mountain-ranges, the oceanic basins, and the island chains extend. These trends extend in a general north-easterly and north-westerly direction, and intersect each other nearly at right angles. North-east Trends.—A straight ruler can be so placed along the south-eastern coasts of Greenland and the south- eastern coasts of North America that its edge will touch most of their shore lines. Its general direction will be north-east. It can be similarly placed along the south-eastern coast of South America, the north-western coast of Africa, and most of the western coast of Europe; along the south- eastern coasts of Africa; the south-eastern coast of Hin- dostan; and along the eastern coast of Asia, without its general direction differing much from north-east. North-west Trends.—A straight ruler can be so placed as to touch most of the western shores of North America. and part of the western coast of South America; most of the western coasts of Greenland, or the north-eastern coasts of North America, and part of the western coasts of Africa. All these courses are sensibly north-west. If placed with one end at the mouth of the Mackenzie River, and the other on the south-western extremity of Lake Michigan, it will cut nearly all the great lakes in Central British America. The direction of the island chains of the Pacific Ocean in particular is characterized by these two trends, many of the separate islands being elongated in the direction of the trend of their chain. 88. Continental Contrasts. — The main pro- longation of the western continent extends in the line of the north-western trend, while that of the eastern continent extends in the line of the north- eastern trend. The axes of the continents, or their lines of general direction, therefore, inter- sect each other nearly at right angles. The western continent extends far north and south of the equator, while the eastern lies mainly north of the equator. The Western Continent, therefore, is characterized by a diversity of cli- mates; the Eastern Continent, by a similarity. The distribution of vegetable and animal life in each continent is necessarily affected by the . peculiarities of its climate. It is from the prevalence of the lines of trend that the ISLANDS. 389 general shape of the continents is mainly triangular. An excellent system of map-drawing has been devised on this peculiarity. The following peculiarities exist in the coast lines of the continents: The coast lines of the northern continents are very irregular, the shores being deeply indented with gubfs and bays, while those of the southern con- tinents are comparatively simple and unbroken. The continents are most deeply indented near the regions where the pairs of northern and south- ern continents are nearly separated from each ‘other. These regions correspond with the lines of great volcanic activity, and appear to be areas over which considerable subsidence has occurred. The continents differ greatly from one another in their indentations. Europe is the most indented of all the continents. The area of her peninsulas, compared with that of her entire area, is as 1 to 4. Asia comes next in this respect, the proportion being 1 to 53, while in North America it is but 1 to 14. The following Table gives in the first column the area of each of the continents, in the second the length of coast line, and in the third the number of square miles of area to one mile of coast line: Sq. m. of CONTINENTS. AREA. COAST LINE. ee of coast. AGI Alesccessessscesess 17,500,000 sq. miles. |35,000 miles.| 500 AfTICA wecccseeseeees 12,000,000 16,000 750 North America..| 8,400,000 “é 22,800 “ 368 South America...| 6,500,000 . 14,500 “ 449 Europe... 3,700,000 sf 19,500 “ 190 Australia......... «| 3,000,000 s 10,000 “ 300 Europe has, in proportion to its area, About three times as much coast line as Asia. © About four times as much as Africa. About twice as much as North America. More than twice as much as South America. Europe is the most, and Africa the least, deeply indented of the continents. —-0503 00 ——_. CHAPTER III. Islands. 89. Relative Continental and Insular Areas.— Of the 53,000,000 square miles of land, nearly 3,000,000, or about one-seventeenth, is composed of islands. 90. Varieties of Islands.—Islands are either continental or oceanic. Continental Islands are those that lie near the shores of the continents. They are continuations of the neighboring continental mountain-ranges or elevations, which they generally resemble in geological structure. They may, therefore, be re- garded as projections of submerged portions of the neighboring continents. Continental islands have, in general, the same lines of trend as the shores of the neighboring mainland. Continental islands, as a rule, are larger than oceanic islands. This is caused by the shallower water in which continental islands are generally situated. Papua and Borneo have each an area of about 250,000 square miles; either of these islands is more than twice as large as the combined areas of Great Britain and Ireland. 91. American Continental Island Chains. (1.) The Arctic Archipelago comprises the large group of islands north of the Dominion of Canada. It consists of detached portions of the neighboring continent. (2.) The Islands in the Gulf of St. Lawrence and its neighborhood are apparently the northern prolongations of the Appalachian mountain-sys- tem. (3.) The Bahamas lie off the south-eastern coast of Florida, to which they belong by position and structure. Their general trend is north-west. (4.) The West Indies form a curved range, which connects the peninsula of Yucatan with the coast-mountains of Venezuela. Here both trends appear, though the north-western pre- dominates. Fig, 33, West India Island Chain. 1, Cuba; 2, Hayti; 3, Jamaica; 4, Porto Rico; 5, Caribbee Islands; 6, Bahamas. (5.) The Aleutian Islands form another curved range, which connects the Alaskan Peninsula with Kamitchatka; their general trend is north-east. They are connected with the elevations of the North American continent. 40 PHYSICAL GEOGRAPHY. (6.) The Islands west of the Dominion of Can- ada and Alaska. These are clearly the summits of submerged northern prolongations of the Pa- cific coast ranges. (7.) The Islands of the Patagonian Archi- pelago are the summits of submerged prolonga- tions.of the Andes of Chili. 92. Asiatic Continental Island Chains consist of a series of curved ranges extending along the entire coast, and intersecting each other nearly at right angles. (1.) The Kurile Islands are a prolongation of , the Kamtchatkan range. (2.) The Islands of Japan extend in a curve from Saghalien to Corea. (3.) The Loo Choo Islands extend in a curve from the islands of Japan to the island of For- mosa. (4.) The Philippines form two diverging chains, which merge on the south into the Australasian Island chain. The eastern chain extends to the southern extremity of Celebes, and the western to that of Borneo. The Asiatic chains belong to a submerged mountain- range extending from Kamtchatka to the Sunda Islands. Their general direction is parallel to the elevations of the coast. 93. The Australasian Island Chain. The Australasian Island chain is composed of a number of islands extending along curved trends over a length of nearly 6000 miles, from Sumatra to New Zealand. The islands extend along three curved lines, whose general direction ‘is north-west. AUSTRALIA Fig. 34, Australasian Island Chain, 1, Sumatra; 2, Java; 3, Sumbawa; 4, Flores; 5, Timor; 6, Borneo; 7, Celebes; 8, Gilolo; 9, Ceram; 10, Papua; 11, Louisiade Archipel- ago; 12, New Caledonia; 13, New Zealand; 14, Admiralty Islands ; 15, Solomon’s Archipelago; 16, Santa Cruz; 17, New Hebrides. 4 The Australasian chain was probably connected with the Asiatic continent during recent geological time, and sepa- rated from it by subsidence. Its numerous volcanoes and coral formations prove that subsidence is still taking place. , 94. Peculiarity of Distribution—The follow- ing peculiarity is noticed in the distribution of — continental islands: Each of the continents has an island, or a group of islands, near its south-eastern extremity. For example, North America has the Bahamas and the West Indies; Greenland has Iceland; South America has the Falkland Islands; Africa has Madagascar; Asia has the East Indies; and Australia has Tasmania. 95. Oceanic Islands are those situated far away from the continents. They occur either in vast chains, which generally extend along one or the other of the two lines of trend, or as isolated groups. Oceanic Island Chains. The following are the most important: (1.) The Polynesian Chain ; (2.) The Chain of the Sandwich Islands; (8.) The Tongan or New Zealand Chain. Fig. 35. Polynesian Island Chain. 1, Marquesas; 2, Paumotu; 3, Tahitian; 4, Rurutu group; 5, Her- vey group; 6, Samoan, or Navigator’s; 7, Vakaafo group; 8, Vaitupu; 9, Kingsmill; 10, Ralick; 11, Radack ; 12, Carolines; 13, Sandwich. The Polynesian Chain consists of a series of parallel chains, extending from the Paumotu and the Tahitian Islands to the Carolines, the Ralick, and the Radack groups. Their general direction is north-west; the total length of the chain is about 5500 miles. The Chain of the Sandwich Islands extends in a north-westerly direction. Its length is about 2000 miles. The New Zealand Chain extends north-east as - ISLANDS. far as the Tonga Islands, cutting the Australasian chain at right angles. 96. Isolated Oceanic Islands are mainly of two kinds: the Volcanic and the Coral. As a rule, the Volcanic islands are high, while Coral islands sel- ‘dom rise more than twelve feet above the water. Volcanic Islands are not confined to isolated groups, but occur also in long chains. The Poly- nesian, Sandwich, and New Zealand Chains con- tain numerous volcanic peaks. But the high, iso- lated oceanic islands are almost always of voleanie origin, and, consisting of the summits of subma- rine volcanoes, are generally small. Some of the Canary and Sandwich Islands, which are of this class, rise nearly 14,000 feet above the sea. 97. Coral Islands, or Atolls, though of a great variety of shapes, agree in one particular: They consist of a low, narrow rim of coral rock, enclosing a body of water called a lagoon. Fig. 36, A Coral Island, 98. Mode of Formation of Coral Islands.—The reef forming the island is of limestone, derived from countless skeletons of minute polyps that once lived beneath the surface of the waters. The skeletons, however, are not separate. The polyp propagates its species by a kind of bud- ‘ding; that is, a new polyp grows out of the body of the old. In this way the skeletons of count- less millions of polyps are united in one mass and assume a great variety of shapes. One of the most common species of reef-forming corals, the madrepora, is shown in Fig. 37. Many other forms exist. The delicate coral structures, together with shells from various shellfish, are ground into frag- ments by the action of the waves, and by the in- Fig, 37, Coral, filtration of water containing lime in solution, they become compacted into hard limestone, on which new coral formations grow. The growth of the coral mass is directed up- ward, and ceases when low-water mark is reached, because exposure to a tropical sun kills the polyps. But the action of the waves continues, and the broken fragments are gradually thrown up above the general level of the water. In this way a reef is formed, whose height is limited by the force of the waves, and seldom exceeds twelve feet. On the bare rock, which has thus emerged, a soil is soon formed and a scanty vegetation ap- pears, planted by the hardy seeds scattered over it by the winds and waves. The coral island never affords a very comfortable resi- dence for man. The palm tree is almost the only valuable vegetable species; the animals are few and small, and the arable soil is limited. Moreover, the island is subject to occasional inundations by huge waves from the ocean. 99. Distribution of Coral Islands. —According to Dana, the reef-forming coral polyp is found only in regions where the winter temperature of the waters is never lower than 68° Fahr. Some varieties, however, will grow in colder water. Coral islands are confined to those parts of tropical waters where the depth does not greatly exceed 100 feet, and which are protected from cold ocean-currents, from the influence of fresh river- waters, muddy bottoms, and remote from active vol- canoes, whose occasional submarine action causes the death of the coral polyp. Though some coral polyps grow in quiet water, the greater part thrive best when exposed to the breakers. The growth ts therefore more rapid on the side toward the ocean than on the side toward the island. ‘ 42 PHYSICAL GEOGRAPHY. Coral islands are most abundant in the Pacifie Ocean. The following groups contain numerous coral islands: the Paumotus, the Carolines, the Radack, the Ralick, and the Kingsmill groups, and the Tahitian, Samoan, and Feejee Islands, and New Caledonia. In the Indian Ocean the Laccadives and the Maldives are most noted. In the Atlantic Ocean the West Indies and the Bermudas are examples. 100. Varieties of Coral Formations.— There are four varieties of coral formations : _(.) Fringing Reefs, or narrow ribbons of coral rock, lying near the shore of an ordinary island. (2.) Barrier Reefs, which are broader than Fringing Reefs, and lie at a greater distance from the shore, but do not extend entirely around the island. A barrier reef off the coast of New Caledonia has a length of 400 miles. One extends along the north-eastern shore of Australia for over 1000 miles. Barrier reefs are not continuous, but often have breaks in them through which vessels can readily pass. (3.) Encircling Reefs are barrier reefs extend- ing entirely around the island. As a rule, en- circling reefs are farther from the shores of the island than barrier reefs. Tahiti, of the Society Islands, is an example of an encircling reef. (4.) Atolls—This name is given to reefs that encircle lagoons or bodies of water entirely free from islands. The varieties of reefs just enumerated mark successive steps or stages in the progress of for- mation of the coral island. When a more careful study of the habits of the reef- forming coral polyp disclosed the fact of its inability to live in the ocean at greater depths than 100 or 120 feet, the opinion, which formerly prevailed, of coral islands rising from profound depths, had to be abandoned. The idea had its foundation in the fact that a sounding-line, thrown into the water near the shore of a coral island, almost invariably showed depths of thousands of feet, and yet brought up coral rock. In no case, however, did the rock contain living polyps. An ingenious hypothesis of Darwin, which appears well sustained by the extensive observations of Dana and others, explains the great depth f coral formations. : 101. Darwin’s Theory of Coral Islands.—Ac- cording to this distinguished naturalist, the coral formation begins near the shore of an island that is slowly sinking. If the growth of the reef up- ward equals the sinking of the island, the thick- ness of the reef is limited only by the time during which the operation continues. In Fig. 38 is shown, in plan and section, an island with elevations A, and B, and river a. The coral island begins as a fringing reef somewhere off the coast of an ordinary island at c¢, c, c, when the conditions are favorable, The SP Fig, 38. Growth of a Coral Island, coral reef must gradually extend around the island, since its growth toward the ocean is soon limited by the increasing depth, and toward the shore of the island by the muddy | waters near the surf and the absence of the breakers. Meanwhile, as the island is sinking, the channel sepa- rating the reef from the coast increases in breadth. A barrier reef is thus formed, which at last completely sur- rounds the island, and becomes an encircling reef. The higher portions of land, which are still above the waters, form islands in the central lagoon. Opposite the mouth of the river a, the growth is prevented by the fresh water, and a break in the reef is thus produced. These breaks are sometimes sufficient to permit a ship to enter the lagoon, At last all traces of the old island disappear, and its situation is marked by a clear lake, surrounded by a narrow rim of coral which follows nearly the old coast line. A coral island, therefore, is always of an ap- proximately circular or oval form, and encloses a clear space in the ocean. Extended systems of coral formations occurring in any region are a proof of subsidence. ——-050300—. CHAPTER IV. Relief Forms of the Land. 102. By the Forms of Relief of the Land is meant the elevation of the land above the mean level of the sea. The highest land in the world is Mount Ever: est, of the Himalayas; it is 29,000 feet high. The greatest depression is the Dead Sea, in Pales- tine, which is about 1812 feet below the level of the ocean. The sum of these is somewhat less than six miles. An elevation of six miles is insignificant when RELIEF FORMS OF THE LAND. _ 48 compared with the size of the earth. If repre- sented on an ordinary terrestrial globe, it would be scarcely discernible, since it would project above the surface only about the z5,th of the diameter. The highest elevations of the earth are proportionally much smaller than the wrinkles on the skin of an orange. 4000 miles, 2000 miles. 1000 « 500 « 250 « > Wy —— Fig. 39, Relative Height of Mountains, Tf, as in Fig. 39, a sphere be drawn to represent the size of the earth, its radius will be equal to about 4000 miles. If, now, the line A B be drawn equal to the radius, it will represent a height of 4000 miles. One-half this height would be 2000 miles; one-half of this 1000, and successive halves 500 and 250 miles. An elevation of 250 miles would not therefore be very marked. Although the irregularities of the surface are comparatively insignificant, they powerfully affect the distribution of heat and moisture, and conse- quently that of animal and vegetable life. An elevation of about 350 feet reduces the tempera- ture of the air 1° Fahr.—an effect equal to a difference of about 70 miles of latitude. High mountains, therefore, though under the tropics, may support on their higher slopes a life similar to that of the temperate and the polar regions. 103. The Relief Forms of the Land are divided into two classes : Low Lands and High Lands. The boundary-line between them is taken at 1000 feet, which is the mean or average elevation of the land. Low Lands are divided into plains ond hills. High Lands are divided into plateaus and mountains. If the surface is: Scoreparaticele flat or level, it is called a plain when its elevation above the sea is less than 1000 feet, and a plateau when its ele- vation is 1000 feet or over. 6 If the surface is diversified, the elevations are called hills when less than 1000 feet high; and mountains when 1000 feet. or over. . Plains and Hills cover about one-half of the land surface of the earth. In the Eastern Continent they lie mainly in the north; in the Western, they occupy the central portions. Plains generally owe their comparatively level surface to the absence of wrinkles or folds in the crust, in which case the general level is preserved, but the surface rises and falls in long undulations: these may therefore be called undulating plains. The flat surface may also be due to the gradual settling of sedimentary matter. In this case the plains are exceedingly level. They are called marine when deposited at the bottom of a sea or ocean, and alluvial when deposited by the fresh water of a river or lake. Alluvial plains occur along the lower course of the river or near its mouth. Marine and alluvial plains, from their mode of forma- tion, are generally less elevated than undulating plains. 105. Plateaus are generally found associated with the mountain-ranges of the continents. Their connection with the adjacent plains is either ab- rupt, as where the plateau of Anahuac joins the low plains on the Mexican Gulf; or gradual, as where the plains of the Mississippi Valley join the plateaus east of the Rocky Mountains. 106. Mountains.—In a mountain-chain the crest or summit of the range separates into a num- ber of detached portions called peaks; below the peaks the entire range is united in a solid mass. The breaks in the ridge, when extensive, form mountain-p asses. The influence of inaccessible mountains, like the Pyr- enees and Himalayas, in preventing the intermingling of nations living on their opposite sides, is well exemplified by history. In the past, mountains formed the boundaries of different races. Some mountains, like the Alps and the Appalachians, have numerous passes. A Mountain-System is a name given to ceveral connected chains or ranges. Mountain-systems are often thousands of miles in length and hun- dreds of miles in breadth. The Axis of a Mountain-system is a line extend- ing in the general trend of its chains. Where several mountain-axes intersect one an- other, a complicated form occurs, called a Moun- tain-Knot. The Pamir Knot, formed by the fo earueationl of the Karakorum, Belor, and Hindoo-Koosh Mountains, is an example. It lies on the southern border of the elevated plateau of Pamir. 44 PHYSICAL GEOGRAPHY. Fig. 40, A Mountain-Pass, 107. Orology treats of mountains and their formation. The force which upheaved the crust into moun- tain-masses and plateaus had its origin in the contraction of a cooling globe. There are good reasons for believing that no extensive mountains’ existed during the earlier geological ages, since the crust was then very thin, and would have been fractured before sufficient force could accu- mulate to upheave it into mountain-masses. The great mountain-systems of the world are formed from sedimentary deposits that slowly ac- cumulated over extended areas until they acquired very great thickness. The deposits forming the Appalachians, according to Dana, were, in places, 40,000 feet in depth, and covered the eastern bor- der of the continent from New York to Alabama, varying from 100 to 200 miles in breadth. After the accumulation of these strata they were, through the contraction of the crust, sub- jected to the gradual effects of lateral pressure, by which they were sometimes merely flexed or folded, but more frequently crushed, fractured, or mashed together, and thus thickened and thrust upward. That side of the deposit from which the thrust came would have a steeper slope than the opposite side, which received a thrust arising from the resistance. This theory of mountain-formation, which is generally accepted, explains the following facts: (1.) All mountains have two slopes—a short steep slope, facing the ocean, and a long gentle slope, facing the interior of the continent. (2.) The strata on the short steep slope are generally highly metamorphosed; those on the long slope are in general only partially metamor. phosed, or wholly unchanged. (3.) The mountain-systems are situated on the borders of the continents where the sedimentary strata collected. (4.) Slaty cleavage, or the readiness with which so many of the rocks of mountains cleave or split in one direction, is a proof of these rocks having been subjected to intense, long-acting, lateral pres- sure, since such pressure can be made to develop slaty cleavage in plastic material. Isolated Mountains.—Nearly all high isolated moun- tains were formed by the ejection of igneous rocks from ' the interior; that is, they are of volcanic origin and have been upheaved by a vertical strain or true projectile force, as in the volcanic range of Jorullo in Mexico. 108. Valleys in mountainous regions are either longitudinal or transverse. Longitudinal Valleys are those that extend in the dire¢tion of the length of the mountains. Transverse Valleys extend across the moun- tain. | It is in transverse vaileys that most passes occur, Although valleys, like mountains, owe their origin to the contraction of a cooling crust, yet their present shapes are modified by the operation of other forces. By the action of their water-courses, valleys are deepened in one place and filled up in another. Extensive land-slides often alter their configuration. During the Glacial Period many valleys were greatly changed by the action of huge mov- ing masses of ice. Fiord-valleys were formed in this manner. In level countries valleys generally owe their origin to the eroding power of water. 109. Peculiarities of Continental Reliefs.— The following peculiarities are noticeable in the relief forms of the continents: (1.) The continents have, in general, high bor- ders and a low interior. (2.) The highest border lies nearest the deep- est ocean; hence, the culminating point, or the highest point of land, lies out of the centre of the continent. ' (8.) The greatest prolongation of a continent is always that of its predominant mountain-sys- tem. (4.) The prevailing trends of the mountain- masses are the same as those of the coast lines, and are, in general, either north-east or north-west. * In describing the relief forms of the continents we shall observe the following order: (1.) The Predominant System, ora system of RELIEF FORMS OF THE CONTINENTS. 45 elevations exceeding all others in height, and con- taining the culminating point of the continent. (2.) The Secondary System or Systems, inferior to the preceding in height. 3.) The Great Low Plains. Fig, 41, Orographic Chart of North America, (Light portions, mountains; shaded portions, plains.) 1, Rocky Mountain System; 2, System of the Sierra N evada and Cascade Ranges; 3, Sierra Madre; 4, Great Interior Plateau; 5, Wahsatch Mountains; 6, Appalachians; 7, Plateau of Labrador; 8, Height of Land; 9, Arctic Plateau; 10, Mackenzie River; ll, Nelson River; 12, St. Lawrence River; 13, Mississippi River. CHAPTER V. Relief Forms of the Continents. I. NORTH AMERICA 110. Surface Structure.—The Predominant Mountain-System lies in the west, The Secondary Systems lie in the east and north. The Great Low Plains lie in the centre. lll. The Pacific Mountain-System, the pre- dominant system, extends, in the direction of the greatest prolongation of the continent, from the Isthmus of Panama to the Arctic Ocean. It con- sists of an immense plateau, from 800 to 600 miles in breadth, crossed by two nearly parallel mountain-systems: the Rocky Mountains on the east and the system of the Sierra Nevada and Cascade ranges on the west. The eastern moun- tain-system is highest near the south; the west- ern range is highest near the north. Between these lie numerous parallel ranges enclosing lon- gitudinal valleys, connected in places by trans- verse ranges forming basin-shaped valleys. The Rocky Mountain System.—The Rocky Mountains rise from the summits of a plateau whose elevation, in the widest part of the system, varies from 6000 to 7000 feet above the sea; therefore, although the highest peaks range from 11,000 to nearly 15,000 feet, their elevation above the general level of the plateau is comparatively inconsiderable. The plateau on the east rises by almost imperceptible slopes from the Mississippi River. The upper parts of the slopes, near the base of the mountains, form an elevated plateau called the “Plains,” over which, at one time, roamed vast herds of buffalo or bison. This ani- mal is rapidly becoming extinct. Though the name “ Rocky Mountains” is generally con- fined to those parts of the chain which extend through British America and the United States, yet, in connection with the Sierra Nevada Mountains, it is continued through Mexico by the Sierra Madre Mountains, and by smaller ranges to the Isthmus of Panama. 46 PHYSICAL GEOGRAPHY. Fig, 42, On the Plains, The Rocky Mountain System forms the great watershed of the continent, the eastern slopes draining mainly through the Mississippi into the Atlantic, and the western slopes draining through the Columbia and the Colorado into the Pacific. It slopes gradually upward from the Arctic Ocean toward the Mexican plateau, where it attains its greatest elevation in the volcanic peak of Pepo- catepetl, 17,720 feet above the sea. The System of the Sierra Nevada and Cascade) Mountains extends, in general, parallel to the Rocky Mountain System. It takes the name of Sierra Nevada in California and Nevada, and of the Cascade Mountains in the remaining portions of the continent. It reaches its greatest eleva- tion in Mount St. Elias, in Alaska, 19,500 feet above the sea. This is the culminating point of the North American continent. In the broadest part of the plateau of the Pacific system, between the Wahsatch Mountains on the east, and the Sierra Nevada and Cascade ranges on the west, lies the plateau of the Great Basin. Its high mountain borders rob the winds of their moisture, and the rainfall, except on the mountain-slopes, is inconsiderable. The Great Basin has a true inland drainage. The heights of all mountains, except those much fre- quented, must generally be regarded as but good approxi- mations, since the methods employed for estimating heights require great precautions to secure trustworthy results. Even the culminating points of all the continents have not, as yet, been accurately ascertained. _ 112. The Secondary Mountain-Systems of North America comprise the Appalachian system, the Plateau of Labrador, the Height of Land, and the Arctic Plateau. The last three have but an inconsiderable elevation. The Appalachian Mountain System consists of a number of nearly parallel chains extending from the St. Lawrence to Alabama and Georgia. It is high at the northern and southern ends, and slopes gradually toward the middle. The highest peaks at either end have an elevation of about 6000 feet. The Appalachian system is broken by two deep depres- sions, traversed by the Hudson and Mohawk Rivers. Be- tween the foot of the system and the ocean lies a low coast plain, whose width varies from 50 to 250 miles. 118. The Great Low Plain of North America lies between the Atlantic system on the east and the Pacific system on the west. It stretches from the Arctic Ocean to the Gulf of Mexico. Near the middle of the plain the inconsider- able elevation of the Height of Land divides it into two gentle slopes, which descend toward the Arctic Ocean and the Gulf of Mexico. > \ Jaa Fig. 76, Currents caused by Difference of Temperature. Thus in Fig. 76, the mountain-like accumula- tion is shown as having its crest at about the lati- tude of the polar circle. The arrows show the direction of the currents. At the equatorial re- gions, the surface water is warmer and lighter, and at the polar regions, probably, colder and lighter. As a rule, the warm currents are on the surface, and the, cold currents, from their greater density, are underneath them. In shallow oceans, however, the cold currents come to the surface, thus displacing the warm currents and de- flecting them to deeper parts of the ocean. Had the earth no rotation on its axis, this in- terchange would be due north and south, or would take place directly between the equatorial and polar regions. On account of the earth’s rota- tion, however, and a variety of other causes, these north-and-south directions are consider- ably changed. The principal of these deflecting causes are— (1.) The earth’s rotation ; (2.) The position of the land masses (8.) The winds ; (4.) Differences of density caused by evapora- tion ; (5.) Differences of level caused by evapora- tion. The changes in direction caused by the earth’s rotation and the position of the land masses are as follows: as the waters are in constant motion, the polar waters reach the equatorial regions with an eastward motion less than that of. the earth. In the equatorial regions, therefore, the waters are unable to acquire the earth’s motion toward the east, and are left behind; that is, the earth, slipping from under them, causes them to cross the ocean at a, a’, Fig. 77, from east to west, although they are in reality moving with the earth toward the east. Reaching the western borders of the oceans, near J, b’, the continents prevent their going farther west, and de- fiect them into northern and southern branches, and they begin to move toward the poles. » From ¢, to d, and from ec’, to d’, the poleward-moving waters are deflected toward the east in both hemispheres. The waters on reaching ¢, from a, and J, still retain the eastward motion they acquired while moving with the —z_d y ry Ke eee re errr Wee ae Zz Su SoZ d’ Fig. 77. Deflections of Ocean Currents. earth. This motion is greater than that of the earth be- tween c,and d. Betweén these points, therefore, the water is acted on by two forces, one tending to carry it toward the poles, and the other tending to carry it eastward. The resultant of these forces carries the water from ¢, to d, and from c’, to d’, or toward the north-east in the North- ern, and toward the south-east in the Southern Hemisphere. Between d, and e, and d’, and e’, the waters still retain this excess of eastward motion, and, therefore, move in the directions shown. Between e, and a, and e’,and a’, the waters in both hemi- spheres are deflected toward the west because they are unable to acquire the earth’s motion toward the east. Another, and perhaps the main, cause of this westward. deflection is the depression caused by the westward move- ment of the equatorial waters at a, and a’. The action of the winds is to tend to move the surface waters in the direction in which they are blowing. This action is by some authorities regarded as the principal cause of constant currents. : The difference in the density of the water, caused by evaporation, leaving the water salter and denser in some parts, and fresher and lighter in others, probably acts to some extent as a deflecting cause. For example, the water evaporated near the equator, and precipitated, for the greater part, in regions near the borders of the tropics, renders the regions salter and denser from which it was evaporated, and fresher and less dense where it is precipi- tated. The difference in level caused by the greater evapora- tion in the equatorial regions north of the equator than in corresponding latitudes in the Southern Hemisphere ' has been ascribed as one of the causes of the flow of Ant- arctic waters toward the equator. 222. General Features of Constant Currents.— The following motions of the surface currents are common to all the three central oceans: (1.) A movement of the equatorial waters, a, a, from east to west ; (2.) Their deflection into northern and south- ern branches (6 and c), on reaching the western borders of the ocean ; (3.) A movement of the waters beyond the equator from west to east (d, e); Page 67. 160 140 120 100 80 60 ae 1a se ee te leg CG Ses tte 4 SS g MAP OF THE WORLD “ REFERENCES. Al eee me showing the direction : Pa iacetor i of the ~ » Sea Weed. OCEAN CURRENTS. | Z Ocean Currents. ee Ce ae LONIGITUDE WEST FROM GREENWICH LONG}TUDE EAST FROMIGREENWICH. 160 * 140, 120 100 80 60 20 0 +0 60 100 120 160 82 PHYSICAL GEOGRAPHY. (4.) A separation of these latter currents into two branches (f, g and h, 7), one continuing toward a—Equator. Fig. 78. Chart of Constant Currents, - the poles, and the other toward the equator, where they join with the equatorial currents, thus com- pleting a circuit in the shape of a vast ellipse ; (5.) A flow of the Arctic waters along the western border of the ocean (j), and of the Ant- arctic along the eastern (k). Since the Indian Ocean is completely closed on the north, only part of the above movements are observed. In the Pacific, an equatorial counter-current crosses the ocean from west to east. 223. Currents of the Atlantic—The equatorial current crosses the ocean, from east to west, in two branches: a south equatorial current, which comes from the Antarctic, and a north equatorial current, which comes mainly from regions north of the equator. The north equatorial current flows along the northern coast of South America, and, separating, part of it enters the Caribbean Sea and Gulf of Mexico, and part flows north, passing east of the Bahamas. The Gulf Stream flows along the eastern coast of North America, with a velocity of from four to five miles per hour, and in mid-ocean, between Newfoundland and Spain, divides, one branch flowing toward Norway, Spitzbergen, and Nova Zembla, the other flowing southward, down the coasts of Africa, where it forms the main feeder of the north equatorial current. The south equatorial current, after crossing the | ocean, flows south along the Brazilian Goast, and | divides near Rio Janeiro, the main part flowing ,eastward and mingling with the Antarctic cur- \vent, and the remainder continuing down the east- ern coast of South America. Cold currents from the Arctic flow down the coasts of Greenland and Labrador. A broad polar current sweeps from the Antarctic Ocean, and forms the main feeder of the south equatorial current, but passes in greater part eastward, south of Africa’ A small elliptical current flows near the equator, between the north and south equatorial currents. 224. Currents of the Pacific—North and south equatorial currents flow from east to west, and between them a smaller, less powerful equatorial counter-current, from west to east. The south equatorial current, fed by the broad Antarctic current, is the larger of the two. The-north equatorial current, on reaching the Philippine Islands, divides into northern and southern branches; a portion of its southern branch returns with the equatorial counter-cur- rent, while the northern branch, the main por- tion, flows north-east along the Asiatic coast as the Kuro Sivo, the counterpart of the Gulf Stream. At about Lat. 50°, this flows east- wardly as a North Pacific current, and off the shores of North America it returns, in an ellip- tical path, southerly to the north equatorial cur- rent, forming its main feeder. A small current flows through the eastern side of Bering Strait, into the Arctic Ocean. The south equatorial ewrrent of the Pacific is broken into numerous branches during its passage through the islands in mid-ocean. Reaching the Australian continent and the neighboring archi- pelagoes, it sends small streams toward the north, but the main portion flows south, along the Aus- tralian coast, when, flowing eastward, it merges with the cold Antarctic current. The Antarctic current moves as a broad belt of water toward the north-east, when, flowing up the western coast of South America, it turns to the west, and forms the main feeder of the south equatorial current. A part of the Antarctic cur- rent flows eastward, south of South America, and enters the Atlantic as the Cape Horn current. A small cold current from the Arctic flows through Bering Strait, down the Asiatic coast, 225. Currents of the Indian Ocean.—Only a south equatorial current exists, which flows down the eastern and western coasts of Madagascar, and down the African. coast to Cape Agulhas, when, turning eastward, it merges with the Antarctic current, and flows up the western coast of Aus- tralia, where it joins the equatorial current. SYLLABUS. 83 The north equatorial current in this ocean is indistinct— (1.) Because the ocean has no outlet to the north; (2.) Powerful seasonal winds, called the monsoons, move the waters alternately in different directions, as huge drift eurrents. Sargasso Seas.—Near the centre of the ellip- tical movement in each of the central oceans, masses of seaweed have collected where the water is least disturbed. These are called sargasso seas, 226. Utility of Currents: (1.) They moderate the extremes of climate by carrying the warm equatorial waters to the poles, and the cold polar waters to the equator; (2.) They increase materially the speed of ves- sels sailing in certain directions ; (3.) They transport large quantities of timber to high northern latitudes. OSE III SYLLABUS. 2020400 Ocean water contains about three and one-third pounds of various saline ingredients, in every one hundred. ‘Chlo- ride of sodium; sulphates and carbonates of lime, mag- nesia, and potassa; and various chlorides, bromides, and iodides, are the principal saline ingredients. The salt of the ocean is derived either from the washings of the land, or is dissolved out from the por- tions of the crust which are continually covered by its waters. The ocean is salter in those parts where the evaporation exceeds the rainfall. Seas like the Mediterranean, which are connected with the ocean by narrow channels, and in which the evaporation is greater than the rainfall, are salter than the ocean. Others, like, the Baltic, in which the rainfall exceeds the evaporation, are fresher than the ocean. Most of the bed of the ocean is covered with a layer of dense water, at about the temperature of its maximum density. The Pacific and Atlantic Oceans occupy about three- fourths of the entire water-area of the earth. South of the southern extremities of South America, Africa, and Australia, the meridians of Cape Horn, Cape Agulhas, and South Cape in Tasmania, are assumed as the eastern boundaries of the Pacific, Atlantic, and Indian Oceans. The articulation of land and water assumes four distinct forms: Inland Seas, Border Seas, Gulfs and Bays, and Fiords. Inland Seas characterize the Atlantic; Border Seas, the Pa- cific; Guifs and Bays, the Indian Ocean; and Fiords, the Atlantic and Pacific. The telegraphic plateau lies between Ireland and New- foundland. Its average depth is about two miles. The bottom of the ocean is not as much diversified as tne surface of the land. Its plateaus and plains are be- lieved to be much broader than are those of the land. The profound valleys of the ocean are called deeps, its shallow parts, rises. The greatest depth of the ocean that has as. yet been accurately sounded is about 5% miles. ae is probably deeper than this in some places. Over extended areas, the floor of the ocean is uniformly covered with a deposit of fine calcareous mud or ooze, formed of the hard parts of the bodies of minute animal- cule. The movements of the oceanic waters may be arranged | under the three heads: waves, tides, and currents. The height and velocity pf a wave depend upon the force of the wind and the depth of the oceanic basin. In ordinary wave motion, the water rises and falls, but does not move forward. Tides are the periodical risings and fallings of the water, caused by the attraction of the sun and moon. The rising of the water is called flood tide; the falling, ebb tide. If the earth were uniformly covered with a layer of water, two high tides would occur simultaneously; one on the side of the earth directly under the sun or moon, the other on the side farthest from the sun or moon. The tidal wave crosses the ocean from east to west, fol- lowing the moon in the opposite direction to that in which the earth passes under it while rotating. Its progress is considerably retarded by the projections of the continents, and the shape of the oceanic beds. Had the moon no real motion around the earth, there would be two high and two low tides every twenty-four hours, or the high and ~ low tides would be exactly six hours apart. Spring Tides are caused by the combined attractions of the sun and moon on the same portions of the earth. Neap tides by their opposite attractions. The parent tidal wave is considered as originating in the great water-area of the Pacific on the south. Co-tidal lines are lines connecting places which have high tides at the same time. When the progress of the tidal wave is retarded by the shelving coast of a continent, what the tide loses in speed, it gains in height. The highest tides, therefore, occur where the co-tidal lines are crowded together. Bores, Races, and Whirlpools are tidal phenomena. Oceanic currents are either temporary, periodical, or constant. The heat of the sun and the rotation of the earth are the main causes of constant oceanic currents. The following peculiarities characterize the constant currents in the three central oceans: (1.) A flow in the equatorial regions from the east to the west; (2.) A flow in extra-tropical regions from the west to the east; (3.) A division of the eastwardly flowing extra-tropical waters in mid-ocean into two branches; one of which flows toward the poles, and the other toward the equator, where it merges into the equatorial currents. 84 PHYSICAL GEOGRAPHY. The principal cause of constant ocean currents is the difference in the density of the equatorial and polar waters, produced by differences of temperature. The cold, dense waters of the polar regions tend to mix with the warm, light waters of the equatorial regions along due north-and-south lines. This tendency to north and south direction is prevented by the following causes: (1.) The rotation of the earth ; (2.) The position of the continents; (3.) The direction of the winds; (4.) The difference in the saltness of the water; (5.) The inequality of the evaporation and rainfall. In the Pacific, a counter-current crosses the ocean in the equatorial region, from west to east, In the Indian Ocean, the directions of the currents are modified by the land masses, which surround the northern part of its bed. In the northern hemispheres, the western borders of the oceans are colder than the eastern borders in the same lati- tude, because the former receive the polar currents and the latter the equatorial. Currents moderate the extremes of climate, by carry- ing the warm equatorial waters to the poles, and the cold polar waters to the equator. REVIEW QUESTIONS. ——0be300——_ How much heavier is salt water than fresh water ? What is the freezing-point of ocean water? | Explain the origin of the saltness of the oceanic waters. In the equatorial region, where is the water the colder, at the surface or near the bottom of the ocean ? How do the areas of the Pacific and Atlantic compare with each other in size? Of the Antarctic and Arctic? Define inland sea; border sea; gulf or bay; fiord; give examples of each. Define deeps; rises. What, most probably, is the shape of the bed of the At- lantic? Of the Pacific? Of the Indian Ocean ? Describe the Telegraphic Plateau. How does the greatest depth of the ocean compare with the greatest elevation of the land? Upon what does the height of a wave depend? On what does its velocity depend? What proof is there that during wave motion in deep water there is no continued onward motion of the water? Distinguish between ebb and flood tides. What proofs have we that tides are occasioned mainly by the attraction of the moon? What are spring tides? Neap tides? During what phases of the moon do they each occur? Why should the moon, which is so much smaller than the sun, exert a more powerful influence in producing tides? Where does the parent tidal wave originate? What are co-tidal lines? Why does the tidal wave progress from east to west? Explain the nature of the influence which the tidal wave exerts on the rotation of the earth. In what parts of the ocean will unusually high tides occur? Why? By what are races and whirlpools occasioned ? Distinguish between temporary, periodical, and constant oceanic currents. Explain the origin of constant currents. How are the directions of constant currents affected by the rotation of the earth and the shapes of the continents? What features of constant currents are common to each " of the three central oceans? On which side of the northern oceans do the polar cur- rents flow? On which side of the southern oceans? What are sargasso seas? How are they formed? What effect is produced by ocean currents on the ex- tremes of climate? Of what value are ocean currents to navigation? MAP QUESTIONS. ——-093.00——_ Point out, on the map of the river-systems, the inland seas of the Atlantic; of the Pacific; of the Indian Ocean. Point out the border seas of the Atlantic; of the Pacific. Point out the gulfs or bays of the Atlantic; of the In- dian Ocean. Point out the principal regions of fiords. How many hours does it take the tidal wave to progress from Tasmania to the Cape of Good Hope? From Tasma- nia to Newfoundland? From Tasmania to the British Isles? (See map of the co-tidal lines.) In what parts of the Atlantic does the tidal influence progress most rapidly ? If the velocity of any kind of wave motion in water in- creases with the depth of the basin, what parts of the At- lantic appear to be the deepest? What portions of the Pacific? What portions of the Indian Ocean? Trace on the map of the ocean currents, the motion of the Antarctic currents in each of the three central oceans. Where is the Cape Horn current? Is it hot or cold? What points ef resemblance exist between the north and south equatorial currents in the Atlantic and Pacific Oceans? 