When we look at a map or globe of the world, we are struck by several
peculiarities which require explanation. In the first place, nearly
every peninsula, large and small, points toward the _south_--and this
is even true of vast bodies, such as Africa, South America and India.
Secondly, the distribution of the land and water upon the surface
of the earth is peculiar--nearly all the land lying in the northern
hemisphere, while the water occupies the southern half of the globe.
Further, if a map be made of the land-area of the northern hemisphere,
looking at a globe from the point-of-view of the North Pole, and this
be laid over a similar map, drawn from the point-of-view of the South
Pole, it will be found that land hardly ever falls on land, but that
land in one hemisphere almost invariably coincides with water in the
other. The only exception to this rule, of any importance, is that
a portion of South America will be found to lie over a portion of
northern China.
Why is this?
One of the newer theories of the formation of our earth explains
these odd facts in a rather ingenious manner. It has been shown that
a spherical or round body, when subjected to great pressure, tends to
collapse into a triangular or “tetrahedral” form. The reason for this
is that a “tetrahedron” presents the greatest amount of surface of any
body, next to a sphere. A “tetrahedron” is composed of four equilateral
triangles, and may readily be constructed by cutting four triangles of
the kind out of cardboard, and pasting them together at the edges--when
it will be found that you have a top-shaped figure, with a flat surface
at the top, and a point at the bottom.
Now, it has been found, by recent researches, that our earth is
slightly top-shaped. This is doubtless due to the tendency of the earth
to collapse into a tetrahedron, as it cools and contracts--whereas
there is also a tendency for the earth to maintain its spherical form,
by reason of its rotation.
If the tetrahedron constructed of cardboard be examined, it will be
found that the sides are much nearer the center of gravity of the
figure than the points; and if water could be made to stay upon the
surface of this figure, it would naturally tend to flow onto the smooth
sides, leaving the points exposed. These “points” would then be found
to correspond, roughly, with the continents or earth-surfaces of our
globe, while the oceans would be found to correspond, largely, with the
smooth surfaces.
There are, of course, differences to be noted, such as the large land
area, which is not to be found on the South Pole, but it is thought
that these changes of land and water areas of our globe have been
gradually brought about, through millions of years, until they present
the approximate surfaces which we note today.
This theory at least explains many facts which before had been
puzzling, and there is much to be said in its favor. It was suggested
by Mr. Lothian Green, of Cambridge, England.