en hotter, until at length we
seem to see the temperature increase to a red heat, from a red heat we
look back to a still earlier age when the earth was white hot, back
further till we find the surface of our now solid globe was actually
molten. We need not push the retrospect any further at present, still
less is it necessary for us to attempt to assign the probable origin of
that heat. This, it will be observed, is not required in our argument.
We find heat now, and we know that heat is being lost every day. From
this the conclusion that we have already drawn seems inevitable, and
thus we are conducted back to some remote epoch in the abyss of time
past when our solid earth was a globe molten and soft throughout.

A dewdrop on the petal of a flower is nearly globular; but it is not
quite a globe, because the gravitation presses it against the flower and
somewhat distorts the shape. A falling drop of rain is a globe; a drop
of oil suspended in a liquid with which it does not mix forms a globe.
Passing from small things to great things, let us endeavour to conceive
a stupendous globe of molten matter. Let that globe be as large as the
earth, and let its materials be so soft as to obey the forces of
attraction exerted by each part of the globe on all the other parts.
There can be no doubt as to the effect of these attractions; they would
tend to smooth down any irregularities on the surface just in the same
way as the surface of the ocean is smooth when freed from the disturbing
influences of the wind. We might, therefore, expect that our molten
globe, isolated from all external interference, would assume the form of
a sphere.

But now suppose that this great sphere, which we have hitherto assumed
to be at rest, is made to rotate round an axis passing through its
centre. We need not suppose that this axis is a material object, nor are
we concerned with any supposition as to how the velocity of rotation was
caused. We can, however, easily see what the consequence of the rotation
would be. The sphere would become deformed, the centrifugal force would
make the molten body bulge out at the equator and flatten down at the
poles. The greater the velocity of rotation the greater would be the
bulging. To each velocity of rotation a certain degree of bulging would
be appropriate. The molten earth thus bulged out to an extent which was
dependent upon the fact that it turned round once a day. Now suppose
that the earth, while stil