3 Trace the progress of the Gulf Stream. What points of resemblance exist between the Gulf Stream and the Japan current? How far to the north-east do the waters of the Gulf Stream extend? What distant shores are warmed by the waters of the Gulf Stream? By those of the Japan current? Why do not the heated waters of the Gulf Stream exert amore powerful influence on the climate of the eastern sea-board of the United States? Point out the, principal cold currents; the principal warm currents. Which currents would aid, and which would retard, the progress of a vessel in sailing from New York to San Fran- cisco? From America to Europe? -From America to India or Australia? PART IN. THE ATMOSPHERE. We live at the bottom of a vast ocean of air, which, like the ocean of: water, is subject to three general movements—waves, tides, and currents. By means of waves, its upper surface is heaved in huge mountain-like masses in one place, and hollowed out in deep valleys in another. By means of currents, circulatory movements are set up, which effect a constant interchange between the air of the equatorial and the polar regions. By means of tides, the depth of the atmosphere is increased in some places and decreased in others. Of these three movements of the atmosphere, currents are of the greatest importance. Aérial cur- rents, or winds, are similar to oceanic currents, but are more extensive and rapid, owing to the greater mobility of air. By retaining and modifying the solar: heat, absorbing ri distributing moisture, supplying animals with oxygen and plants with carbonic acid, the atmosphere plays an Important part in the economy of the earth. Meteorology is the science which treats of the atmosphere and its phenomena. Oe ee Seer rhoO NL: THE ATMOSPHERE. ——n$¢00—_ CHAPTER I. proportion, by weight, of nearly 77 per cent. of nitrogen to 23 per cent. of oxygen.. To these must be added a nearly constant quantity of car- bonie acid, about 5 or 6 parts in every 10,000 227. Composition.— The atmosphere is a me- parts of air, or about a cubic inch of carbonic acid chanical mixture of nitrogen and oxygen, in the to every cubic foot of air, and a very variable pro- 85 General Properties of the Atmo- sphere. 86 PHYSICAL GEOGRAPHY. portion of watery vapor. The gaseous ingredients, though of different densities, are found in the _ same relative proportions at all heights, owing to a property of gases called diffusion. The oxygen and carbonic acid are the most important of the gaseous constituents. Oxygen supports combustion and respiration, and is thus necessary to the existence of animal life. Carbonic acid, composed of carbon and oxy- gen, is the source from which vegetation derives its woody fibre, and is thus necessary to the existence of plant life. In respiration, animals take in oxygen and give out car- bonic acid; in sunlight, plants take in carbonic acid and give out oxygen. In this way the relative proportions of the substances necessary to the existence of animal and plant life are kept nearly constant. 228. Elasticity.—The atmosphere is eminently _ elastic; that is, when compressed, or made to oc- cupy a smaller volume, it will regain its original volume on the removal of the pressure. Air also expands when heated and contracts when cooled. 229. Pressure.—So evenly does the atmosphere press on all sides of objects that it was long be- fore it was discovered that air possesses weight. The discovery was made by Torricelli, an Italian philosopher and pupil of the famous Galileo. The instrument Torricelli employed is called a Ba- rometer. Fig. 79. Barometer, 230, The Barometer.—The principle of the barometer is as follows: A glass tube, about 33 inches in length, is closed at one end and filled with pure mercury. Placing a finger over the open end, the tube is reversed and dipped below the surface of mercury in a cup or other vessel. On removing the finger, a column of mercury remains in the tube, being sustained there by the pressure of the at- mosphere. Near the sea-level this column is about 30 inches high; on mountains it is much lower; in all cases, the weight of the mercurial column being equal to that of an equally thick column of air, extending from the level of the reservoir to the top of the atmosphere. Any variation in the pressure of the atmosphere is marked by a corresponding variation in the height of the mercury in the barometer, the column rising with in- creased, and falling with diminished, pressure. The entire atmosphere presses on the earth with the same weight as would a layer of mer- cury about 80 inches in depth. A column of mercury 80 inches high, and one square inch in area of cross section, weighs about 15 pounds. Therefore, the pressure which the atmosphere exerts on the earth’s surface, at the level of the sea, is equal to about 15 pounds for every square inch of surface. The entire weight of the atmosphere, in pounds, is equal to 15 times the number of square inches in the earth’s surface. The atmospheric pressure is not uniform on all parts of the earth at the same level. From a few degrees beyond the equator the pressure increases in each hemisphere up to about lat. 35°, where it reaches its maximum, decreasing in the northern hemisphere to lat. 65°, when it again in- _ ereases toward the poles. 231, Height-of the Atmosphere.—If the air were everywhere of the same density, its height could be easily calculated ; but, on account of its elasticity, the lower layers are denser than the others, because they have to bear the weight of those above them. The density must, therefore, rapidly diminish as we ascend. If by pressure on a gas we diminish its volume one- half, its density will be doubled; conversely, if the den- sity be diminished one-half, the volume will be doubled. The following table, calculated from the law of increase in volume with diminished pressure, gives the barometric height, the volume, and the density of the air at different elevations above the sea. The elevation of 3.4 miles is the result of observation; the other distances are estimated. Estimated Distance ab. Sea, in Miles. Barometric Vol. of Given Height in Inches.} Weight of Air, | Density. 30.00 15.00 7.50 3.75 1.87 .93 It appears from the above table that by far the greater part of the air by weight lies within a few miles of the surface, nearly three-fourths being below the level of the summits of the highest mountain-ranges. The height of the upper limit of the atmosphere has been variously estimated. Calculations based upon the. diminution of pressure with the height, place it at from 45 to 50 miles above the level of the sea; others, based on the duration of twilight, place it at distances varying from 35 to 200 miles. The form of the atmosphere is that of an ob- late spheroid, the oblateness of which is greater than that of the earth. CLIMATE. 87 By carefully observing the decrease in pressure with the elevation, at different altitudes, and making proper correc- tions, the heights of mountains can be readily determined by the barometer. The measurement of heights by the barometer, or similar means, is called Hypsometry. ——00 $f,0-0—_—_. CHAPTER. il, Climate. 282. The Climate of a country is the condi- tion of its atmosphere as regards heat or cold. The climate of a country also embraces the con- dition of the air as regards moisture or dryness, and healthiness or unhealthiness, which are de- pendent on the temperature. ; 233. Temperature——The temperature of the atmosphere is determined by means of an instru- ment called a thermometer. The thermometer consists of a glass tube of very fine bore, furnished at one end with a bulb. The tube is care- fully dried and the bulb filled with pure mercury and heated in the flame of a spirit-lamp; the mercury expands, and, filling the fine capillary tube, a portion runs out from the open end, thus effectually expelling the air. A blowpipe flame is then directed against the open end and the tube hermetically sealed. As the bulb cools, the mer- cury contracts, and leaves a vacuum in the upper part of the tube. The instrument will now indicate changes in temperature; for, whenever the bulb grows warmer, the column of mercury expands and rises; and when it grows colder, it contracts and falls. In order to compare these changes of level they are referred to certain fixed or standard points: the freezing- and boiling-points of pure water. These are obtained by marking the respective heights to which the mercury rises when the thermometer is plunged into melting ice and into the steam escaping from boiling water. In Fuhren- heit’s scale the freezing-point is placed at 32°, the boil- ing-point at 212°, and the space between these two points divided into 180, (212 —32) equal parts, called degrees. In the Centigrade scale the freezing- and boiling-points are re- spectively 0° and 100°. Fahrenheit’s degrees are repre- sented by an F., thus, 212° F.; Centigrade’s by a C., as 100° C. 234. Astronomical and Physical Climates— Astronomical climate is that which would result were the earth’s surface entirely uniform and of but one kind: all land or all water. Physical climate is that which actually exists. Since the physical climate is only a modification of the astronomical, we shall briefly review the causes which tend to produce a regular decrease in temperature from the equator to the poles. Astronomical Climate—The sun is practically the only source of the earth’s heat. On account of the earth’s spherical shape, those portions of the surface are most powerfully heated. which re- ceive the vertical rays, and these are confined to a zone reaching 23° 27’ on each side of the equa- tor. Beyond these the rays fall with an obliquity which increases as we approach the poles. 235. Causes of the greater heating power of the vertical rays of the sun than of the oblique rays. Je Id e ke Ja ! te ik WE \ 80. Causes of the Greater Heating Power of the Vertical than of the Oblique Rays, (1.) The vertical rays are spread over a smaller area, Equal areas of the sun’s surface give off equal quantities of heat. If, therefore, the bun- dle of rays a 6, and ¢ d, come from equal areas, the amounts of heat they emit will be equal; but while the heat given off from a 0, the more ver- tical rays, is spread over the earth’s surface from J, to g, that from e d, is spread over the greater area hi; the area f g, therefore, which receives the more vertical rays, is much warmer than h j, where the obliquity is greater. (2.) The vertical rays pass through a thinner layer of air. Only a part of the sun’s heat reaches the surface of the earth; about 28 per cent. of the vertical rays are absorbed during their passage through the atmosphere. The amount of this absorption must increase as the length of path increases. In the figure, the light shading represents the atmosphere. It is clear that the oblique rays pass through a thicker stratum of air than the more direct ones, and, therefore, are deprived of a greater amount of heat. According to Laplace, the thickness of the stratum of air traversed by the rays when the sun is at the horizon is 35.5 times greater than when it is directly overhead. A similar absorption of light affects the comparative bright- ness of daylight in different latitudes. (3.) The vertical rays strike more directly, and, therefore, produce more heat. The heating WO 10° poate eeeeeeeeee| = 7) ee o er ah 52°23 és R-90n30, TROPICOF|CAPRICORN __ MAP OF THE WORLD © | REFERENCES. een _--|_ANTaRoTICLoIRCLE showing the BEBE Torr: ac aoa ere aaa aa Se ; Z| ISOTHERMAL LINES Pe 5 Cire are Note. The figures after the names of Citves, give the average . and the boundaries of the 7) Pemperate Zones. temperatures tor Jannaryand July.thus, Quebec 10°67 indicates that POS ICATS ZONES: ; : [7] Frigid Zones. the average temperature for January ts 10‘and tor July 67° 80 & : 40 20 0 6 Oia 80 100 120 140 { : CLIMATE. 89 power of the more nearly vertical rays is greater than that of the rays which strike obliquely. 236. Variations in Temperature.—The differ- énces in the heating power of the vertical and ob- lique rays of the sun. cause the temperature of the earth’s surface to decrease gradually from the equator toward the poles. The differences of tem- perature thus effected are further increased by the difference in the length of daylight and darkness. While the sun is shining on any part of the earth the air is gaining heat; when it is not shining the air is losing heat.. When the length of daylight exceeds that of the darkness, the gain exceeds the loss; when the darkness exceeds the day- light, the loss exceeds the gain. The excessively low temperatures that would result from the oblique rays in high latitudes are prevented by the great length of daylight during the short summers, thus allowing the sun to con- tinue heating the surface during longer periods. The warmest part of the day in high latitudes sometimes equals that in the equatorial regions. During the long winters, however, the continued loss of heat makes the cold intense. Hence in the tropics we find a continual sum- mer; in the temperate-zones, a summer and winter of nearly equal length; and in the polar zones, short, hot summers, followed by long, intensely cold winters. The true temperature of the air is ascertained by hang- ing a thermometer a few feet above the ground, so as to be shielded from the direct rays of the sun, and yet be in free contact on all sides with the air. 237. Manner in which the Atmosphere re- ceives its Heat from the Sun.—The atmosphere receives ‘its heat from the sun— (1.) Directly. As the sun’s rays pass through ‘the air, about 28 per cent. of the vertical rays are directly absorbed, thus heating the air. The remainder pass on and either heat the earth, or are reflected from its surface. (2.) From the heated earth. The sun’s rays heat the earth and the heated earth heats the air. It does this in three ways: (a.) By the air coming in contact with the heated earth. (b.) By the heated earth radiating its heat, or sending it out through the air in all directions. After the sun’s heat has been absorbed by the earth and radiated from it, a change occurs. which renders the rays much more readily absorbed by the air. (¢.) By the heat being reflected from the earth 11 : ® and again sent through the air. But little heat is imparted to the air in this way. It is mainly the aqueous vapor the atmosphere contains that absorbs the sun’s heat. Dry air allows the greater part of the heat to pass through it; therefore variations in the quantity of vapor in the air must necessarily produce corresponding variations in the distribution of heat. 238. Isothermal Lines are lines connecting places on the earth which have the same mean temperature. The Mean Daily Temperature of a place is ob- tained by taking the average of its temperature during twenty-four consecutive hours. The Mean Annual Temperature of a place is the average of its mean daily temperature throughout the year. If the physical climate were the same as the astronomical, the isothermal lines would coincide with the parallels of latitude. An inspection of the map of the isothermal lines shows that their deviations from the parallels, though well /~marked in all parts of the earth, are greatest in the north- ern hemisphere. Wherever, from any cause, the mean tem- perature of a place is higher, the isothermal lines are found nearer the-poles ; when lower, nearer the equator. The former effects are noticed~particularly in portions of the ocean traversed by warm currents; the latter, in crossing por- tions of the ocean traversed by cold currents. In the map of the isothermal lines the influence of elevation is re- moved by adding 1° for every 1000 feet of elevation. 239. Physical Zones.—The Physical Torrid Zone lies on both sides of the equator, between - the annual isotherms of 70° Fahr. The Physical Temperate Zones lie north and south of the Physical Torrid Zone, between the annual isotherms of 70° and 30° Fahr. The Physical Frigid Zones lie north and south of the Physical Temperate Zones, from the an- nual isotherms of 30° Fahr. to the poles. The greatest mean annual temperature in the ‘eastern hemisphere is found in portions of North Central Africa, and in Arabia near the Red Sea, in the southern part of Hindostan, and in the northern part of New Guinea and the neighbor- ing islands; in the western hemisphere, in the northern parts of South America and in Central America. ‘240. Modifiers of Climate:— The principal causes which prevent the isothermal lines from coinciding with the parallels of latitude are: (1.) The Distribution of the Land and Water Areas.—Land heats or cools rapidly, absorbing or emitting but little heat. This is because the land 90 PHYSICAL GEOGRAPHY. — has a small capacity for heat, and also because the heat passes through but a comparatively thin layer. Therefore,a comparatively short exposure of land to heat produces a high temperature, and a comparatively short exposure to cooling, a low temperature. Water heats or cools slowly, ab- sorbing or emitting large quantities of heat. This is because water has a great capacity for heat. The heat penetrates a comparatively deep layer, and then, too, as soon as slightly heated, the warm water is replaced by cooler water. Therefore, the water can be exposed to either long heating or long cooling without growing very hot or very cold. Hence, the land is subject to great and sudden changes of temperature; the water, to small and gradual changes. Places situated near the sea have, therefore, a more equable, uniform climate than those in the same latitude in the interior of the continent. The former are said to have an oceanic climate ; the latter, a continental climate. In the polar regions, a preponderance of moder- ately elevated land areas causes a colder climate than an equal arew of water, because land loses heat more rapidly than water. In the tropics, a preponderance of land areas causes a warmer climate than an equal area of water, because land gains heat more rapidly than water. (2.) The Distribution of the Relief Forms a the Land Masses. (1.) Elevation.—The temperature of the atmo- sphere rapidly decreases with the elevation. The decrease is about 3° Fahr. for every 1000 feet. The increased cold is caused as follows: (1.) Since the air receives so much of its heat indirectly from the earth’s surface, the farther we go upward from the surface, the colder it grows. (2.) In the upper regions of the atmosphere the de- creased density and humidity of the air prevent it from ab- sorbing either the direct rays of the sun, or those reflected or radiated from the earth. The effect of elevation is so powerful that on the sides of high tropical mountains the same changes occur in the vegetation that are observed in passing from the equator to the poles. (2.) Direction of the Slopes—That slope of an elevation on which the sun’s rays fall in a di- rection the more nearly at right angles to its sur- face will be the warmest. ~ In the northern hemisphere the southern slope of a hill is warmer in winter than the northern slope, because the rays fall more nearly at right angles to its surface, (3.) Position of the Mountain-Ranges,— A mountain-range will make the country near it warmer if the wind from which it shields it is cold; it will one it colder if such wind is warm. The position of the mountain-ranges of a country also greatly affects the distribution of its rainfall. Thus, the tropical Andes are well watered and fertile on their east- ern slopes, but dry and barren on their western. The pre- vailing moist trade winds, forced to ascend the slopes, deposit all their moisture on them in abundant showers, and are dry and vaporless when they reach the other side. (4.) Nature of the Surface—The temperature of a tract of land is greatly affected by the nature of its surface. If covered with abundant vege- tation, like a forest, or if wet and marshy, its sur- face heats and cools slowly, and has a compara- tively uniform temperature; but if destitute of vegetation, and dry, sandy, or rocky, it both heats and cools rapidly, and is sup ject to great extremes of temperature. (8.) Distribution of Winds and Moisture —The principal action of the winds, and their accom- panying moisture, is to moderate the extremes of temperature by the constant interchange between the heat of the equatorial and the cold of the polar regions. Both wind and vapor absorb and render latent large quantities of heat in the equa- torial regions, and give it out, in higher latitudes, on cooling. In cold countries the climate is ren- dered considerably warmer by the immense quan- tity of heat thus emitted by the condensed vapor. (4.) Ocean Currents.—Since the warm waters move to the polar regions, and the cold waters to the equatorial regions, the general effect of ocean currents on climate is to reduce the extremes of temperature. The combined effects of the action of the winds, moisture, and ocean currents are seen in the north- ern continents, whose western shores, under the in- fluence of the prevailing south-westerly winds, copious rains, and tropical currents, are consider- ably warmer than the eastern shores in the same latitude. The coasts of Great Britain are warm and fertile, while Labrador, in the same latitude, is cold and sterile. The island of Sitka, in the Pacific, is warmer than Kamtchatka from similar causes, —_c0t94 0o—_—_. CHAPTER III. The Winds. 241. Origin of Winds—Winds are masses of air in motion. They resemble currents in the ocean, and result from the same causes—differ- THE WINDS. 91 ences of density. caused by differences of tem- perature. d eee v — Md HEATED AREAZ yy LY jy Fig, 81. Origin of Winds, The equilibrium of the atmosphere is disturbed by differences of temperature as follows: When any area becomes heated, as at a a, Fig. 81, the air over it, expanding and becoming lighter, is pressed upward by the colder air which rushes in from all sides. Thus result the following currents: ascending currents, b 6, over the heated area ; lateral, surface currents, ¢ c, from all sides toward the heated area; upper currents, d d, from the heated area; and descending currents, ¢ e. It is the lateral currents which flow toward or from the heated area that are felt mainly as winds. The ascending currents rise until they reach a stratum of air of nearly the same den- sity as their own, and then spread laterally in all directions toward the areas where the air has been rarefied by the movements of the lat- eral surface currents, until they finally descend, and recommence their motion toward the heated area. These circulatory motions continue as long as the heated area remains warmer than surround- ing regions. In speaking of winds, reference is always made to the surface currents, unless otherwise stated. 242. Origin of the Atmospheric Circulation. — The hottest portions of the earth are, in general, within the tropics; hence in the equatorial regions ascending currents continually prevail. To sup- ply the partial vacuum so created, lateral sur- face currents blow in toward the equator from the poles, while the ascending currents, after reaching a certain elevation, blow as upper. cur- rents toward the poles. Thus result currents by which the entire mass of the atmosphere is kept in constant circulation, and an interchange effected between the air of the equator and the poles. The most important of these currents are the following: (1.) Polar currents, or the lateral surface cur- rents, which flow from the poles to the equator; and (2.) Equatorial currents, or the upper currents, ‘which flow from the equator toward the poles. It will be noticed that wherever the surface wind blows in any given direction, the upper wind blows in the opposite direction. In several instances the ashes of volcanoes have been carried great distances in directions opposite to that in which the surface wind was blowing. The smoke from tall chim- neys at first takes the direction of the surface wind, but rising, is soon carried in the opposite direction by the upper currents. The clouds are often seen moving in a direction opposite to that indicated by vanes placed on the tops of the houses. A current of air is named according to the di- rection from which tt comes; a current of water, according to the direction in which it is going. Thus, a north-east wind comes from the north- east; a north-east current of water goes toward the north-east. 243, Effect of the Earth’s Rotation on the Direction of the Wind.—Were the earth at rest, the equatorial and polar currents would blow due north and south in each hemisphere; but by the rotation of the earth they are turned out of their course in a manner similar to the oceanic currents already studied. The polar currents, as they approach the equa- tor, where the. axial velocity toward the east is greater, are left behind by the more rapidly moy- ing earth, and thus come, as shown in Fig. 83, from the north-east in the northern hemisphere, and from the south-east in the southern. The equatorial currents, under the influence of the earth’s eastward motion, are carried toward the east as they approach the poles, and thus come, as shown in Fig. 83, from the south-west in the northern hemisphere, and from the north-west in the southern. Wherever the polar winds prevail, their direc- tion, when unaffected by local disturbances, will be north-east in the northern hemisphere, and south- east in the southern. Near the equator their di- rection is nearly due east. Wherever the equatorial currents prevail, their direction will be south-west in the northern hemi- sphere, and north-west in the southern. In Fig. 82, the equatorial currents are repre- sented as continuing to either pole as upper cur- rents, and the polar winds as surface currents to the equator. If this were so, constant north-east- erly winds would prevail in the northern hemi- 92 PHYSICAL N. WIND. S. WIND. N. WIND. Fig. 82, Direction of Wind as Affected by Rotation. sphere, and constant south-easterly winds in the southern. Several causes, however, exist to pre- vent this simple circulation of the air between the equatorial and polar regions. The equatorial currents do not continue as upper eurrents all the way to the poles, but fall and become surface currents, replacing the polar winds, which rise and continue for a while toward the equator as upper currents. 244, Causes of Interchange of Surface. and Upper Currents.—The causes which produce this” shifting of the equatorial and polar currents are: (1.) The equatorial currents become cold— (a.) By the cold of elevation ; (6.) By expansion ; (c.) By change of latitude. The equatorial currents therefore fall and are replaced by the polar currents, which have been gradually ‘growing warmer by continuing near the surface of the earth. (2.) As the equatorial currents approach the poles they have a smaller area over which to spread, and, being thereby compressed, are caused to descend and become surface currents. This interchange between the equatorial and polar cur- rents takes place at about lat. 30°. It varies, however, with the position of the sun, moving toward the poles © when the sun is nearly overhead, and toward the equator when the sun is in the other hemisphere. The interchange in the position of the equatorial and polar currents is represented in Fig. 83. As the equatorial currrents fall, they divide, GEOGRAPHY. Zone of Variable Winds. Calms of Cancer. Zone of the North-east Trades. Zone of the Calms. A | Zone of the South-east Trades. * Calms of Capricorn. Zone of Variable Winds. y Zone of Polar Winds, s Fig. 88. Interchange of the Equatorial and Polar Currents, Wind Zones. part going to the poles, and part returning to the equator. The general system of the aérial circulation thus indicated is more regular over the oceans than over the land. Over the continents the greater heat of the land during summer causes a general tendency of the wind to blow toward the land; similarly, the greater cold of the land during winter causes a tendency of the wind to blow toward the sea. 245. Classification of Winds.—Winds are di- vided into three classes: (1.) Constant, or those whose direction remains the same throughout the year. (2.) Periodical, or those which, for regular pe- riods, blow alternately in opposite directions. (8.) Variable, or those which blow in any di- rection. ~ 246, Wind Zones.—The principal wind zones are the zone of calms, the zones of the trades, the zones of the calms of Cancer and Capricorn, the zones of the variable winds, and the zones of the ‘polar winds. Zone of Calms.—In parts of the ocean near the equator the ascending currents are sufficiently powerful to neutralize entirely the inblowing polar currents, and thus produce a calm, which, however, is liable at any moment to be disturbed by powerful winds. The boundaries,of the zone vary with the season; they extend from about 2° to 11° north latitude. THE WINDS. : 93 Zones of the Trades.—From the limits of the zone of calms to about 30° on each side of the equator the polar currents blow with great steadi- ness throughout the year. The constancy in their direction has caused these winds to be named “trade winds,” from their great value to com- merce. Their direction is north-east in the north- ern hemisphere, and south-east in the southern. Zones of the Calms of Cancer and Capricorn. —Between the zones of the trades and the vari- ables, where the interchange takes place between the equatorial and polar currents, zones of calms occur. Their boundaries are not well defined, and. are dependent on the position of the sun. Zones of the Variable Winds—Beyond the limits of the preceding zones to near the latitude of the polar circles, the equatorial and polar cur- rents alternately prevail. Here the equatorial and polar currents are continually striving for the mastery, sometimes one and sometimes the other becoming the: surface current. During these conflicts the wind may blow from any quarter; but when either current is once estab- lished it often continues constant for some days. This is especially the case over the ocean, where the modifying influences are less marked. Though the winds in these zones are variable, still two directions predominate: south-west and north-east in the northern hemisphere, and north- west and south-east in the southern. Westerly winds, however, occur the most frequently in nearly all parts of these zones. The equatorial currents are sometinfes called the Return Trades, or the Anti-trades, because they blow in the oppo- site direction to the trades. Between about lat. 25° and 40°, N. and S., over parts of the ocean, the winds are nearly periodical, blowing during the hotter portions-of the year in each hemisphere from the poles, and during the remainder of the year from the equator. This zone is often called the Zone of the Sub- tropical winds. Polar Zones.—From the limits of the zones of the variables to the poles, there are regions of pre- vailing polar winds. These winds are most fre- quently north-east in the northern hemisphere, and south-east in the southern. 247. Dove’s Law of the Rotation of the Winds.— The equatorial and polar currents usually displace each other, and become surface winds in a regular order, first discovered by Prof. Dove of Berlin. In the northern hemisphere, before the polar current is permanently established from the north-east, the wind blows in regular order from the west, north-west, and north. .The displacement of the polar by the equatorial currents occurs in the opposite direction: from the east, south-east, and south, before the general south-west current is perma- nently established. In the southern hemisphere these motions are reversed. This rotation of the winds, together with the effects produced on the thermometer and barometer, is indicated in the following diagram. Since the equatorial currents are warm, moist, and light, when they prevail the ther- mometer rises and the barometer falls. On the establish- ment of the polar currents, however, the thermometer falls and the barometer rises. NORTHERN HEMISPHERE, SOUTHERN HEMISPHERE. S. S. Fig. 84. Rotation of the Winds (after Dove), The “warm waves” of the zones of the variable winds are caused by the prevalence of the equa- torial currents. Similarly, the “cold waves” are caused by the prevalence of the polar currents. 248. Land and Sea Breezes——During the day the land near the coast becomes warmer than the sea. An ascending current, therefore, rises over the land, and a breeze, called the sea breeze, sets in from the sea. At night the land, from its more rapid cooling, soon becomes colder than the water; the ascending current then rises from the water, and a breeze, called the land breeze, sets in from the land. The strength of these winds de- pends upon the difference in the temperature of the land and water; they are, therefore, best de- fined in the tropical and extra-tropical regions, though they may occur in higher latitudes during the hottest parts of the year. Land and sea breezes are periodical winds. , 249. Monsoons are periodical winds, which dur- ing part of the year blow with great regularity in one direction, and during the remainder of the 140 10¢ IY ‘ 60 80 100 120 140 160 POLAIR ( NORTH ee WINDS AN - = L EY? 3 ye DRIZZLIN b G AUTUMN, WINTERS DRY. Vee oft TeleiRcle ae Z| BUT Gx NER Ble AN eee Tl Mee ans / 4 es f << UMS MAP OF THE WORLD 76 REFERENCES. ee 7 ae nA Gee | | BES Lquatorial Calms. (HEY Zones of the Variables. ae Lager with, c (=) Calms of tanceré Capricorn|__\ Zones of the Polarwinds. QCEAN ROUTES. 1 Zones of the Trades. (GMB) Monsoon Regions. LON|GITUDE WEST me GREENWICH LONGITUDE EAST FROM GREENWICH. 80 60 40 20 0 20 40 60 THE WINDS. 95 year in the opposite direction. They are in real- ity huge land and sea breezes, caused by the dif- ference in temperature between the warmer and colder halves of the year. They occur mainly in the regions of the trades, and are in reality trade winds which have been turned out of their course by the unequal heating of land and water. During winter, in either hemisphere, the oceans, being warmer than the land, cause a greater regularity in the trades; but during summer, the tropical continents become intensely heated, and their powerful ascending currents cause the equa- torial currents to blow toward the heated areas as surface winds, and thus displace the trades. The interval between the two monsoons is gener- ally characterized by calms, suddenly followed by furious gales, that may blow from any quarter. 250. Monsoon Regions.—There are three well- marked regions of monsoons—the Indian Ocean, the Gulf of Guinea, and the Mexican Gulf and Caribbean Sea. The first is the largest and most distinctly marked. Monsoons of the Indian Ocean.—Here the trades are deflected by the overheating of the continents of Asia, Africa, and Australia. In the northern hemisphere the north-east trades prevail with great regularity over the Indian Ocean during the cooler half of the year: from October to April, but during the warmer half: from April to October, the heated Asiatic continent deflects the trades, and the equatorial currents prevail from the south-west. The same winds also pre- vail south of the equator, on the western border of the ocean, along the eastern coast of Africa as far south as Madagascar. In the southern hemisphere, in the south-eastern portion of the ocean, the south-east trade is similarly deflected by the Australian continent. Here the winds blow south- east during the southern winter, and north-west during its summer. Monsoons of the Gulf of Guinea.—Here the north-east trades are deflected by the intensely heated continent of Africa. The south-west sum- mer monsoon blows over the land as far inland as the Kong Mountains. Monsoons of the Mexican Gulf and Caribbean Sea.—In this region the north-east trade winds are deflected by the overheating of the Missis- sippi Valley.. The Northers of Texas, which are cold winds blowing for a few days at.a time over the Texan and Mexican plains, may be considered as connected with the winter monsoons. Besides the preceding well-marked regions, nearly all the coasts of the continents in and near the tropics have small monsoon regions, as, for example, the western coasts of Mexico, the eastern and western coasts of South Amer- ica, and the western and northern coasts of Africa, 251, Desert Winds.—The rapid heating and cooling of deserts make them great disturbers of the regular system of winds. Currents al- ternately blow toward and from the heated area. The latter are intensely hot and dry. The Etesian Winds During summer the barren soil of the Desert of Sahara, becoming intensely heated, causes strong north-east winds to blow over the Mediterranean Sea. These are called the Etesian winds, and continue from July to September; they are strongest during the day- time. Hot Desert Winds.—F rom the Sahara a period- ical wind, called the Harmattan, blows on the south- west, over the coasts of Guinea; on the north, the Solano blows over Spain, and the Sirocco blows over Southern Italy and Sicily. Though some- what tempered during their passage across the Mediterranean, these winds dre still exceedingly hot and oppressive. From the deserts of Nubia and Arabia in- tensely hot, dry winds blow in all directions over the coasts of Arabia, Nubia, Persia, and Syria. These winds are known under the general name of the simoom or samiel. From their high tem- perature and the absence of moisture, they often cause death from nervous exhaustion. During the prevalence of the simoom, particles of fine sand are carried into the atmosphere and obscure the light of the sun. Becoming intensely heated, these particles, by their radiation, increase the temperature of the air, Fig. 86. “Sand Storm in the Desert, which sometimes rises as high as 120° or 130° Fahr. When powerful winds prevail, dense clouds of sand are carried about in the atmosphere, producing the so-called sand storms. The sand-drifts which are thus formed constantly change their position. 96 PHYSICAL GEOGRAPHY. The Khamsin blows at irregular intervals over Egypt from the south; but when established, generally continues for fifty days. It is intensely hot and dry, like the simoom, and is loaded with fine sand. : 252. Mountain Winds.—During the day the elevated slopes of mountains heat the air over them hotter than at corresponding elevations over the valleys. Currents, therefore, ascend the val- leys toward the mountains during the day. During the night, however, the air near the summits be- comes colder than that near the base. Currents, therefore, descend the valleys from the mountains during the night. —.09300—— CHAPTER bv; Storms. 2538. Storms are violent disturbances of the ordinary equilibrium of the atmosphere by wind, rain, snow, hail, or thunder and lightning. During storms the wind varies in velocity from that of a scarcely perceptible breeze to upwards of 200 miles per hour. VELOCITY AND POWER OF WINDS. Velocity of Wind in Miles, per hour. Common Names of Winds. 5 3 1 Hardly Perceptible Breeze, _ 4605 Gentle Wind. 10 to 15 Pleasant Brisk Gale. 20 to 25 Very Brisk. 30 to 35 High Wind. 40 Very High. 50 Storm. 60 Great Storm. 80 Hurricane. 100 Violent Hurricane. 80 to 200 Tornado. 254. Cyclones are storms of considerable ex- . tent, in which the velocity of the wind is much greater than usual, and the air moves in eddies or whirls, somewhat similar to whirlwinds, but of vastly greater power and diameter. In all such storms the wind revolves around a calm centre; over the calm centre the barometer is low, but on the sides, and especially on that side toward which the storm is moving, it is high. Besides the rotary motion of the wind, there is also a progressive motion, which causes the storm to advance bodily, moving rapidly in a parabolic path. The general term Cyclone has been ap- plied to these storms on account of their rotary motion. They have also various local names. Cyclones originate in the tropical regions, but frequently extend far into the temperate zones, Fig, 87, A Storm at Sea, 255. Regions of Cyclones.—The following are the most noted regions: The West Indies, where they are generally . called hurricanes. The China Seas, where they are known as typhoons. The Indian Ocean. In each of these regions the storms occur about the time of the change of the regular winds, and have their origin in marked differences of tem- perature; thus in the Indian Ocean and the China Seas, they generally occur at the change of the mon- soon, after the great heat of summer. They are at- tended with the condensation of moisture and in- tense electrical disturbance. 256. Cause of Cyclones.—Cyclones originate in an area of low barometer caused by the ascending. current of air that follows the overheating of any region. As the air rushes in from all sides it is deflected by the earth’s rotation, and assumes a rotary or whirling motion around the heated area. The centrifugal force generated by this rotation causes the barometric pressure of the area to be- come lower and the area to grow larger. Mean- while the inflowing air, ascending, is chilled by the cold of elevation and by expansion sufficiently to condense its vapor rapidly. The heat energy, previously latent in the vapor, is now disengaged, and causes the air to mount higher and condense still more of its vapor. It is to the energy thus rapidly liberated by the condensation of the vapor that the violence of the cyclone is due. Cyclones, therefore, acquire extraordinary violence only when an abundance of vapor is present in the air. STORMS. 97 As the inblowing winds come near the heated area, they must blow with increased violence in order to permit the same quantity of air to pass over the constantly narrowing path. Besides the rotary motion of the wind, the storm moves or progresses over a parabolic path, which in the tropics is generally toward the west, and in the temperate zones toward the east. This progressive motion of the storm is like'the similar July to October. Q5° “ 30° “ 35° 40° « 45° “ce Fig. 88. Chart showing Path and Direction of Cyclone. motion often noticed in a rapidly spinning top. It is due to the combined influences of the inrush of air, the earth’s rotation, and centrifugal force. 257. Peculiarities of Cyclones.—Cyclones rage most furiously in the neighborhood of islands and along the coasts of continents. They are most powerful near their origin. As they advance the spiral increases in size and the fury of the wind gradually diminishes, because the amount of moist- ure in the air is less. The rotary motion varies from 80 to 100 miles an hour. The progressive motion of the calm centre is more moderate— from 20 to 50 miles an hour. This progressive motion is least in the tropics and greatest in the temperate regions. The wind invariably rotates in the same direc- tion in each hemisphere; in the northern, it ro- tates from right to left, or in the direction oppo- site to that of the hands of a watch ; in the south- ern, from left to right, or in the same direction as the hands of a watch. The cause of the regu- NORTHERN HEMISPHERE, °%, te, 0 x + 2 Yor 0} yoo¥ SOUTHERN HEMISPHERE. R, Rag, ° burn ous e x 40 Suan 04 ae “Pig, 89, Cause of the Rotation of the Wind, larity of rotation is seen, from an inspection of Fig. 89, tb, be due to the rotation of the earth. The wind, blowing in from all sides toward the heated area, is so deflected by the rotary motion of the earth as to move in vast circles, from right to left in the northern hemisphere, and from left to right in the southern. The force of the wind in these storms is tremendous. So furiously does the wind lash the water that its tem- perature is often sensibly raised by the friction. The intelligent navigator always endeavors to avoid the centre of the storm, since it is the most dangerous part. This he can do by remembering the direction of the rota- tion of the wind in the hemisphere he may be in; for if, in the northern hemisphere, he stands so that the wind blows directly in his face, the calm centre is on his right, while in the southern hemisphere #¢ és on his left; and in- stead of running with the storm, hoping to outsail it, he will boldly steer toward its circumference. 258. Tornadoes and Whirlwinds are the same as cyclones, except that they are more limited in area. Their violence, however, often exceeds that 98 PHYSICAL GEOGRAPHY. of cyclones. Tornadoes appear to be due to ro- tary motion of the air occurring above the earth’s surface, which results in a rapid sucking up of the warmer surface air. 259. Water-spouts.— When tornadoes or whirl- winds occur on the water they cause a water-spout. A rapid condensation of vapor takes place, both from the different temperature of the winds and from the rarefaction produced at the centre of the revolving mass of air. Portions ofthe clouds are sometimes drawn down from above and whirled around in the form of an immense funnel-shaped mass; finally the whirl reaches the water, and a column of spray is thrown up, which unites with the mass above and moves over the surface of the water ‘as an immense pillar. Though of formidable ap- pearance, water-spouts have never been known seriously to damage large vessels. Similar phenomena are noticed on the land when tornadoes occur. Here, however, only the cloud cone is observed. 260. The North-Easters and other Storms of the United States—The following important facts have been discovered in regard to the extended storms which occur in the United States: (1.) All our great storms are attended by an immense whirling of the wind, and are, in fact, species of cyclones. (2.) The great north-east storms of our eastern sea-board usually originate in the west, in an area of low barometer, somewhere between Texas and Minnesota. In the front and rear of this area the barometer is high. (8.) The calm centre of the storm, or the area of low barometer, usually moves toward the north- east. The shape of the calm centre is longer from north to south than from east to west. (4.) The storms begin by the winds blowing toward the area of low barometer. (5.) During the prevalence of the storm the winds are north-east, east, or south-east; toward the end, north-west, west, and south-west. 261. Sailing Routes.—A knowledge of the di- rections of the winds and ocean currents has ma- terially diminished the time required by sailing vessels to go from one port to another. Opposing. winds and currents often render it advisable for the vessel to begin its journey in a direction consider- ably out of the direct line of the desired port. Hurope—America.—The Gulf Stream and prevailing westerly winds render the passage across the ocean from east to west considerably longer than from west to east. The general route, in either direction, varies with the season of the year. : New York—San Francisco.