themselves indicate, for all positive values of the time, a possible
solution which continually tends to the form of a uniform diffusion of
heat.

But if we attempt to ascend the stream of time by giving to its symbol
continually diminishing values, we are led up to a state of things in
which the formula has what is called a critical value; and if we
inquire into the state of things the instant before, we find that the
formula becomes absurd.

We thus arrive at the conception of a state of things which cannot be
conceived as the physical result of a previous state of things, and we
find that this critical condition actually existed at an epoch not in
the utmost depths of a past eternity, but separated from the present
time by a finite interval.

This idea of a beginning is one which the physical researches of
recent times have brought home to us, more than any observer of the
course of scientific thought in former times would have had reason to
expect.

But the mind of man is not, like Fourier's heated body, continually
settling down into an ultimate state of quiet uniformity, the
character of which we can already predict; it is rather like a tree,
shooting out branches which adapt themselves to the new aspects of the
sky towards which they climb, and roots which contort themselves among
the strange strata of the earth into which they delve. To us who
breathe only the spirit of our own age, and know only the
characteristics of contemporary thought, it is as impossible to
predict the general tone of the science of the future as it is to