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