— After leaving New York the course is considerably to the east, in order to clear the South American coast in the region of the trades. After doubling Cape Horn the course is westward. The zone of the north-east trades is entered about 118° W. long. America—India—Australia.—In sailing from Amer- ica to India or Australia the vessel takes the same route as between Eastern America and San Francisco. About opposite Rio Janeiro, however, the routes diverge. On entering the Indian Ocean the direction is dependent on that of the prevailing monsoon. Europe—India—Australia.—The vessels either pass through the Mediterranean Sea and the Suez Canal, or around the Cape of Good Hope. The broad expanse of ocean in the southern hemisphere, in the zone of the vari- ables, renders the westerly winds very steady. Vessels sail- ing from Atlantic ports of America or Europe generally find it preferable to go by the eastward route, around the Cape of Good Hope, and return by the westward route, around Cape Horn, thus circumnavigating the globe. California—Japan.—The southerly route, from east to west, is aided by the north-east trades and the north equa- torial current of the Pacific; the northerly route, from west to east, is necessary in order to avoid the trade winds. ; The general sailing routes hetween some of the most important ports are traced on the map of the winds. 2 PIA SYLLABUS. 0028300 — Atmospheric air is composed mainly of a mixture of ni- trogen and oxygen, in the proportion, by weight, of about 77 parts of nitrogen to 23 of oxygen in every hundred parts. The atmosphere also contains small quantities of carbonic acid and the vapor of water. The oxygen of the air is necessary to combustion and respiration; the carbonic acid and the vapor of water, to plant-life. At the level of the sea the atmosphere presses on every square inch of the earth’s surface with a force of about 15 pounds. The upper limit of the atmosphere has been variously estimated at from 50 to 200 miles above the level of the sea. A barometer is used for measuring the pressure of the at- mosphere; a thermometer, for measuring its temperature. The vertical rays of the sun are warmer than the oblique rays—l. Because they are spread overa smaller area of the earth. 2. Because they pass through a thinner stratum of air, and consequently lose less of their heat by absorption. 3. Because they strike the earth more directly, and there- fore produce more heat. . REVIEW QUESTIONS. 99 Continual summer is found in the tropics; summer and winter of nearly equal length in the temperate zones; short, hot summers, followed by intensely cold winters, in the polar zones. The atmosphere is heated—1. Either by direct absorp- tion of the rays while passing through it; or 2. By con- tact with, or by radiation and reflection from, the heated earth. -Isothermal lines connect places whose mean temperature is the same. The mathematical zones are bounded by the parallels of latitude; the physical zones, by the isotherms. The mathematical and physical zones do not coincide— 1. Because of the unequal distribution of the land and water areas. 2. The irregularities in the surface of the land. 3. The distribution of the winds and moisture. 4. The ocean currents. 5. The difference in the rainfall. The temperature of the air decreases with the altitude ~ —1, Because the air receives most of its heat from the earth’s surface, so that it must grow continually colder the farther we go above the surface. 2, The decreased den- sity and humidity of the air prevent it from absorbing either the direct rays of the sun or those reflected or ra- diated from the earth. ‘ Places situated near the sea have a more equable, uni- form climate than those in the same latitude in the inte- rior of the continent. Whenever any part of the earth’s surface is heated more than the neighboring parts, ascending currents occur over the heated area, lateral surface currents blow in toward the heated area, and upper currents blow from the heated area. The general system of the atmospheric circulation con- sists mainly of the following currents: 1. The polar cur- rents, blowing from the poles toward the equator. 2. The equatorial currents, blowing from the equator toward the poles. The direction of these currents is modified by the rota- tion of the earth. Thus modified, the equatorial currents are south-west in the northern hemisphere, and north- west in the southern. The polar currents are north-east in the northern hemisphere, and south-east in the south- ern. When a wind at the surface blows in any direction, there is generally an upper current blowing in the opposite di- rection, The equatorial currents do not continue as upper cur- rents to the poles—1. Because they become cooled and fall. 2. From the contracted space of the higher latitudes when compared with that of the equator. We distinguish the following wind zones: the zone of calms; the zones of the trades; the zones of the calms of Cancer and Capricorn; the zones of the variables; and the zones of the polar winds. Land and sea breezes are caused by the unequal heating of the land and water during day and night; monsoons, by their unequal heating during summer and winter. Monsoons occur on the coasts of tropical countries within the limits of the trade zones. They are most frequent in the Indian Ocean, in the Gulf of Guinea, and in the Mex- ican Gulf and neighborhood. The Etesian Winds blow over the Mediterranean toward the Desert of Sahara. The Hot Winds caused by the deserts of Sahara and Arabia are the Harmattan, over Guinea; the Solano, over Spain; the Sirocco, over Italy; the Simoom, over Arabia, Nubia, and Persia; and the Khamsin, over Egypt. In most mountainous regions winds blow up the valleys toward the mountains during the day, and down the val- leys from the mountains during the night. Cyclones are caused by the wind blowing in from all sides toward an area of low barometer caused by the overheating of the area. The centrifugal force thus gen- erated increases both the size of the area and the differ- ence of pressure as compared with regions surrounding it. The fury of the storm is increased by the heat energy liberated by the condensation of the vapor in the uprush- ing air. Storms occur whenever the ordinary equilibrium of the atmosphere is violently disturbed by wind, rain, snow, hail, or thunder and lightning. Nearly all powerful storms are attended with a rotation of the wind. Such storms are known under the general names of Cyclones, Hurricanes, Typhoons, and Tornadoes. The north-easters and other great storms of the United States are species of cyclones. REVIEW QUESTIONS. ——-059500-——— Of what use is the atmosphere in the economy of the earth? Define meteorology. Describe the construction of a barometer. What proof have we that the greater part of the atmo- sphere, by weight, lies within a few miles of the earth’s surface ? Define hypsometry. Describe the construction of a thermometer. Why are the vertical rays of the sun warmer than the oblique rays? What is the characteristic climate of the tropics? Of the temperate regions? Of the polar-regions? In what different ways does the atmosphere receive its heat from the sun? State the boundaries of the mathematical torrid zone. Of the physical torrid zone. Of the mathematical and physical temperate zones. Of the mathematical and phys- ieal frigid zones. 12 In what parts of the eastern hemisphere is the greatest mean annual temperature found? In what parts of the western hemisphere? What influence is produced on the climate of high lati- tudes by a preponderance of moderately elevated land masses? On the climate of the tropics? Why should the temperature of the atmosphere decrease with the altitude? Name all the causes which prevent the mathematical climatic zones from coinciding with the physical climatic zones. ~ What is the origin of winds? Name the currents of which the atmospheric circulation principally consists. Explain the action of the rotation of the earth on the direction of the equatorial and polar currents. Name the causes which produce the shifting of the equa- torial and polar currents. 100 PHYSICAL GEOGRAPHY. Name the principal wind zones of the earth. Explain, in full, the origin of land and sea breezes. In what respect do monsoons resemble land and sea breezes? Name the principal monsoon regions of the earth. Describe the origin of desert winds? Name the winds which are caused by the desert of Sa- hara. By the deserts of Arabia and Nubia. What are storms ? . What are cyclones? Where do they originate? In what direction does the wind rotate in the northern hemisphere? In the southern hemisphere? In what di- rection does the storm progress in each hemisphere? Ex- plain the cause of the rotation of the wind. What are hurricanes? Typhoons? Explain the formation of a water-spout. Is the water in the upper part of a water-spout salt or fresh? Name the important facts which have been discovered respecting the north-easters and other severe storms of the United States. MAP QUESTIONS. —— 0294 0o———_ Trace on the map of isothermal lines the areas of great- est heat in the eastern hemisphere. In the western hemi- sphere. Show from the map of the isothermal lines. wherein the physical torrid zone differs in position from the mathematical torrid zone. In which hemisphere do the isothermal lines deviate more from the parallels of latitude, in the northern or the southern ? Trace on the map of the isothermal lines the limit of the Arctic drift ice. Of the Antarctic drift iee. What are the mean summer and winter temperatures of Sitka? Of Quebec? What causes exist to render the climate of Sitka so. much warmer than that of Quebec, notwithstanding the difference of their latitudes? What are the mean summer and winter temperatures of Mexico, Madras, Singapore, Berlin, London, Philadelphia,— Algiers, Melbourne, and Rio Janeiro?” What instances can you find on the map of the in- crease in the mean annual temperature of places through the influence of ocean currents? Of winds? Of rain- fall ? ~Name similar instances of places whose mean annual temperature is lowered by such causes. Trace on the map of the winds the boundaries of the various wind zones. State the direction of the wind in each of these zones. Point out the limits of the monsoon regions of the world. What hot winds blow over Arabia? Over Egypt? Over Greece and Italy? Over Guinea? What cold wind blows over Texas? Describe the path of the West India hurricanes. How far to the north do these storms extend ? Describe the path of the Mauritius hurricanes. Where do these storms criginate? How far to the south do they extend ? Describe the region of the typhoons. Describe the route a vessel would take in sailing from America to Europe. From New York to San Francisco. From America to Australia. PRECIPIRATION) OF MOISTURE. GHAPTER, i Precipitation of Moisture. 262. Evaporation—F rom every water surface, and even from masses of ice and snow, there is constantly arising, at all temperatures, an invisible vapor of water. Water vapor is about three-fifths as heavy as air. It diffuses readily through the air, and is borne by the winds to all parts of the earth. This giving off of vapor from the surface of water is called evaporation. It is evaporation which dries the wet earth, when the moisture is unable either to pass off the earth’s surface by drainage, or to soak through the porous strata. About one-half, by weight, of the vapor of the atmo- sphere is within a little over a mile above the mean sea level. 263. The Rapidity of Evaporation is influ- enced by the following circumstances: (1.) The temperature of the atmosphere. The capacity of the air for absorbing moisture in- creases with an increase of temperature. Warm air can retain more vapor than cold air. (2.) The extent of surface exposed. Evapora- tion takes place only’from the surface; therefore, the greater the surface, the greater the evapora- tion. (3.) The quantity of vapor already in the air. Dry air absorbs moisture more rapidly than moist air. All evaporation ceases when the air is com- pletely saturated. (4.) The renewal of the air. During very calm weather, the air in contact with a water surface becomes saturated, and so prevents further evapo- ration. Gentle breezes, by renewing the air, in- crease the rapidity of evaporation. (5.) Pressure on the surface. A diminished atmospheric pressure increases the rapidity of evaporation. 264, The Dew Point.— When the air contains as much vapor as it is capable of holding, it is said to be at tts dew point. The quantity of moisture necessary to saturate a given quantity of air and bring it to the dew point, varies with SeCTLO Nee MOISTURE OF THE ATMOSPHERE. 2038300 the temperature. Cold air requires less moisture to satu- rate it than air which is warmer, and, therefore, may feel damper than warm air, which may contain more vapor. We thus distinguish between the actual humidity, or the . amount actually present in a given volume of air, and the relative humidity, or the relation between the amount present and that required to saturate the air at the given temperature. The humidity of the air is determined by means of an instrument called a hygrometer. Weight in grains of aqueous vapor in ONE cubic foot of SATURATED AIR at different temperatures. (Silliman.) Temperature, Fahr. Weight in Grains. Approximate Values, 0° 0.545 0.6 10° 0.841 0.9 20° 1.298 1.3 30° 1.969 2.0 40° 2.862 2.9 50° 4.089 4.1 60° 5.756 5.8 70° 7.992 8.0 80° 10.949 11.0 90° 14.810 15.0 100° 19.790 20.0 No matter how much aqueous vapor a given quantity of air contains, if its temperature be lowered, tt will grow relatively moister until, if the fall of temperature be sufficient, its dew point is reached; and as soon as the temperature falls below the dew point, a deposition of moisture will begin, either in the liquid or solid state. 265. Precipitations.—The invisible vapor may be precipitated from the atmosphere and become visible, either as dew, mist, fog, cloud, rain, sleet, hail, or snow. These are called precipitations. Law of Precipitations. In order that any precipitation may occur, the air must be cooled below the temperature of its dew point. 266. Distribution of Precipitations—The quan- tity of moisture in the air depends on its tempera- ture, and its vicinity to the sea. The amount of precipitation regularly decreases as we pass from the equator to the poles, and from the coasts of the continents toward the interior. 267. Dew.—If, during a warm day, a dry glass be filled with cold water, the outside of the glass will soon become covered with small drops of water, derived entirely from the air. The air 102 PHYSICAL GEOGRAPHY. which comes in contact with the cool sides of the glass has its temperature lowered below the dew point, and deposits as vapor the moisture it no longer can retain. The dew which is deposited during certain sea- sons of the year on plants and other objects on the earth, has a similar origin. Objects on the earth cool more rapidly than the surrounding air, which deposits its moisture on them whenever they lower its temperature below the dew point. When the objects are colder than 82° Fahr., the dew is deposited as hoar-frost. Dew falls or is deposited more heavily on some objects than on others; this is because some ob- jects radiate or give off their heat more rapidly than others, and thus becoming cooler, they con- dense more of the moisture of the air. More dew is deposited during a clear night than during a cloudy one, because objects cool more rap- idly when the sky is clear than when it is cloudy. Thick clothing keeps the body warm, not because the clothes give any heat to the body, but because they are non- conductors,and prevent the escape of heat from the body. In like manner the clouds, acting as blankets to the earth, prevent its losing heat rapidly. More dew falls or is deposited during a still night than during a windy one. The air must remain long enough in contact with cold objects to enable them to lower its tem- perature and collect its moisture. Powerful winds prevent this, while gentle breezes favor the depo- sition, by bringing fresh masses of air into contact with the cold objects. In the tropics, during seasons when the sky is clear, the dew is so copious that it resembles a gentle rain. In the deposition of dew, the moisture is derived from a comparatively thin stratum of air in the immediate neigh- borhood of the cool object. All other kinds of precipita- tions are produced by the cooling of a large mass of air. “~ 268. Fogs and Clouds—Whenever the tem- perature of a large mass of air is reduced below its dew point, its moisture begins to collect in minute drops, which diminish the transparency of the air, and form fogs or mists, when near the surface, and clouds, when in the upper regions of the atmosphere. fogs and clouds are the same in their origin and composition, and differ only in their elevation. The minute drops of water that form clouds and fogs, though formed of a substance about eight hundred times heavier than air, are pre- vented from settling rapidly by the resistance of the air. This is rendered possible by the minute size of the drops, which are much smaller than the relatively heavier dust-particles, which are wafted about by the winds. Whenever the drops exceed a certain size, they fall as rain or snow.** It was once believed that the moisture in fogs and clouds existed in the form of hollow bubbles or vesicles, filled with air, and that the clouds or fogs ascended, whenever the contained air expanded the bubbles and rendered them specifically lighter. This idea is now generally abandoned. Clouds or fogs result whenever a mass of air is cooled below the temperature of its dew point, as, for example, when two bodies of air of dif- ferent temperatures are mingled, especially if, as is generally the case, the warmer of the two is the moister. On the contrary, clouds or fogs disappear on the approach of a dry, warm wind. Clouds are higher in the tropics than in the polar regions, and generally are higher during the day than during the night. Off the banks of Newfoundland, the warm, moist air of the Gulf Stream is cooled by the cold, moist air of~the Labrador ocean current. Hence result the dense fogs so frequent over this part of the ocean. ‘_ 269. Classification of Clouds—Clouds assume such a variety of shapes, that it is difficult to classify them. Meteorologists, however, have rec- ognized the existence of four primary forms: the cirrus, the cumulus, the stratus, and the nimbus. : = Fig. 90. Primary Forms of Clouds, ~v Cirrus. ~ + Cumulus. The Cirrus Cloud consists of fleecy, feathery masses of condensed vapor, deposited in the higher regions of the atmosphere. The name cirrus is derived from the resemblance the cloud bears to a lock of hair. These clouds are called PRECIPITATION OF MOISTURE. 103 by sailors cats’ tails or mares’ tails. From their elevation, the moisture is, probably, generally in the condition of ice-particles. Halos, or circular »bands of light around the sun, are caused by light passing through cirrus clouds. The Cumulus, or Heap Cloud, is a denser cloud than the cirrus, and is formed in the lower re- gions of the air, where the quantity of vapor is greater. Cumulus: clouds generally consist of rounded masses, in the shape of irregular heaps, with moderately flat bases. They are caused by ascending currents of air, which have their moist- ure condensed by the cold produced by expan- sion and elevation. Cumulus clouds occur dur- ing the hottest part of the day. Their height seldom exceeds two miles. Fig, 91. Primary Forms of Clouds, ~ Nimbus. + ~ Stratus. The Nimbus, or Storm Cloud, is any cloud from which rain falls. Any of the various forms of clouds may collect and form a nimbus cloud. The nimbus is not considered as a distinct form of cloud by some meteorologists. The Stratus, or Layer Clouds, form in long, horizontal sheets or bands. These clouds are most common in the early morning and evening, when the ascending currents are weak. They are caused by the gradual settling of cumulus and other clouds. The stratus is the lowest form of cloud; it sometimes falls to the surface of the earth, and becomes a fog. The cirrus, stratus, and cumulus clouds assume a variety of shapes, producing various secondary forms. 270. Secondary Forms of Clouds.—The cirro- stratus, the cirro-cumulus, and the cumulo-stratus are the most prominent secondary forms of clouds. ‘The first two are modifications of the cirrus cloud; the latter, of the cumulus. Fig, 92, Secondary Forms of Clouds. ~ Cirro-Cumulus. ~ +-Cirro-Stratus. ~~~ Cumulo-Stratus. The Cirro-Cumulus is a cirrus cloud, arranged in little rounded masses, shaped something like cumuli. They are sometimes called “ wool sacks,” and indicate dry weather. The Cirro-Stratus is a cirrus cloud which has settled in bands or layers. The bands are not continuous, but are arranged in blotches or bars, and often give to the sky the speckled appear- ance of a mackerel’s back, producing the so-called mackerel sky. The appearance of a mackerel sky indicates—1. That the moisture of the upper strata of air is condensing; 2. That it is growing dense enough to arrange itself in layers. Therefore, a mackerel sky generally indicates approaching rain. The Cumulo-Stratus is the form produced by _ the heaping together of a mountain-like mass of cumulus clouds; the. base partakes of the nature of the stratus cloud, but the top clearly resembles cumuli. These clouds differ but little from the nimbus, or storm cloud. 271. Rain—When, during the formation of a cloud, the condensation of moisture continues, the drops of which the cloud is composed increase in size, and, uniting, fall to the earth as rain. Rain which freezes while falling forms sleet. As 104. PHYSICAL GEOGRAPHY. the drops fall through the cloud they grow larger by the addition of other drops which unite with them. Raindrops, therefore, are larger when the clouds are thicker. They are, in general, larger in the tropics than in the polar regions, and dur- ing the day than at night. To produce rain, it is necessary that the tem- perature of a large mass of air be reduced con- siderably below its dew point. There are several ways in which this cooling may be effected: (1.) By a change of latitude. A warm, moist- ure-laden wind may blow into a cold region. The equatorial currents of air deposit their moisture in the temperate and polar zones on account of the chilling experienced as they recede from the equator. (2.) By a change of altitude. By an ascending current of air, which carries the moisture of the lower strata into the upper regions, where the cold there existing, together with that produced by the rapid expansion of both air and vapor under the diminished pressure, condenses the moist- ure of the air. It is mainly in this manner that the rains of the tropical regions are caused. The rain in mountainous districts has a similar cause. A moist wind, reaching a mountain-range, is forced by the wind back of it to ascend the slopes. Contact with the cold, upper slopes causes condensation of the vapor as rain. (3.) The mingling of masses of cold and warm air. By this means heavy clouds and a moderate rainfall may be produced; but the precipitation can never be considerable, because the cooler air will be warmed by the mixing, and, therefore, will have its capacity for moisture increased in- stead of diminished. 272. Distribution of the Rainfall—The dis- tribution of rain may be considered both as re- gards its periodicity and its quantity. The distri- bution of the rain is dependent upon the direction of the winds. Each wind zone has a character- istic rainfall. The following simple principles determine the rainfall in any particular wind zone: (1.) The equatorial currents are rain-bearing, because they are moist, and while on their way to the poles, their temperature and consequent capacity for moisture, is constantly decreasing. (2.) The polar currents are dry, because they are constantly increasing in temperature as they approach the equator; hence they take in, rather than give out, moisture. When they have reached the zones of the trade winds, the polar currents may bring abundant rains, provided they have previously crossed an ocean. They then dis- charge the moisture with which they are saturated, either by an ascending current, or by blowing against the ele- vations of the continent. 273. Periodical Rain Zones. The Zone of Calms.—In the zone of calms it rains nearly every day. In the early morning the sky is cloudless; but near the middle of the day, as the heat increases, the ascending currents, rising higher, begin to condense their moisture ; cumuli clouds form, and, increasing rapidly, soon cover the sky, when torrents of rain descend, ac- companied by thunder and lightning. After a few hours the rain ceases, and the sky again be- comes clear. In this zone it seldom rains at night. 274, The Zone of the Trades.—Since the trades are generally dry winds, it is only when their tem- perature is considerably decreased that they can cause rain. In the zone of the trades, except in mountainous districts and on the windward coasts of a continent, the rainfall occurs during the greatest heat of the season, when the sun is di- rectly overhead and the ascending currents are powerful. Hence, it rains during a few months in summer, when immense quantities of water fall; the remainder of the year is dry. Copious dews, however, occur at. night. The precipitation is not continuous throughout the en- tire summer. Since the rain only falls when the sun is nearly overhead, a brief interval of dry weather occurs in regions near the equator, thus dividing the season into two parts: one, during the passage of the sun over the zenith; the other, on his return to the zenith from the adjacent tropic. Near the limits of the zone, however, the two seasons are merged into one. Over the ocean, during most of the year, there is no rain in the zone cf the trades, although the actual humidity of the air is quite high. Between latitude 24° and 30°, in both the Northern and Southern Hemispheres, there are regions of comparatively scanty rains. Here the summers are not hot enough to cause rain by the ascending currents, but are sufficiently hot to prevent the equatorial current from bringing much rain. Here also the return branch of the equatorial cur- rent becomes drier on its return to the equator. 275. The Monsoon Region of the Indian Ocean.-~ During the prevalence of the winter monsoon, the north- east winds bathe the eastern shores of Hindostan in copious rains, while the western shores, shielded by the ranges of the Ghauts, are dry. During the summer monsoon, the south-west winds bathe the western shores and the south- ern slopes of the Himalayas in heavy rains, while the eastern shores are dry. This monsoon also brings rains to the western coasts of the peninsula of Indo-China. , PRECIPITATION OF MOISTURE. 105 276. Non-Periodical Rain Zones. The Zones of the Variable Winds.—In these zones rain may occur at any season of the year, and at any hour of the day or night. Here it is the equatorial currents which bring the rain. These regions are sometimes called the zones of perennial rains, or of constant precipitation. In the greater part of these zones, the equatorial currents are more frequent in summer than in winter. The rainfali is, therefore, greatest dur- ing summer. Rainfall in the Zone of the Polar Winds—In these zones the winters are dry, because the dry, cold polar currents then prevail; but during the summer the equatorial currents sometimes pre- vail, and bring with them dense clouds and fogs, accompanied by drizzling rains. The snows occur mainly in spring and autumn. ‘~ 277, Quantity of Rain—The quantity of rain which falls in a given time on any area is deter- mined by means of an instrument called the rain- gauge or pluviometer. The rain-gauge is generally constructed in the form of a cylindrical vessel with a horizontal base, surmounted by a funnel-shaped top. A vertical glass tube communi- cates with the bottom of the vessel from the outside, and allows the water to mount in it to the same height as that in the inside. The rain-gauge is placed in an ex- posed position, where it is free from eddies or whirls. If, during any given time, the water in the instrument is one inch deep, then during that time the rainfall over the area equals one inch. In speaking of the rainfall of a country, the moisture which may fall as snow is always included. An inch of rain over a surface a square yard in area equals in weight 46 pounds: on the sur- face of an acre, it is nearly equal in weight to 100 tons. The annual rainfall is distributed, as regards quantity, as follows: Irrespective of the elevations of the surface, more rain falls in the tropies than in the temperate regions, and more in the temperate than in the polar regions. The quantity thus decreases with moderate regularity from the equator toward the poles. This is caused by a similar decrease in the quantities of heat and evaporation. While the amount of rain that falls decreases from the equator to the poles, the number of cloudy or rainy days increases, being greater at the poles than at the equator. More rain falls on the coasts of a continent than in the interior, since near the ocean the winds are moister. That coast of a continent which first receives the prevailing. wind has the greatest rainfall. More rain falls in the Northern Hemisphere than in the Southern. This is due to the greater extent of the land-area of the Northern Hemisphere. Mountains receive a heavier rainfall than the plains below, because the moist winds, in order to cross the mountains, are forced to ascend their slopes and thus pass into a colder region of the atmosphere. Therefore, the sources of rivers are generally found in mountainous districts. Moun- tains are among the most important causes of rain. When the mountains are high, the winds may reach the opposite slopes dry and vaporless. The tropical Andes of South America afford an excel- lent example of this. Plateaus, though higher than plains, receive, as a rule, less rain, because they are generally sur- rounded by mountain chains, which rob the winds of their moisture. Moreover, the air over a pla- teau is warmer than at a corresponding height in the atmosphere, and therefore dissolves, rather than condenses, the moisture. The rainfall of the New World, both in the tropical and temperate regions, ts greater than that of the Old; thus, in the tropics of the New World, 115 inches of rain fall yearly, while the same portions of the Old World receive but 77 inches.. In the temperate zones in America the annual rainfall is 39 inches, while in Europe it is but 84 inches. The mean annual rainfall at Philadelphia, according to Prof. Kirkpatrick, is 46.93 inches. The figures are based on observations during 16 consecutive years. The preceding principles find ample illustration in the following tables: TABLE OF ANNUAL RAINFALL (H. K, Johnston). Rainfall in the Tropics. OLD WORLD. Inches. Hindostan, mean of t! Sierra Leone, Guinea.... Macao, China NEW WORLD. San Luis de Mararhio, Brazil Cayenne, Guiana Paramaribo, Guiana, Grenada, Lesser Antilles.. . LA Vadis CUDBsccctsesscoedeecessesevescccdosesnbesdistcsiescocese’ 106 PHYSICAL GEOGRAPHY. Rainfall in the Temperate Zone. EUROPE. Inches. Inches. Madeira. ............+++0+029.82 | Southern France........ 23.54 Sicilyno iit aoncisisencees 23.55 | Southern Germany.....26.64 W. side of Apennines..35.17 | Netherlands .............. 26.70 E. ef ee ..26.70 | British Islands, Plain..27.00 Sere eo SAI DSio. Sieeee 57.87 ff i Mts....50.00 N. MS Pacskessccests 35.27 | W. Coast Scandinavia..82.12 Mean Rainfall in Europe in the Temperate LONG sccrssceeaetccwesueseecses mi Sacwmaneaaweasstertsnnestese 34 inches. AMERICA. Inches Rey. West, Bloridaiveccc.csves21s veccetnocsstcesisascceseseccats 35.26 Charleston, S. C....... --47.60 Washington, D. C.. ‘ Marietta, Ohio......... West Chester, Penna... Cambridge, Mass...... 600 ins. == 500 “ 400 “ 301 ins. 300 “ 200 “ 100 « OES ins. 82 ins. Burlington, Vt... 39.44 Eastport, Maine... 36.28 New York.... Sea cceecertatts Siincitccereteee ncsoeesaes 36.28 Mean Rainfall in the United States in the Temperate Zone, ....ccasccssssecssacsesscsssecssenedes 89 inches. 46.9 ins. 38 ins. 32 ins. nee Cherrapon- Mahabulesh- Vera gi, India. war, India, Cruz. Fig, 93. Comparative Rainfall, St.Do- Bergen, Philadelphia, Cambridge, British Alexandria, mingo. Norway. Penna, Mass. Isles. Egypt. (Lhe figures represent the annual rainfall in inches.) 278. Rainless Districts—In some parts of the world, rain is either entirely absent, or falls only in limited quantities, at long intervals. The most extensive rainless districts are found in the east- ern continent. Desert Belt of the Eastern Continent—From the western shores of Northern Africa eastward to the Great Kinghan Mountains in Asia, extends an almost uninterrupted belt of desert lands. It includes the great desert of the Sahara, the Ara- bian and Persian Deserts, and the Desert of Mon- golia. The aridity is most absolute in the west, where, in the Sahara and in the desert of Arabia, rain seldom, if ever, falls. Toward the east, in Persia and Mongolia, scanty rains occur, but the country has the appearance of a desert. The cause of this:immense desert tract is to be found in the dry trade winds, which blow over most of the region. Having previously crossed the vast continent of Asia as upper currents, they arrive at the deserts dry and vaporless. Even that portion of the region which receives the winds from the Mediterranean has no rainfall, because any clouds that may form, are soon dis- sipated by the hot air of the desert. Persia and Mongolia owe their deserts to their high mountain borders, which rob the clouds of their moisture before they cross the interior pla- teaus. The high system of the Himalayas effect- ually prevents any of the moisture of the south- west currents from penetrating the plateau of Mongolia. Arid tracts occur in the Kalahari desert, in Africa, and near the tropic of Capricorn, in Australia. Desert Belt of the Western Continent.—The desert lands of the Western Continent are more contracted in area. In North America, the largest desert is in the Great Interior Plateau. Here the mountain borders, especially the Sierra Nevada on the west, deprive the interior of rain. The aridity is not absolute, since scanty rains occur over parts of the region. Portions of the penin. sula of California and of the Mexican Plateau also resemble deserts. In South America, on the western slopes of the Andes, between the parallels of 27° and 23°S., is found the desert of Atacama. Here rain never falls, although the ground is oceasionally refreshed by mists'and dews. The cause of the absence of rain is to be traced to the high Andes, which con- dense all the moisture of the trades on their east- HAIL, SNOW, AND GLACIERS. 107 ern slopes, the winds thus arriving dry and va- porless at the western. Cause of Deserts—Deserts are caused entirely by the absence of moisture. Their soil, though gen- erally finely pulverized, or sand-like, does not dif- fer, save in the absence of vegetable mould, from that of other areas. Thus neither the nature of its temperature, nor its soil, is the cause of the desert of Sahara, since a vigorous vegetation ai- ways follows the appearance of water, on the suc- cessful boring of an artesian well. It is probably true that deserts, once formed, tend to perpetuate themselves, by the influence their naked surfaces exert on the rainfall. —00$f0-0——__ CHAP TER il: Hail, Snow, and Glaciers. 279. Hail falls when considerable differences of temperature exist between higher and lower strata of air, and the moisture is suddenly con- densed in the presence of great cold. . Generally, several layers or bands of dark, grayish clouds are seen. Hail falls most frequently in summer, near the close of an excessively warm day. Structure of the Hailstone.—If a large hailstone be placed on a hot surface until one-half is melted, the struc- ture can be readily examined. Concentric layers, similar to those of an onion, will be noticed, arranged around a central nucleus, sometimes of ice and sometimes of snow, though generally the latter. The stones are more or less oblately spheroidal in shape. Their general weight varies from a few grains to several ounces, but they have been known to weigh several pounds. Fig, 94. Structure of a Hailstone, Origin of Hail—The cause of hail is not ex- actly understood, and several-theories have been framed to account for it. One of these is the Rotary Theory. The wind is supposed to rotate as in a cyclone, only the axis of the whirl is horizontal instead of vertical. Two horizontal layers of cloud exist—the upper layer of snow, the lower, of rain. The snowflakes, which form the nu- clei of the hailstones, are caught in the whirl, and dipped 13 in rapid succession into the two clouds, thus receiving al- ternate coatings of ice and snow, until] at last they are hurled to the ground. Fig. 95. Rotary Theory of Hail, Thunder and lightning are the invariable attendants of hailstorms, and some authorities have attributed the for- mation of the stones to successive electrical attractions and repulsions of the snowflakes between a snow and a rain cloud. Others have imagined a number of alternate layers of snow and rain, and have attributed the hail- stones to drops of rain falling through the successive clouds. 280. Snow.—When the moisture of the air is condensed at any temperature below 32° Fahr., the vapor crystallizes, and snowflakes are formed. The snowflakes grow, as they fall, by condensing addi- tional moisture from the air. They are larger in mild than in cold weather. Snow-crystals assume quite a variety of forms, but are built up by various groupings of minute rhombohedrons of ice. The star-shape is the most common. Fig. 96, Snow-Crystals, If the temperature of the air near the surface is much warmer than 32° Fahr., any snow that is formed in the upper regions will melt before reaching the ground. Hence, in the temperate zones, as a rule, snow falls only in winter, while in the tropics it never falls, except near the sum- mits of lofty mountains. It is a mistake to suppose that the fall of snow is greater in regions near the poles than elsewhere; for in high lati- eee 108 PHYSICAL GEOGRAPHY. tudes there is comparatively little moisture in the air. The fall is heaviest in the cool temperate regions. 281. Snow Line.—Regions of Perpetual Snow. —The snow which falls on mountains is slowly pressed down the slopes by the weight of the snow above. The distance it will move down the mountain before melting depends on a number of circumstances, The lower limit of the line is -ealled the snow line, above which are the regions of perpetual snow, in which the ground is covered with snow throughout the year. The height of the snow line depends— (1.) On the amount of the snowfall. The greater the fall, the farther down the mountain the snow will move before melting. (2.) On the temperature of the valley. The warmer the valley the higher the snow line. The snow line is, therefore, highest in the trop- ical regions, and lowest near the poles. (3.) On the inclination of the mountain slope. The steeper the slope, the more rapidly the snow will move, and the farther it will go before melt- ing, therefore, the lower the snow line. According to Guyot, the snow line, subject to variations, is about three miles above the sea in the tropics; rather less than two miles in the temperate latitudes; and less than a mile near the northern extremities of the conti- nents; while still farther north, on the polar islands, the snow line is but a few hundred feet above the sea. Over the polar oceans, the winter snows are but partially melted, and help to produce the huge ice-floes of these regions, SNOW LINE. Europe.—Norway, lat. 70° N....ceec.sceeeeees 3,400 feet. “« «“ SCE GQOaN err eeterces 5,500“ 3 Alps, lat. 46° N. (south side) 9,200 “ es Ee S “(north side). 8,800 “ Asia.—Altai Mountains, lat. 50° N..... 7,000 ‘ “Himalayas, lat. 31° N..........ccceeeees 17,000 “ Africa.—Kilimandjaro, lat. 3° S..ceseeseee 16,000 “ North America.— Rocky Mountains, lat. ABOM NE Gen coos ea eee TS 12,467“ South America.—Andes, Ecuador, lat. 1° 8. 15,800 “ « ‘i See Tapa bactS he ces 3,700“ The snow line is generally lower in a moist atmosphere than in dry air, because of the greater fall of snow in the former case than in the latter. As a rule, that slope of a range which is exposed to the prevalent wind has a lower snow line than the opposite slope. The position the slope occupies in relation to the vertical rays of the sun, also exerts an influence on the height of the snow line. 282 Glaciers are immense masses of ice and snow, which move almost imperceptibly down the higher mountain valleys or slopes. Their upper parts are formed of soft snow; their lower por- tions of clear, hard ice. Their origin is as fol- lows: The weight of the huge snow fields, which form above the snow line, presses the mass slowly down the slopes. The pressure, due to the weight of the layers, but especially the pressure which is produced when the mass is forced through a con- traction in the valley, squeezes out the confined air, to which snow, in great part, owes its white color, and the lower part of the glacier thus be- comes changed into a compact mass of pure ice. The alternate thawing and freezing to which the mass is subjected below the snow line, also con- tribute to the change from snow to ice. The change is most thorough in the lower parts of the glacier, where the ice is marvellously clear. Its color, when seen in great depths, is of a deep azure blue; in the middle portions of the glacier the ice is coarse and white. The higher region of but partially changed snow is called the névé region. Here the snow occurs in coarse white grains. The process of formation is a continuous one. The névé region is supplied by fresh falls of snow, which replace those pressed down the slopes. \, 288. Drainage of Snow and Ice.—Glaciers closely resemble rivers, since they receive the drainage of their basins through the solid mate- rial which flows into them; their motion, how- ever, is much slower. Like rivers, they have their tributaries, and their peculiarities of flow and velocity. Several glaciers often unite and flow on as one mass; but their solid condition prevents the in- termingling which occurs in rivers, and the sepa- rate streams can generally be distinctly traced throughout the remainder of their course. Like rivers, the top and middle portions move more rapidly than the sides or bottom, owing to the diminished friction. \ 284. Peculiarities of Glaciers—The surface of the glacier is often comparatively smooth; but when irregularities occur, either in the direction of the valley, or in the slope of its bed, the glacier is broken into deep fissures, called crevasses. These are most numerous on the sides, from which they extend either obliquely up the stream, or directly across, in deep transverse fissures. The former are generally due to a bend in the valley, one side being compressed and the other extended; the latter, to steep and abrupt descents in the bed. Crevasses are, therefore, rapids in the ice stream. Crevasses vary in breadth from mere crevices, that a knife-blade can scarcely penetrate, to yawning chasms over 100 feet in width. The depth of the wider crevasses is generally profound. Their vertical walls afford a con- venient opportunity for studying many peculiarities of formation. Looking down the walls of the crevasses, the ice appears of a deep azure blue. The surface ice is a dirty white. HAIL, SNOW, AND GLACIERS. 109 The crevasses gradually disappear below the cause of disturbance, the fractures rejoining by a process called regelation. Regelation is the property which fragments of moist ice have of becoming firmly cemented together, when their surfaces are brought into contact under pressure. The water derived from the melting of the ice issues from a cavernous arch at the end of the glacier. The volume of the issuing stream, which is often considerable, is dependent on the tempera- ture, being greater during the warm months of the year. Many rivers have their origin in these glacier streams; as, the Rhone and the Rhine, in Europe, and the Ganges, in Asia. The distance the glacier extends below the snow line depends on the mass and velocity of the ice, and the rapidity with which it is melted. When the winter snows are light, and the following sum- mer unusually warm, the end of the glacier re- treats up the mountain. On the contrary, heavy snowfalls in winter, followed by a cool summer, permit the end of the glacier to advance far into the valley below. 285. Transporting Power of Glaciers.— All along the borders of the valleys, stones and dirt roll down the declivities, and, accumulating on the surface of the moving mass, are carried with it to a lower level. These accumulations of dirt and stones are called moraines; they are most sharply marked at the sides of the glaciers, where they are called dateral moraines. Where two gla- ciers flow into one common valley a moraine called the medial moraine marks the junction of their * meeting edges. At the end of the glacier, a ter- minal moraine extends in a wide curve across the vailey. Medial moraines are sometimes over a hundred feet in height. Terminal moraines some- times attain the height of several hundred feet. The masses of stone transported by glaciers are often of great size. Some have been found 100 feet long, 50 feet wide, and 40 feet high. 286, Erosion.—Such immense masses of ice must deepen considerably the valleys through which they move. When they have deserted their former valleys, evidences of their previous existence are to be found in the long lines of unstratified rocks and mud left by their moraines and boulders, and especially in the deep grooves, or scratches, cut in the bottom or sides of the valleys by rocks imbedded in the moving ice mass. These scratches are parallel, and show the direction of the motion. The water which issues from the terminal cave is deeply charged with a fine sediment, the result.of erosion. This sediment is exceedingly fertile, and, spread out by the rivers on the flood-grounds, becomes a source of agricul- tural wealth. ~ Fiords and Glacial Lakes.—Valleys cut by glaciers are characterized by parallel sides. Gla- cial valleys, when formed on mountains that slope down to the ocean, if the region is subjected to subsequent depression and the valleys partially submerged, are penetrated by the sea, and form arms of the sea extending far into the mountains. Such valleys are called fiords. The following are the most important fiord regions : (1.) On the coasts of Norway. (2.) On the western coasts of the Dominion of Canada and Alaska. (8.) On the coasts of Greenland, where the valleys are still covered with ice masses. The numerous lakes of glacial regions owe their origin either to the erosion of softer rocks, or to the damming up of rivers by the terminal mo- raines left by a retreating glacier. 287. Geographical Distribution of Glaciers.