no water could have existed on the earth's surface except in the
form of ice; there would have been scarcely any evaporation, and
the geological changes due to erosion could not have taken place.
Moreover, the commencement of the geological operations of which
we speak is by no means the commencement of the earth's existence.
The theories of both parties agree that, for untold aeons before
the geological changes now visible commenced, our planet was a
molten mass, perhaps even an incandescent globe like the sun.
During all those aeons the sun must have been in existence as a
vast nebulous mass, first reaching as far as the earth's orbit,
and slowly contracting its dimensions. And these aeons are to be
included in any estimate of the age of the sun.

The doctrine of cosmic evolution--the theory which in former times
was generally known as the nebular hypothesis--that the heavenly
bodies were formed by the slow contraction of heated nebulous
masses, is indicated by so many facts that it seems scarcely
possible to doubt it except on the theory that the laws of nature
were, at some former time, different from those which we now see
in operation. Granting the evolutionary hypothesis, every star has
its lifetime. We can even lay down the law by which it passes from
infancy to old age. All stars do not have the same length of life;
the rule is that the larger the star, or the greater the mass of
matter which composes it, the longer will it endure. Up to the
present time, science can do nothing more than point out these
indications of a beginning, and their inevitable consequence, that
there is to be an end to the light and heat of every heavenly
body. But no cautious thinker can treat such a subject with the
ease of ordinary demonstration. The investigator may even be
excused if he stands dumb with awe before the creation of his own