atter intensely heated, and, in many
instances, in a constant state of fusion. We have first, then, to
inquire, whence is this heat derived?

It has long been a favorite conjecture, that the whole of our planet was
originally in a state of igneous fusion, and that the central parts
still retain a great portion of their primitive heat. Some have
imagined, with the late Sir W. Herschel, that the elementary matter of
the earth may have been first in a gaseous state, resembling those
nebulae which we behold in the heavens, and which are of dimensions so
vast, that some of them would fill the orbits of the remotest planets of
our system. The increased power of the telescope has of late years
resolved the greater number of these nebulous appearances into clusters
of stars, but so long as they were confidently supposed to consist of
aeriform matter it was a favorite conjecture that they might, if
concentrated, form solid spheres; and it was also imagined that the
evolution of heat, attendant on condensation, might retain the materials
of the new globes in a state of igneous fusion.

Without dwelling on such speculations, which can only have a distant
bearing on geology, we may consider how far the spheroidal form of the
earth affords sufficient ground for presuming that its primitive
condition was one of universal fluidity. The discussion of this question
would be superfluous, were the doctrine of original fluidity less
popular; for it may well be asked, why the globe should be supposed to
have had a pristine shape different from the present one?--why the
terrestrial materials, when first called into existence, or assembled
together in one place, should not have been subject to rotation, so as
to assume at once that form which alone could retain their several parts
in a state of equilibrium?

Let us, however, concede that the statical figure may be a modification
of some other pre-existing form, and suppose the globe to have been at
first a perfect and quiescent sphere, covered with a uniform ocean--what
would happen when it was made to turn round on its axis with its present
velocity? This problem has been considered by Playfair in his
Illustrations, and he has decided, that if the surface of the earth, as
laid down in Hutton's theory, has been repeatedly changed by the
transportation of the detritus of the land to the bottom of the sea, the
figure of the planet must in that case, whatever it may have been
originally, be b