— The best known glacial system in the world is found in Europe, in the region of the Central Alps. Here no less than 1100 glaciers are found, one hundred of which are of large size. One of the best known of the European glaciers is that of the Mer de Glace (Sea of Ice). It descends from the slopes of the range of Mont Blanc, and is formed by the confluence of three large glaciers: the Glacier du Géant, the Glacier de Léchaud, and the Glacier du Taléfre. Fig. 97, The Mer de Glace, Glaciers occur also in the Pyrenees Mountains; in the Caucasus range; and in the Scandinavian plateau, from which they descend into the Norwegian fiords to less than 1000 feet from the level of the sea. They also occur in the Patagonian Andes : 110 PHYSICAL GEOGRAPHY. In the Arctic zone glaciers are particularly numerous and extensive. Here they generally reach down into the sea. They are found in the islands of the Arctic Archipelago, in Greenland, Iceland, Jan Mayen, and Spitzbergen. The Humboldt Glacier, in Greenland, is sixty-nine miles broad at its lower extremity in the sea. In all the Arctic glaciers, the névé region is more extended than in those of more southern latitudes. The terminal moraines are found at the bottom of the sea, near the foot of the glacier. fe In the lofty mountain-ranges of the Himalayas and in the Karakorum, occur other less known, though exten- sive, regions of glaciers. 288. Icebergs— When the glacier extends into the sea, the base is undermined by the warmer waters of the ocean, and great fragments are broken off by the waves, forming floating moun- tains of ice, called icebergs. Icebergs are narticu- larly numerous in the North Atlantic, iy which they descend from the extensive Arctic glacial region already described. The limits of the Arctic and Antarctic drift ice are shown in the map of the isotherms. Fig, 98, Icebergs, The ice floes of the polar seas have their origin in the snow which falls into the cold water, re- maining partially dissolved and subsequently freezing, thus adding to the thickness of the ice formed. ; 289. The Glacial Epoch of the Earth.—Toward the close of the Mammalian Age, a change occurred in the cli- mate of the earth, and extensive glaciers covered most of the northern continents, reaching, in many instances, far toward the south. In the United States, their southern limit appears to have been at about lat. 39° N., in Southern Pennsylvania, Ohio, Indiana, Illinois, and Iowa. In Eu- rope, they extended as far south as the 50° N. lat. In South America, they probably extended as far toward the equator as 41° S. lat. The evidences of the existence of ancient glaciers are found in the presence of accumulations of unstratified material, called the drift; in the presence of old moraines; © in glacial scratches and grooves on rocky slopes; in eroded valleys; and in the presence of numerous large boulders, which are found at great distances from their places of origin. —_-0594 00o—_——. CHAPTER Jd; Electrical and Optical Phenomena. 290. Nature of Electricity —Electricity is now generally believed to be, due to a peculiar wave motion in the luminiferous ether, the medium which transmits the waves of light and heat. When a body is electrified it acquires a certain power of doing work, called electric potential. Electric potential is measured in units called volts. The path through which an electric dis- charge passes is called the circuit. All circuits offer a measurable resistance to the passage of an electric discharge. Electric resistance is meas- ured in units called ohms. The rate at which electricity passes through a circuit is called the current, and is measured in units called ampéres. An ampére is the current which would pass in a circuit whose resistance is one ohm, under a potential of one volt. Though electricity is probably not a fluid, yet it resem- bles a fluid in many respects, and the units already re- ferred to are, to a certain extent, based on this resem- blance. The quantity of liquid that flows through a pipe in a given time depends on the pressure on the liquid, and the resistance offered by the pipe. The quantity-per-sec- ond corresponds to the ampéres ; the pressure which causes the flow, to the volts; and the resistance which limits the flow, to the ohms. Electricity may be produced in bodies by a variety of causes: such as friction, heat, chemical action, magnetism, and animal or vegetable life. There are two distinct forms of electrical excitement: the positive and the negative. A body with a high potential is generally assumed to be positively charged; one with a low potential, negatively charged. The current is assumed to flow from the higher to the lower potential, or from the positive to the negative. Bodies charged with electricity ELECTRICAL AND OPTICAL PHENOMENA. 111 of the same kind, repel one another; if charged with dif- ferent kinds, they attract, and if the bodies are free to move, they approach, when the opposite excitements neu- tralize each other. In case the electrical excitement is considerable, the union is accompanied by a sharp crack, and a flash of light, called the electric spark. 291. Conductors of electricity are bodies which allow its ready passage through them. Metals, charcoal, acids, aqueous solutions, and various animal and vegetable substances, are good con- ductors. Non-conductors are those which do not allow the electricity to flow freely through them. Gums, resins, glass, silk, and dry air are non-con- ductors. The higher the conducting power of a circuit the lower will be its resistance, and, consequently, the greater the current which will be sent through it by a given poten- tial. ; : 292. Atmospheric Electricity —Electric excite- ment is always present in the atmosphere. The electricity of the air is generally positive, although it often changes rapidly to negative on the ap- proach of clouds or fogs. It is feeblest within a few feet of the surface, and increases with the elevation above the general surface of the earth. Origin of Free Atmospheric Hlectricity.—The elec- tricity of the atmosphere is caused by a variety of circum- stances, the chief of which are evaporation and condensa- tion; unequal heating of the earth by the sun’s rays; combustion; animal and vegetable life; and the friction of winds against each other or against the earth’s sur- face. 293. Lightning occurs when the electricity of a cloud discharges to the earth or to a neighbor- ing cloud. The discharge is attended by a vivid spark, called lightning. The destructive effects of lightning are due to the discharge between the clouds and the earth. Thunder.—The heat of the spark vaporizes the rain-drops, and enormously expands the air, pro- ducing, on their subsequent cooling, a partial vacuum, which is further increased by the mo- ‘mentary pushing aside of the air by the discharge. The surrounding air rushing violently into this vacuum produces the sound called thunder. The potential of the lightning flash is enormously higher than that produced by artificial means, and must be equal to many millions of volts. This high potential is due to the enormous decrease in the surface of a single rain-drop from the thousands of smaller drops which have coalesced. to form it. 294, Varieties of Lightning.—There are five varieties of lightning: zig-zag or chain, sheet, heat, globular, and vol- canic lightning. Zig-zag Lightning probably owes its forked shape to the resistance which the air offers to its passage through it. The air-particles, being crowded together in the path of the spark, the lightning darts to one side, where the air is less dense. Sheet Lightning generally accompanies thunder- storms, and appears as an expanded flash, which illu- mines the clouds. Heat Lightning, or lightning without thunder, is gener- ally seen near the horizon, during hot weather. It is probably caused by the reflection of lightning from a storm below the horizon. Globular Lightning. On rare occasions, the lightning appears in the form of a globe of light, which remains stationary in the air or moves slowly through it. Its cause is unknown. Volcanic Lightning. During the eruption of volca- noes, vivid flashes of lightning often occur in the air near the craters. Volcanic lightning is probably caused by the rapid condensation of the vast volumes of vapor emitted with the ashes and lava. 295. Lightning Rods, invented by Franklin, protect the buildings on which they are placed, by quietly discharging the electricity from the over- hanging cloud. They generally effect this by an opposite electricity passing from the earth up the rod, and neutralizing that of the cloud. Unless the rods are placed in good metallic connection with the earth, and with all conductors near them, they are sources of danger rather than of protection. 296. St. Elmo’s Fire—When the. atmosphere is highly charged with electricity, faint tongues of fire are often seen on the ends of bodies in Fig. 99, St Elmo's Fire, connection with the earth, like the masts of ships, steeples, etc., due to an electric discharge, known as the brush-discharge. They are called St. Elmo’s fire, and are harmless. 112 PHYSICAL GEOGRAPHY. 297. The Aurora Borealis, or northern light, is a phenomenon of marvellous beauty, occurring ia the sky of high latitudes in both the northern and southern hemispheres. It appears in a va- riety of forms; at times huge pillars of fire move rapidly across the heavens, or the entire northern sky is lighted as by a drifting storm of luminous snow. The commonest appearance, however, is that of an arch of fire, from which streamers flash toward the zenith. Auroras are most frequent in high latitudes, though not in the immediate vicinity of the poles. Auroras are caused by the passage of electricity through the rare air of the upper regions. The proofs are as fol- lows: During the continuance of an aurora, the telegraph wires show the presence of an unusual electrical disturb- ance, and the magnetic needle is subject to frequent oscil- lations; moreover, the same phenomena can be produced by the passage of an electrical current through rarefied gases, as in the Geissler tubes—different colors arising from its passage through different gases, Fig. 100, Aurora Borealis, 298. Magnetism.—The recent researches of Herz leave little doubt that electro-magnetic phe- nomena are due to a wave motion in the lumi- niferous ether. Magnets are bodies which have the power of attracting particles of iron or the opposite poles of other magnets. All magnets possess an atmosphere of influence surrounding them, called the magnetic field. The magnetic field is traversed by lines of force, which come out of the magnet at one point and enter it at another, thus forming a magnetic cirewit. The points where the lines come out are called poles; the former being the positive or north pole, and the latter the negative or south pole. Magnets are either natural or artificial. Nat- ural magnets are found in lodestone, a species of ° iron ore composed of oxygen and iron. Pieces of hardened iron or steel may be magnetized, by rubbing them with a lodestone, or by passing electrical currents around them, thus forming what are called electro-magnets. All magnetiz- able substances become magnetized when they are brought into a magnetic field. If a magnetized bar or needle be suspended at its centre of gravity so as to move freely in a horizontal plane, after a few oscillations it will come to rest, with one of its ends pointing nearly to the geographical north pole of the earth. This end of the magnet is called its north pole, the op- posite end its south pole, and the magnet itself, a magnetic needle. Fig. 101, The Magnetic Needle, 299. Magnetic Attractions and Repulsions.—If a magnet is brought near a magnetic needle, attraction or repulsion will ensue—repulsion, when the poles are of the same name; attraction, when they are of opposite names. Thus, when a north pole is approached to a north pole, or a south pole to a south pole, they repel each other; but when a north pole is approached to a south pole, or a south pole to a north pole, they attract. If the approaching magnet is powerful, it will deflect the magnetic needle, although several feet distant from it; and if placed per- manently in this position, the magnetic needle will no longer point to the north, but will turn toward the disturbing magnet. 300. The Magnetic Properties of the Earth.—- The Magnetic Needle—The magnetic needle points to the north for the same reason that the opposite poles of magnets point to each other when they are sufficiently near. The entire earth acts as one huge magnet, with its poles in the neigh- borhood of the extremities of its avis, and the mag- netic needle points toward these poles on account of their attraction. ELECTRICAL AND OPTICAL PHENOMENA. 113 The earth, like all magnets, possesses a magnetic field. Lines of magnetic force come out of its north pole, pass around the earth through the air, and enter the earth at jts south pole. A magnetic needle, placed in the earth’s field, if free to move, will come to rest with the earth’s lines of force passing into its south pole and passing out of its north pole. That pole of the needle which points to the geographical north is, therefore, of opposite magnetic polarity to the earth’s polarity in the Northern Hemi- sphere. In the United States, the Northern Hemisphere is regarded as possessing south magnetic polarity; in France, as possessing north magnetic polarity. 301 Origin of the Earth’s Magnetism—The exact cause of the earth’s magnetism is unknown. Currents of electricity circulating around a con- Electrical currents ductor render it a magnet. are generated in nearly all substances, when they are unequally heated. The earth appears to owe its magnetism to the circulation around it of cur- rents of electricity, produced, most probably, by _ the unequal heating of different portions of its surface by the sun’s rays. These currents would follow the sun in its apparent motion from east to west. Since the earth’s magnetism appears to have its remote cause in the sun’s heat, variations in the temperature should be followed by corre- sponding variations in the intensity of magnetism. This is found to be the case. Magnetic storms, or unusual variations in the earth’s magnetism, have been noticed to Bae q| e| Fig. 102, Declination Chart, (West Declination is represented by the continuous lines; East Declination by the dotted lines; the Agones by the heavy lines.) correspond with outbursts of solar activity, as manifested by the unusual occurrence of new spots. 802. Variations in the Manifestations of Mag- netic Properties.—The earth’s magnetic poles do not correspond with its geographical poles. The magnetic needle, therefore, except in a few local- ities, does not point to the true geographical north, but to the east or to the west of it. This deviation from the true north is called the declination or vari- ation, and is east or west according as the needle points to the east or the west of the true or geo- graphical north. The amount of this variation differs in different parts of the earth. The position of the magnetic poles of the earth is not always the same, but changes slowly from year to year, thus producing corresponding changes in the declination of the needle. This change is called secular variation. The needle, at any place, points more and more to the east, following the change of the poles. At length, after a long period, it becomes stationary, and then begins to move toward the true meridian, which it at length reaches; \ when, continuing its motion, the declination becomes west. ~ Isogonal Lines.—Lines connecting places which . have the same declination, are called isogonal lines. Lines connecting these places, when the needle points to the true north, are called agones, or lines of no declination. The direction of the isogonal lines is shown in the de- 114 PHYSICAL GEOGRAPHY. clination chart, the figures near the lines giving the value of the declination in degrees. The agone in each hemi- sphere is marked 0. In the New World it enters South America near Rio Janeiro, curves to the eastward around the Antilles, passes near Washington, through the western part of Hudson Bay, and enters the magnetic pole at Boothia Felix. The agone, in the Old World, passes through the west of Australia, near the western coasts of Hindostan, through Persia, the eastern part of the Cas- pian Sea, and through the White Sea, in Europe. The eval curves in Eastern Asia seem to indicate a secondary magnetic pole. In nearly all Europe, in the whole of Africa and Ayvabia, in eastern North and South America, and in nearly all the Atlantic and Indian Oceans, the declination is west. It is also west along part of the eastern shores of Asia, around the secondary magnetic pole. In the remainder of the world the declination is east. 303. The Inclination or Dip of the Needle— The lines of force of the earth’s magnetic field are in most places inclined to the earth’s surface. The position of the needle is, therefore, horizontal in but a few localities. In most places, one of the poles is inclined to the earth. This is called the inclination or dip of the needle. In the Northern Hemisphere, it is the north pole, and in the south- ern, the south pole that is inclined. 304. Magnetic Equator—The angle of dip is greater, the nearer we approach either magnetic pole. At the pole, the needle points vertically downward; midway between the poles, the needle is horizontal; the last position is called the mag- netic equator. Lines connecting places which have the same angle of dip are called isoclinal lines. They correspond in a very remarkable manner with the isothermal lines. This seems to show the dependence of the intensity of magnetism on the distribution of the sun’s heat. The inclination is also subject to secular changes, like the declination. ~ 805. Optical Phenomena are caused by changes in the direction, intensity, or composition of sun- light during its passage through the atmosphere. Sunlight, when passed through a prism, is dis- persed or separated into a great number of differ- ent colored lights. The following seven groups of eolors are prominent: violet, indigo, blue, green, yellow, orange, and red. These are called the pris- matic colors, or, collectively, a spectrum. They differ in the ease with which they are refracted, or turned out of their course, in passing from one medium to another of different density. The above prismatic colors seen in the spectrum are named in the order of their refrangibility, begin- ning with the violet, the most refrangible, and ending with the red, the least refrangible. 306. Rainbows are arches of the prismatic colors, caused by the dispersion of the light during its passage through the falling drops of rain. The rays entering the drop, are reflected from the surfaces farthest from the sun, and emerge separated into the prismatic colors. Rainbows are seen when the observer stands with his back toward the sun. They are largest when the sun is nearly setting. A secondary bow sometimes occurs outside the primary, with the order of its colors reversed. Tt is caused by the light which is twice reflected from the back of the drops. 307. The Sunset Tints of the Sky are yellow, orange, and red. The rays of the setting sun are dispersed, during their passage through the clouds, or through accumulations of vapor at the horizon, and only the colors that are least turned out of their course, the ‘yellow, the orange, and the red, pass through and light up the western sky. 308, The Blue Color of the Sky is caused by the diffusion through the air and their subsequent reflection from its particles of the more refrangi- ble rays of light: the indigo and the blue. 309. Halos and Corone are rings of prismatic colors surrounding the sun and moon. Halos are caused by the presence in the air of small crystals of ice or snow. Parhelia, or mock suns, and Paraselene, or mock moons (bright spots which somewhat resemble suns and moons), are frequently seen where the complicated circles of halos intersect each other. Corone are circles of light, seen most frequently around the moon. They are caused by the presence of a small quantity of condensed vapor in the air. They generally indicate changes in the weather. Fig. 103, Halo, 310. The Mirage is a general term applied to the appearance which objects present when viewed by means of rays of light that have passed through SYLLABUS. 115 strata of air, which gradually increase or decrease in density. In this way the objects appear either inverted or erect, but always out of their true position. Sometimes the objects are repeated, one being seen above the other. The mirage occurs both over water and land. It is caused by the turning of the rays of light out of their original direction. The Mirage of the Desert occurs over hot, arid surfaces, whenever the strata of air increase rap- idly in density from the surface upward. The rays of light from distant objects, such as trees, are reflected from one of the lower layers of air, and, entering the eye of the observer, appear to come from inverted objects, which seem to be surrounded by a sheet of water. The image of a real tree is seen, but out of its true situation, so that when the observer reaches the place he finds nothing. | The mirage frequently occurs on the sea. Ves- sels that are too far below the horizon to be di- rectly visible, become visible by refraction. This phenomenon is called looming. The vessels are seen both erect and inverted, and sometimes ap- pear suspended in the clouds. Distant islands are sometimes visible from the same cause. RR III SYLLABUS. ——050400——_ The rapidity of evaporation increases—1. With the tem- perature of the atmosphere. 2. With the extent of sur- face exposed. 3. With a decrease in the quantity of va- por already in the air. 4. With the renewal of the air; and, 5. With a decrease of the pressure on the surface. When air can hold no more moisture in an invisible state, it is said to be saturated or at its dew point. Whenever the air is lowered below the temperature of its dew point, its moisture is deposited as cloud, mist, snow, hail, sleet, or rain. More dew is deposited on clear nights, when the wind is moderate, than on cloudy nights, when the wind is high. In fogs, mists, and clouds, the moisture is condensed as minute drops. Clouds owe their variety of forms to the action of aérial currents, and their constant tendency to settle. The dense fogs so common off the banks of Newfound- land are caused by the chilling of the warm, moist air of the Gulf Stream by the cooler air of the Labrador cur- rent. The primary forms of clouds, are the cirrus, the cumu- lus, the nimbus, and the stratus. The secondary forms of clouds, are the cirro-stratus, the eirro-cumulus, and the cumulo-stratus. Rain falls whenever the temperature of a mass of air is lowered considerably below the temperature of its dew point. This reduction of temperature may occur—1l. By a change of altitude by means of ascending currents. 2. ' By a change of latitude, as by the warm equatorial cur- rents flowing into colder regions nearer the poles. 3. A comparatively small rainfall. may be caused by the inter- mingling of moist cold and moist warm air. As a rule, the equatorial currents bring rain, the polar currents, drought. In the zone of calms, it rains during the hottest part of the day, or in the afternoon, when the ascending currents are strongest. : In the zone of the trades, it rains during the hottest part of the year, or in summer. 14 Between lat. 24° and 30°, both N. and S., the rainfall is scanty, and in some localities almost absent. In the zone of the variables, it may rain at any hour of the day or night, or at any time of the year. In the polar zones, the winters are clear; snows and drizzling rains occur in spring and autumn. Between lat. 30° and 35°, both N. and S., it is dry in summer during the prevalence of the polar currents. The rest of the year is wet. The rainfall of any place is determined by means of an instrument called a rain-gauge or pluviometer. An inch of rain on the surface of a square yard is equal in weight to 46.75 pounds; an inch on the surface of an acre, to the weight of about 100 tons. The quantity of rain decreases from the equator to the poles, and from the coasts of the continents toward the interior. More rain falls on mountains than on plains; more on plains than on plateaus; more in the Northern Hemi- sphere than in the Southern. In the tropics of the New World, the annual rainfall is 115 inches; in the Old World, only 77 inches. In the temperate regions of the New World, the annual rainfall is 35 inches; in the Old World, but 34 inches. The average rainfall of Europe, betveen lat. 36° and 60° N., is 34 inches. The average rainfall in the United States, between 24° 30’ and 45° north latitude, is 39 inches. The desert belt of the eastern continent extends from the western shores of Northern Africa eastward to the Great Kinghan Mountains in Asia. It includes the Sa- hara, the Arabian and Persian Deserts, and the Desert of Mongolia. The aridity of this immense tract is caused by the absence of rain. ; The desert tracts near the summits of high mountains are caused by the absence of heat and liquid moisture. Hail falls when bodies of warm and intensely cold air are rapidly commingled. Snow falls when the moisture is condensed at tempera- tures at or helow 32° Fahr., under conditions favorable to 116 PHYSICAL GEOGRAPHY. gradual crystallization while the moisture is condensing. Sleet is frozen rain. The snow line is the distance above the sea where snow remains throughout the year. The snow line in the tropics is found at about three miles above the level of the sea; in the temperate regions, at rather less than two miles; near the northern extremi- ties of the continents, at less than one mile; while still farther north, on the polar islands, it is but a few hundred feet above the sea. ‘ The height of the snow line, depends— (1.) On the amount of the snowfall. (2.) On the temperature of the valley. (3.) On the inclination of the slopes. Glaciers are immense masses of ice, formed by the snow ‘which accumulates on the slopes of mountains above the snow line. They move slowly by gravity.down the moun- tain slopes, bearing with them accumulations of dirt and stones, called moraines. The upper surface of the glacier is generally broken into deep fissures, called crevasses. The water derived from the melting of the glacier issues in a stream from the lower end of the ice mass. It is highly charged with sediment derived from the erosion of the glacier. It often forms the source of a powerful river. The following mountains contain glaciers: the Alps, the Pyrenees, the Caucasus, the Scandinavian Mountains, the Himalayas, and the Karakorum. When glaciers descend into the sea, the waters under- mine them, and detach huge masses, which float away to great distances. These masses are called icebergs. Toward the close of the Mammalian Age, a change oc- curred in the climate of the earth, by which all the north- ern contineuts were covered with glaciers. The unit of electric potential is called a volt; the unit of current is called an ampére; the unit of resistance is called an ohm. Comparing the flow of electricity to that of a current of water in a pipe, the volt corresponds to the pressure ‘causing the flow, the ohm to the friction or other resist- ance opposing it, and the ampére to the quantity of the flow per second. The free electricity of the air is generally positive. Lightning results when the electricity of a cloud dis- charges to the earth, or to a neighboring cloud. There are five kinds of lightning: zig-zag, heat, sheet, globular, and volcanic. When the air contains an unusually great quantity of electricity, faintly luminous balls are seen on the ends of tall objects. These are called St. Elmo’s fire. Auroras are caused by the passage of electricity through the rare air of the upper regions of the atmosphere. The earth acts like a huge magnet. It possesses a mag- netic field, and has lines of force entering its south pole in the Northern Hemisphere, and coming out of its north pole in the Southern Hemisphere. A magnetic needle, if free to move, will come to rest in the earth’s field with the lines of force of the earth pass- ing in at its south pole and coming out at its north pole. The magnetic needle points to the north, from the action of the magnetic poles of the earth. The cause of the earth’s magnetism is not certainly known. It is probably due to electrical currents which circulate around it. Magnetic storms, or unusual variations in the earth’s magnetism, correspond with outbursts of solar activity as manifested by sun-spots. The deviation of the needle from the true north, is called its declination; the deviation from a horizontal plane, its inclination. Both declination and inclination are subject to diurnal, annual, and secular variations. Isogonal lines connect places which have the same dec- lination. Isoclinal lines connect places which have the same inclination. Isoclinal lines are nearly coincident with the isothermal lines. Rainbows are caused by the action of light on falling raindrops. Halos are caused by snow crystals in the air; Coronez, by minute particles of water. The Mirage is caused by the bending cf the rays of light from their original direction, while passing from one me- dium to another of different density. REVIEW QUESTIONS. ——-005,00— What do you understand by evaporation? Name the circumstances upon which the rapidity of evaporation depends. Define dew point. What condition is necessary in order that the invisible moisture of the atmosphere may become visible in any form of precipitation ? Under what circumstances is dew deposited ? Why is more dew deposited on a clear night than on a cloudy night? Why is more dew deposited on a still night than on a windy one? ; Under what circumstances are fogs, or mists, produced? How do fogs or mists differ from clouds? What is the condition of:the particles of water which form the clouds? Are they minute drops, or hollow vesi- eles? Describe the appearance of the cirrus cloud. How does its height compare with that of other clouds? During what parts of the day are stratus clouds most common? To what do they owe their banded appearance? Describe the cumulus cloud. During what part of the day is it most common? Why should the cirro-stratus clouds generally indicate approaching rain? Name three conditions under which rain may be caused. By which are the heaviest rains generally produced ? Ave the equatorial currents likely to bring rain or drought? The polar currents? Why? Name the periodical rain zones, When does it rain in the zone of calms? In the zone of the trade winds? Why? In what portions of the zone of the variable winds is the rainfall approximately periodical? Describe the rainfall in the zone of the variable winds. In the zone of the polar winds. Describe the construction of a rain-gauge or pluvi- ometer. Why should more rain fall on a mountain than on the lowlands at its base? Why should more rain fall on the _ coasts of a continent than in the interior? REVIEW AND MAP QUESTIONS. 117 Compare the mean annual rainfall of the tropics of the Old and New Worlds. Of the temperate regions of the Old and New Worlds. Name the rainless districts of the Eastern Continent. Of the Western Continent. What is the cause of the almost total absence of rain in these districts? Under what circumstances is hail produced? Describe the structure of a hailstone. Explain the rotary theory of hail. Define the snow line. Upon what does the height of the snow line depend? At what height above the sea- Jevel is it found in the tropics? In the temperate re- gions? In the polar zones? How are glaciers formed? In what respects do they resemble rivers? What are crevasses? How are they formed? Name some rivers which take their origin in the melt- ing of glacial ice. Define lateral moraines; medial moraines; terminal moraines. Explain the manner in which fiord-valleys were formed. What is the probable origin of lakes in all glacier districts? Name some of the European mountain systems which contain extended glacier regions. Name two Asiatic mountain ranges which contain such regions. How are icebergs formed? Is the ice of which they are composed salt or fresh ? What are ice floes? State their origin. What appears to have been the southern limit of the glaciers in the United States, during the glacial epoch, which occurred toward the close of the Mammalian Age? What is the origin of free atmospheric electricity ? Define volt; ohm; ampére; potential; circuit. Under what circumstances does lightning occur? What is the cause of the accompanying thunder? Name five varieties of lightning. By what are auroras caused ? What is the cause of the directive tendency of the mag- netic needle? What is believed to be the cause of the earth’s magnet- ism? What do you understand by the earth’s magnetic field? Define isogonal lines; isoclinal lines. With what lines are the isoclinal lines nearly coinci- dent? Explain the phenomenon of the rainbow. What is the cause of the sunset tints of the sky? Of the blue color of the sky? What are halos and corone? By what are they caused? Explain the cause of the mirage of the desert. What do you understand by the phenomena of loom- ing? MAP QUESTIONS. ——+030300— Trace on the map of the winds and rains, the portions of the world included in the zone of calms. When does it rain in the zone of calms? Trace in a similar manner the portions included in the zones of the trades, and the zones of the variables. What is characteristic of the rainfall in each of these zones ? Why should the eastern shores of tropical South Amer- ica be moist, and the western dry? To what peculiarity of position does Northern Africa owe its scanty rainfall? Trace on the map of the isothermal lines the southern limit of the Arctic drift ice; the northern limit of the Antarctic drift ice. Trace on the declination chart, the agone, or line of no declination, in the Western Hemisphere. Trace the line of no declination in the Eastern Hemi- sphere. What smaller line of no declination exists in this hemisphere ? Notice that in the Western Hemisphere the isogonal lines all meet in a point near Hudson Bay. What does this meeting indicate? Paes PLANT LIFE, ANIMAL LIFE, AND MINERALS. He TO =e SET Tun variety and luxuriance of life found on the surface of the earth are far greater than is at first apparent. Besides the larger species of animals and plants, myriads of microscopic forms inhabit the land, the water, and the air. From the burning sands of tropical deserts, to the eternal snows of the poles, widely differing forms occur, each being peculiarly fitted for its own conditions of growth. An organic form differs in many respects from one that is inorganic. The animal or plant has its origin in a germ; grows from nourishment taken into its structure; has a regular development in growth, passing, by successive stages, from birth to maturity, when it reproduces its kind, and passes on to decay and death. A crystal, which may be taken as the type of the inorganic world, grows by additions from without, does not reproduce its kind, has no regular development or growth, being perfect from its first existence, and has no decay or death. ee Ca) Se SECTION l.. PLANT LIFE. —059200——_ CHAPTER I. cells, or approximately spherical masses, consist- ; ing of a peculiar form of jelly-like matter called Plant Geography. protoplasm, composed of various complex combi- nations of carbon, hydrogen, oxygen, and sulphur, 811. Living Matter—AlIl life, whether vege- called proteids. At its beginning all life-consists table or animal, consists of various groupings of of a minute germ cell, filled with more or less 118 transparent protoplasm, and containing a darker opaque spot called the nucleus. Examined by a sufficiently powerful glass, all living protoplasm is seen to be in constant motion, currents passing through the different parts in somewhat definite directions. As the germ cell develops, in all the higher forms of life, it multiplies, and various organs appear, peculiar to the form of life from which the germ cell was derived. All living bodies contain organs, and living matter is therefore sometimes called organic matter, to distinguish it from non-living or inorganic matter. Science has not yet disclosed the nature of the change whereby non-living matter is converted into living pro- toplasm. To produce living matter the intervention of already living matter is, so far as is known, absolutely necessary. 3 312. Intermediate Position of Plants—Proto- plasm forms an essential part of both plants and animals. Plants alone, however, possess the power of manufacturing protoplasm directly from inor- ganic or non-living matter. Plants prepare food for animals, who are, consequently, dependent on plants for their existence. Both plants and ani- mals are consumers of the proteid compounds. Plants alone are producers. In the scale of ex- istence plants, therefore, occupy a position inter- mediate between minerals and animals. 313. Plant Geography treats of the distribu- tion of plant-life over the earth. Plant geography differs essentially from botany. Bot- any arranges plants into regular classes, according to pe- culiarities in their organs of growth and reproduction. ' Plant geography considers them only in reference either to the more prominent appearances, by which they give a distinct character to the vegetation of a country, or in regard to their general usefulness to man. In this limited view, all the minuter differences in structure or organization are passed over, the general form being the main geographical element of a plant, and the element with which physical geography is principally in- terested. The plants of any section of country, taken collectively, are called its flora. 314, Conditions Requisite for Plant Growth — Plants require for their growth certain conditions of light, heat, and moisture; and since the requi- site amount of each of these varies with different species of plants, we find in every climatic zone a characteristic flora. The soil must contain those mineral ingredients which form a)part of the structure of the plant, and, moreover, must con- tain them in a condition in which they can be readily assimilated by the plant. PLANT. GEOGRAPHY. 119 ‘The substance of plants consists mainly of water derived from the air and the soil. Analy- sis shows that vegetable matter is composed almost entirely of water, and various compounds of' car- bon, hydrogen, oxygen, and sulphur. The water is derived from the moisture of the soil and of the air; the carbon, from the carbonic acid of the air. The exceedingly small proportion of mineral mat- ter comes directly from the soil. i The nature of the soil, then, is far from being the most important element in the distribution of mere vegetation ; for, even when a soil is absent, if the other requisites of light, heat, and moist- ure are present, the simpler vegetable forms soon appear, and slowly prepare, even on a bare, rocky surface, a soil which is able to sustain higher and still higher species. This is effected by the breaking up of the hard mineral matter, and the accumulation, year after year, of the de- caying plants. In this way a vegetable mould is produced. The bare surfaces which the conti- nents possessed, when they first emerged from the oceans, gained their covering of soil principally in this way. Moisture, Heat, and Light are the prime essen- tials of vegetation, and it is on their distribution that the distribution of vegetation is principally dependent. ‘\ 815. Distribution of Vegetation—The influ- ence of heat and moisture is noticed as we pass from the equator to the poles, or from the base of a tropical mountain to the summit. Thus arises a horizontal and a vertical distribution of vegetation. The greatest luxuriance of vegetation is found in the equatorial regions, where both heat and moisture are most abundant. Here a greater va- riety of species occurs, and the individual plants are larger, and more brilliantly colored, both in their leaves and flowers. As we pass toward the poles, the number of the species diminishes; trees disappear, being replaced by shrubs and herbs, and these, in turn, by lichens and mosses, until ‘finally, amid the snows of the polar latitude, even the simplest forms of vegetable life are often wanting. 316.\Horizontal Distribution of Vegetation. (1.) According to Meyen, we may divide the earth’s surface into zones according to the latitude, and the moun- tainous elevations into zones according to the altitude. Since. the distribution of heat is not only dependent on the latitude or altitude, we may advantageously modify this plan as has been suggested by Dove, and divide the | zones by the isotherms. 1205 °° PHYSICAL GEOGRAPHY. (2.) According to Schouw, we may divide the earth’s surface into regions characterized by assemblages of pecu- liar floras, and separated by natural barriers. The great number of the regions required to give thor- -oughness to Schouw’s system, renders its use inadvisable in an elementary book. (3.) According to Humboldt and others, we may divide the earth’s surface into zones, according to the physiognomy of the plants inhabiting them. Here plants of entirely different species are grouped by their mere out- ward resemblances into what are called forms. The first method is the one most suitable for our pur- poses. We shall follow, in the main, Dove’s modification, as adopted by A. R. Johnston, and divide the surface of the earth into zones, according to the isotherms, or lines of mean annual temperature. The values of the isotherms are given in round numbers. This system is based on the fact, that the character of the vegetation is dependent mainly on the temperature, which, in-its turn, regulates the quantity of moisture. 317. Horizontal Zones of Vegetation. (1.) The Tropical Zone, extends between the isotherms of 73° Fahr. on each side of the equa- tor. (2.) The Sub-Tropical Zones, extend in each hemisphere from the isotherm of 73° Fahr. to 68° _ Fahr. (3.) The Warm Temperate Zones, extend in each hemisphere from the isotherm of 68° Fahr. to 56° Fahr. (4.) The Cold Temperate Zones, end in each hemisphere from the isotherm of 55° aoe to 41° Fahr. (5.) The Sub-Arctic Zone, extends in the north- ern hemisphere from the isotherm of 41° Fahr. to the September isotherm of 36.5° Fahr. (6.) The Polar Zone, extends in the northern hemisphere from the September isotherm of 36.5° Fahr. to the poles. 318. The Tropical Zone, or the zone of palms, bananas, spices, and aromatic plants, lies on each side of the equator, between the isotherms of 73° Fahr. It includes most of the land within the tropics of both hemispheres. The excessive heat and moisture of this zone produce an especial luxuriance in the vegetation. Trees attain enormous size, the foliage is bright, the flowers brilliant, and the number of species great. The forests are characterized by the great variety of trees, and when allowed to attain their densest growth, are almost impenetrable, from the numerous parasitic plants with which they are covered, or the gigantic, rope-like climbers that twine among them. Palms, bananas, tree-like grasses, and orchids are among the most characteristic plants. Orchids are curious plants, inhabiting damp forests. They attach themselves to trees and rocks, drawing nearly ne Fig, 104.’ Palm-Trees, all their nourishment from the air. Asa class, they are noted for the fragrance, vivid coloring, and curious forms of their flowers. The well-known vanilla bean is obtained from an orchid. The humble grasses of our latitude, in this zone, are represented by the bamboo, which often at- tains the height of 60 feet. The banyan-tree,. a species of fig-tree, is found in the Fig, 105. Banyan-Tree, East Indies. From a colossal trunk numerous air-branches are sent out, which, descending to the ground, take root, Page 121. Wl OF £IF B TROPIC oO canckr inca a a beAsce an Alyy h oe, Rice gar Cocoa, Ranana ] g 3 “aa ; tal) Orange fregion of the Co, oe Mue Pak EQUATOR : : eS a TROP : 9, On OL CSpot Dey elon og a Te nae Pine aes YRS 8242 | = Pearse tO EL OLO EOE ALC OREY By MAP OF THE WORLD © oo REFERENCES. showing the distribution of as] | Tropical Zone. mee ase {Anarene [einexe | VEGETATION according to the Zones of DA Sub Tropical Zones [SASubAretic Zone. | 4 wz PHYSICAL CLIMATE. Warm lemperatefones\.—\Polar Zone. LONGITUDE WEST FROM GREENWICH . LONG}TUDE EAST FROM|GREENWICH. 80 60 40 20 | 0 20 40 60 122 PHYSICAL GEOGRAPHY. ’ and in their turn send out other branches, and in this way an extended area is covered. A single tree has been known sufficiently large to give shade to 7000 men at the same time. The Llanos of the Orinoco are found in the tropical zone. During the dry season, they are almost entirely devoid of vegetation ; but during the wet season, they are covered with grasses. The Indian Archipelago affords an excellent illustration of the wonderful luxuriance of the vegetation of the tropics. Here the gigantic Rafflesia bears flowers three feet in diameter! In the northern and southern portions of the tropical zone, where the mean annual temperature ranges from 79° to 73° Fahr., the vegetation, though similar to that of the equatorial regions, begins to lose its density and luxuriance. The forests contain less undergrowth and fewer para- sitic plants. Tree-like ferns and figs are espe- cially abundant, and some authorities have ar- ranged these portions into separate zones, called the zones of tree-ferns and figs. 319. The Sub-Tropical Zones, or the Zones of Laurels and Myrtles, extend in each hemisphere, from the isotherm of 73° Fahr. to 68° Fahr. Here, the heat of summer, though sufficient to ripen most of the tropical fruits, is not as intense as in the tropical zone. The winters are mild, and scarcely arrest the vegetation. The palms and bananas of the preceding zones are still common, but the characteristic vegetation is found in the abundance of trees with thick, shining leaves, such as the laurels, magnolias, and myrtles. 320. The Warm Temperate Zones, or the Zones of Evergreen Trees, or trees which do not shed their leaves, extend in each hemisphere, from the isotherm of 68° Fahr. to 55° Fahr. In this zone, trees with thick, shining leaves occur, mingled with oaks, beeches, and others similar to those found in our own forests. No palms occur, but in their place we find a number of glossy- leaved evergreen trees, and handsome evergreen shrubs. In those portions of this zone which are in the neigh- borhood of the Mediterranean, the bay, myrtle, laurel, fig, and the olive, are characteristic. The cork oaks, chest- nuts, and pomegranates, are frequent. The vine, said to be a native of this zone, attains here its greatest growth, the stem often reaching a thickness of half a foot. In America, oaks, pines, and tulip-trees occur. The southern warm temperate zone includes portions of New Zealand and Australia, and in South America the Pampas of the Rio de la Platte, where tree-like grasses abound. 321. The Cold Temperate Zone, or the Zone of Deciduous Trees, or those which drop their leaves in autumn, extends in the northern hemisphere, from the isotherm of 55° Fahr. to 41° Fahr. For- ests of deciduous trees are the main characteristics of this zone ; oaks, birches, beeches, chestnuts, wal- nuts, maples, elms, larches, alders, and sycamores, are among the most common of the deciduous trees. Mosses and lichens frequently cover the trunks of the trees, and a rich and varied under- growth occurs; the holly, clematis, wild rose, hon- eysuckle, and rhododendron, are examples. Extensive meadows, covered with grasses, are found in this zone. The deciduous character of the trees, and the almost total absence of evergreens, produce a marked contrast between winter and summer. During winter, the foliage almost entirely disappears, and snow covers the ground for long periods. This zone is essentially one of extensive forests. In connection with, the warm temperate zone of the northern hemisphere, it has always contained the most highly civilized races of men, and is es- pecially rich in the number and luxuriance of its food-plants. 