REVIEW SS Se Aqueous rocks may contain fossils. Igneous rocks never contain fossils. Metamorphic rocks, in rare instances, may contain fragments of fossils. Geological time is divided into Archxan, Palzozoic, Meso- zoic, and Cenozoic. _ Archean Time includes the Azoic and the Eozoic Ages. Paleozoic Time, or, as it-is sometimes called, the Pri- mary, includes the Silurian, Devonian, and Carboniferous Ages. Mesozoic Time, or the Secondary, includes the Age of Reptiles. Cenozoic Time includes the Age of Mammals, or the Ter- tiary, and the Era of Man, or the Quaternary Age. ~ he changes to which the earth’s crust is now subject are produced by the following agencies: 1. By the winds; 2. By the moisture of the atmosphere; 3. By the action of running water; 4. By the action of ocean waves; 5. By the agency of man; 6. By the con- traction of a cooling crust. ss. There is more water than land surface on the earth, in proportion of 25: 9, or as 57: 3”. The land-masses surround the north pole in the shape of an irregular ring. Nearly all the land-areas are collected in one hemi- sphere, and the water-areas in another. The Land Hemisphere comprises the whole of North America, Europe, and Africa, all of Asia except a small part of the Malay Peninsula, and the greater part of South America. The Water Hemisphere comprises the whole of Australia and the southern portions of South America and the Ma- lay Peninsula. : The northern continents are almost entirely in the tem- perate latitudes; the southern are mainly in the tropics. The land-masses may be divided into three doublets, consisting of pairs of northern and southern continents, almost or entirely separated from each other. There are two great systems of trends or lines of direc- tion, along which the continents, the coast lines, the mountain-ranges, the oceanic basins, and the island chains are arranged. These trends are north-east and north-west. The northern continents are characterized by deeply in- dented coast lines; the southern are comparatively simple and unbroken. Europe is the most, and Africa the least, deeply indented of the continents. In proportion to her area, Europe has three times as much coast line as Asia, and four times as much as Africa. One-seventeenth of the land-area is composed of islands. Islands are either continental or oceanic. There are four successive stages in the formation of a coral island or atoll: 1. The fringing reef; 2. The barrier reef; 3. The encircling reef; 4. The coral island or atoll. The greatest elevations and depressions in the earth’s surface are small when compared with its size. QUESTIONS. 55 Low lands are either plains or hills. High lands are either plateaus or mountains. Plains are—l. Undulating; 2. Marine; 3. Alluvial. - Mountains were produced by the contraction of the crust, producing a lateral pressure on thick, extended de- posits of sedimentary rocks. Slaty cleavage was caused by this tateral pressure. Valleys are either longitudinal or transverse. All continents have high borders and a low interior. The highest border faces the deepest ocean. The greatest prolongation of a continent is that of its predominant mountain-system. The culminating point is always out of the centre. North and South America resemble each other in the arrangement of their relief forms. Their predominant systems are in -the west; their secondary systems are in the east; their great low plains are between the predomi- nant and secondary systems. The predominant system of North America is the Pa- cific mountain-system. The secondary systems are—the Appalachian system, the plateau of Labrador, the Height of Land, and the Arctic plateau. The predominant system of South America is the sys- tem of the Andes. The secondary systems are—the pla- teaus of Guiana and Brazil. The great low plains are— the Llanos of the Orinoco, the Selvas of the Amazon, and the Pampas of the La Plata. Europe and Asia resemble each other. . Their predomi- nant systems are in the south; their great low plains are north of their predominant systems. The predominant system of Europe is in the south. The secondary systems are—the mountains of the Scan-- dinavian Peninsula, the Ural Mountains, and the Caucasus Mountains. ; The predominant mountain-system of Asia is the pla» teau of Thibet. The secondary systems are—the plateau of Gobi, the Thian-Shan and Altai Mountains, the plateau of Indo- China, the plateau of Deccan, the plateau of Iran, the pla- teau of Asia Minor, and the plateau of Arabia. Africa and Australia resemble each other. Their pre- dominant systems are in the east; their secondary systems are in the west and north; their depressed areas are be- tween the two. The predominant mountain-system of Africa includes the mountains of the eastern coast. The secondary systems include the Nieuveldt and Snow Mountains in the south, the Mocambe, Crystal, Cameroons, and Kong Mountains in the west, and the Atlas Mountains in the north. The predominant mountain-system of Australia includes the mountains of the eastern coast. The secondary systems include those found in the south, west, and north. REVIEW QUESTIONS. ——-05G5 0o ——_. What two elementary substances form the greater part by weight of the earth’s crust? Into what classes may rocks be divided according to their condition? According to their origin? According to the presence or absence of fossils? What is paleontology? Define Archean Time, Paleozoic Time, Mesozoic Time, and Cenozoic Time. Explain the nature of the changes, which the atmo- sphere is now effecting in the earth’s surface. Which the water is effecting. Which man is effecting. What must be the areas of two squares whose areas