322. The Sub-Arctic Zone, or the Zone of the Cone-Bearing Trees, extends in the northern hemi- sphere, from the isotherm of 41° Fahr. to regions where the mean annual temperature for the month Fig, 106, Pine-Trees. of September is 36.5° Fahr. In this zone, both forests and grassy meadows abound. The forests are especially characterized by cone-bearing trees, with evergreen, shining, needle-shaped leaves, such PLANT GEOGRAPHY. 123 as the pine, spruce, hemlock, cedar, and fir. In the northern portions of the zone, beeches and alders are found, and willows, when the soil is moist. The meadows are covered with grasses and flowers, and afford abundant pasturage. The northern limit of trees is marked on the map of the plant regions. 323. The Polar Zone, or the Zone of Alpine Shrubs, Mosses, Lichens, and Saxifrages, extends from the limits of the sub-arctic zone to the pole. In this zone, no trees occur except those of a stunted growth. Alpine shrubs, or those of tortuous, com- pact growth, such as the Alpine rhododendra, the dwarf birch, willow, and alder, occur. Sedges and grasses are found. The pastures of the preceding zones are absent; in their place we find extended areas covered with lichens. The northern plains of Siberia are covered with exten- sive marshes, called Tundras, where the ground, during most of the year, is frozen to great depths. The short summers only suffice to thaw the surface, when a few mosses and lichens appear. : 25,000 feet. 20,000 Near the extreme northern limits of the North Polar zone, from the limit of the isotherm of 41° Fahr. for the month of July, such plants only are found as can thrive during the brief Arctic sum- mer of from four to six weeks. Shrubs are en- tirely absent; lichens and mosses occur, together with stunted Alpine herbs. In Spitzbergen, lich- ens and mosses are found, the former being espe- ‘cially numerous. 324, The Vertical Distribution of Vegetation.—It is difficult to make a good systematic arrangement of vege- tation into vertical zones, since the temperature and moisture, on which such an arrangement must be based, are subject to very considerable variations. Thus, the position of the mountain-ranges as regards the prevalent wind, the direc- tion of the mountain slopes, and the extent of the elevated plateaus, all exert such a powerful influence on the mean annual temperature and the rainfall, that even in the same range, opposite slopes, or even different parts of the same slope, afford very marked climatic contrasts. In ranges that are widely separated, the differences are still greater. The following chart exhibits the characteristic flora in tropical America, Africa, Europe, and Asia, at similar elevations. 15,000 10,000 5,000 (1.) Between the level of the sea and 5000 feet, the vegetation is, in general, the same as in the tropical and sub-tropical zones. Palms, bananas, and tree-ferns oc- cur in the lower parts, and barley, potatoes, sugar-cane, rice, cotton, etc., as marked on the chart. (2.) Between 5000 and 10,000 feet, the vegetation is, in general, the same as in warm temperate zones. In America, the birch and cedar occur in the lower portions © of the region, and Peruvian bark and the cinchona trees, so useful in medicine, in the upper portions. In Africa and Europe, the pine, birch, and oak occur; and in Asia, the oak ; here also the vine is cultivated. (3.) Between 10,000 and 15,000 feet, the vegeta- tion, in general, is that of the cold temperate zones. De- ciduous trees occur; rye, wheat, barley, and oats are cul- tivated. (4.) Between 15,000 and 20,000 feet, the flora cor- responds, in general, to that of the polar and .arctic zones. A few rhododendrons and birches occur on the warmer Asiatic slopes, and occasionally crops of barley are culti- Fig. 107, Vertical Distribution of Vegetation. (After BLack.) vated. The greater part of this zone is covered by eternal snow, as is the case with all greater elevations, In the descriptions here given, it will be noticed that the correspondence of the vertical and horizontal zones is but of a very general character. The names of the plants on the chart mark the limits at which they will grow. 325. Plant Regions——In some localities, a few plants occur over extended areas, in such vast numbers as to give a characteristic appearance to the country they cover. A brief mention will be made of such regions, especially as they illustrate the influence of the presence or absence of moist- ure on the vegetation. : . 826. Forests occur wherever the moisture is abundantly and regularly distributed throughout the year. Asa rule, forests are limited to those portions of the world where the rain falls at all 124 PHYSICAL GEOGRAPHY. times of the year, or is abundant during the sea- son the tree is growing, as in the zones of the variable winds. Forests may also occur in por- tions of the tropics where moisture is abundant. The forests of the cold temperate zones are de- ciduous; those of the other zones, evergreen. 327. Steppes—When the moisture is not well distributed throughout the year, but the rainfall is periodical, and long droughts occur in the in-* tervals between the rainy seasons, the forests are replaced by areas called steppes, which, during the wet seasons, are covered with grasses, shrubs, or herbs; but during the dry seasons are almost destitute of vegetation. Steppes are found in the Llanos and Pampas in South America, in the Great Plains of North America, in the grassy steppes of Australia, Russia, and Asia, in the German heaths, and in the African savannas. 828. Meadows and Prairies.—These, like the preceding, are covered with tall grasses, but the vegetation is more permanent, the droughts being only occasional. They are found, therefore, in the temperate zones, in the regions of constant rains. An extended prairie region is found in the valley of the Mississippi, on both sides of the stream. Fig. 108. Desert Scene, 329. Deserts are regions characterized by an almost entire absence of vegetation; they are found mainly in the zones of the trade winds, and are to be ascribed entirely to the absence of moisture. Their bare surfaces are subject to great and sudden changes of temperature, being, as a rule, excessively warm during the day, and often quite cool at night. These changes are due to the readiness with which a bare surface receives and parts with heat. —10$840-e—_—_. CHAPTER II. Cultivated Plants. 830. Plants appear to have been originally confined, by conditions of soil or climate, to cer- tain localities. In many instances, however, plants furnishing materials for food, clothing, or other staples for the human family, have been trans- planted and widely diffused by man. In most of these cases, their successful cultivation is limited to regions where suitable climate and soil ex- isted either naturally, or have been artificially produced. 331. Distribution of the Cereals—The cereals include barley, rye, oats, wheat, maize or Indian corn, and buckwheat; together with the potato, they form the more important food-plants of the temperate zones. Barley, thought to be a native of Tartary and Sicily, can be grown farther north than any other grain; in Lapland, as far as 70° N. lat. Rye is found as far north as lat. 67° N. in Nor- way. It is the most common grain in Russia, Germany, and in portions of France. Oats is probably a native of the Caucasus; its northern limit in Norway is about 65° N. lat. Fig, 109, Maize, or Indian Corn, Wheat is probably a native of Tartary. It is the most important of the cereals, and has a wide CULTIVATED PLANTS. 125 vertical and horizontal distribution. Its northern limit, in Norway, is 64° N. lat. Maize, or Indian Corn, a native of America, is extensively cultivated from the southern part of Chili to high latitudes in North America. Its northern European limit is perhaps near the iso- therm of 65° Fahr. Buckwheat, probably a native of the colder portions of the Chinese Empire, is extensively cultivated in Siberia, on the plateaus of Central Asia, and generally in the cool temperate regions of the rest of the world. Buckwheat is especially _ valuable on account of the ability it possesses of thriving in sandy or moory soils, where other similar food-plants will not succeed. Potatoes.—The native country of the potato appears to have been either Chili or Peru. Though cultivated in both the tropical and tem- perate regions, it is to be regarded as a food- plant of the temperate zones. It possesses a very remarkable range, being cultivated from the ex- tremity of Africa to Lapland: the requisite cold in the tropical regions being found on mountain- slopes. 332. The Food-Plants of the Tropical Regions, are rice, dates, cocoa-nuts, bananas and plantains, cassava, bread-fruit, sago, yams, ete. Rice is cultivated in tropical Africa, Egypt, Nubia, Persia, China, the Americas, and the West Indies. It requires considerable heat and an abundance of moisture. Rice forms the main food of a large portion of the world. Dates form an important article of food in North Africa, both for man and beast. Dates are obtained from the date-palm, a native of a strip of land on the southern slopes of the Atlas Mountains, where the tree occurs so plentifully as to give to the country the name of Beled-el-Jerid, or the Land of Dates. Different varieties of the date are found in the Saharan oases, and in other parts of the world. Cocoa-nuts are the product of the cocoa-palm, which is valuable for its food, timber, foliage, and fibres. The cocoa-palm is a native of Southern Asia, but is cultivated throughout the: tropical regions of Ceylon, Sumatra, Java, and the islands of Polynesia. . Bananas and Plantains are thought to be na- tives of Southern Asia. They are extensively cultivated throughout the tropical zones, both north and south of the equator. Since their fruit is very nutritious, and the-yield of a given 15 area great, they form an exceedingly important staple of food. Fig, 110, Banana. Cassava is obtained from the manioc, a shrub with a fleshy root, several feet long, and nearly as thick as a man’s arm. Tapioca is one of the varieties of cassava. Some species of the man- ioc are poisonous, when raw, but become edible when cooked. The manioc is a native of Brazil, but is abundantly cultivated in Western Africa, in Congo and in Guinea. is : Fig. 111, Bread-Fruit, Bread-Fruit is the pulpy fruit of a tree which grows only in the tropics. The fruit, when baked, resembles potato bread in taste. The tree yields 126 PHYSICAL GEOGRAPHY. fruit during most of the year, and is said to be a native of the South Sea Islands, though it is now quite common in the Friendly and Society groups, and in many of. the neighboring islands. Sago is a starchy substance, obtained from the pith of several species of palm trees, which grow in the Moluccas. A single tree is said to yield from 600 to 800 pounds of sago. Yams are the large tubers of a number of plants, resembling potatoes. They are cultivated in Africa, in South America, and in Cuba. 338. Sugar-Cane is probably a native of India, but is now extensively cultivated through- out the tropical and warm tem- perate zones of both hemispheres, in the West Indies and South- ern United States, Guinea and Brazil, Mauritius and Bourbon, Bengal, Siam, China, Java, and the neighboring islands. _ 334, Fruits of the Tropical and Warm Temperate Zones.— Besides those already enumer- ated, we find the following: oranges, lemons, limes, citrons, gy Lu pine-apples, SOV ny mangoes, figs; and in the cooler por- tions cherries, peaches, apri- cots, and pome- granates. 335. Distri- Plants yield- ing Bever- ages.—The principal plants yielding beverages by infusion are tea, coffee, and cocoa. Tea consists of the dried leaves of a number of evergreen shrubs, natives of China or there- abouts. Tea is cultivated in China and India, from the equator as far north as lat. 45°. It ap- pears to thrive best between 25° and 33° N. lat. It is extensively cultivated in Malacca, Java, and in various portions of the English possessions in India. Tea was introduced into Europe by the Dutch, in 1610. Coffee is the berry of a tree found native in Abyssinia. The tree attains a height of from Fig. 112, Sugar-Cane, 15 to 20 feet, but when cultivated, it is generally kept lower by cutting. The tree has shining Fig, 113, Tea-Plant. green leaves, and bears beautiful white flowers, which are followed by reddish-brown berries, each ‘of which contains two grains of. coffee. The coffee-tree is cultivated extensively in Arabia, Java, the Philippines, Ceylon, Brazil, and in the West Indies. Fig. 114. Coffee. Cocoa.—The cocoa-tree is cultivated in Central America, Guiana, Chili, India, Japan, and in several islands in the Indian Ocean. The tree attains a height of about 20 feet. Chocolate is prepared from the seed of the cocoa-tree. 336. Spices, such as pepper, cloves, nutmegs, and cinnamon, are cultivated mainly within the trop- ics. Vanilla, used in flavoring, is also limited to this region. Pepper.— The black pepper of commerce is ob- tained from the dried seed of a climbing shrub, which grows wild on the western coasts of Hin- SYLLABUS. 127 dostan. ed, or Cayenne pepper, is grown in Guiana and the East. Cloves are the dried flower-buds of an ever- green tree, thirty or forty feet high, which grows in the Moluccas. The cultivation of the tree is confined mainly to the little island of Amboyna. Nutmegs. —The tree from which nutmegs are obtained is found mainly on the Banda Islands, south of Ceram. The nutmeg is covered by several layers of vegetable matter, one of which is the mace of commerce. Cinnamon is the inner bark of a tree, which is cultivated mainly on the island of Ceylon. Vanilla is obtained from the dried, fragrant pods of a plant grown mainly in Mexico, Cen- tral. America, and Brazil. 337. The Principal Narcotics used in different countries are opium, prepared from a species of poppy; the betel-plant, a native of Hindostan: the leaves of the betel-plant are chewed, together with the areca-nut; hasheesh, a narcotic used in India; and tobacco, the dried leaves of a plant grown extensively in Mexico, Cuba, Brazil, and in the United States. 338. Plants Valuable as giving Materials for Clothing, are cotton, hemp, and flax. Cotton, a native of India, is now grown exten- sively in East India, Persia, on the eastern shores of the Mediterranean, in various parts of Europe, and in North and South America. Hemp and Flax are cultivated in the temper- ate regions of Russia, and throughout Great Britain and the United States. The plants producing medicines, and products employed in the arts or manufactures, are: The Cinchona-Tree, found on the upper slopes of the tropical Andes. Quinine is obtained from the bark of the tree. Gum Arabic, obtained from ie East Indies, Egypt, and Africa. Indigo, a blue dye, obtained from the indigo- bearing plants. Brazil-Wood, Nicaragua-Wood, and Log-Wood, yield reddish dyes. Quercitron and Black Oak, yield a yellow dye. Turpentine and Rosin, are products of the pine tree. Caoutchoue, or India-rubber, is the juice of several tropical plants. Olive. Oil is derived from the olive-tree, culti- vated on the borders of the Mediterranean. Cocoa-nut, Palm, Flaxseed and Cotton-Seed Oils, are obtained respectively from the cocoa- nut, palm-tree, and the seeds of flax and cotton. TRE IAU SYLLABUS. ——-020$ 00 ——_. All life consists of groupings of cells or spherical masses, consisting of a transparent jelly-like substance called pro- toplasm. All life originates in a germ cell produced through the agency of pre-existing life. Protoplasm forms an essential part of all plants and ani- ‘nals. Both plants and animals consume protoplasm dur- ing their growth. Plants, alone, produce protoplasm. Ani- mals are dependent on plants for their existence. Plants require for their vigorous growth certain condi- tions of light, heat, moisture, and soil; of these, heat and moisture are the most important. Plant geography treats of the distribution of plants. It differs essentially from botany, which treats of the pecu- liarities in the structure of plants. The plants of any section of country, taken eotecuvely; are called its flora. The differences in the distribution of heat and moisture, produce corresponding differences in the distribution of vegetation. The distribution of heat and moisture, there- fore, forms the true basis for the distribution of plant life. If a soil be wanting in any section of country, but the proper conditions of light, heat, and moisture be present, the simpler vegetable forms will appear, and gradually prepare a soil fitted for the higher kinds of vegetation. The variety and luxuriance of vegetation decrease as we pass from the base to the summit of a mountain, or from the equator to the poles; this decrease is caged by a corresponding decrease in the amount of heat and moisture. According to the horizontal distribution of plants, the surface of the earth is divided into the following zones: the tropical, sub-tropical, warm temperate, cold temper- ate, sub-arctic, and polar. The tropical zone is characterized by the prevalence of palms, bananas, spices, and aromatic plants. The sub-tropical zones are characterized by the preva- lence of laurels, myrtles, and magnolias. The tropical and sub-tropical zones, especially the former, are particularly characterized by an especial luxuriance of their vegetation. The warm temperate zones are characterized by forests of evergreen trees. The cold temperate zones are characterized by forests of deciduous trees. Deciduous trees are those which cast their leaves in 128 PHYSICAL GEOGRAPHY. autumn. Oaks, birches, beeches, chestnuts, walnuts, ma- ples, elms, larches, alders, and sycamores are among the most common of the deciduous trees. Extensive grass-covered meadows are found in the cold temperate plant zones. The sub-arctic zone is characterized by cone-bearing trees. The polar zone, by Alpine shrubs and mosses. Forests require, for their luxuriant growth, an abun- dance of moisture, evenly distributed throughout the year, or during the time the trees are growing. Steppes are regions covered with a scanty vegetation ; they are produced either by insufficient moisture, or its irregular distribution throughout the year. The principal cereals are barley, rye, oats, wheat, maize, corn, and buckwheat. The principal food-plants of the tropical regions are rice, dates, cocoa-nuts, bananas, plantains, cassava, sago, yams, and bread-fruit. Some of the most important plants cultivated for the beverages they yield, are tea, coffee, and cocoa. The principal spices are pepper, cloves, nutmegs, and cinnamon. The principal narcotics are opium, betel, hasheesh, and tobacco. Cotton, hemp, and flax are valuable as furnishing mate- rials for clothing. - The cinchona-tree yields quinine. REVIEW QUESTIONS. ——-059500—_. What is protoplasm? Of what does all life consist? In what respect are animals dependent upon plants for their existence? Define plant geography. In what respect does it differ from botany? Name the conditions requisite for plant growth. How do these conditions compare with each other in importance? Describe the formation of soil. Why is soil of comparatively less importance to the ex- istence of vegetation than heat or moisture? What do you understand by the horizontal distribution of vegetation? By the vertical distribution ? : What is the main cause of the difference in the flora of different parts of the world? Why should the isothermal lines generally form the boundaries of the plant zones? Name the horizontal zones of vegetation. State the boundaries of each of these zones. What is the characteristic flora of the tropical zone? Why should the vegetation of the tropics be so much more luxuriant than that of the rest of the world? Why should the same change be noticed in the vegeta- tion of a high tropical mountain, in passing from its base to its summit, as in passing along the earth’s surface from the equator to the poles? Describe the vertical vegetable zones. To what hori- zontal zone does each of these correspond? Name the conditions requisite for the luxuriant growth of forests. How do the forests of the cold temperate zones differ from those of other zones? By what climatic conditions are steppes produced ? What conditions are requisite for the production of meadows and prairies? How are deserts produced? Name some of the more important cereals. Which of the cereals form the principal food-plants of the temperate zones? Which of the cereals has the far- thest northern range? Which is the most important? Name the principal food-plants of the tropical regions. What is the principal region for the cultivation of dates? Name the principal regions in the world noted for the successful cultivation of the sugar-cane. Name the fruits of the tropical and warm temperate zones. In what portions of the world is coffee successfully cul- tivated? Where is tea cultivated? From what tree is chocolate obtained ? From what plant is black pepper obtained? Where is the plant cultivated? From what are cloves obtained? Where is the tree cul- tivated? Where are nutmegs grown? What is mace? In what part of the world is cinnamon cultivated ? Namé the principal narcotics used in different parts of the world. Name the plants which furnish valuable materials for clothing. From what tree is quinine obtained ? Name some of the principal vegetable dyes. MAP QUESTIONS. —-050300—_ Trace on the map showing the distribution of vegeta- tion, the parts of the world included in the tropical zone. Name the plants of the tropical zone which are charac- teristic of South America. Name those of Africa. Of India and Australia. Describe the principal region of the cocoa-nut palm, bread-fruit, sago, and yam in the eastern continent. Describe from the map the limits of the sub-tropical zones. Describe the characteristic flora of those por- tions of each of the continents which lie within these zones. Describe the limits of the warm temperate zones. Of the cold temperate zones. Of the sub-arctic zone. Of the polar zone. Trace on the map the northern limit of trees. Trace the southern limit of trees. Name some of the trees of the warm temperate zones, Of the cold temperate zones. Of the sub-arctic zones. In what parts of the world are pasture-lands found? Name the characteristic plants of the regions which lie north of the arctic circle. Trace on the map showing the vertical distribution of vegetation, the characteristic plants found in Africa, be- tween the level of the sea and 5000 feet.. In Europe. In Asia. In America, ZOOLOGICAL GEOGRAPHY. ShCrliON Ee ANIMAL LIFE. —n$9300——_. CHAPTER I. Zoological Geography. 339. Zoological Geography treats of the dis- tribution of animal life. The animals found in any region of country are called its fauna. Like plants, animals appear to have been originally created in certain localities, from which they have spread, more or less, over adjoining areas. Though able to move about freely from place to place, animals are, nevertheless, restricted, by conditions of food and climate, to well-defined areas. Animals derive their sustenance, either directly or indirectly, from plants. 340. Distribution of Animal Life—The distri- bution of heat, moisture, and vegetation forms the true basis for the distribution of animal life. We distinguish a horizontal and a vertical dis- tribution of animal life. 25,000 feet. 20,000 15,000 10,000 5,000 passing from the base to the summit of a tropical mountain, the same change is noticed in the spe- cies of animals, as in passing along the surface of the earth from the equator to the poles. In the above chart, the names of the animals are placed at the greatest elevation at which they are found. The power of locomotion possessed by animals renders it extremely difficult to arrange the fauna in zones according to the altitude. In As a rule, the luxuriance and diversity of ter- restrial animal life decrease as we pass from the equator to the poles. A similar decrease is no- ticed in passing from the coasts of the continents toward the interior. Within the tropics, where the abundant heat and moisture produce a vigor- ous vegetation, all forms of terrestrial animal life, save man, attain the greatest development in size, intelligence, and activity. As we proceed toward the poles, the species are less developed, although, in the temperate regions, large and vigorous ani- mals are still numerous. In the polar zones, the reindeer and white bear are the only representa- tives of the larger land animals. In marine animal life, the law of distribution is reversed, both the number and size of the species increasing from the equator toward the poles. This is probably due to the more equable temperature of the ocean in high latitudes. 341, The Vertical Distribution of Life—In general, however, the animals found on the slopes of tropical mountains, at elevations included be- tween the sea-level and from 5000 to 7000 feet, correspond to those inhabiting the tropical zone ; between 5000 or 7000 feet and 15,000 feet, to those of the temperate zones. The condor is found in the high Andes, far above the snow line. The fauna of high mountain-ranges are often sharply 130 PHYSICAL GEOGRAPHY. marked. A particular species, at a given elevation on one range, is frequently entirely wanting on a neighboring disconnected range, even when the same conditions of heat, moisture, and vegetation exist. The temperature of the intervening lower country, through which the ani- mals would have to pass in order to reach the adjoining slopes, forms an impenetrable barrier. 342, Natural Boundaries of Zones of Animal Life.—Large bodies of water, deserts, or moun- tain-ranges, mark the boundaries of regions of animals as well as of plants; but the influence of temperature is so important, that even when these natural barriers are wanting, the horizontal range of animals is sharply marked by the iso- thermal lines. In North America, there are well-marked zones of ani- mals, which extend from east to west across the continent. Here, although no natural barriers exist to limit the wider range of the animals, yet they seem unable to permanently pass the limits of the isotherms, which mark the climatic conditions necessary to their vigorous growth. This in- ability doubtless arises from the distribution of the flora, on which, directly or indirectly, they are dependent for their food. 343, Acclimation—The power of becoming acclimated, or being able to live in a climate dif- fering from that in which they were first created, _ appears to be possessed by animals, as a class, to an exceedingly limited extent. ‘Man, and his faithful friend, the dog, form an exception to most other animals in this respect. They are able to endure both the severe heat of the tropics, and the rigor of the Arctic regions. The reindeer thrives amid the snows of Lapland or Greenland, but perishes from the heat of St. Petersburg. Monkeys are indigenous to the tropics, but die with consumption, even in the compara- tively mild climate of the north temperate zones. | 844, Horizontal Distribution of Animal Life. —The vast number of species of animals, the pe- culiar laws of their growth, and their power of adaptation to change of circumstances, render their accurate distribution into zones or regions a task far beyond the scope of an elementary book.- It will be sufficient for our purpose to divide the fauna of the earth into those found, in general, in the three mathematical climatic zones: the Torrid, the Temperate, and the Polar. The accurate limits of these zones would be found in | the isotherms, but in a general description, little © difference would be noticed. On the map, the actual limits of some of the more important ani- mals are given. These limits, it will be noticed, in most cases follow the general direction of the isotherms. 345. Characteristic Fauna.—aA careful study of the map of the distribution of animal life, will show that each continent possesses a fauna pecu- liar to itself. This arises, generally, from some clearly traceable peculiarity in the distribution of the heat and moisture, or in the nature of the vegetation. Some of these peculiarities will be discussed in a brief review of the characteristic fauna of each of the continents. The following are the characteristic tropical, temperate, and are- tie fauna. 346. Tropical Fauna.—The abundance of heat, moisture, and vegetation of the’ torrid zone causes its fauna. to excel all the others in the number and diversity of terrestrial species, as well as in their size, strength, and sagacity. The following animals are found mainly within . the regions of the earth included between the Tropics of Cancer and Capricorn. Mammalia are represented as follows: Monkeys, by the man-like orang-outang, the chimpanzee, gorilla, baboon, and other species. Fig, 116, Lion, Carnivora, or flesh-eating mammals, by the lion, tiger, panther, and puma. : Herbivora, or plant-eating mammals, by the ele- phant, rhinoceros, tapir, and hippopotamus, the horse-like zebra and quagga, the giraffe or camel- opard, and the camel. Cetacea, or whales, by the sperm whale, found only in tropical or temperate waters. Cheiroptera, or bats, by a number of species. Marsupials, by the kangaroo of Australia. Birds are represented, in tropical regions, by District of Jee Zone of the Tropical Eau TROPIC OF|CAPRICORN BH) A showing the distribution ~_ — | Tropical Fauna. : ; : ; of tts aman Temperate Fauna. eA C Tir Cc Ne PRINCIPAL ANIMALS. [ESS) Arctic Fauna. : LON/GITUDE WEST FROM GREENWICH. i LONG}TUDE EAST FROMIGREENWICH.. 3G 160 2 80) _ 60 40 20 2 40 60 MAP OF THF WORLD ~— ANTARCTIC CIRCLE REFE R ENCES, ; i : ee pap rns sot oo Le 1382 PHYSICAL GEOGRAPHY. species noted for their great size and strength, or for the brilliant colors of their plumage. Among those noted for their size may be mentioned the condor, ostrich, eagle, ibis, flamingo, and cassowary ; among those especially noted for their plumage, the birds of paradise, peacock, and parrots, and the humming-birds of South America, which lat- ter, though in less brilliantly-colored plumage, extend nearly to the extreme limits of the north and south temperate zones. Reptiles are represented by the crocodile, all- gator, iguana, gigantic lizards, and turtles ; among serpents, the enormous boa-constrictor, and num- bers of hooded and other venomous serpents. The Fish of tropical waters, though large and brightly colored, are not so well adapted for food as the more sombre varieties of the temperate or colder waters. 347. Temperate Fauna—tThe following ani- mals are found mainly between the tropics and polar circles. Though fewer of the higher spe- cies of animals are found in the temperate zone than in the torrid zone, yet many of the fauna are of large size, and among them are found ani- mals most useful to man. The physical tropical zone, as will be seen from an in- spection of the map of plant life, actually extends, in the eastern continent, far into the mathematical north tem- perate zone, and in these portions the corresponding trop- ical species occur. Thus, in Northern Africa and South- ern Asia, are found the ape, tiger, lion, panther, camel, and rhinoceros. 7 Mammalia are represented as follows: Flesh-eating mammals, by the lyna, hyena, wolf, jackal, dog, fox, raccoon, bear, seal, and walrus. Plant-eating mammals, by the wild boar and hog, the horse, ass, ov, sheep, goat, and chamois, many of which have been domesticated, as the moose, elk, reindeer, stag, antelope, buffalo, camel, lama, and numerous others. Cetacea, or whales, by the sperm and white whales. Rodentia, or gnawing mammals, by the beavers, squirrels, rats, and porcupines. Marsupials, by the kangaroo of Australia. The birds of the temperate zones are repre- sented by the condor, vulture, hawk, eagle, owl, Fig. 118, Eagles, and parrot (near the southern limit of the zone). The turkey, pheasant, and our common domesti- cated fowls also are natives of this zone. Here occur numerous birds which are noted for the sweetness of their song, as the wren, thrush, robin, nightingale, and lark; the pelican, albatross, and the cassowary are found in this zone. Reptiles are represented by the alligator, eroco- dile, and lizard, and the rattlesnake, copperhead, and various other serpents, both poisonous and harmless. 348, Arctic Fauna.—The following animals are found mainly between the polar circles and the poles. The south arctic fauna is but little known; the following description, therefore, re- fers mainly to the northern hemisphere: In the arctic regions of the world, the large land animals are, with a few exceptions, replaced by numerous smaller furry species. Throughout CHARACTERISTIC FAUNA OF THE CONTINENTS. 133 the northern portions of the north temperate zone, and the southern portions of the arctic, fur-bearing animals are especially numerous and valuable. The white polar bear, the reindeer, moose, and the musk-ox, are among the largest of the land species; but in warmer regions of the oceans, nu- merous species exist, of which the whale is among the largest of the animal world. The Greenland whale, which sometimes attains the length of seventy feet, and is covered with blubber to a thick- ness of two or three feet, is found only in this zone. A similar, though smaller, species occurs in the southern waters. The seal and walrus are also found in this zone. Ho, Seals and Walrus. Besides the larger animals, numerous smaller species, such as minute zodphytes, mollusks, and erustaceans, which form the food of the whale, and which, in some places, exist in immense numbers, inhabit the waters. Among birds, in- numerable water-fowl occur. T97 G Le vified Low wt, CHAPTER. Il. Characteristic Fauna of the Conti- nents. 349. Characteristic Fauna of the Continents. —FEach of the continents is characterized by some peculiarity in its fauna. This peculiarity arises either from the nature of the vegetation, or the distribution of the heat and moisture, and affords an excellent example of the intimate connection between the physical features of a country, and its flora and fauna. Only the general character- istics of the fauna will be given. For the particular animals inhabiting each continent, the student is referred to the map of the distribution of animal life. 350. North American Fauna.—The chief cha- racteristic of the North American fauna is found in the preponderance of plant-eating mammals. This feature is due to the abundance of pasture- lands, and their luxuriant vegetation. From its extensive lake and river systems, North America is peculiarly fitted to sustain aquatic life; hence, its numerous water-fowl and beaver. 801. Fur-bearing animals are particularly nu- merous and valuable. Three natural districts of fur-bearing animals exist: the forest region, the prairie region, and the barren regions of the north, each of which is characterized by a pecu- liar fauna. Forest Region —Here, among carnivora, are found the black bear, marten, ermine, mink, otter, the silver fox, the black fox, and the lynx; among the rodentia, the beaver and musk-rat ; and among the ruminants, the moose and rein- deer. The wolverine and wolf are found both in the for- est region and the barren grounds. Barren Grounds.—The brown and polar bears, the polar fox, and the polar hare are characteristic. Prairie Region.—The grizzly bear, the most formidable animal of the continent; the prairie wolf, and the gray fox are also found here. The’ puma, or the American lion, which is found also over the greater part of South America, is the most powerful representative of the lion and tiger tribe of the East. 352. South American Fauna.—The chief cha- racteristics of the South American fauna arise from the extreme luxuriance of its vegetation, due to the abundance of its moisture. In vast districts, as the Selvas of the Amazon, the vege- table world usurps the ground nearly to the ex- clusion of the higher forms of animal life. The fauna is, therefore, as a rule, characterized by its fitness for existing in connection with either an abundance of water or of vegetation. Insect Life is peculiarly characteristic of the continent. Nowhere else are the species so nu- merous, so brilliantly colored, or so large. Here are found the largest of the beetles, and the most beautiful of the butterflies. Reptiles are largely represented. They find, in the tepid, sluggish waters of the huge rivers, conditions most favorable to rapid growth. Here 134 PHYSICAL GEOGRAPHY. live the crocodile, gigantic lizards, and many venomous serpents. Among Birds, the water species are in the as- cendance. Humming-birds, which occur also in North America, are found in great abundance in the southern continent. The condor is found on the higher slopes throughout the Andes; the os- trich, toucan, and parrot are also characteristic. Among the Mammalia, the ant-eaters and sloths peculiarly characterize the continent. The tapir and peccary are the only representatives of the elephant, rhinoceros, and hippopotamus of the Eastern continents. The lama, puma, and the. prehensile-tailed monkeys are also characteristic of the region. The South American district of fur-bearing animals ex- tends through parts of Chili and the Argentine Republic. The marsh beaver is the principal animal. 353. Asiatic Fauna.—F rom the great mass of land within the tropics, the fauna of Asia, besides its numerous arctic and temperate species, contains a great variety of tropical forms. Taken in connection with Northern Africa, Asia is essentially the region of extensive dry plains and arid tracts. The vegetation through- . Fig. 120, Elephant. out its temperate climes is greatly inferior to that of America, but its animal life is marked by a much greater variety in the higher forms. Fore- - plumage abound. most among these are the man-like monkeys, the orang-outang, the elephant, the royal tiger, and others. Fur-bearing animals are also numerous. Among birds, those with bright, gay-colored Reptiles also are repre- sented, though not to such an extent as in South America. When we bear in mind that in Asia, the horse, ass, goat, sheep, camel, swine, elephant, buffalo, and ox are found in great numbers, it will be seen that Asia, the home of primitive man, is also peculiarly the home of domesticated animals ; that is, of the animals which man has trained to labor for him. The Asiatic district of fur-bearing animals includes Si- beria, Kamtchatka, and the basin of the Amoor River in Mantchooria. The following animals are characteristic: the brown bear, badger, weasel, ermine, sable, otter, marten, and many others. The furs of the sable, black fox, otter, and the ermine, are considered the most valuable. 854. African Fauna.—The peculiarities of the northern portion of the continent have been al- ready pointed out in connection with Asia. It is a fact worthy of notice, that the great deserts of the world, like the Sahara, though nearly desti- tute of any vegetation, are able to sustain many of the highest species of animals. Over these tracts are found the lordly lion, the leopard, and the panther, and the numerous ani- mals on which they prey, such as the antelope, the zebra, the quagga, and others. All these possess powers of rapid locomotion, which pe- culiarly fit them for the arid plains over which they roam. In the remaining portions of Africa, the luxu- riant vegetation is capable of sustaining animals of a larger growth. Here occur the largest of the Mammalia, such as the elephant, rhinoceros, and hippopotamus ; here also is found the giraffe, the largest of the ruminantia; man-like monkeys are also characteristic. 355. Australian Fauna.—The more nearly per- fect isolation of Australia than any of the other continents, together with the peculiar distribu- tion of its heat and moisture, causes its fauna and flora to-differ markedly from those of all the other continents. Australia is essentially the home of the marsu- pials. These are both carnivorous and herbivor- ous. The kangaroo is, perhaps, the most cha- racteristic of the marsupials. Large and power- ful animals are entirely absent; in this respect the continent offers a sharp contrast to Africa. DISTRIBUTION OF THE HUMAN RACE. 1385 The birds are also of peculiar species, such as the emu, cassowary, dodo, and apterix. —°059400—— CEVA iE Ee: The Distribution of the Human Race. 356. Ethnography is that department of phys- ical geography which treats of the varieties of the human race, and their distribution. The range of the distribution of man is much greater than that of the lower animals, which, as we have already seen, with the trifling exception of a few that have been domesticated, are confined to certain limited localities. Man has far greater powers of adapting himself to a change of cir- cumstances, and is found in nearly all the climatic zones, from the equator to the poles, and at all elevations, from the level of the sea to the edge of the snow line. 357. Unity of the Human Race.—Although the different races of men vary greatly in color, size, stature, and intelligence, still a number of circumstances point to their descent from a single family or species. (1.) The Anatomical Structure is invariably the same in all races. (2.) Gradual Modification of Types presented by the different races. The more marked out- ward peculiarities, which serve as the basis for classification, pass into each other, by almost in- sensible gradations, from the highest race to the lowest. This points to a gradual modification of a single, original race by changes in external cir- cumstances, thus producing the present varieties. It would appear that all the varieties of the race have descended from the Caucasians,.or whites. (8.) Similarity of Earlier Myths and Legends. Since the earlier myths and legends of nearly all nations resemble each other, it is fair to infer that their remote ancestors originally dwelt together. (4.) Close Resemblance of Language of Widely Separated Races. This may be regarded as the strongest proof of unity. If we examine the words used in different na- tions to express the most common ideas, we will find a remarkable similarity between many of them. For example, our word father is pita in Sanscrit, pater in Latin, pater in Greek, vater in German, and pére in French. The same similar- ity is noticeable in the words for mother, sister, brother, daughter, God, and many others. The only rational explanation for the resemblance is, that the words were derived from the same parent language, the present differences having been gradually acquired, as the descendants of this earlier people wandered farther and farther from, their common home. An extended comparison made in this way between dif- ferent languages, has shown the common origin of the lan- guages of Europe and a large part of Asia. It has been conclusively proved that these tongues owe their origin to one parent nation, which dwelt, during pre-historic times, in the neighborhood of Mt. Ararat and Mesopotamia. Other families of languages, such as the Chinese and Semitic, have been studied, but thus far the connection between the different families has not been certainly es- tablished. / NEGRO. Fig. 121. Primary Races of Men, MONGOLIAN. 358. The Races of Men Among the varieties of the human race, three strongly-marked types are found: the Caucasian, the Mongolian, and the Negro. These, which may be regarded as the primary races, are grouped around three geograph- ical centres, which correspond nearly to the cen- tres of the three divisions of the Old World. The Caucasian type is found in most of Europe and in South-western Asia; the Mongolian type, in those parts of Europe and Asia not occupied by the Caucasian; the Negro type, in Africa. The other parts of the world are peopled mainly by three other races, which, in general, bear close resemblances to the preceding. These are the Malay, the American, and the Australian. ‘They TROPIC G Hawatik Cc Lt EQUATOR . Bel Ae TROPIC OF| CAPRICORN esians REFERENCES. i JOGRAI Bee Ce eee GS Caucasian. GBB Malay. showing the distribution Nae Mongolian. American. RACES OF MEN. LI Ethiopian. Australian. = ° I 2 LONGITUDE WEST FROM GREENWICH. eal CaUCastan (Mixed.) 140 120 60 60 40 20 0 20 40 60 LONGJTUDE EAST FROM|GREENWICH. DISTRIBUTION OF THE HUMAN RACE. 1387 are called the secondary races, and appear to be modifications of the Mongolian. 859. Cranial Characteristics.—The primary races are - sharply distinguished by the following types of skull: Caucasian. The skull is nearly oval, and the arch of the cheek-bones moderate. Mongolian. The skull is nearly round, the occipito- frontal diameter, or the distance from the forehead to the back of the head, is slightly greater than the parietal diameter, or that between the temples. Negro. The skull is elongated from the back of the head to the forehead; that is, the occipito-frontal diam- eter greatly exceeds the parietal. The cheek-bones are large and projecting. A 360. The Caucasian, or White Race is charac- terized by a round or oval head; symmetrical features; vertical teeth; round or oval face; arched forehead; fair complexion, and ample beard. The Caucasian race inhabits South-western Asia (Hindostan, Persia, and Arabia), Northern ‘Africa, and nearly the whole of Europe. The descendants of the race now people large portions of America, Australia, and Southern Africa. 361. Divisions of the Caucasian Race.—The Caucasian race may be divided into three branches: the Hamitic, the Semitic, and the Japhetic. (1.) The Hamitie Races originally inhabited Palestine, the shores of the Arabian Peninsula, and the valley of the Nile. They are now, how- ever, scarcely distinguishable from the other branches of the Caucasian race, with whom they have intermarried. (2.) The Semitic, or Syro-Arabian Races, com- prise the modern Syrians, the Jews or Hebrews, the inhabitants of Arabia and Abyssinia, and the greater part of Northern Africa. Among the ancient peoples belonging to this branch of the Caucasian race, are the Assyrians and Babylonians, the Israelites, Moabites, Ammonites, Edomites, Ishmael- ites, and Pheenicians. ; _(8.) The Indo-Europeans, or the Aryan Race, comprise the Japhetic race. They are the most civilized peoples of the world, and include the following nations: (1.) Celtic Nations, including the Irish, Welsh, Scots, and the Bretons of France. (2.) Romanic Nations, comprising the Italians, Pbanlendss Portuguese, and the French. (3.) The ancient Greeks. (4.) Germanic Nations, comprising the Germans, Anglo- Saxons (English), Dutch, Flemish, Danes, Swedes, and the Norwegians. (5.) Slavonic Nations, comprising the Russians, Poles, Croats, and Czechs. (6.) Nations of the Iranian Plateau, comprising the Per- sians, Belooches, and the Afghans, (7.) The Hindoos. 16 . broad head; 362. The Mongolian, or Yellow Race.—The chief characteristics of the Mongolian race are: angular face; high cheek-bones; small, obliquely-set eyes; straight, coarse, black hair; scanty beard, and short stature. The color of the skin varies from pale lemon to brownish yellow. The Mongolian race includes the inhabitants of all of Asia, except a small part of the Malay Peninsula, and those portions of the continent occupied by the Caucasians. . It also includes the Lapps and Finns, inhabiting the northern por- tions of Europe, the Turks of Europe, and the Magyars of Hungary, In America, the race is represented by the Esquimaux, who inhabit Greenland and the northern borders of the North American continent. In Central Asia, the race is represented by the Thibetans, Chinese, Indo-Chinese, and others. In Northern Asia, by the Samoides, inhabiting the shores of the Arctic Ocean, from the Petchora to the Yenisei, and south to the Altai Mountains; the Ugrian, or Finnic races, inhabiting the upper valley of the Obe, and a part of Northern Europe; the Tchooktchees, the Tungusians, and the Yakuts, of North-eastern Asia. Other branches of the race, are the Coreans, Japanese, Kamtchatdales, Koriaks, and the Mongols. 363. The Negro, or Black Race.—The chief characteristics of this race are: narrow and elon- gated head; crisp and curly hair; projecting jaws; thick lips; soft and silky skin; color black or dusky ; scanty beard, especially on upper lip; broad feet, and projecting heel-bones. The race inhabits the entire continent of Africa, excepting those ae occupied by the Caucasians. The following are the most important varieties of the race: the Jalofis, Mandingoes, and Ashantis, in the west- ern part; the Tibboos, in the north central; the Gallas, in the eastern; the Congo Negroes, in the south central; and the Hottentots and Kaffirs, in the extreme south. The Negro tribes differ greatly in their civili- zation: the Gallas, though cruel and vindictive, are a handsome, gifted race; the Hottentots, on the contrary, are among the most debased creat- ures in existence. 364, The Secondary Races—The Malay, or Brown Race; the Australian; and the American, or Copper-colored Race, are modifications of the Mongolian Race. 365. The Malay, or Brown Race,—The princi- pal characteristics of this race are the same as those which distinguish the Mongolian ; the eyes, however, are horizontal, the face flat, and the hair 138 PHYSICAL GEOGRAPHY. less coarse and straight. The color of the skin varies from a clear brown to a dark olive. In the Papuans, it is dark brown, and even black. ol, AUSTRALIAN. AMERICAN INDIAN. Fig, 122, Secondary Races of Men, This race inhabits the southern part of the Malay Peninsula, the island of Madagascar, and the islands of the Indian and Pacific Oceans. The different peoples included under the Malay race present the most strongly marked contrasts. The Papuans, for example, differ widely in their appearance from the normal Malay. They are, perhaps, allied more closely to the Australians than to any others. 366. The Australian Race is to be regarded as a sub-variety.of the Papuan branch of the Ma- lays. It inhabits all the continent of Australia not settled by the whites. The Australian race possesses the following characteristics: the head is large; eyes deep-set ; nose broad; hair dark; beard abundant. The color of the skin varies from dark brown to deep black. The Australians are almost wholly desti- tute of civilization. 367. The American, or Copper-colored Race, though containing many widely differing varie- ties, yet possesses, In some respects, many com- mon features. Its general resemblance to the Mongolian is evident, but the top of the skull is more rounded, and the sides less angular. This race, though once numerous and powerful, is now rapidly disappearing before the whites. In Lower California, Mexico, Peru, and Bra- zil, the old races have become mixed with Span- ish and other elements. The ruins of temples, and once populous cities, are com- mon on the high Andean plateaus. These parts of the earth were inhabited at the time of the discovery of the continent by a people who had made considerable progress in the art of working metals, and who were probably of Asiatic origin. The plateaus of Central America contain the traces of a still higher, though more ancient civilization, the origin of which is unknown, though some trace it to a Semitic or an Egyptian source. ORR IA OT SYLLABUS. —-058$ 00—_ The animals of any section of country are called its fauna. Notwithstanding their powers of locomotion, animals are restricted, by conditions of food and climate, to well- defined areas. Since animals are dependent for their existence upon plants, the heat and moisture of any given section of country form the true basis for the distribution of its fauna. We distinguish a horizontal and vertical distribution of animal life. The same change is noticed, in the species of animals, in passing from the base to the summit of high tropical mountains, as in passing along the surface of the earth from the equator to the poles. Terrestrial animal life attains its greatest development, both as regards luxuriance and diversity, within the tropics. Marine animal life attains its greatest development in the colder waters of the polar regions and vicinity. Man attains his greatest mental development in the temperate zone. As regards the vertical distribution of life, the fauna of regions between the sea level and 5000 or 7000 feet, resem- ° bles, in general, that of the tropics; between the preced- ing and 15,000 feet, that of the temperate zones. The boundaries of animal regions are, in general, to be found in the isothermal lines. As a class, animals appear to possess to but a limited de- gree the power of living in a climate differing greatly from that in which they were first created. The fauna of the earth may be conveniently arranged | under three heads: the tropical, temperate, and arctic. The tropical fauna are characterized by the number and diversity of terrestrial species, as well as their size strength, and sagacity. — REVIEW QUESTIONS. 139 In tropical fauna, the mammalia are represented as fol- lows: Monkeys, by the orang-outang, chimpanzee, gorilla, and baboon. Flesh-eating mammals, by the lion, tiger, panther, and puma. Plant-eating mammals, by the elephant, rhinoceros, ta- pir, hippopotamus, zebra, quagga, giraffe, and camel. Marsupials, by the kangaroo. Birds are represented by the condor, ostrich, eagle, ibis, flamingo, cassowary, bird of paradise, peacock, and parrot. Reptiles are represented by the crocodile, alligator, iguana, and turtles. The temperate fauna, though characterized by fewer of the higher species of animals, yet contain many of large size, and among them animals of great use to man. In temperate fauna, the carnivorous mammalia are rep- resented by the lynx, hyena, wolf, jackal, dog, fox, rac- coon, bear, seal, and walrus. The herbivorous mammalia, by the wild boar, hog, horse, ass, ox, sheep, goat, chamois, moose, elk, reindeer, stag, antelope, buffalo, camel, and lama. The gnawing mammals, by the beaver, squirrel, rat, and porcupine. The whale, by the sperm and white whale. The marsupials, by the kangaroo. Birds, by the condor, vulture, hawk, eagle, owl, parrot, turkey, pheasant, wren, thrush, robin, nightingale, lark, pelican, and albatross. The arctic fauna contain but comparatively few large land species; the chief characteristics are numerous smaller furry species. The terrestrial arctic fauna are characterized by the fol- lowing animals: the white polar bear, the reindeer, the moose, and the musk-ox. The marine arctic fauna are characterized by the Green- land whale, the seal, and the walrus. The whale is among the largest species of the animal world. The peculiar distribution of the vegetation of the con- tinents produces corresponding peculiarities in their cha- racteristic fauna. The North American continent is characterized by the preponderance of its plant-eating mammals. The cause of this peculiarity is to be found in the abundance of its pasture lands. Fur-bearing animals particularly characterize the north- ern and central portions of North America. There are three natural districts of fur-bearing animals in North America: 1. The forest region; 2. The barren grounds; 3. The prairie regions. The South American continent is especially character- ized by the predominance of reptilian life, aquatic birds, and insects. The cause of the peculiarity is traceable to the predominance of the vegetable life over the animal. . The Asiatic continent is especially characterized as being the original home of most of the animals which man has domesticated. The cause of this peculiarity is traceable to the fact that Asia was the primitive home of man himself. : The great deserts of Africa are characterized by the presence of animals which are peculiarly noted for their swiftness of locomotion. In the remaining portions of Africa, the luxuriant vege- tation sustains animals of a larger, bulkier growth; as, for example, the elephant, rhinoceros, hippopotamus, and the giraffe. Australia is peculiarly characterized by the presence of the marsupials. It is the home of the kangaroo, the most important of the marsupials. Ethnography treats of the varieties of the human race, and their distribution. ‘ Man has a wider range of distribution than any other animal. It is believed by most that all the varieties of the hu- man race were originally descended from one family. Though greatly different in color, size, stature, and in- telligence, the general anatomical structure, the basis on which all other animals are classified, is invariably the same, even in the most widely differing races. The languages of Europe and of a large portion of Asia, appear to owe their origin to one parent nation, which dwelt, during pre-historic time, in the neighborhood of Mount Ararat and Mesopotamia. The primary races are the Caucasian, the Mongolian, and the Negro. The secondary races are modifications of the Mongolian: they are the Malay, the American, and the Australian. The Caucasian race inhabits South-western Asia, North- ern Africa, and nearly the whole of Europe. The Caucasian race may be divided into three branches: the Hamitic, the Semitic, and the Japhetic, or the Indo- Europeans. The Mongolian race inhabits all of Asia, except a small part of the Malay Peninsula and those portions of the continent occupied by the Caucasians. The Chinese, Japanese, Esquimaux, Lapps, Finns, Turks, and Magyars are the most important of the Mongolians. The Negro race inhabits all the continent of Africa not occupied by the Caucasians. The Malay race inhabits the southern part of the Malay Peninsula, Madagascar, and the islands of the Indian and Pacific Oceans. The Australian race inhabits all the continent of Aus- tralia not settled by the whites. REVIEW QUESTIONS. ——-0£9300——. Define zéological geography. Fauna. Why should the distribution of heat and moisture form the true basis for the distribution of animal life? Distinguish between the horizontal and the vertical dis- tribution of animals. What difference exists between terrestrial tropical fauna and marine tropical fauna? Between what limits, in the vertical distribution of ani- mals, do the fauna of a tropical mountain-range resemble that_of the tropical horizontal zone? Of the temperate zone? What lines generally form the boundaries of animal regions? Which possesses the greater power of acclimation, man or the inferior animals? State the characteristics of the tropical fauna, naming 140 PHYSICAL GEOGRAPHY. the principal carnivora, herbivora, cetacea, cheiroptera, Define ethnography. marsupials, birds, and reptiles. ‘What arguments can be adduced to show the probable State the characteristics of the temperate fauna, naming. unity of the human race ? the principal carnivora, herbivora, rodentia, cetacea, mar- Name the primary races. supials, birds, and reptiles. Name the secondary races. State the characteristics of the arctic fauna, naming the Into what three branches may the Caucasian race be characteristic terrestrial and marine species. divided? What peculiarities characterize the fauna of North What peoples have descended from the Aryans, or the America? What is the cause of these peculiarities? Indo-Europeans? What are the peculiarities of the fauna of the South Name the principal Celtic nations. American continent? What is the cause of these pecu- What nations have sprung from the ancient Romans? liarities? What nations have descended from the Germans? What is the main peculiarity of the Asiatic fauna? Name the Slavonic nations. The Iranians. Describe the districts of fur-bearing animals of North Name the parts of the world inhabited by each of the America. Of Asia, primary and secondary races. For what peculiarity are the animals of the deserts of Describe the peculiarities of each of these races. Africa and Arabia noted ? Name a few of the peoples which belong to each of the What is the main characteristic of the Australian fauna? races. MAP QUESTIONS. ——0583 00 —_ Trace on the map of the Vertical Distribution of Ani- Locate the chief districts of venomous serpents in the mal Life, the characteristic fauna in those parts of each eastern and western hemispheres. of the continents, lying between the level of the sea and Describe the region of the musk-ox. Of the grizzly 5000 feet. Between 5000 and 10,000 feet. Between 10,000 bear. Of the buffalo. and 15,000 feet. Between 15,000 and 20,000 feet. State, from the Ethnographic Map, the portions of the Name from the map of the Distribution of Animals, the world inhabited by the Caucasian race. The Mongolian tropical species of the Americas. Of Africa. Of Asia. race. The Ethiopian race. The Malay race. The Amer- Of Australia. ican race. The Australian race. Name, in a similar manner, the temperate and arctic | What different peoples dwell north of the arctic circle? species of the Americas. Of Europe. Africa. Asia. Aus- South of the tropic of Capricorn? tralia. Trace on the map the northern limit of permanent In what portions of the world is the seal found? The habitation. The southern limit. walrus? The whale? What race inhabits Hindostan? What people? What Trace on the map the southern limit of the polar bear. race inhabits Abyssinia? What people? Greenland? Of the reindeer. Of monkeys. Of the elephant and rhi- Patagonia? China? Mexico? France and Spain? North- noceros. The northern limit of the camel. Of monkeys. ern Norway and Sweden? Arabia? Madagascar ? MINERALS. 141 SECTION LIE MINERALS. —_00$6{0-0-——_ GHA PT Et. - Minerals. 868. General Distribution of Minerals—The distribution of the various mineral substances that form parts of the earth’s crust, unlike the distribution of the earth’s plant and animal life, is independent of the distribution of heat and moisture. Mineral products, therefore, cannot be arranged in zones, according to latitude and alti- tude, as can the plants and animals. The absolute dependence of plants and animals on the distribution of heat and moisture necessarily limits them to those parts of the earth in which the requisite condi- tions exist. Moreover, while some animals, to a certain degree, possess the ability to become acclimated, that is, to accommodate themselves to changes in climate, yet they are necessarily limited to the regions in which the vegetable food exists on which they are directly or in- directly dependent. Mineral substances, on the contrary, are not, to any marked degree, dependent on existing cli- matic or surface conditions, since the conditions under which they were formed or deposited no longer exist. Since some mineral substances are practically limited to certain geological formations, a fairly good distribution might be based on the geological strata, were it not for the fact that, in many cases, through the agency of ero- sion, such substances have been distributed through the rocks of later formations. Moreover, in many cases, the mineral products are found in nearly all the geological formations. No attempt, therefore, will be made to arrange the earth’s mineral products in characteristic zones or regions. ; 369. Value of Mineral Products.—The civil- ization of man is largely dependent on the char- acter and extent of the earth’s mineral products. His progress would have been seriously retarded had the earth contained no metallic substances from which he could fashion tools, build machines, form the rails for steam and electric roads, or the electric conductors for telegraph, telephone, elec- tric light and power lines, and had he no metals suitable for coining or, for ornamentation. Had no stores of energy been placed in the earth’s crust for his use, in beds of coal, in peat-bogs, or in recesses filled with coal-oil or natural gas, or did he fail to find among the earth’s mineral treasures, beds of sandstone, granite, marble or other similar materials with which to build his houses, his ability to adapt himself to various climates would have been seriously restricted. Moreover, if the mineral products now employed for their medicinal or curative properties were denied to him, life and health would have been markedly decreased. 370. Varieties of Mineral Substances.—Min- eral substances occur in a gaseous state, as in natural gas; in the liquid state, as in petroleum or coal-oil; and in the solid state, as in the various building stones, coal, rock-salt, and metal- lic ores generally. The solid state is by far the most common. Mineral substances occur at varying depths and are obtained by different mining processes. Sometimes, as in the case of gold, the mineral occurs near the surface, in beds of sand or gravel. Here, hydraulic mining, or the washing away of the deposits by powerful streams of watzr, may be adopted. -Generally, however, the deposits occur at fairly considerable distances below the surface, in which case shaft-mining is necessary ; 7%. é., pits, shafts, or galleries are cut through the crust so as to reach the deposits. Building stones are generally obtained from - open cuttings or quarries, since the cost of taking out such substances from great depths would be restrictive. It is generally believed that large and valuable metallic deposits exist at depths below which mining operations have, as yet, been carried on. 871. Classification of Mineral Products—For convenience of study, mineral products may be divided into the following classes: (1.) The metals and their ores. (2.) Coal, peat, coal-oil and natural gas. (8.) Clay, kaolin, marls, salt, sulphur and graphite. (4.) Building stones. (5.) Precious stones or gems. 372. The Metals and their Ores——The most important metals are gold, silver, platinum, iron, 142, i PHYSICAL GEOGRAPHY. copper, tin, lead, zinc, mercury, nickel, antimony and aluminium. Gold, silver and platinum are sometimes called the precious metals. Metals occur either in the pure or native state or condition, uncombined with other substances ; in combination with other metals as alloys; or in combination with non-metallic substances as ores, such as oxides, sulphides, chlorides, carbon- ates, etc. Gold, silver, platinum and copper frequently occur in the native or metallic state or alloyed with other metals. 873. Gold, the most valuable of the metals, does not readily rust or tarnish on exposure to air, and is extensively employed for coinage and jewelry. It occurs most extensively in the native or metallic state in small granules or irregular masses, called nuggets; in veins in quartz rocks; in the sand or gravel of river beds; or in alluvial deposits called placers. Native gold is found usually slightly alloyed with other metals. The deposits in the western parts of the United States are the richest in the world. Those of Australia, are, perhaps, next in importance. Mexico, Central America, South America, Alaska, Western and Southern Africa, New Zealand and portions of the regions adjoining the Ural Mountains, have also rich deposits. Perfectly pure gold is too soft to be employed for coins or jewelry. In order to render it sufficiently hard for use it is usually alloyed with silver or copper. 374. Silver and Platinum.—Silver, like gold, is largely employed for coinage and for jewelry. It does not easily oxidize, but readily blackens on exposure to gases containing sulphur. Silver isa widely-distributed metal. It occurs sometimes in the native or pure state, but is usually either mixed or alloyed with other metals, or occurs as a sulphide. It is frequently associated with de- posits of copper, lead and other metals. The richest silver deposits in the United States are situated in the western parts, especially in Colorado and Nevada. Mexico and South America also have valuable deposits. Platinum, one of the heaviest metals known, occurs native and alloyed with other metals. It resembles silver in color. It is extensively em- ployed for the leading-in wires of incandescent electric lamps. Its exceedingly high melting point renders it especially fitted for use in the construction of small vessels, such as crucibles, or retorts, that are required to resist exposure to high temperatures. The principal deposits of platinum are in the region of the Ural Mountains. 375. Iron, Copper, Tin, Lead, Zinc, Mercury, Nickel and Antimony.—These valuable metallic substances, with the exception of tin, are very ‘generally distributed and rich deposits occur in all the continents. Iron occurs in vast deposits in nearly all parts of the world. Iron possesses a number of prop- erties which render it by far the most useful of all the metals. Pure or wrought iron, when softened by heat, can readily be rolled into sheets or forged into any desired state. It may readily be drawn into wire. Its great tenacity renders it extremely valuable as a building material. When mixed with a small quantity of carbon, iron readily fuses and it may then be cast into any desired shape. Combined with a small quantity of carbon it forms the well-known substance, steel. Copper, so extensively employed in the electri- cal industries, possesses properties that give ita prominent place among the useful metals. It is malleable and ductile; 7. ¢., may readily be beaten or rolled out into sheets, or drawn out into wires. It forms a number of valuable alloys ;—such as brass with zinc; and gun-metal and bronze, with tin. The deposits of native copper in the Lake Superior dis- tricts, in the United States, are the richest in the world. Zine and Lead are valuable metals. Zinc is readily rolled into sheets, and is not readily oxid- ized or rusted. Galvanized iron, or iron covered with a layer of metallic zine, resists oxidation. Lead is employed for water-piping, the lining of tanks, bullets, ete. It forms valuable alloys, and is largely employed in the production of paints. The most extensive deposits of lead in the United States occur in Colorado. Zinc is found in Missouri and adjoin- ing States. Tin is the well-known metal employed in tin- ware. Tin-plate consists of sheets of iron covered with a thin layer of tin. The principal ore of tin is the oxide. Valuable deposits occur in Cornwall, England; in the Island of Banca; in Australia; and in Mexico. : Mercury is distinguished from the ordinary metals by being liquid at ordinary temperatures. It is extensively employed in thermometers and barometers. Its power of forming alloys with gold and silver is utilized in the amalgamating process of extraction. An amalgam of mercury and tin is employed for the reflecting surfaces of mirrors. Valuable deposits of cinnabar, the red sulphide of mer- cury, occur at Almaden in Spain; in California; and in Asia Minor. MINERALS. 148 Nickel is a metal which does not readily tarnish. It is extensively employed for electro-plating iron and other readily-oxidizable metals. number of valuable alloys, one of which is Ger- man silver. Nickel is employed to some extent in coinage. Antimony is a metal which when alloyed with lead is extensively employed as type- metal. .This alloy possesses the property of tak- ing sharp casts, thus permitting the type to be readily made. Valuable deposits of its ore occur in the United States and in Europe. Aluminium is a remarkably light metal, ob- tained from clay. It is not oxidized by exposure to air, and possesses valuable properties. 376. Coal, Peat, Coal-oil and Natural Gas form a group of natural fuels of great use to man. Coal is by far the most important of the natural fuels. Its formation is practically limited to the carboniferous age. (See paragraph 75.) Valuable deposits of coal are found in nearly all parts of the world. The deposits of the United States are prob- ably richer than in any other country. (See paragraph 417.) Peat, an inferior form of fuel, is a carbonaceous deposit that occurs in marshy districts in moist climates. Exten- sive peat-bogs exist in Ireland and in the United States. Coal-oil or petroleum, a valuable form of natural fuel, exists in reservoirs, as already described in paragraph 167. Valuable oil-fields exist in Western Pennsylvania; in Rus- sia; and in other parts of the earth. Natural gas exists in great quantities in the neighbor- hood of the coal-oil districts in the United States and elsewhere. (See paragraph 420.) 377. Clay, Kaolin, Marl, Salt, Sulphur and Graphite——Besides the mineral products already described there is a great variety of others that are employed for various purposes in the arts or sciences. Some of the more important of them are clay, kaolin, marl, salt, sulphur and graphite. Clay and kaolin are extensively employed in the manufacture of bricks, pottery, terra-cotta ware, stone- ware, china and porcelain. Marls are various mixtures of clay and lime, and are employed for fertilizing lands. Clay and marls are extensively found in all parts of the earth. Common salt, or chloride of sodium, is one of the principal saline ingredients in ocean water, and in the waters of inland seas or steppe lakes. It occurs also in vast deposits as rock-salt where it has been derived from the gradual evaporation of saline waters. Various saline or salt springs exist. (See paragraph 166.) Sulphur exists in a native or pure state in volcanic dis- tricts, or combined with various metallic substances as sulphides, it is generally distributed.. It is extensively employed in the manufacture of sulphuric acid. Graphite is a form of carbon extensively employed in lead pencils, and is valuable as a lubricant. In addition to the above mineral products are beds of sand, suitable, when mixed with burnt lime, to form mor- It forms a _ tars and cements; or to form glass, when fused with potash or other basic substances. 378. Building Stones are found in immense deposits near the surface in various parts of the earth. A material to be suitable for building purposes must possess marked strength and tena- city and be able to resist being crushed by the weight placed upon it. It must especially resist disintegration or breaking up under the action of the weather. The more important building stones are granite, gneiss, blue-stone, sandstone, magnesian lime- stone, marble and slate. 379, The Precious Stones or Gems.—Besides the mineral substances already referred to, which with some few exceptions occur in extensive deposits in nearly all parts of the world, there are others which either occur very rarely, or, if common, are but seldom found in fine specimens, free from flaws or other blemishes. These min- erals are called the precious stones or gems, and are highly prized as articles of jewelry. The principal precious stones, or gems, are the diamond, the sapphire, the ruby, the topaz, the emerald, the beryl, the opal, and the garnet. ‘The diamond is a crystallized form of pure carbon. Its value depends on its lustre and color, on its freedom from flaws, and on its size, especially the latter. In the natural state it is generally lustreless and requires to be cut and polished: in order to bring out its fire or lustre. Its value is rated by the carat (approwimately 3 grains). The principal diamond-fields of the world are in South Africa, New South Wales, the Ural Mountains and Brazil. The sapphire is a beautiful blue stone; the best speci- mens are found in Brazil. The ruby has a deep red color; perfect specimens of more than two carats in weight are more valuable than the diamond; the best specimens are found in Siam. The topaz is a yellow stone of various shades; the best specimens are found on Topaz Island in the Red Sea. The emerald is a gem of a beautiful green color; the finest specimens are found in New Granada. The beryl is a stone which occurs in the form of six-sided prisms, usually either blue, green, or yellow, but some- times colorless. The opal, with its changing hues and blending colors, has a strange beauty which defies imita- tion. The garnet occurs in a variety of colors and is quite abundant, being found in all the continents. Other minerals used for ornamentation and jewelry, but less valuable than the above, are turquoise, lapis-lazuli, malachite and quartz. Quartz is a crystal stone of some beauty; amethyst, cat’s-eye, chalcedony, onyx, sardonyx, carnelian, jasper, agate, blood-stone, plasma, and chrysoprase are varieties of quartz of different colors and markings. Pearls are deposits of carbonate of lime and organic matter; they are found within the shells of the pearl oyster and other mollusks; they occur on the tropical coasts of Asia and America, the best specimens are found on the coasts of Ceylon. 144 - PHYSICAL GEOGRAPHY. - SYLLABUS. —-050$ 00——_. The earth’s mineral products cannot be arranged in zones according to the altitude or latitude as can its plants and animals. : The civilization of man is largely dependent on the character of the earth’s mineral products. Mineral substances occur either in the gaseous, the liquid or the solid state; the last is by far the most common. The earth’s mineral products may be conveniently grouped under the following classes :—namely, (1) Metals and their ores. (2) Coal, peat, coal-oil and natural gas. (3) Clay, kaolin, marl, salt, sulphur and graphite. (4) Building stones. (5) The precious stones or gems. The most important metals are gold, silver, platinum, iron, copper, tin, lead, zinc, mercury, nickel, antimony and aluminium. Gold, silver and platinum are sometimes called the precious metals. : The principal natural fuels are coal, peat, coal-oil and natural gas. Clay, kaolin, marl, salt, sulphur and graphite are ex- tensively employed in the arts. The principal building stones are granite, gneiss, blue- stone, sandstone, magnesian limestone, marble and slate. The principal precious stones or gems are the diamond, the sapphire, the ruby, the emerald, the beryl, the topaz, the opal, and the garnet. REVIEW QUESTIONS. OO ree Why cannot the earth’s mineral products be readily arranged in characteristic zones or regions? -In what manner is man’s progress dependent on the character and distribution of mineral products. In what different states or conditions do the earth’s mineral products occur? Which of these is the most common ? How may the earth’s mineral products be classified ? Name the precious metals. Name some of the most im- portant of the more common metals. Name any five common metals, and some practical uses to, which each may be put. Name the principal natural fuels. For what purposes are clays and kaolins employed ? What are marls? Name some of the principal sources of common salt. ‘ Name the principal building stones. What are diamonds? Where are they found? How is their value estimated? Upon what does it depend? Name some other precious stones, Page 143. CHeny sere Q) merle Sound A PY (Hatteras — i “psound ~~ \ & —— : REFERENCES. | ® showing the i DP Le A Lands S SURFACE STRUCTURE ; ay ; SEO ees AND ISOTHERMAL LINES. : : Low Lands. Cascade Range and ReckyMountain 15,000 ft. ‘ Sierra Nevada System. ystem. 10,000 w 1 = ~ + AT S 15,000f%. ao PACLFIC THE GREAT BASIN ae ee ‘ Appalachi O00 E SO ery SLOPE THE GREAT PLAINS wuie MISSISSIPPI VALLEY PPSystem. Soe Bono [Pacitic Ocean CALIFORNIA [NEVADA]U T A H| COLORADO se ae eee ay Se, THE PHYSICAL FEATURES OF THE UNITED STATES. ——-0505 00 —— The civilization and development of a country are dependent, in a marked degree, on the pecu- liarities of its physical features. life, and these, in turn, react on man. The soil and climate exert their influence on the vegetable and animal If proper soil and climate exist; if the peculiarities of the surface structure permit of ready intercommunication, and if extensive deposits of coal and velnplole metals occur, the future development of the country is assured. The physical features of the magnificent domain of the United States are such as seem to destine it to become the theatre of the civilization of the future. The peculiarities of its position and extent, the nature of its soil, the climate, and rainfall, the size and constancy of its navigable rivers, and the extent and variety of its valuable mineral deposits, eminently fit it to sustain a very high order of civilization. ee CHA Pika: Surface Structure of the United States, exclusive of Alaska. 380. Situation and Extent.—The United States occupies the entire breadth of the North American continent, between lat. 49° N., and 24° 30’ N. and extends from long. 66° 50’ W. from Greenwich, to 124° 31’ W. The total area, exclusive of Alaska, is 3,026,500 square miles. 146 381. Coast Line—The coast line is compara- tively simple and unbroken. On the east, the Atlantic Ocean extends into the land in three wide curves; on the south, is the deep indenta- tion of the Mexican Gulf; on the west, the land is thrust out into the Pacific in an almost unbroken curve. The total coast line, exclusive of the ad- joining islands and Alaska, is about 12,609 miles. 382. Gulfs and Bays.—The principal indenta- tions on the eastern coast are Long Island Sound, Delaware and Chesapeake Bays, and Albemarle SURFACE STRUCTURE OF THE UNITED STATES. 147 and Pamlico Sounds. On the western coast are the Gulf of Georgia and the fine harbor of the Bay of San Francisco. The Atlantic shores slope gently toward the ocean; the Pacific shores are abrupt. 383. Islands—The islands of the Atlantic coast are of three distinct classes: those north of Cape Cod are, for the most part, rocky, and are de- tached portions of the mainland; those south of Cape Cod are generally low and sandy, and are, for the most part, of fluvio-marine formation ; those off the coast of Florida are of mangrove forma- tion. On the Pacific coast are the Santa Barbara Islands, a rocky group south-west of California; and Vancouver Island, north-west of Washington. Fig. 123, View on the Ooast of Mount Desert Island, Maine. 384, Mangrove Islands.—Mangrove trees grow in dense jungles, on low muddy shores, in tropical regions. From both trunks and branches the trees throw out air-roots, which spread so as to cover the adjoining spaces in an almost intermin- able network of roots and branches. The area of surface covered by the trees is still further in- creased by the curious property which the seeds possess of sprouting while on the tree, subse- quently floating away, and afterward affixing themselves to the bottom of the jungle, to form new growths. In this way, the trees form man- grove islands, which at first are not true islands, the trees simply standing above the water by means of their intertwined roots. In course of time, however, sediment, collecting between the roots of the trees, forms islands. These islands are common in the shallow water off the coasts of Florida. 385. Coral Reefs of Florida.—The peninsula of Florida, south of the northern extremity of the Everglades, and probably as far north on the 17 eastern coast as St. Augustine, is, according to Agassiz, a species of coral formation, formed, however, under different conditions than are the coral islands of the Pacific. Fig, 126. Everglades, Reefs, and Keys of Florida, (LeConte.) Figure 124 is a map of Florida with its reefs and keys, Figure 125, is a section along the line A.A. In Fig. 124 the line a a, shows what was at one time the limit of the southern coast of Florida. 6}, is the present limit of the southern coast. cc, are the keys, which are low islands. dd, is the growing coral reef. e, is the Everglades, dotted with islands, called hunmocks. Between cc, and d d,_is the ship channel. Outside the growing coral reef dd, are the profound depths of the Gulf Stream G. 8. The growth of the reef-formations is explained by LeConte as follows (Fig. 125): a, was at one time the limit of the southern coast of Florida. 8, is the present southern coast, which at one time was a coral reef like d. Upon 8, a line of coral islands gradually formed connecting it with the old southern coast a. The ship channel between a, and }, gradually filled up and formed the Everglades e. Meanwhile, another reef formed, in the position of the present keys, ¢, the ship channel being between 5b, and c. This reef has now grown to be a line of coral islands, and the ship channel, between }, and ¢, converted into shoals and mud flats, f. The present ship channel is between c,and d. In course of time the southern coast will extend to the present line of keys, c, and the shoal water f, will become another Everglades. Outside the present keys c, another coral reef d, is growing, to which the coast will ultimately extend, and which will mark the limit of the formation, owing to the deep waters 148 PHYSICAL GEOGRAPHY. of the Gulf Stream, immediately beyond it. In Figure 125, the dotted lines show the successive steps of the formation. 386. Forms of Relief—The United States is traversed by two distinct mountain-systems: the Pacific System—the predominant system—on the west, and the Appalachian System—the secondary system—on the east. 387. The Pacific System, consists of a broad plateau, traversed by two distinct mountain-sys- tems: the Rocky Mountains, and the Pacific mountain-chains. It embraces about one-third of the entire territory of the United States proper. 388. The Rocky Mountain System, consists of a number of parallel chains connected by numer- ous cross ranges. They rise from the summits of an elevated plateau, which in some places ‘is fully 7000 feet above the sea. The chains are broken in several places by transverse valleys or passes, traversed by important rivers. The most import- ant of these passes is South Pass, in Wyoming, traversed by the Sweet Water. River, a tributary of the Platte. The Missouri, Rio Grande, and other rivers also flow through similar depressions. The chains are separated into northern and southern sections by a gap occupied by an elevated plateau, over which the Union Pacific Railroad passes. Among the many lofty peaks of this mountain- system are Long’s Peak, 14,050 feet ; Pike’s Peak, 14,216 feet ; and Fremont’s Peak, 13,570 feet high. A remarkable feature of these mountains is the basin- shaped valleys, called parks, formed by transverse ranges connecting the parallel ranges. these parks are North, South, and Middle Parks. They are nearly rectangular in outline, and are hemmed in by huge mountain-ranges. Each park gives rise to an im- portant river. The rich verdure of these deeply-sunken basins is rendered the more striking by contrast with the desolate mountains surrounding them. The Yellowstone National Park, in the north-western part of Wyoming, is traversed by some of the head-waters sof the Yellowstone River. It is a region of hot springs, deep gorges, high mountain-peaks, and magnificent scenery. It has been set apart by the government for the purposes of a public park. The Great Plains, an elevated plateau, lie along the eastern side of the Rocky Mountains. They are undulating plains, which slope by almost imperceptible gradations, to the valley of the Mississippi. They are treeless, and near the base of the mountains have but a scanty vegetation. Near the lower part of the slope they merge into prairies, covered with a luxuri- ant growth of grass. r The most important of |_ 389. The Pacific Mountain-Chains extend through California, Oregon, and Washington, and, in general, are parallel to the Rocky Moun- tains. They comprise the Cascade Mountains in Oregon and Washington, and the Sierra Nevada and the Coast Mountains in California. The famous gold regions of California lie mainly west of the Sierra Nevada and the Coast Mountains. The loftiest peaks of the Pacific Mountains— chain exceed those of the Rocky Mountains in height. The highest peaks are Mt. Rainier in the Cascade Range, 14,444 feet high; and in the_ iS o 4 e Sierra Nevada Range, Mt. Shasta, 14,482 feet —}* high, and Mt. Whitney, 14,800 feet high. The eee point of the Pacific Mountain- chains is MouaSt=kes, in Alaska, which is es- timated to Be 19, 500 feet high. The Cascade Mountains contain numerous ex- tinct volcanoes. The Great Basin lies between the Wahsatch on the east. and the Sierra Nevada and Cascade ranges on the west, Fig, 126, The Great Gatton 0 of Colorado, It possesses a true inland drainage. East of the Wahsatch Mountains and the western flanks of the elevated peaks = iad SURFACE STRUCTURE OF THE and ranges of Colorado, lies a region drained by the head- waters of the Colorado. This region, together with the country lying in the middle courses of the river, is a won- derful section of country, traversed by streams that have eroded their valleys and flow through deep cafions, some of which are over 6000 feet deep. A view of apart of one of the most noted of these cafions is shown in Fig. 126. 390. The Appalachian System, sometimes called the Alleghany Mountains, extends from Georgia to Maine, nearly parallel to the Atlantic. The chain varies in breadth from 150 to 200 miles. The system consists of an elevated plateau, bearing several mountain-chains, separated by wide valleys. In the northern and southern parts of the chain, where the elevation is the greatest, the system is formed of irregular groups, without any definite direction. In the centre, low parallel chains occur separated by fertile val- leys. These valleys generally take the names of the rivers which flow through them. The system is highest in North Carolina, where Mt. Mitchell, 6707 feet high, forms its culminat- ing point. Beginning in the north, the system includes the White Mountains in New Hampshire, with Mount Fig, 127, The Natural Bridge (Virginia). Washington, 6294 feet high ; the Green Mountains, in Vermont; the Adirondacks, in New York, with UNITED STATES. 149 the culminating peak of Mount Marcy, 5379 feet high; the Catskill Mountains, the Blue Mountains, the Alleghanies, the Blue Ridge, the Cumberland Mountains, and others. The Natural Bridge, in Rockbridge County, Virginia, “is, from its peculiar formation, an object of interest to tourists. 391. Plains—There are two great low plains in the United States: the Atlantic Coast Plain and the Plain of the Mississippi Valley. The Atlantic Coast Plain lies along the eastern flanks of the Appalachian Mountains. It varies in width from 50 to 250 miles. Along the coast the soil is comparatively sandy, and has been formed by the combined action of the rivers and ocean. - The extensive swamps which occur in this region—such as Cypress Swamp, in Delaware, Dismal Swamp, north of Albemarle Sound, Alligator Swamp, between Albemarle and Pamlico Sounds, and Okefinokee Swamp, in Southern Georgia—are of fluvio-marine origin. The Everglades, in Florida, are the result of a coral formation. Farther from the coast, the plain is more elevated ; long valleys occur, which are very fertile, particularly near the river bottoms. The Mississippi Valley lies between the predomi- nant and the secondary mountain-systems. It is over 300,000 square miles in area, and includes some of the most fertile land in the country. Much of it is covered with forests or prairies. 392. River- and Lake-Systems.—The United States is particularly noted for the number and extent of its navigable rivers. Oceanic Drainage—Atlantic System.—Among the important rivers emptying directly into the Atlantic Ocean are the Penobscot, Merrimac, Connecticut, Hudson, Delaware, Susquehanna, Fig. 128, Scene on the Mississippi. Roanoke, Cape Fear, Santee, Savannah, Altar maha, and the St. John’s. 150 : PHYSICAL GEOGRAPHY. Of the rivers flowing into the Mexican Gulf, the Appalachicola, Alabama, Mississippi, Sabine, Trinity, Brazos, Colorado, and the Rio Grande are the most important. The Mississippi, taking its origin in the head-waters of the Missouri—which is the true parent stream—is the long- est river in the world, its length being 4490 miles. Its _ tributaries are, in general, navigable for great distances, and thus afford ready communication with different parts of the basin. The important tributaries of the Mississippi on the west are the Minnesota, the Missouri, the Arkansas, and the Red. On the east, the Wisconsin, the Illinois, and the Ohio. The Pacific System.—The principal rivers emp- tying into the Pacific Ocean are the Columbia, Sacramento, San Joaquin, and the Colorado. 393. Inland Drainage—The rivers and lakes of the Great Basin have no outlet to the ocean, and therefore form true steppe systems. Great Salt and Humboldt lakes are the principal lakes, and the Humboldt and the Reese, the principal rivers. There are two regions in the United States below the mean level of the sea: (1.) In the southern part of California, in Soda Valley, 200 feet below the sea. (2.) Death Valley in Eastern California. These regions are extremely arid. ; 394, Lake-Systems.—The most important lake- system of the United States lies in the northern part. It includes, among numerous others, five of the largest fresh-water lakes in the world: Superior, Michigan, Huron, Erie, and Ontario. From their immense extent, they resemble great inland seas. Numerous fluviatile or river lakes occur near the borders of the middle and lower courses of the Mississippi and its tributaries. They are nearly all found in the States west of the Mississippi. 039400 CEEA PE Ree Meteorology. 395. Climate——The United States, exclusive of Alaska, lies entirely within the limits of the mathe- matical north temperate zone. Physical Zones.—>Direction of Wind ©+++ Track of Storm Centre. Pemba ——— } \\ isan ON aio doe Cliscgs ee, Ti Mobile% CStan \ —aP i 7 ¢ ES i Va i . ¢ ee ie n Mo: evar | Es nsbury, 1 Y | \ 30.0 a i j Helena lyininesge Love lity § ae 2 ih a 202 ree EN Done Y Set Ly PPS, Ae s Dereve WEATHER SIGNALS. Terep erature STORM SIGNALS. . a = - INFORMATION SIGNAL, i SE winds, a KarWeather "Sig Wiwinds. SWwinds. NE winds. fair Warmer: Weather. Tes io CAUTIONARY SIGNALS. | Colder or Snow. ‘ \ Wo Ratna Cold farmer - - ay or Snow | : or Snow Wave Fair Weather: Fair followed by followed pieauier. Cold Wave Pie Cold Wave NMWwinds. SWwinds. NEwinds. Skwinds, METEOROLOGY. coast and Great Lakes of the approach of danger- ous storms, and to collect such information as would be of value to shipping and other interests. In 1890, the direction of the Weather Bureau was, by Act of Congress, taken from the War Department and transferred to the Department of Agriculture. There are about 500: stations established by the Weather Bureau in- different sections of the United States. At these stations there are trained and intelligent observers, who several times each day are simultaneously required to make careful observations of the temperature, humidity, and pressure of the air, the direction and force of the wind, the clearness or cloudiness of the sky, and the amount of rain or snow that has fallen during a given time. These observations are telegraphed to the Cen- tral Office at Washington, so that the Bureau is ~ enabled to see the actual meteorological condi- tions which exist throughcut the country at any given time, and from such knowledge, guided by previous experience, to prepare “synopses” of the weather and “indications,” or forecasts. For the preparation of the “indications” the officer in charge prepares a number of graphic charts, based on the various data telegraphed to the Central Office, as the result of the simultaneous observations at the different stations. These charts exhibit the actual meteorological conditions that then exist, those that-existed during the previous eight hours, and the previous twenty-four hours, and the conditions normal for the place at that particular time of the year. The data shown on these charts include the temperature, barometric pressure, humidity of the air, precipitation, condition of sky, force and direction of wind, etc. The “ indications” are telegraphed to the press throughout the country. In general about 85 per cent. of these indications are verified. Tt should be borne in mind, in considering this very large percentage of verified forecasts, that the indications are predicted for extended areas, and, therefore, although the change may not have occurred in some limited section of the predicted area, it may have occurred in nearly all ‘the other portions of the region. Changes in the Weather—Passage of a Great Storm.—Since nearly all the great storms of the United States are species of cyclones, that move over the country in a general easterly direction, when such a storm is once started it is not a dif ficult matter to predict its general path, and thus foretell coming changes in the weather. The principal elements of uncertainty ‘are the exact path in which the storm will move over the country, and the velocity.of such motion. These the b.reau can predict, approximately, from a comparison o£ all the previous storms of which it has records. / The whirling direction of the wind in the Northern Hemisphere is in the opposite Carection to that of the - a hands of a watch. Therefore, as the eastern side of a storm approaches any section of country, the winds blow generally from the south toward the north. The approach of a cyclone is generally attended by a fall of rain or snow. As the cyclone moves onward, and its western side passes over any locality, the general direction of the wind is from the north to the south. The passing of the cyclone is generally attended by clearing, cooler weather. Cold Waves.—On the edges of a cyclone the barometer is nigh. When one storm follows an- other at a short interval, the area of high ba- rometer between them causes the wind to blow in all directions from the centre of high barometer, and a cyclonic movement of the air is thus es- tablished, possessing a progressive motion like a true cyclone. Since the direction of rotation of such a storm is opposite to that of a cyclone, it is called an anti-cyclone. Cold waves generally originate in anti-cyclones. The Weather Signals consist of signal-flags designed to indicate the probable weather and temperature of the coming day. The temperature signal indicates warmer weather when placed above the other flags, and colder weather when placed below them. The cold-wave flag indicates a de- . cided fall in temperature. X The Storm Signals are displayed at all ports on the Great Lakes or the Atlantic seaboard whenever it is considered probable that within twelve hours there will be experienced at those ports, or within one hundred miles thereof, a wind dangerous to navigation. The information signal is intended to notify ship-masters that, on application to the local observer, information will be given them relative to an approaching storm, which it is thought will be dangerous to vessels about to sail to certain ports. The cautionary signal is displayed on the Lakes only, when the winds expected will be severe, but not dangerous to well-equipped vessels. To reach the different cities, towns, and villages, and the hamlets of the rural districts, the indications, or forecasts, are telegraphed every midnight from the Central Office to centres of distribution, situated in different States. These reports are at once printed at each of these distributing stations, enclosed in envelopes, and forwarded to every post-office which can be reached by the swiftest mail facilities by 2 P.M. of, the next day. Great benefit is thus conferred. on agricultural interests. Warnings of coming floods, movements of river ice, sudden or unusual change of level in rivers, are also given as the occasion warrants. The warning is given whenever the water rises above a certain level, called the danger level. Another series of reports are for the benefit of internal navigation. They consist in’ the announcement, from day to day, of such changes of temperature for different sec- tions of the country as would be likely either to stop navigation by the freezing. of the canals, or temporarily 154 PHYSICAL GEOGRAPHY. s to open them sufficiently to enable ice-bound vessels to be pressed forward to the termini of the canals. The value of the Weather Bureau can scarcely be over- estimated; the saving of shipping effected by the timely warning of a single severe storm may more than pay the entire expenses of the bureau for a large portion of the year. We append the following résumé of the work of | the bureau: (1.) The announcement of probable weather changes by the publication of “indications.” (2.) The timely warning of the approach of severe storms. (3). The display of signals indicating coming changes in the weather. (4). The publication of farmers’ bulletins. (5.) The river and canal reports. (6.) The display of symbol-maps, showing the actual state of the weather throughout the entire country. (7.) The publication of daily weather maps, monthly charts, and charts which give the results of the observa- tions of years. (8.) The publication of cotton-region reports, embracing reports of rainfall and maximum and minimum tempera- ture throughout the cotton districts from April 1 to October 31. The International Weather Service ——The suc- cess of the meteorological observations of the U.S. Weather Bureau has led to the establishment of stations for simultaneous observations over a large portion of the northern hemisphere and some sta- tions in the southern hemisphere. By simulta- neous observations of the meteorological conditions of the whole earth, many things yet unknown as to weather predictions are likely to be discovered. Tornadoes resemble cyclones in that they are whirling motions of the air. The area over Fig, 129, A Tornado, which they extend is more limited, but the velocity of the wind is higher than in cyclones, and, therefore, their destructive power is very great. When they pass over any section of country they leave devastation and ruin in their track. Tornadoes are of frequent occurrence in the central and western portions of the Mississippi Valley. Tornadoes have their origin in a rotary motion imparted to a mass of warm moist air that is temporarily imprisoned below a mass of colder air. The whirling motions begin at the upper ex- tremity of the column, near the cold air, and gradually extend downwards. This produces the characteristic inverted funnel-shaped mass of dark cloud by which the approach of a tornado is generally heralded. The path of the tornado, like that of the cyclone, is generally eastward. Weather Maps.—The actual condition of the weather over the United States, on any day, is represented in weather maps published by the bureau. Two such maps are shown on page 152. The upper map shows the meteor- ological conditions prevailing on a certain day in April. On that day an area of low barometer existed in Colorado, Nebraska, and Kansas, within which the barometer was below 29.5 inches, as shown by the isobar, or line of mean barometric pressure, of 29.5. The country around this area had a gradually increasing barometric pressure, as indicated by the successive isobars 29.6; 29.7, 29.8, 29.9, etc. At the same time a storm was moving toward the north-east, as shown by the line of crosses. The rate of progress of the storm being known, the bureau issued the following 7 Indications. For New England, fair weather followed by light rains to-morrow, north to east winds, slight rise in temperature. For the Middle Atlantic States, increasing cloudiness and rain, winds shifting to east and south, slightly warmer weather, lower barometer. For the South Atlantic States, local rains, warmer, partly cloudy weather, south-east to south-west winds, lower ba- trometer. For the East Gulf States, threatening weather and rain, followed by clearing weather, southerly to westerly winds, slight rise in temperature, followed in west portion by a slight fall in temperature. For the West Gulf States, local rains, followed by clear- ing weather, winds shifting to west and north, nearly sta- tionary, followed by lower temperature, and rising barom- eter to-morrow. For Tennessee and the Ohio Valley, cloudy weather and rain, southerly to westerly winds, rising temperature, fall- ing barometer and severe local storms, followed to-mor- row in west portion by cooler weather and higher barom- eter. For the Lower \Lake Region, threatening weather and rain, east to south winds, lower barometer and rising temperature. ? For the Upper Lake Region, threatening weather, with rain or snow, north-vasterly winds becoming variable, fall- ing followed by rising barometer, slight rise, followed by falling temperature. VEGETABLE AND ANIMAL LIFE. 155 © For the Upper Mississippi Valley, threatening weather and rain, severe local storms, winds shifting to west and north, followed by higher barometer and colder weather. For the Missouri Valley, rain or snow, generally colder, cloudy followed by partly cloudy weather, dangerous local storms in southern portion, winds shifting to north and west, with colder weather and higher barometer. Light rains are indicated to-morrow for New England. and the Middle Atlantic States with warmer weather. Clearing and fair weather is indicated for the West Gulf States and thence northward over the Upper Mississippi, Missouri Valleys, and Lake Region. The Ohio River, Cumberland, Tennessee, and the Mis- sissippi at St. Louis, Cairo, Vicksburg, and New Orleans, will continue slowly falling. Cautionary signals continue at Milwaukee, Chicago, Grand Haven, Detroit, Toledo, Sandusky, Cleveland, Erie, and Buffalo. The lower map shows the actual conditions of the weather on the following day. The area of low barometer, or storm- centre, has moved eastward and the storm is now central over Western Pennsylvania and the adjoining States. The actual condition of the weather, showing the correctness of the predictions, will be seen from an inspection of the following synopsis issued by the bureau: Synopsis for the Past Twenty-four Hours. The severe storm which was central in the Lower Mis- souri Valley yesterday morning moved directly east, ' causing dangerous gales on the Lakes and general rains in the Southern States, the Middle States, and the Ohio Valley. Snow and rain continue in the Lake Region this morning. Thredtening weather is reported from New England, and colder, fair weather from the north-west and south-west. The temperature has fallen about 10° in the Mississippi, Ohio, and Missouri Valleys and Upper Lake Region, with north to west winds; and it hasrisen slightly in the districts on the Atlantic coast, with north-easterly winds in New England and on the Middle Atlantic coast, and south-westerly winds in the South Atlantic States. The barometer is unusually low near Pittsburg, and it is highest in Nebraska. A light norther prevails on the Texas coast. ——08a400——_. CHAPTER III. Vegetable and Animal Life. - 402. Vegetation.—The distribution of vegeta- tion throughout the United States is in accord- ance with the distribution of the rainfall. Four characteristic plant regions are found : the Forest, - the Prairie, the Steppe, and the Pacific Region. 403. The Forest Region.—The chief requisite of forest growth—an abundant rainfall, well dis- tributed throughout the year or during the time the trees are growing—is found especially in the country east of the Mississippi, where luxuriant forests exist, unless removed by civilization. The pine, spruce, hemlock, fir, larch, juniper, and deciduous trees, such as the beech, maple, birch, alder, and poplar, are common in the North. Fig. 130. Scene in a Pine Woods, Deciduous trees characterize the middle por- tions of the forest region. In the number and variety of its species, the oak is peculiarly cha- racteristic of the middle part of the forest region. In the southern portion of the forest region evergreen trees, such as the live-oak and the magnolia, are characteristic. Fig. 181, Rafting. The forests have been removed, over extended areas, from all three parts of the forest region. 156 PHYSICAL GEOGRAPHY. The cut logs, when the river-courses are suf- ficiently large, are transported to different sec- tions of the country in huge rafts. 404. The Prairie Region—West of the Mis- sissippi Valley, to the Plateau of the Great Plains, the comparatively scanty rainfall pro- duces extensive prairies, covered with grasses and flowering herbs. Forests are wanting, ex- cept along the river-courses. 405. The Steppe Region—From the western limits of the Great Plains to the Sierra Nevada and Cascade ranges, lie the elevated plateaus of the predominant mountain-system. Here the rainfall is irregular and scanty, and’ the vege- tation presents the peculiarities of a true steppe. But few species of plants occur; the cactus and wild sage are characteristic. 406. The Pacific Region—From the western limits of the steppe region to the Pacific coast, lies a region whose features, in some respects, resemble those of the forest region. In Washington and Oregon dense forests of fir and spruce trees occur. The cedar, larch, maple, oak, and chestnut are common. In California the periodical rainfall nearly excludes the forest from the valleys and plains; but on the mountain-slopes, where rains are more frequent, well-marked forests abound. The pine, fir, and oak are characteristic. On the slopes of the coast mountains and the Sierra Nevada and Cascade Ranges, dense forests of pine and fir trees are found. In some parts of these regions the trees frequently attain an immense size, many of them exceeding 300 feet in height. The largest are the celebrated “‘ mam- moth trees of California,’ a species of pine. Some of these trees are 350 feet high, and have a circumference of 110 feet at the base. In some of the fallen trees, the hollow, decayed trunks readily permit the passage of a man and horse. _ 407. Animal Life—The large animals now found in the United States are principally those which have been domesticated, such as the horse, cow, sheep, mule, goat, and the dog. In some of the sparsely-settled regions of the East, and over large areas in the West, a few wild animals are yet to be found. In parts of the Appalachian system, the black bear, panther, and /” deer are found. The moose is found in the north¢ ern parts of the United States. The immense herds of buffalo that once roved over the Plains west of the Mississippi are nearly extinct./ The grizzly bear and the wolf are found on the’ moun- tains of the Pacific slope. In the South, the warm, sluggish waters of the lower courses of the rivers and swamps, harbor numerous alligators. A number of species of serpents occur, but only two, the rattlesnake ands the ¢ fe are venomous. Nort pir The manatee, or sea-cow, a curious herbivorous animal with paddle-like legs, found in the shal- low waters of the coast of Florida, sometimes attains a length of ten feet. Some species of the manatee in the North Pacific, off Alaska, reach thirty feet in length. : —10 S640-0——_. CEA PERV. Agricultural and Mineral Produc- tions. 408. Agricultural Productions.*—The princi- pal agricultural productions of the United States are wheat, corn, rye, oats, barley, buckwheat, hay, hops, potatoes, flax, tobacco, rice, cotton, and sugar. 409. The Cereals, wheat, corn, rye, oats, barley, and buckwheat, are grown principally north of the 36° of north latitude. According to the census of 1890, the States giving the largest yield of corn were Jowa, Illinois, Kansas, and Nebraska, while those yielding the most wheat were Min- nesota, California, Illinois, and Indiana. The yield of corn is greater than that of any other cereal; the corn-crop of the year 1893, in the United Fig, 132, Corn-Field, States, amounted to 1,619,496,131 bushels. The wheat- crop of 1893 amounted to 395,131,725 bushels. * For Synopsis of Census Reports, see Table, page 175. AGRICULTURAL AND.MINERAL PRODUCTIONS. = 1b 410. Tobacco and Flax are raised in large . quantities in various sections of the country. The principal tobacco-producing States are Kentucky, Virginia, North Carolina, Tennessee, Pennsylvania, and Wisconsin. The entire yield of tobacco in 1893 was 483,023,963 pounds. Fig, 133, Tobacco Field. The principal flax-producing States are Minne- sota, Iowa, South Dakota, and Nebraska. The total value of flax-products in 1893 was $11,137,896. 411, Cotton, Rice, and Sugar are cultivated mainly south of the 36° north latitude. The principal cotton-producing States are Texas, Mississippi, Alabama, South Carolina, Georgia, Arkansas, and Louisiana. Fig, 134, Cotton. The cotton-crop of the year 1894 in the United States 18 amounted to 7,527,211 bales, of an average net weight of 440 pounds per bale. 412, The principal rice-producing States are South Carolina, Louisiana, Georgia, and North Carolina. The rice-fields are confined to low, flat, marshy tracts, near the coast or river bottoms. Fig, 185, Rice Swamp, The principal sugar-producing State is Louis- jana, the plantations being confined mainly to the rich lands in the neighborhood of the Mississippi Delta. Sugar is also grown in South Carolina, Tennessee, and Texas. Fig, 186, Sugar-Cane Field, The total production of cane-sugar in 1893 amounted to 450,000,000 pounds. Beet-sugar is produced in several of the States, princi- 158 PHYSICAL GEOGRAPHY. pally in California.: The entire production in 1893 was 7,083,322 pounds. ; Maple-sugar is produced in Vermont, New York, Ohio, New Hampshire, Michigan, and Indiana. The total pro- duction in 1893 amounted to 3,220,000 pounds. 413, Mineral Productions.—The United States are particularly noted for the richness and variety of their mineral deposits. Nearly all the import- ant metals are found in various portions of the country, some of the deposits extending over areas of enormous extent. 414, Precious Metals.—Gold, silver, and plati- num occur. large. Gold—tThe principal deposits of gold occur in the mountainous districts in the eastern and western portions of the country. The Californian region, which embraces the entire western coast and much of the country as far east as the Great Plains, is the richest. The deposits are especially valuable in the basins of the Sacramento and San Joaquin Rivers. Gold is found either in quartz veins or in alluvial deposits. Silver is found either in the gold-fields already mentioned, or in deposits of galena, one of the most valuable ores of lead. It also occurs pure or native in the copper regions of Lakes Superior and Michigan. : Platinum has been found in small quantities in both the eastern and western portions of the country. 415. Ordinary Metals.—Iron, copper, zine, and ‘lead occur in various portions of the eastern, cen- tral, and western sections of the country. Iron, which intrinsically is the most valuable of all the metals, is, perhaps, the most. widely distributed. Valuable deposits of various iron ores, mainly oxides and carbonates, occur in many parts of the country. The deposits are ex- ceedingly rich in Northern Michigan and Wis- consin; in the neighborhood of the Adirondacks in New York; in Pennsylvania; in Missouri, where the deposits at one time actually formed two mountains of iron; in the district of Lake Superior; in Alabama, and elsewhere. The de- posits in Pennsylvania are the most valuable, from their vicinity to beds of coal and limestone, which are necessary for the reduction of the ore. Copper occurs in large quantities in the east- ern, western, and central sections of the country. The ores are principally sulphides or oxides, or the native or metallic copper. The most valu- able deposits are found in the neighborhood of The deposits of gold and silver are . cury or cinnabar. Keweenaw Point, Lake Superior, where large beds of the native material occur. Zine.—The most valuable deposits are found in Missouri, Wisconsin, and Kansas. It also occurs in the Atlantic States, from Maine to Virginia. - Lead.— Valuable deposits are found in the East, from Maine to North Carolina. The largest and richest districts, however, are in the interior, in Colorado and Utah, where it occurs with silver, and in the Mississippi Valley; in Wisconsin, Towa, Illinois, and Misscuri. ‘416. Among: other valuable metals, tin, mer- cury, chromium, nickel, cobalt, antimony, bis- muth, manganese, are found in small quantities. Tin occurs in limited quantities both in the East . and in the West. So far as is known, the deposits are richest in the Black Hills in Dakota. Mercury is found either pure or in combina- tion. The principal ore is the sulphide of mer- The deposits in California are the most important. Chromium is found in moderately large quan- tities in various portions of the Atlantic States, | as far south as Virginia. Nickel, cobalt, antimony, bismuth, and man- ganese are found in limited quantities. 417. Coal,—The coal-fields of the United States are the richest in the world. Immense deposits occur in the eastern, central, and western sections of the country. So far as is known, the eastern Fig. 137, Coal-Mine, coal-field, which covers portions of Pennsylvania, Ohio, Virginia, Kentucky, Tennessee, and Ala- bama, is the most extensive. AGRICULTURAL AND MINERAL PRODUCTIONS. 159 Other coal-fields occur in Illinois and Missouri, in Texas, Michigan, Rhode Island, and New Brunswick and Nova Scotia. The area of the coal-fields of Western Europe is estimated by Dana at about 20,000 square miles, while the total area of those of the United States probably exceeds 125,000 square miles. In the United States, Pennsylvania possesses the most extensive and the richest deposits, the total area of the deposits in this State being nearly 20,000 square miles, or equal to those of Western Europe. The richness of the American coal-fields cannot fail to exert an import- ant influence on the future development of the country. 418. Peat-Bogs of Massachusetts——Peat con- sists of a black, carbonaceous deposit which ac- cumulates in badly-drained regions of humid climates. The surfaces of the peat-marshes are often covered with a thin crust, formed. by the interlacing roots of vegetable growths. Below this crust is a treacherous, oozy quagmire. When peat is dried it is suitable for fuel. Dana estimates that Massachusetts contains fifteen ‘billion cubic feet of peat. Large deposits occur in _ the Great Dismal Swamp, in North Carolina and Virginia. 419. Petroleum, or Coal Oil, is found in various Fig, 138, Oil Well and Tank. sections. ‘The most valuable deposits occur in a region embracing Western Pennsylvania, Vir- ginia, Ohio, and Michigan. Petroleum is found also in the West. The oil is obtained by boring. The wells so produced are similar to artesian wells, except in the material discharged. In many instances the oil issues in powerful streams, which continue to flow for considerable periods. The crude oil is generally stored in huge tanks, from which it is transferred to barrels or iron tanks for trans- portation. Much is also distributed for great dis- tances through lines of pipes called pipe-lines. For most commercial uses it is necessary to re- fine or purify the oil. 420. Natural Gas.——Accumulations of natural or rock-gas occur in nearly all portions of the United States, but such deposits are especially rich in the regions where coal oil is found. Western Pennsylvania, and the adjoining States, yield great quantities of such gas. ‘The gas is obtained by borings similar to those made for artesian wells or coal-oil wells. From the gas wells thus formed the gas issues forth with great velocity. When lighted it burns with a flame similar to that of ordinary illuminating gas. Like ordinary gas it burns with a pale bluish flame when mixed with air, and affords an excellent source of artificial heat. - Natural gas has been known for many years past, but it is only recently that its great extent and quantity have been ascertained. In many districts—notably in the city of Pittsburgh and vicinity—natural gas has practically superseded illuminating gas as a source of light, and has almost entirely replaced ordinary coal as a source of heat. The value of such a natural product in any manufacturing centre can scarcely be overestimated, and its successful in- troduction in any locality has in. all cases been attended with a marked growth in the extent and variety of its manufactures. Although such deposits must in perhaps a comparatively short time become exhausted, as yet they show but little signs of failure. The gas escapes from the well under great pressure. Before its delivery to consumers, through pipes like ordi- nary gas-pipes, the pressure is reduced by suitable contri- vances; so that its consumption is not attended with any greater risk than that attending ordinary illuminating gas. 421. Salt——Beds of rock-salt occur in Louisi- ana, Virginia, and in various parts of the West. Large quantities are obtained by evaporating the waters of saline or brine springs. These are of common occurrence. The most valuable are found in New York, in the neighborhood of Salina and Syracuse; in Virginia, Michigan, Ken- tucky, and in the Far West. 422. Building Stones.—Large deposits of valu- able building stones are found in all parts of the country. Among the most common are various kinds of sandstone, marble, granite, slate, mag- nesian limestone, serpentine, gneiss, and mica 160 PHYSICAL GEOGRAPHY. schist. Valuable deposits of clay occur, from which excellent bricks are made. —— 0.0595 00-——_ CHAPTER V. Alaska. 423. Extent of Territory—The Territory of Alaska, now a part of the domain of the United States, embraces the north-western part of the North American Continent, and extends south from the shores of the Arctic Ocean to about 54° of N. lat. The main part of the Territory lies west of the 141° E. long. from Greenwich. South of Mt. St. Elias, however, it embraces a narrow strip extending south-eastwardly along the coast of British Columbia. The Territory of Alaska embraces an area of about. 530,000 miles, or, approximately, about one-sixth of the whole area of the remainder of the domain of the United States. This country was purchased from Russia by the United States in 1867, at a cost of $7,200,000. Indentations of the Coast.—The coast-line of Alaska is exceedingly irregular, its entire length | amounting to as much as 8000 miles. The shores of the Arctic are the least indented. The western and southern coasts are deeply indented. Bering Sea and Straits separate Alaska from Asia. The Pacific Ocean enters the wide curve of the southern coast as the Gulf of Alaska. Smaller indentations on the western coasts are found in Norton Sound, Kuskovitch Bay, Bristol Bay, and in the numerous bays and inlets on the southern coasts, in which true fiords occur. 424, Islands.— Numerous islands lie off the western and southern coasts. The principal of these are St. Lawrence Island and Nunivak, on the western coast; the Aleutian Islands, which ex- tend in a curve from the Alaskan Peninsula nearly to Kamtchatka; Afognak and Kadiak islands, off the southern shores of the peninsula; and Baranoff, Chichagof and Prince of Wales islands off the south-eastern shores. 425. Surface Structure.——The northern Portions of Alaska are low and flat, and the plains, drained by a few small, sluggish streams, are, for the most » part, frozen moor-lands, similar to the tundras of Northern Siberia. They form a dreary, desolate country, for the greater part unexplored, covered during the brief summer by a comparatively dense growth of grasses. The rest of Alaska is generally mountain- ous, being traversed by prolongations of the Pacific Mountain-System. tions are those of the south-eastern coast, Mt. St Eis being 99508 feet above the level of the sea. Mts. Crillon and Fairweather are scarcely inferior in height. ‘These mountains contain nu- merous glaciers which descend nearly to the level of the sea. The chain of the Aleutian Islands is mountainous, and, like the mountains of the south-western coast, contains many. volcanic peaks. 426. Drainage System.—The principal river of Alaska is the Yukon, which, so far as known, has a length of at least 2000 miles. It is one of the largest rivers in North America, so far as the volume of its discharge is concerned, which appears to be as great as that of the Missis- sippi.- In some portions of its lower course it is, in places, 20 miles wide. An extensive delta formation occurs at the mouth of the river. The Lewis and the White, its principal tributaries, are situated near the head-waters of the Yukon, in the Dominion of Canada. The Kuskovim is the only other important river. Unlike the delta-mouth of the Yukon, the Kuskovim discharges its waters into Bering Sea through a wide estuary. The spring tides sometimes rise in this estuary to the height of over 50 feet. The glaciers of the south-eastern coast feed a number of lakes, so near together as to permit the establishment of portage-routes of travel. 427. Climate—The climate of Alaska is, gen- erally, cold and wet, although the influence of the Japan Current, and the westerly winds and rain, render the mean annual temperature much warmer than corresponding latitudes in the inte- rior, or even on the eastern coasts of the North American Continent. Fogs and rains are fre- quent. The annual rainfall at Sitka, on Baranoff Island, is about 85 inches. 428. Vegetation—Dense grasses cover por- tions of the tundras, river valleys, and hillsides during the brief summer. The wet climate, how- ever, renders the curing of hay a difficult matter, and, consequently, the rearing of cattle is attended with difficulty. Portions of the lower mountainous slopes and river valleys are covered with forests of yellow cedar and spruce. In the greater part of the The highest eleva- Territory no timber grows at an altitude greater than 1000 feet above the sea. Turnips, potatoes, and radishes have been cultivated in southern portions of the Territory with fair success. 429, Animal Life—tThe rivers are visited dur- ing the breeding season by myriads of salmon. This fish forms the principal food of the inhabit- ants, who, at the beginning of the season, desert the interior for the banks of the rivers. Halibut, herring, codfish, and mackerel, are caught off the coasts of the Territory . The fur seal, the walrus, and the sea-otter are caught in great numbers for their valuable fur. The whale is found in the Arctic waters of the northern coast. The polar bear, the brown bear, the mink, the black or silver fox, the moose, and SYLLABUS. 161 the reindeer are also found in the Territory. Dense swarms of bloodthirsty mosquitoes and black flies occur in nearly all parts of the country. 430, Minerals—Beds of coal of an inferior quality have been discovered in various parts of the country. Deposits of silver, gold, cop- per, lead, and cinnabar also occur. 431, Inhabitants—The inhabitants of Alaska consist principally of the Esquimaux or Innuit, the Indians, and sthe Aleuts, or the inhabitants of the Aleutian Islands, the Creoles or Russian half-breeds, and the inhabitants of the remaining archipelagoes, together with a few whites. Sitka, on Baranoff Island, is the principal set- tlement. SYLLABUS. ——0585 co. The area of the United States, exclusive of Alaska, is about 3,000,000 square miles. The coast line is comparatively simple and unbroken. The principal indentations on the east are Long Island Sound, Delaware and Chesapeake Bays, and Albemarle and Pamlico Sounds; on the west, the Gulf of Georgia and the Bay of San Francisco. The slope of the Atlantic shores is gradual; that of the Pacific shores is abrupt. On the Atlantic coast, the islands north of Cape Cod are for the most part rocky; those south of Cape Cod are gen- erally low and sandy. Mangrove islands are formed by sediment collecting around the closely intertwined roots of mangrove trees. These islands occur in the shallow waters off the coast of Florida. Nearly all of Florida, south’ of the. Everglades, and probably as far north on the eastern coast as St. Augus- tine, consists of a peculiar variety of coral formation. The Pacific system is the predominant mountain-system ; the Appalachian system is the secondary system. The Pacific system consists of the Rocky Mountains, the Sierra Nevada, the Cascade, and the Coast Mountains. The highest peaks are found in the Cascade Mountains. Portions of the Pacific Mountain ranges contain extinct volcanoes. The Appalachian system, or the system of the Allegha- nies, includes the White Mountains, the Green Mountains, the Adirondacks, the Catskills, the Blue Ridge, and the Cumberland Mountains. There are two great low plains in the United States: the Atlantic Coast Plain and the Plain of the Mississippi Valley. The principal rivers draining into the Atlantic Ocean are the Penobscot, Merrimac, Connecticut, Hudson, Dela- ware, Susquehanna, Roanoke, Cape Fear, Santee, Savan- nah, Altamaha, and St. John’s. The principal rivers draining into the Mexican Gulf are the Appalachicola, Alabama, Mississippi, Sabine, Trinity, Brazos, Colorado, and the Rio Grande. The principal rivers draining into the Pacific Ocean are the Columbia, Sacramento, San Joaquin, and the Colorado. The Great Basin, between the Wahsatch and the Sierra Nevada Mountains, has an inland drainage. Soda Valley, in Southern California, and Death Valley, in Eastern California, are below the level of the sea. The Great Lakes, Superior, Michigan, Huron, Erie, and Ontario, form the largest system of fresh-water lakes in the world. The United States extends from the isotherm of 40° Fahr. to 77° Fahr., and therefore lies in the physical north tem- perate and the torrid zones. A marked contrast exists between the temperature of the eastern and the western coasts of the northern half of the country. The eastern coasts are colder than the western. The greater warmth of the western coasts is caused by warm ocean currents, westerly winds, and heavy rainfalls. The Atlantic seaboard is colder than corresponding lati- tudes on the western shores of Europe or on the western shores of the United States. From observations dating back to the year 1738 it ap- pears that from that.time the climate of the United States has undergone no decided change. The United States lies in the zone of the variable winds; westerly winds predominate. The heaviest annual rainfall is 65inches. It occurs near the borders of the Gulf States and along the Pacific sea- board in Washington and Oregon. The smallest annual rainfall is found in the Great Basin, it varies from 5 to 10 inches. East of the 100th meridian from Greenwich the average fall is 40 inches. On the Atlantic coast rain is especially abundant during spring; on most of the Pacific coast, during winter. 162 PHYSICAL GEOGRAPHY. The Weather Bureau was established for the observation of the meteorological conditions of the country. There are four characteristic plant regions in the United States: the Forest, the Prairie, the Steppe, and the Pacific. The forest region lies mainly east of the Mississippi; the characteristic trees are the pine, spruce, hemlock, fir, juni- per, beech, maple, birch, alder, oak, and poplar. The principal large animals of the United States are those which have been domesticated, as the horse, ox, cow, sheep, mule, goat, and dog. Among wild animals are the black bear, panther, deer, grizzly bear, wolf, and manatee or sea-cow. The principal agricultural productions are wheat, corn, rye, oats, barley, buckwheat, hay, hops, flax, tobacco, rice, cotton, and sugar. The principal metals are gold, silver, platinum, iron, copper, zine, lead, tin, mercury, chromium, nickel, cobalt, antimony, bismuth, and manganese. Deposits of coal, rock-salt, marble, coal oil, and natural gas are found, and many varieties of durable building- stone. Extensive peat-bogs occur in Massachusetts and Virginia. The Territory of Alaska has an area of about 530,000 square miles and is nearly one-sixth that of the area of the rest of the domain of the United States. The coast line of Alaska is very irregular, and has a length of at least 8000 miles. Bering Sea on the west, and the Gulf of Alaska on the south, are the principal indentations of the coast. Norton Sound and Kuskovitch and Bristol Bays are among the most important of the smaller indentations. The principal islands are St. Lawrence Island, Nunya, the Aleutian Islands, Afognak, Kadiak, Baranoff, Chicha- gof, and Prince of Wales. The northern portions of Alaska are low and flat, and are covered by tundras or frozen moor-lands. The rest of the country is generally mountainous, and is traversed by prolongations of the Pacific Mountain system of North America. Mts. St. Elias, Fairweather, and Crillon are the principal peaks. The principal river of Alaska is the Yukon, which is some 2000 miles long, and is one of the largest rivers of the North American Continent. The Kuskovim is the only other important river. The Yukon has a delta mouth—the Kuskovim, an estuary. The climate of Alaska is cold and wet, though, under the combined influences of the Japan current, the rains, and the warm south-westerly winds, the climate is less severe than at corresponding latitudes in the interior, or on the Atlantic coast. ; Dense growths of grasses abound during the brief sum- mer. Forests of yellow cedar and spruce occur. The chief animals are the polar and brown bears, the mink, black or silver fox, the moose, and the reindeer. The whale is found in the waters off the northern shores, and the walrus, the seal, and the sea-otter are sources of wealth by reason of their valuable furs. Salmon, hali- but, cod, and herring, are the principal food-fish. Deposits of coal, silver, gold, lead, and cinnabar occur in different parts of the country. The inhabitants consist of various elements, the princi- pal of which are the Esquimaux, the Indians, the Aleuts, the Creoles, and the people of the archipelagoes of the southern and south-eastern coast. Sitka, on Baranoff Island, is the principal settlement. REVIEW QUESTIONS. ——0bez00— State the geographical position of the United States. Describe the peculiarities of its coast lines. Name the principal indentations of the eastern coast. Of the western coast. In what respect do the islands which lie north of Cape Cod differ from those which lie south of it? What is the origin of the islands off the southern coast of Florida? Describe the Pacific Mountain system. Locate the Great Plains. The Great Basin. Describe the Appalachian Mountain system. Name the great low plains of the United States. Name the important rivers which drain directly into the Atlantic ; name those which drain into the Atlantic through the Gulf of Mexico; name those which drain into the Pacific. What system of inland drainage is found in the United States ? Describe the lake-systems of the United States. In what mathematical zone is the United States situated ? In what physical zones? Between what isothermal lines does the United States extend?’ Describe the general direction of the isotherm of 40° Fahr. Of 55° Fahr. Of 60° Fahr. What difference exists between the climate of the eastern and western coasts? What are the causes of this difference? Has the climate of the United States undergone any de- cided change during the last hundred years ? In what wind zone does the United States lie? In what parts of the country does the heaviest annual rainfall occur? The smallest annual rainfall? What is the rainfall of the upper Mississippi Valley? Of the lower Mississippi? At what season of the year do the heaviest rains occur on the Atlantic coast? On the Pacific coast? For what was the Weather Bureau established ? What are tornadoes? Under what four characteristic plant regions may the vegetation of the United States be arranged? Describe the location of each of these regions. Name the principal forest trees of the United States. Name the principal domesticated and wild animals of the United States. Enumerate the principal agricultural productions. Name the principal corn-producing States. The prin- cipal wheat-producing States. Name the principal cotton-producing States. The prin- cipal rice-producing States. The principal sngar-producing States. What valuable metals are found ‘in the United States? What other valuable mineral substances occur? What are the limits of the Territory of Alaska? State its boundaries. What is its area? GENERAL SYLLABUS. 163 What sum was paid for Alaska by the United States Government? Name the principal indentations of the coast of Alaska. What is the extent of its coast line? Name the principal islands of the western coast. Of the southern coast. Describe the surface structure of Alaska. To what gen- eral system of mountains do its elevations belong? Name some of the principal peaks. Are any of them volcanic? Describe the river-system of the Yukon. Where is the Kuskovim River? Which of these rivers has a delta mouth? Which has an estuary? What is the general climate of Alaska? How does the climate compare with that of corresponding latitudes in the interior of the country or on the Atlantic coast? Why is this? Describe the vegetation of Alaska. What are the prin- cipal trees? Name the principal food-fish of Alaska. Name the prin- cipal fur-bearing animals. What other large animals are found in the country ? Which is the principal settlement? Name some of the different people who inhabit Alaska. MAP QUESTIONS. ——-0595,00—__. Describe from the Physical Map of the United States the surface structure of the country, giving the relative position of the High Lands and Low Lands. : Describe the Pacific Mountain System. Describe the Appalachian Mountain System. Locate the following: the Black Hills; the Wahsatch Mountains; the Sierra Madre; San Louis Park; Pike’s Peak; Long’s Peak; Fremont’s Peak. Describe the drainage of the Great Lakes. Name the principal rivers which empty into the Atlantic. Into the Gulf of Mexico. Into the Pacific. Name the principal tributaries of the Mississippi. Where are the Santa Barbara Islands? The Bahama Islands? Vancouver’s Island? Trace on the map the isothermal ‘line of 45°. What is the cause of the southward deflection of the isothermal lines in the western part of the United States ? Prove from the isotherms that the climate of the northern half of the Atlantic coast is colder than the southern half. In what portions of the United States is the lowest mean annual temperature found? The highest? Name the swamps and sounds of the Atlantic sea- board whose formation is to be traced to fluvio-marine devosits. What swamp is due to coral formations ? GENERAL SYLLABUS. - ——00$6400—\—. Physical Geography treats of the distribution of the land, water, air, plants, animals, and minerals of the earth. The earth moves through empty space around the sun. It is kept in motion in its orbit by its inertia and the attraction of the sun. The rotundity of the earth is proved—l. By the ap- pearance of approaching or receding objects; 2. By the cir- cular shape of the horizon; 3. By the shape of the earth’s shadow; 4. By the great circle of illumination; 5. By _ actual measurement. Exact geographical position is determined by reference to certain imaginary lines called parallels and meridians. Representations of the whole or of parts of the earth’s surface are made by means of maps. Maps are drawn on different projections: the Equa- torial, the Polar, and Mercator’s projection are in the most general use. § The length of daylight in either hemisphere depends on the extent to which that hemisphere is inclined towards the sun ; the iongest day in the northern hemisphere occur- ring June 21st, when the sun is vertical over the Tropic of Cancer. The change of seasons is occasioned by the revolution of the earth, together with the inclination of the earth’s axis at an angle of 66° 33’ to the plane of its orbit, and the constant parallelism of the axis with any former position. The Torrid Zone is the hottest part of the earth, because, at one time or another throughout the year, every part of its surface receives the vertical rays of the sun. The following different opinions are held concerning the condition of the interior of the earth: (1.) That the earth has a solid centre and crust, with a heated layer between. (2.) That the crust only is sclid, and the remainder suf- ficiently heated to be in a fused or pasty condition. (3.) That the earth is solid throughout, but highly heated in the interior. The proofs of the present highly-heated condition of the interior of the earth are as follows: 1. In all parts of the earth, the deeper we penetrate the crust, the higher the temperature becomes; that is to say, the entire interior is heated. 2. The presence of volcanoes, which, in all latitudes, eject melted rock from the inside of the earth; that is to say, the entire interior is filled with matter sufficiently hot to melt rock at ordinary pressures. 3. The occurrence of earthquake shocks in all parts of the earth. 164 PHYSICAL GEOGRAPHY. The original fluidity of the earth is rendered probable by the following circumstances: ’ (1.) By the spherical shape of the earth. (2.) The crystalline rocks, or those formed in the presence of great heat, underlying all others. (3.) The warmer climate of the earth during the geolog- ical past. Volcanoes eject from the interior of the earth—1. Melted rock or lava; 2. Showers of ashes or cinders; 3. Vapors or gases. These materials are brought up from great depths into the volcanic mountain by the force caused by a contract- ing globe. They may escape from the crater—1. By the pressure of highly-heated vapors; 2. By the pressure exerted by a column of liquid lava. All volcanoes are found near the coasts of the continents, or on islands. The movements of the earth’s crust produced by earth- quake shocks are—1, A wave-like motion around the centre of disturbance; 2. An upward motion; 3. A rotary motion. The following facts have been discovered as regards earthquakes : (1.) Their place of origin is not very deep seated. (2.) The area of disturbance increases with the energy of the shock and the depth of its origin. (3.) The shape of its origin is that of a line and not that of a point. (4.) The shape of the area of disturbance varies with the elasticity of the materials through which the shock moves. (5.) The earthquake motion travels as spherical waves, which move outward in all directions from their point of origin. The most violent earthquake shocks continue but for a short time. Earthquakes are generally caused by the strain produced by the contraction of the crust. Earthquake shocks are of more frequent occurrence—1. In winter than in summer; 2. At night than during the day; 3. During the new and full moon, than during any other phase. Earthquake shocks may occur in any part of the world, but are of most frequent occurrence in the neighborhood of volcanoes. Rocks may be divided, according to their origin, into three classes: 1. Igneous; 2. Aqueous; 3. Metamorphic. They may be divided according to their condition, into— 1. Stratified ; 2. Unstratified. Unstratified rocks are either igneous or metamorphic. Rocks which contain organic remains are said to be fossiliferous; if destitute of these remains, non-fossil- iferous. Stratified rocks are sometimes called fragmental. Un- stratified rocks are sometimes called fragmental. Aqueous rocks are sometimes called sedimentary. During the geological past extensive changes occurred in the land and water surface of the earth, and in the plants and animals inhabiting it. The changes now occurring in the earth’s crust are caused—l. By the winds; 2. By the moisture of the atmosphere; 3. By the action of running water; 4. By the agency of man; 5. By the action of the heated in- terior. Of the 197,000,000 square miles of the earth’s surface, 144,000,000 square miles are covered by water, and 53,000,000 by land. The proportion between the land and water is very nearly as the square of three is to the square of five. The continents extend farther to the north than to the south; they are crowded together near the north pole. Their southern projections are separated from each other by extensive oceans. Nearly all the land masses are collected in one hemi- sphere, and a large part of the water in another. There are two great systems of trends or lines of direc- tion, along which the shores of the continents, the moun- tain-ranges, the oceanic basins, and the island chains extend. The main prolongation of the eastern continent is in the direction of the north-eastern trend; the western, in that of the north-western trend. The coast lines of the northern continents are very irreg- ular, the shores being deeply indented with gulfs and bays, while those of the southern continents are comparatively simple and unbroken. Of the 53,000,000 square miles of the land, 3,000,000, or about one-seventeenth, is composed of islands. Islands are either continental or oceanic. Continental islands are detached portions of the neigh- boring continents. Oceanic islands are the summits of submarine mountain- chains. They are either high or low: the high oceanic jslands are generally of volcanic formation ; the low islands are of coral formation. Mangrove islands occur off the coasts of Florida. There are four varieties of coral formations: 1. Fringing - reefs; 2. Barrier reefs; 3. Encircling reefs; 4. Atolls. A peculiar variety of coral reef occurs off the coasts of Florida. The subsidence of the ocean’s bed is proved—i. By the exclusive occurrence of volcanoes on the shores of the con- tinents or on islands; 2. By the occurrence of atolls or coral islands; 3. By the general direction of the continen- tal island chains. The earth’s surface is composed of high lands and low lands. The dividing line is 1000 feet above the level of the sea. High lands are either mountainous or plateaus. Low lands are either hills or plains. About one-half of the land surface of the earth is occu- pied by plains. Plains are 1. Undulating; 2. Marine; 3. Alluvial. Mountains were formed by the contraction of the earth’s crust, producing a lateral pressure on extended, thick de- posits of sedimentary rocks. Slaty cleavage was caused by this lateral pressure. The following peculiarities are noticeable in the relief forms of the continents: 1, The continents have, in general, high borders and a low interior. 2. The highest border lies nearest the deepest ocean; hence, the culminating point, or the highest point of land, lies out of the centre of the continent. 3. The greatest prolongation of a continent is always that of its predominant mountain-system. 4, The prevailing trends of the mountain masses are the same as those of the coast lines, and are, in general, either north-east or north-west. Water acquires its maximum density at about the tem- perature of 39.2° Fahr. Water requires more heat to warm it, and gives out more on cooling, than any other common substance. During the constant washings to which the continents GENERAL SYLLABUS. 165 are subjected by the rains, their surfaces are cleansed of the decaying animal and vegetabie matters which cover them. The drainage of the land is of two kinds: subterranean and surface drainage. Surface drainage is either oceanic or inland. According to the size of their reservoirs, springs are either constant or temporary ; according to the depth of the reservoirs, they are either cold or hot; according to the nature of the mineral substances lining their reservoirs, they become charged with various mineral substances; if their reservoirs discharge through a siphon-shaped tube, they are periodical; if their reservoirs are formed of con- cave layers, they are called artesian springs. The quantity of water discharged by a river depends— 1. On the size of its basin. 2. On the amount of its rain- fall. 3. On the climate of its basin, a dry, hot air dimin- ishing the quantity by evaporation. 4. On the nature of jts bed or channel, whether leaky or not. 5. On the features of its basin, whether wooded or open. The material eroded by a river is deposited—i. In the channel of the river. 2. On the alluvial flats or flood- grounds, 3. At the mouth, 4. Along the coast near the mouth. In the upper courses of rivers erosion occurs mainly on the bottom of the channel; in the lower courses, at the sides. The Atlantic and Arctic Oceans receive the waters of nearly all the large river systems of the world. Lakes connected with the system of oceanic drainage are generally fresh; those connected with the inland drainage are generally salt. The bed of the ocean is less diversified than the surface of the land. The greatest depth of the ocean is probably greater than the greatest elevation of the land. The articulation of land and water assumes four dis- tinct forms,—inland seas, border seas, gulfs and bays, and fiords. Inland seas characterize the Atlantic; border seas, the Pacific; gulfs and bays, the Indian; fiords, the Atlantic and Pacific. A deposit of fine calcareous mud or ooze, formed of the hard parts of minute animalcule, occurs over extended areas of the floor of the ocean. Tides are caused by the attraction of the sun and moon; spring tides by their combined attractions; neap tides, by their opposite attractions. Constant ocean currents are occasioned by the heat of the sun and the rotation of the earth. The vertical rays of the sun are warmer than the oblique rays—l. Because they have a less depth of air to pass through. 2. Because they are spread over a smaller area. 3. Because, striking the surface more directly, they produce greater heat. : Continual summer characterizes the tropics ; summer and winter of nearly equal duration, the temperate zones ; and short, hot summers, followed by long, intensely cold win- ters, the frigid zones. The irregular distribution of heat over the earth is caused—1. By the irregularities of the surface. 2. By pecu- liarities in the distribution of the land- and water-areas. 3. By the influence of the winds and ocean currents. 4. By the nature of the surface. Winds are caused by the disturbance of the equilibrium of the atmosphere by heat. The general motion of the surface winds is towards an 19 area of greatest heat; of the upper currents, towards an area of least heat. The general atmospheric circulation is from the equator to the poles, and from the poles to the equator. In storms, the wind has a rotary motion around an area of low barometer, which, at the same time, progresses along the surface. In the northern hemisphere, the rotary motion is in an opposite direction to the hands of a clock ; in the southern hemisphere, in the same direction as the hands of a clock. Moisture may be precipitated from the air in the form of dew, mist, fog, cloud, rain, hail, sleet, or snow. In order that any form of precipitation may occur, the air must be reduced below the temperature of its dew- point. Glaciers are immense masses of ice and snow, which move with extreme slowness down the higher valleys of mountain-ranges. They resemble rivers in that they re- ceive through the drainage of their basins, the solid material which flows into them. The snow line is the distance above the sea where the snow remains throughout the year. The height of its lower level above the sea depends (1.) On the amount of the snowfall. (2.) On the temperature of the valley. (3.) On the inclination of the slope. The unit of electric potential is called a volt; the unit of current an ampére; the unit of resistance an ohm. Comparing the flow of electricity to a current of water in a pipe, the volt corresponds to the pressure causing the flow, the ohm to the resistance, or friction, opposing it, and the ampére to the quantity of flow per second. The principal electrical phenomena of the atmosphere are thunder and lightning, St. Elmo’s fire, and the aurora. The principal optical phenomena are the rainbow, the mirage, halos, and corone. The earth acts like a huge magnet. Its magnetism is probably due to the circulation around it of electrical cur- rents, generated by the sun’s heat. The true basis for the distribution of vegetation is the distribution of the light, heat, and moisture, upon which its existence mainly depends. The variety and luxuriance of vegetation decrease as we pass from the equator to the poles, or from the base of a mountain to the summit. The principal food-plants of the tropical regions are rice, bananas, plantains, dates, cocoa-nuts, cassava, bread-fruit, sago, and yams. Coffee, tea, cocoa, pepper, cloves, nutmegs, and vanilla are also products of the tropics. The principal food-plants of the temperate zones are barley, rye, wheat, oats, maize or Indian corn, buckwheat, and the potato. Animals are restricted, by conditions of food and climate, to certain regions of the earth. ' They are dependent for their continued existence upon plants, the distribution of which therefore forms an excel- lent basis for the distribution of animals. With a few exceptions, animals possess but little power of becoming acclimated, or living in a climate differing greatly from that in which they were created. The grassy meadows and prairies in North America cause the fauna of the continent to be characterized by a pre- ponderance of plant-cating mammals. Its extensive lake- and river-systems harbor a great number and variety of waterfowl. South America is characterized by the predominance of its reptiles and insects. Birds are also numerous. a el 166 Asia is the home of domesticated animals. Australia is the home of the marsupials. The luxuriant vegetation of the south of Africa sustains some of the largest of the mammalia, such as the elephant, rhinoceros, hippopotamus, and giraffe. The entire human family has descended from a single pair or species. The primary races of men are the Caucasian, the Mongo- lian, and the Negro. The secondary races are the Malay, the American, and the Australian. The character of the earth’s mineral products has largely influenced the civilization of man. With a few exceptions, the earth’s mineral products that are of the greatest value to man, such as the precious metals, the valuable metals, building materials, and mineral substances used generally in the arts and in the sciences, are so generally distributed over the earth that practically they are found in all the continents. For a substance to be suitable for building purposes it must possess marked strength, ability to resist a crushing weight placed upon it, and to resist disintegration on long exposure to moisture and change. of temperature. The coast line of the United States is comparatively simple and unbroken. 2 PHYSICAL GEOGRAPHY. The predominant mountains are in the west ; the second- ary mountains are in the east. The great low plains of the United States are the Atlantic coast plain and the plain of the Mississippi Valley.. The Unitéd States lies in the physical north temperate and the physical torrid zone. The climate of the northern half of the Atlantic coast is much colder than that of the northern half of the Pacific. The United States lies in the zone of the variable winds. The heaviest rainfall is on the Pacific coast and near the borders of the Gulf States. There are four distinct: plant regions: prairie, the steppe, and the Pacific. The Territory of Alaska occupies an area of 550,000 square miles. The Territory of Alaska is mainly mountainous. The shore lands of the Arctic are frozen moor-lands like the tundras of Asia., The Yukon and Kuskovim are the principal rivers. Myriads of salmon visit the rivers during the breeding season. Valuable food-fish are found in the waters off the coasts. Numerous fur-bearing animals are found in Alaska. the forest, the GENERAL REVIEW QUESTIONS. —059g400-——. Mathematical Geography. What is the earth’s position in the solar system? How much larger is the sun than the earth? /,? Of what use are latitude and longitude? Distinguish between a map of the earth on a Mercator’ 8 projection, and maps on equatorial and polar and conical projections. Explain the cause of the change of day and night. Explain the causes of the change of seasons. The Land. Enumerate the proofs of the present heated condition of the interior of the earth. What is the theory for the exclusive occurrence of vol- “canoes near the borders of the ocean? Why is it unnecessary to consider the interior of the earth as in a fluid condition like that of the lava ejected from volcanoes ? Name the principal regions ef active volcanoes. What facts have been discovered respecting earthquake shocks? Why should the shocks occur more frequently at night than during the day, or during winter than summer? Into what two classes may unstratified rocks be divided ? Explain the origin of coal. Enumerate some of the changes which are now taking place in the crust of the earth. What are the relative land- and water-areas of the earth? Describe the land hemisphere. The water hemisphere. What do you understand by lines of trend? Which of the continents contains, in proportion to its area, the greatest length of coast line? Which the least? Distinguish between continental and oceanic islands; between coral and volcanic islands. Why does the presence of an atoll in any part of the ocean prove the subsidence of its bed at that point? Ex- plain the nature of the coral formations off the southern coast of Florida. What. do you understand by the forms of relief of the land ? Distinguish between a mountain and a hill. and a plain. What peculiarities are noticeable in the general relief forms of the continents? Which of the continents resemble each other in the gen- eral arrangement of their relief forms? In what respect do they all resemble one another? A plateau The Water. Enumerate the prineipal uses of water in the economy of the earth. What effect has the high specific heat of water on the climate of maritime countries? What is the cause of the heat developed during the con- densation of a mass of vapor? Distinguish between Subterranean and surface drainage. Explain in general the origin of springs. Into what different classes may springs be divided ac- cording to the size of their reservoirs? According to the shape? The location? The shape of the outlet tube ? Define calcareous, silicious, sulphurous, chalybeate, brine, and acidulous springs. Define river-system, basin, water-shed, source, channel, and mouth. Explain the origin of waterfalls. By what are the inundations of rivers caused? What is silt? In what different parts of a river-system may silt be deposited? Define fluvio-marine formations. In what respects do the drainage-systems of North and South America resemble each other? GENERAL REVIEW QUESTIONS. 167 In what respects do the river-systems of Africa resemble those of the Americas? Why are the waters of lakes with no outlets generally salt? Name the great fresh-water lake-systems of the world. State the composition of ocean-water. What is its density? Its boiling-point? Its color? How do the five oceans compare with one another in area? Distinguish between inland seas, border seas, and gulfs and bays, and fiords. What facts are known respecting the shape of the bed of the Atlantic Ocean? Of the Indian Ocean? Explain the origin of the ooze-deposits on the ocean’s beds. By what are waves caused? Upon what does their height depend ? 5 How are tides caused ? Distinguish between ebb, flood, spring, and neap tides. Where does the parent tidal wave originate? In what part of the ocean are tides the highest? Why? What are the main causes of constant oceanic currents ? In what respects do the currents in the three central oceans resemble one another? The Atmosphere. What is the-composition of the atmosphere? By what instrument is the pressure of the atmosphere measured ? : What proof have we that the greater weight of the at- mosphere lies within a few miles of the earth’s surface? Define climate. Enumerate the circumstances which influence the climate of a country. Why are the vertical rays of the sun warmer than the oblique rays? In what different ways does the atmosphere «eceive its heat from the sun? Explain the origin of winds. Why should the general direction of the atmospheric circulation be between the equator and the poles? Name the different wind zones of the earth. What is the origin of land and sea breezes ? What resemblance do land and sea breezes bear to monsoons? Describe some of the peculiarities of cyclones. What facts have been discovered in regard to the great storms of the United States? Enumerate the circumstances upon which the rapidity of evaporation depends. State the general law for the occurrence of precipi- tations. 2 Under what circumstances will a heavy deposition of dew occur? Name the primary forms of clouds. forms. Explain the peculiarities of the rainfall in each of the wind zones. Why is the rainfall on mountains heavier than that on plains? : Define snow line. On what three circumstances does the height of the snow line depend ? Describe the formation of a glacier. The. secondary Enumerate the principal electrical and optical phenom- ena of the atmosphere. What is the probable cause of the earth’s magnetism ? Define volt, ohm, ampére. What analogies exist between the flow of water in a pipe and an electric current? Plant Life and Animal Life. Why should the distribution of light, heat, and moisture form the best basis for the distribution of vegetation? Define flora. Distinguish between the horizontal and the vertical distribution of vegetation. State the limits of each of the horizontal zones of vegetation. , What is the characteristic feature of the flora of each of these zones? State the conditions requisite for the existence of forests; of prairies; of steppes; of deserts. Enumerate the principal cultivated plants of the torrid, temperate, and polar. zones. Define fauna. Upon what is the existence of animal life dependent? What is the cause of the change noticed in the fauna in passing from the equator to the poles, or from the base to the summit of a high tropical mountain? Enumerate the characteristic tropical fauna ; the temper- ate fauna; the arctic fauna. What is the characteristic peculiarity of the fauna of each of the continents? Enumerate the proofs of the probable unity of the human race. Naine the portions of the world inhabited by each of the primary and secondary races. Minerals. Name the principal useful metals. Enumerate the most important natural fuels. In what parts of the world are valuable deposits of coal found ? Name the most important gold-fields of the earth. Physical Features of the United States. What is the area of the United States, exclusive of Alaska? Describe the surface structure of the United States. Describe the drainage-systems of the United States. What are the causes of the difference in the temperature of the eastern and western coasts? Between what extremes of mean annual temperature are the United States included? In what wind zone is the United States situated ? Name the four principal regions of vegetation. Enumerate the chief agricultural productions of the country. What large animals are found in the United States? Name the chief mineral productions. What is the area of Alaska? o What are the principal indentations of its coast? Name the principal islands of Alaska. Describe the river-system of the Yukon. Name the principal trees of Alaska. Name its principal fur-bearing animals. Its principal food-fishes. PHYSICAL GEOGRAPHY. GENERAL MAP QUESTIONS. —0£9300—_ Voleanoes and Earthquakes. Describe the volcanic districts of the Pacific Ocean. In what portions of these districts are voleanoes most numerous ? Describe the volcanic districts of the Indian Ocean. In what direction do most of the lines of fracture in this ocean extend? Describe the volcanic districts of the Atlantic. Where are submarine eruptions most numerous in this ocean ? Describe the earthquake district of the Mediterranean Sea and Central Asia. What other portions of the world are especially liable to earthquake shocks? Name the parts of the world shaken by the great earth- quake of Lisbon, in 1755. Oceanic Areas and River-Systems. What two oceans receive the drainage of the greatest areas of the continents? State, from a careful inspection of the direction in which the principal river-systems flow, the direction of inclina- tion of the principal slopes of the continents. Observe that in most of the continents there is a long gentle slope and a short abrupt slope; state the general direction of each of these slopes. Locate the principal systems of inland drainage in each of the continents. Name the principal lakes and rivers belonging to the larger of these systems. Describe in general the river-systems of the Atlantic, or the rivers draining into the Atlantic. Describe the river- systems of the Pacific. Of the Indian. Of the Arctic. Enumerate the five largest rivers belonging to each of these river-systems. Name the principal rivers of the world which have delta mouths. What are the land and water boundaries of each of the five oceans? Ocean Currents. What is the general direction of the equatorial ocean currents? Explain the cause of this general direction. What exception can you find to it? What is the general direction of the Arctic currents? Of the Antarctic currents? What are the causes of these general directions ? Describe the principal currents of the Atlantic; of the Pacific; of the Indian Ocean. Locate the principal grassy seas. Explain the cause of these seas. Name the principal warm ocean currents; the principal cold ocean currents. Name some cold currents. which powerfully affect the climate of different parts of the earth? Name some warm currents which powerfully affect the climate. In what respects do the general directions of the cur- rents in each of the central oceans resemble one another? Name the points of resemblance between the Gulf Stream and the Japan Current. Isothermal Lines and Physical Zones. Point out the most striking deviations in the directions of the isothermal lines from the parallels of latitude. Explain in each case the main cause of these deviations, In what part of the world do the isothermal lines coin- cide most nearly with the parallels? Trace on the map the isothermal line of 79° Fahr. Of 32° Fahr. Of 40° Fahr. In-what parts of the world is the highest temperature found during the month of July? What is the temperature of the greatest cold of Jannary ? Where is it found? What is the mean temperature of London for January ? For July? What other large cities have nearly the same mean July or January temperature as London? What is the mean temperature of Bombay for January ? For July? What other large cities have nearly the same mean July or January temperature as Bombay? Point out the northern limit of drift ice. The southern limit. Why is it advantageous fora vessel sailing from England or America vid the Cape of Good Hope to maintain an easterly direction both going and returning? Describe the boundaries of the physical torrid, tem- perate, and frigid zones. Name the principal countries which lie wholly or in part in each of these zones. Winds, Rain, and Ocean-Routes. State the boundaries of each of the wind zones. What is the general direction of the wind in each of these zones? Name the principal monsoon regions of the world. Enumerate the principal mountain and desert winds. What is the direction of the rotation of the wind in the cyclonic storms of the northern hemisphere? Of thesouth- ern hemisphere? Name the principal storm-regions of the world. Describe the characteristic rainfall in each of the princi- pal wind zones. What would be the general route of a vessel in sailing from America to Europe, and back again? From Europe to San Francisco? ; What two sailing routes are there from Europe to Aus- tralia or India ? Vegetation. Give the boundaries of each of the plant zones. State the countries or portions of countries which lie in each of these zones. Name some of the useful plants of each of these zones. Point out on the map the northern limit of trees. The southern limit. Name the portions of the world from which valuable timber is obtained. What are the principal tea- and coffee-growing countries of the world? Where are the principal forests? GENERAL MAP QUESTIONS. 169 Animals. What limits are assumed as the boundaries of the tropi- cal, temperate, and arctic fauna? Name the principal tropical, temperate, and arctic fauna? What domesticated animals are found in the tropical and temperate zones? . Trace on the map the northern limit of the camel and of the reindeer; of monkeys. The southern limit of the camel; of monkeys; of the polar bear, and of the elephant and rhinoceros. In what parts of the world are the whale, seal, and wal- rus found? Describe the limits of the grizzly bear. Of the musk-ox. What are the characteristic animals of the New World? Of the Old World? State the characteristic fauna of North America. Of South America. Of Europe, Asia, Africa, and Australia. The Races of Men. Trace on the map the northern and southern limits of permanent habitation. Name all the countries of the world inhabited by the Caucasian race. In what parts of the world are the Caucasians mixed with other races? Name the different countries of the world inhabited by the Mongolian race. : Name some of the different peoples belonging to this race. What parts of the world are peopled by the Ethiopian, or Negro race? Name some of the different tribes belonging to this race. Name the different countries of the world inhabited by the secondary races of men ? Give the names of the principal tribes of each of the secondary races. What different races of men inhabit North America? South America? Europe? Asia? Africa? Australia? Physical Map of the United States. Describe from the map the forms of relief of the United States. ‘ Name the principal mountain-ranges belonging to the predominant and secondary mountain-systems. Describe the drainage-systems of the United States. What large lake-system is situated in the north-eastern part of the United States? Trace on the map the general directions of the principal isothermal lines, showing the hottest and coldest portions of the country. Name the principal islands which lie near the coasts of the United States. Name the fluvio-marine formations of the eastern coast. QUESTIONS RELATING TO THE PHYSICAL GEOGRAPHY OF A STATE. —-0505 00 ——. s In what physical region is this State principally situ- ated ? Is the general surface of this State more or less than one thousand feet above the sea level? Into what body or bodies of water do the principal rivers of this State empty? Name the principal lakes located within, or that border on this State, if any. Name the principal rivers or river systems that are partly or wholly situated in this State. What is a navigable river? Name the navigable rivers of this State, if any. Name the navigable lakes in this State, or that border on the State, if any. Name the principal mountain system of this State, if any. Has this State any coast line? If so, name its principal inlets, bays, harbors, points or promontories. Name the islands that lie near the coast, if any. What is the general climate of this State? When is rain most common ? Name the cereals of this State. Name the principal fruits of this State. Name the other agricultural products of this State in addition to cereals and fruits. Are any wild animals found in this State ? Wame the principal mineral products of this State. PRONOUNCING VOCABULARY. SOUNDS OF THE LETTERS. Vowels. Fate, far, fall, fat, a (obscure), as in organ, oval; ah, inter- mediate between 4 and 4, as in al-a-bah’-ma; 44 or 4 long; mé, mét, e, as in berth, ravel; pine or pine, pin, i, as in firm, evil; nd, nét, o, as in sermon, harbor; 00, as in moon; 66, as in good; dw, as in now; @, as in tube; ti, as in tub; ti, the French eu, nearly like u in tub, or fur; y and ey, at end of unaccented syllable, like e in me; ai and ay, like a in fate; au and aw, as a in fall; &@, asiin pit; dw or au, as now or our. Consonants. Th as in thin; TH, as in this; p, as TH, in this; G and K, sound of the German ch, somewhat like our h, strongly aspirated. fi indicates a blending of the sounds of n and y; i, a blending of land y; x and n and Né, nasal, like our ng; R, like rr in terror; , like our v. Pronounce all other letters as in English. The primary or principal accent is marked thus ('); the secondary, thus (‘). In determining the correct pronunciation of a word, first sound the separate syllables distinctly, repeating the process several times; afterward pronounce the whole word smoothly and continuously, being careful to mark the accents; e.g. Nevada, na-va’-d4, nay-vah’-dah; Apache, 4-p4’-cha, ah- pah’-chay; Canada, kan’-a-da, kan’-ith-dth. A. Abyssinia, ab-is-sin’-e-a. Aconcagua, 4-kon-ka/-gwa. Adelsberg, 4/-dels-bérg'. Adriatic, ad‘-re-at/-ic. Afghanistan, 4f-g4n‘-is-tan’. Agulhas, 4-gool’-yAs. Alabama, al-a-bah’-ma. Alaska, 4l-4s’-k4. Albemarle, al-be-marl’. Aleutian, a-lu’-she-an. Algiers, 4l-jeerz’. Alleghanies, al-le-ga’-nees. Altamaha, 4l-ta-ma-haw’. Amazon, am/-a-zon, Amboyna, 4m-boi’-na. Amoo, 4-moo’. Amoor, 4-moor’. Anahuac, 4n-4-w4ck’. Anatolia, 4n-a-td’-le-a. Anticosti, an-te-kos’-tee. Antilles, 4n‘-teel’. Antisana, 4n-te-s4/-n4. Appalachicola, ap‘-pa-lah‘-che-ko’-la. Apennines, ap’-en-ninz'. Appalachian, ap-pa-la’/-che-an. Apsheron, 4p-sha-ron’. Ararat, 4r’-a-rat*. —o0 ht 0-0—_—_ Archangel, ark-dn’-jel. Arequipa, 4-r-kee’-pa. Arizona, ar‘-i-zo’-na. Arkansas, ar-kan’-sas. Armenia, ar-mee’-ne-a. Arveiron, 4r‘-vi-ron’. Asia, 4’-she-a, not 4/-zhe-a. Atacama, 4-t4-k4’-ma. Athabasca, ath’-a-bas’-ka. Auckland, 4wk’-land. Auvergne, 6'-vairh’. Azores, a2z’/-Grs, or az-orz!. Azov, 42/-ov’, or 4-zov’. B. Babylonian, bab-e-lo’-ne-an. Bahamas, ba-ha’-ma. Baikal, bi’-k4l. Baku, ba‘-koo’. Balkan, bal-k4n’. Balkash, bal'-kash’. Baltimore, bawl’-te-more, or bawlt/-e- mor. . Banda, ban’-da. Barbadoes, bar-bd/-doz. Batavia, ba-t4’-ve-a. Baton Rouge, bat’-on-roozh. Bedouins, bed’-oo-inz. Beled-el-Jerid, bél’-ed-el-jer-eed’. Beloochistan, bel-oo'-chis-tan’. Belor, or Bolor, bé-lor’. Bengal, bén-gawl’. Berlin, ber’-lin. Bermudas, ber-moo’-daz. Bernina, bér-nee’-na. Bohemian, bo-hee’-me-an. Bolivia, bo-liv’-e-a. (Spanish pron., bo-lee’-ve-4. ) Bombay, bom-ba’. Boothia Felix, boo’-the-& fe’-liks. Bourbon, biir’-bon. Brahmapootra, brah‘-ma-poo’-tra. Brazos, brah’-zos. Buenos Ayres, bo’-nos 4/-riz, or bo’- nos airz, (Spanish pron., bw4/-noce i/-rés.) C. Cairo, ki’-ro. Calabria, ka-14/-bre-a. Calcutta, kal-ktit’-ta. Cambodia, kam-bd/-de-a. fate, far, fAll, f4t, mé, mat, pine, pin, nd, nbt, organ, berth, firm, sermon, tibe, tiib, thin, ris. 170 PRONOUNCING VOCABULARY. Cambridge, kdme-brij’. Cameroons, cam-er-oons’. Cantabrian, k4n-td/-bre-an. Canton, kan-ton’. Cape Verde, verd’. Caribbean, kar‘-rib-bee’-an. Carpathian, kar-pa’-the-an. Castile, k4s-teel’. Cauca, kow’-k4. Caucasus, kaw’-k4-siis. Cayenne, kA-yénn’, or ki‘-énn’. Celebes, sél’-e-bes. Ceram, sé-ram’. Cevennes, sd‘-vénn’. Ceylon, see’-lon, or sil-dn’. Chagos, cha/-gds. Chamouni, sha‘-moo-nee’ (or Chamo- nix, sh&‘-mo-nee’). Champlain, sham-plane’. Charleston, charlz’/-ton. Chelyuskin, chel-yitis’-kin. Chicago, she-kaw’-go. Chili, chil’-lee. Colima, ko-lee’-m4. Colorado, kol-o-rah’-do. Como, ko’-mo. Comorin, com’-6-rin. Comoro, kom’-o-ro. Congo, kong’-go. Constance, kon-stAnts’. Cosiguina, ko-se-ghee’-na. D. Dakota, da-ko’-ta. Danube, din’-tbe. Deccan, dék’-kan. Demavend, dém‘-4-vénd’. Detroit, de-troit’. ; Dhawalaghire, da-wél'-a-ghér’-ree. Dinaric, de-nar’-ic. Dnieper, nee’-pr. Dniester, nees’-ter. Dra, dra. Duna, dii’-n4. Dwina, dwi’-na, or hwee’-na. E. Ecuador, ék-w4-dor’. Edgecumbe, éj’-kum. Edinburgh, éd’-in-biir-rth. Elbe, élb. (Ger. pron., &l’-beh.) Elbruz, 4)‘-brooz’. Elton, él'-ton’. Euphrates, u-frd’-téz. Everest, év’-ér-ast. Eyre, air. F. Falkland, fawk’-land. Fayal, fi-al’. Feejee, fee’-jee. Fezzan, féz‘-zin’. Finsteraarhorn, fins’-ter-44r-horn. Flores, flo’-rés. Formosa, for-mo’-s4. Fusi Yama, fi-si-y4-m4’. G: Gairdner, gard’-ner. Gallapagos, g4-l4’/-pa-goce. Ganges, gan’-gdz. Gardafui, gar‘-da-fwee’. Garonne, ga‘-ronn’. Gaudaloupe, gw4-d4-loo’-pa. Ghauts, gawts. Gila, heel’-4. Gilolo, je-lo’-lo. Greenwich, grin’-idge. Grenada, gren-d’-da. Grenelle, greh‘-néll’. Guadeloupe, gaw'-da-loop’, or g4-deh- loop’. Guadiana, gw4-de-4’-n4. Guardafui, gwar-d4-fwee’. Guiana, ghe-4’-n4. Guinea, ghin’-nee. Et Halle, hal’-leh. Hartz, harts. Havana, ha-van’-a. Hawaii, ha-wi’-ee. Hayti, ha/-tee. Heela, hék’-14. Himalaya, him-4-la/-ya, or him-a/-la- ya. Hindoo-Koosh, hin’-d55-kddsh. Hindostan, hin‘-do-stan’. Hoang-Ho, ho-ang‘-hd’, nearly whang‘- ho’. Hoogly, hoog’-lee. Humber, hiim’-ber. Hungarian, hung-ga/-re-an. i; Iberian, i-bee’-re-an. Tlaman, or Illimani, eel'-y4-m4/-ne. Illinois, il'-lin-oi’. Indiana, in‘-de-an’-a, or in-de-ah’-na. Indianapolis, in-de-an-ap’-9-lis. Iowa, i’-o-wa. ’ Irrawaddy, ir'-ra-wAd’-dé. J. Jamaica, ja-ma’-ka. Jan Mayen, yan-mi’-en. Japan, j&-pain’. Java, j4’-va, or jah’-va. Jorullo, ho-rool’-yo, or ho-roo’-yo. Ke Kaffa, kAf’-f4. Kalahari, k4l-a-ha/-ré. Kamtchatka, kAm-chat'-ka. Karakorum, k4‘-r4-ko!-riim. Kenia, ké/-ni-a. Kentucky, kén-tik’-ee. Kerguelen, kerg’-e-len. Keweenaw, ke-wee/-naw. Kilauea, ké)-10’-A-4. Kilimandjaro, kil'-e-man‘ja-ro’. Kinghan, kin-gan’. Kiolen, ky-d/-len, or chd’-len. Kodiak, ko’-de-ak. Kong, king. Kosciusko, kos-se-tis’-ko. Kuen-lun, kwén‘-loon’. Kunchinjunga, koon-chin-jung’-ga. Kurile, koo’-ril. He Laccadive, 14k’-ka-div’. Ladoga, 14/-do-ga. Ladrones, l4d-rénz’, Lapland, lap’-land. La Puebla, 14 pwéb’-la. Lauterbrunnen, ldw’-ter-brddn‘-nen. Lima, lee’-ma. Limpopo, lim-pd/-pd. Llanos, l’y4/-nds. Llullayacu, l’yoo-l’yi-l’y4’-ké. Loffoden, lof-fo’-den. Loire, lw4r. Lombardy, lom’-bar-de. Loo Choo, loo‘-chew’. Louisiana, loo-ee-ze-ah’-na. Louisville, loo’-is-vil, or loo’-e-vil. Lowell, 16’-el. Lupata, lu-pa’-ta. M. Macao, mi-kdw’, or m4-k4-o. Mackenzie, mak-kén’-zee. Madagascar, mad'-a-gas’-kar. Madeira, m4-dee’-ra, or m4-da/-ra. Madrid, m4-drid’. (Spanish pron., ma- dreed’.) Magdalena, mag-da-lee’-na. fate, far, fAll, fat, mé, mét, pine, pin, nd, ndt, organ, berth, firm, sermon, tibe, tiib, thin, THis. 172 PRONOUNCING VOCABULARY. Maggiore, mad-jo’-ra. . Malacca, ma-lak’-ka. Malay, ma-la/. Maldive, mal’-div. Manitoba, man-e-to’-ba. Mantchooria, man-choo’-re-a. Maracaybo, m4-ra-ki’-bo. Marietta, md-re-ét’-ta. Marquesas, mar-ka/-sds. Marseilles, mar-sdlz’. Mauna Loa, mow’-n4 lo’-4. Mauritius, maw-rish’-e-iis. Mediterranean, méd‘-e-ter-r4/-ne-an. Melbourne, mél’-biirn. Mesopotamia, més‘-o-po-ta/-me-a. Michigan, mish’-e-gan, formerly mish- e-gan’. Mississippi, mis‘-sis-sip’-pee. Missouri, mis-soo’-ree. Mobile, mo-beel’. Moluccas, mo-lik’-kaz. Monte Rosa, mon'-ta-rds’-sa. Mont Blanc, mdng-bléns’. Moosehead, moos‘-héd’. Moscow, mos’-ko. N. Nanling, nan'‘-ling’. Natchez, natch’-iz. Netherlands, néru’-er-landz. Neusalzwerk, noi’-sAlts-verk. Nevada de Sorata, ne-vah’-da da so- r4/-ta, Newfoundland, nu’-fond-land’. Ngami, n’g4’-mee. Niagara, . ni-ag’-a-rah, originally ne- 4-g4/-ra, Nisaragua, nik-ar-4/-gwa, Niemen, nee’-men. Nieuveldt, nyuw’-velt. Niger, ni’-ger. Norfolk, nor’-fok. Nova Scotia, no’-va sko’-she-a. Nova Zembla, no’-va zém’-bla. Nubia, nu’-be-a. N’yassa, or Nyassi, ne-ds’-see. O. Obe, o/-bee. Okefinokee, o'-ke-fin-3’-kee. Okhotsk, o-Kotsk’. (Russian pron., o-Hotsk’.) Onega, o-nd’-g4. Onimak, oo-ne-mik’. Ontario, on-t4/-ré-o. Oregon, or’-e-gon. Orinoco, or-e-no’-ko. Pe Pamir, pd-meer’. Pamlico, pam’-lee-ko. Pampas, pim’-pds. Panama, pdn-a-ma’, Papua, pap’-oo-a, or p&'-poo’-a. Paraguay, p4-ri-gwa’, or pa-ra-gwi’. Paramaribo, par‘-a-mar’-e-bo. Pasco, pas’-ko. Patagonian, p4-tA-go’-ne-an. Paumotu, pow-md-too’. Peling, pa'-ling’. Persian, per’-she-an. Petchora, pétch’-o-rd, Philippine, fil’-ip-pin. Platte, platt. Polynesia, pol‘-e-nee!-she-a. Pompeii, pom-pa/-yee. Pontchartrain, pont-char-tran’. Popocatepetl, po-po-k4-ta-pétl’. Prussia, priish’-ya, or proo’-she-a. Pyrenees, pir’-en-eez, Q. Quebec, kwe-bék’. Quito, kee’-to. R. Radack, ra’-dak. Ralick, r4’-lik. Reading, réd’-ing. Rhine, rin. Rhone, ron. Riobamba, re-o-b4m’-b4, Rio de la Plata, ree’-o dd 14 pla’-ta. Rio Grande, ree’-o gran’-da. Rio Janeiro, ri’o j4-nee’-ro. Roanoke, ro‘-an-ok’. Rodriguez, ro‘-dreeg’. Russia, riish’-i-a, or roo’-she-a. Russian America, roo’-shan a-mér’- e-ka. S. Sabine, s4-been’. Saghalien, si-ga-lee’-an, or s&-gd- leen’. Sahara, s4-h4’-ra, or s4/-ha-ri,, Saint Helena, sAnt hel-ee’-na. Salina, sa-li/-na. Salzburg, sAlts’-btirg. Samoan, sam-d’-an. Sandwich, sand’-wich, or sand’-wij. San Francisco, sn fran-sis’-ko. San Joaquin, sdn uo-4-keen’, almost wah-keen’, Santa Barbara, sin’-t4 bar-ba-ra. Santa Cruz, sén’-ta kroos. Santorini, sin-to-ree’-nee, Sarmiento, sar-me-én’-to. Saskatchewan, sas-katch’-e-wén. Scandinavian, skan-de-nd/-ve-an. Seine, san, or sén. Senegal, sén‘-e-gawl’. Shasta, shds’-ta. Siam, si-am’, or se-am’. Sicily, sis’-il-e. Sierra Estrella, se-ér’-r4 &s-trél’-ya. Sierra Leone, se-er’-ra le-o’/-nee. Sierra Madre, se-ér’-r4 ma’-pra. Sierra Nevada, se-ér’-r4 na-va’-pa. Singapore, sing‘-ga-pore’. Sir, or Sihon, sir, or seer, see‘-hon’. Sitka, sit’-ka. Spitzbergen, spits-berg’-en. Steppes, steps. St. Louis, sent loo’-is, or sent loo’-ee. St. Petersburg, sent pee’-terz-biirg. St. Roque, sent rok’. St. Thomas, sent tom’-as. Stromboli, strom’-bo-le. Sumatra, soo-m4’-tra. Sumbawa, soom-baw’-wa. Suez, soo’-éz. Suliman, or Suleiman, soo-ld-man’, Syracuse, sir’ra-kiiz. Syria, sir’-e-a. a Tahitian, t4-hee’-tee-an. Tanganyika, t4n-g4n-yé’-ka, Tarim, t4’-rém. Tasmania, taz-ma-ne-a. Taurus, taw’-riis. Tchad, chad. Teneriffe, tén‘-er-iff’. Thames, témz. Thian-Shan, tee'-4n’-shan. Thibet, tib’-ét, or tib-ét’. Timor, te-mor’. Titicaca, te-te-k4/-k4. Tocantins, to-k4n-teens’. Toledo, to-lee’-do. (Spanish pron., to. 14/-Do.) Tongan, tong’-gan. Torrens, tor’-rens. Torres, tor’-rés. Transylvanian, tran-sil-v4’/-ne-an. Trieste, tre-ést’. Trinidad, trin‘-e-dad’. Tristan d’Acunha, tris’-tan da- Pan Tundras, toon’-dra. Tunis, tu’-niss, or too’-niss. Turkestan, toor'-kis-tan’. ————$——______ fate, far, f4ll, fat, mé, mét, pine, pin, nd, nét, organ, berth, firm, sermon, tibe, ttib, thin, rnis. —_—— UW: Urumiyah, 0o-roo-mee’-ya, V. Valdai, vAl’-di. Vancouvers, van-koo’-vers. Venezuela, vén'-éz-wee’-la. Vesuvius, ve-su’-vi-us. PRONOUNCING VOCABULARY. 173 W. Wabash, waw’-bash. Wasatch, wi'-sich. Wener, a’-ner. Weser, wé'-zer. (Ger. pron., #4’-zer.) West Indies, west in’-deez. Wetter, wét’-ter. Winnebago, win'-ne-ba’-go. Winnipeg, win’-e-peg. Wisconsin, wis-kon’-sin. Worcester, w66s’-ter. Yaktusk, y4‘-kootsh’. Yang-tse-Kiang, yang'-tse-ke-Ang’. Yeddo, yéd’-do. Yellowstone, yel’-lo'-stone. Yenisei, yén‘-e-s4/-e, or yén'-e-say’. Yosemite, yo-sem’-e-te. Yucatan, yoo-k4-tan’. Yukon, yu’-kon. Vichy, vee‘-shee’. Vienna, vé-en’-na. Vindhya, vind’-ya. Volga, vol’-ga. Vosges, vozh. Yabloni, y4-blo-noi’. Z. Zagros, z4’-gros’. Zambezi, zAm-ba’-zee. Zealand,zé’-land. Zurrah, ziir’-ra. BRIEF ETYMOLOGICAL VOCABULARY. —00Sf0-0—_—__ Amazon, “ Boat destroyer.” Arabia, “The land of the sunset.” Brahmapootra, “The son of Brahma.” Cameroons, “A shrimp.” Deccan, “The south.” Ecuador, “The equator.” Elton, “Golden lake.” Formosa, “ Beautiful” (island). ° Gallapagos, “Islands of the tortoises.” Ganges, “ Heavenward flowing.” Himalaya, “The.abode of snow.” Hindostan, “The country of the Hindoos,” or “ Negro- Jand.” Hoang-Ho, “ Yellow river.” Holland, “ Muddy or marshy land.” Irrawaddy, “The great river.” Java, “ Rice.” Labrador, “ Cultivable.” Ladrones, “Islands of the thieves.” Lauterbriinnen, “ Nothing but springs.” Maldives, “Thousand islands.” 20 Mantchooria, “Country of the Mantchoos.” Mer de glace, ‘‘Sea of ice.” Mesopotamia, ‘‘ Between the rivers.” Mississippi, “The great water.” Missouri, ‘“ Muddy water.” Netherlands, “The low countries.” Niphon, “ Fountain or source of light.” Nova Scotia, “‘ New Scotland.” Nyassa, “The sea.” Orinoco, “The coiled serpent.” Papua, “ Frizzled hair.” Patagonians, “Men with large feet.” Polynesia, “ Many islands.” Popocatepetl, “Smoking mountain.” Saskatchewan, “Swift current.” Sierra Nevada, “Snow-clad mountain.” Singapore, “City of the lion.” Staubbach, “Dust or mist brook.” Thian-Shan, “The celestial mountain.” Winnipiseogee, “The smile of the great Spirit.” Yang-tse-Kiang, “Son of the great water.” STATISTICAL TABLES. —059300——. Hydrographic Table of the Rivers of the World (from 4. K. Jounston). Area of basin NAME OF RIVER. IRHiNG2 Wee mestencuesakeu sips 65,280 WAT BER es yn ar eter, 56,640 WW DG sey cece ss cntetaan-e ie testueutetis 41,860 Oder... «.. polomepe em cihe 29,040 Niemen accretion cre ctr one sims) 32,180 Cin Gaesce es eeics es ere nie 22,620 Nile See areca yee 520,200 (?) Danube weenie mercon smrescs 234,080 Dnieper ss verge ve etieste Voor 169,680 Obie cre emirates eet 924,800 BYCNISOP ea :ss is elton enre suesars 784,530 GON Atay eres cles ow care eae 594,400 IV Ol pater sniuecteon. Rie ects 397,460 Sirlor;Sihonsijecere testes 237,920 (?) EAI OOTH ysurcol cesetn er celromte! (cute 582,880 Yang-tse-Kiang ...... 547,800 Hoang-Ho ... «2 eee 537,400 Gan gesis asic tie vo ei co lereus ie 432,480 1bGUED Se Geo oo Bb 6-5 812,000 (?) Euphrates ......... 195,680 Arrawaddy ters is: enon ee 331,200 NEW WORLD. St. Lawrence and Great Lakes! 297,600 Delaware... ......2.6 8,700 OvINOCOM ecm. touretccere eis 252,000 Amazon ..........| 1,512,000 Tocantins .....2.e... 284,480 San Francisco ....... 187,200 arblata-ucscecescer emcees 886,400 Mississippis 205.) 16 esos 982,400 Riodel Norte. ....... 180,000 Mackenzie). 26... «© 2,0 441,600 Saskatchewan. ....... 360,000 Columbia....... ecar 194,400 Colorado Siete nes 170,000 Length of. in geographical |stream includ- square miles. jing windings. 600 520 684 480 460 340 2,240 (2) 1,496 . 1,080 2,320 2,800 2,400 2,400 1,208 (?) 2,380 2,880 2,280 1,680 1,960 1,492 2,200 1,800 265 1,352 (?) 3,080 1,120 1,400 1,920 3,560 1,840 (?) 2,120 1,664 1,360 800 (2) Areas of the Principal Lakes of the Earth. AMERICA. Area sq. m. Superior ...... 28,600 Michigan. ..... 26,000 PLUTO Miers cuca 20,400 Great Slave. .... 12,800 RELIC seam sauces con cue are 9,600 Winnipeg ..... 9,600 Georgian Bay. . . . 8,000 Great Bear... .. 8,000 Ontario’ ir 20. 6,300 Maracaibo eit. v0 rt 4,900 PRitiCaACanuncuics snes 4,200 Athabasca ..... 3,000 Nicaragua ..... 2,800 Great Salt ..... 2,200 Green Bay ..... 2,000 Champlain ..... 480 Pontchartrain. . .. 440 iDyTamiderns arses 360 Moosehead ..... 240 Winnebago. .... 212 EUROPE. Tad ogaren co-mewesnes 6,330 Onegairgetuarse aes 3,280 Wiener. irs raliettea. + 2,136 WWietterieenscn 1s) 5 seven Soo, Malar misizelnel | 2400; (In English square miles.) Population of the Earth. North America ...... South America... ..... Africa Area, sq. m. Genevarw is nie 326 Constance... .. 290 Maggiore. ..... 152 ASIA. Caspian Sea . . . . 160,000 Aral ’Sea.2. 0.7. 2% 88,000 Baikcaly eer. se 13,000 Balkash...... 8,600 Zurrah(Afghanistan) 4,000 Wiansettcsr) ts ers 2,200 Urumiyah. .... 1,800 OPE eers erates sse car 560 Dead Sea ..... 400 Tiberias. ..... 200 AFRICA, Victoria Nyanza. . 28,000 Albert Nyanza. . . 26,000 ch ads-ay-us-seraesarsae 15,000 Tanganyika . . . . 13,000 Nyassa ...... 5,000 AUSTRALIA. Wy TO smoteerterenaer sents 3,000 MNOTTEONS' sis) feeiereiets 2,600 Gairdner ..... 2,400 coer we ear erecte 89,250,000 Rae eee Sea 36,420,000 Saat aes 380,200,000 eam eens 850,000,000 Ac epee 127,000,000 . Cee Te ge ae ae 4,730,000 ee ae cas nite 300,000 . . . « 1,487,900,000 STATISTICAL TABLES. 175 NNN «a Tables showing the Area and Product of some of the Cereals, ete., in the United States. (From the Census Reports of 1890.) INDIAN CORN. . State, Acres, Bushels. Iowa. ....... 7,585,522 ..... 313,130,782 MUINGISe ey seuce, to oae 7,860,917 .... . 289,629,705 Kansas. ...... 17,314,765 ..... 259,574,568 Nebraska. ..... 5,480,279 ..... 215,895,996 ‘Missouri ...... 6,069,638 ..... 196,904,915 Ohiowi eens 3,189,558 ..... 113,892,318 Indiana ...... 3,586,190 ..... 108,843,094 Kentucky ..... 2,960,382 ..... 78,434,847 Tennessee... .. DOU BOAT ey Pepcettes fe 63,635,350 Pennsylvania T252'369)) as ieiaen 42,318,279 WHEAT. Minnesota ..... 38,372,627 ..... 52,300,247 California. ..... 2,840,807 ..... 40,869,337 Illinois. .... eee OO COL retkerremee 37,371,081 ANGIANS eve ces we HDL OLOL Ts See vas ents 37,318,798 QHIOs sven cr sate tans 2,269,585 ... +. 35,559,208 Kansas. ...... 41,582,635 ..... 30,399,871 Missouri ..... . 1,946,785 ..... 30,118,821 North Dakota... . 2,708,199 ..... 26,388,455 Michigan. ..... 1,501,225 ..... 24,771,171 Pennsylvania... . 1,318,472 ..... 21,595,499 OATS. Towa .......- 3,752,141 .... . 146,679,289 Illinois. ...... 3,848,897 .... . 187,602,804 Wisconsin ..... 1,627,151 ..... 60,739,052 Minnesota ..... 1,579,258 ..... 49,958,791 Kansas. ......- 41,463,526 ..... 44,629,034 Nebraska. ..... 1,503,515 ....-.- 43,843,640 Ohio. 2 632% Rateirce Hue LO ssoDu seas fais 40,136,732 Missouri ..... . 1,676,706 ..... 39,820,149 New York ..... 1,417,371 . 2.2... 38,896,479 Michigan. ..... 1,085,759... .. 86,961,193 BARLEY. California... ... 815,995 ....- 17,548,386 Wisconsin.....-. 474,914 - 15,225,872 Towa... 6+ eee HLS 295 cae es 13,406,122 Minnesota ..... SOS DLON Wate) a: teat 9,100,683 New York eesti BAD Tlie emanate wore 8,220,242 Michigan. ..... 99,305 fr sererks 2,522,376 Nebraska. .... . 82,590 .. 2... 1,822,111 North Dakota... . LOOMS SOM recess 1,569,167 Washington... .. Bibb 1 secs 1,269,140 Illinois... 2 2 oe 41,390 ..... 1,197,206 RYE. Wisconsin ..... 275,058 . 22. e 4,250,582 Pennsylvania... . 886,041 ..-2.. 8,742,164 New York ..... 236,874 . 2 eos 3,065,623 Kansas .... «+ - 1 O91AG Stason 2,917,386 Illinois. ...... | 165,589 ....- 2,627,949 Michigan. ..... TAQW(540 0S face ew 2,101,713 Towa .-.-+.-s 2. O37 Oia iis seats 1,445,283 Minnesota ..... 62,869 ..... 1,252,663 Nebraska. ..... 81372 ..... 1,085,083 ODIO S ssn steers 59,648 . 2... 1,007,156 BUCK WHEAT. New York .....- 280,029 ..... | 4,675,735 Pennsylvania... 210,488 ..... 8,069,717 Wisconsin. . .+ + - T7408 «we ee 1,064,178 Michigan. .... 70,046 ..... 811,977 Maine ...-+e.. 221895 en wercsnieites 466,411 TOW Leos Op OAS re es vee 286,746 Minnesota .... 22,090 ..... 281,705 Vermont .....- 18,429 2... as 271,216 Ohio..... Suceuate 14,052 ..... 162,833 West Virginia... . 18,696 ..... 120,469 TOBACCO. » State, Acres. Pounds. Kentucky. ..... 323,409 .... - 283,300,000 Varginiaiy.: else re 127,052 ..-.-- 64,034,000 Tennessee .... 67,119 ..... 45,641,000 ORION ssese ae oie 39,105 ...-- 35,195,000 North Carolina ... 57,107... ~~ 25,755,000 Pennsylvania. ... 19,500 ..... 24,180,000 Indiana....... 1S Ob2 eee ced cee 16,153,000 Maryland...... SBiT1D) trot sais 14,017,000 Missouri. ....-. 14126 ..... 18,109,000 Wisconsin. ..... 13,818 ..... 12,846,000 Population of the United States. (From the Census of 1890.) North Atlantic States... .-.- ee eee 17,401,545 MGT G2. tas we phoetelarsmtee-o Ceytern eens seat ae -. + 661,086 New Hampshire .... +--+ eee ees 376,530 Vermont ...-..-. rete trey iis sok sigish ones se 832,422 Massachusetts ..... eb enr el cethamiar eg emicnes: ke 2,238,943 Rhode Island ..... anit ee cha tok s ace tistrs 345,506 @onnecbicute scree, wcoe ef ce ers sonst fe oe . . . 746,258 New York... . +222 see eee . « « « 5,997,853 New Jersey ..- +--+ > SMe tech eeepc: 1,444,933 Pennsylvania .. 6.1 ee ee ee ee es 5,258,014 South Atlantic States. .... PD eicecee eestor 8,857,920 Delaware ...... shee forks, coms oe ee = 168,493 Maryland .......-. Nan accirete tasare enal 0421390 District of Columbia... 6. + eee ee eee 230,392 Virginia. . 2 2 1 ee ee ee See supe nce gscs 1,655,980 West Virginia .....-+.5-. ihe ede oon Oe; hoe North Carolina. ... + 20 ee A Teacteaeeety cn 1,617,947 South Carolina... 1. 62 ee ee ee eee 1,151,149 Georgia ....--. ie Secieaiseeen ce Men vetr oas ome 1,837,353 I OLIC at ct serene on eercueutemeeyee hss uelieuns . « 391,422 North Central States... 2 ee ee eee 22,362,279 (OUT Ows eects ices tok fenee ee ci swesV nom ommoxmron ne iker ds 8,672,316 UTI IAN A Arrayes tos fe) sewers anne is,