through geologic time, may feel compelled by what he knows of causation,
and by the general analogy of nature, to suppose that our solar system
was once a nebulous mass; that it gradually condensed, that it broke up
into that wonderful group of harmoniously rolling balls we call planets
and satellites, and that then each of these underwent its appointed
metamorphosis, until at last our own share of the cosmic vapour passed
into that condition in which we first meet with definite records of its
state, and in which it has since, with comparatively little change,
remained.

The doctrine of uniformity and the doctrine of progression are,
therefore, perfectly consistent; perhaps, indeed, they might be shown
to be necessarily connected with one another.

If, however, the condition of the world, which has obtained throughout
geologic time, is but the sequel to a vast series of changes which took
place in pre-geologic time, then it seems not unlikely that the
duration of this latter is to that of the former as the vast extent of
geologic time is to the length of the brief epoch we call the
historical period; and that even the oldest rocks are records of an
epoch almost infinitely remote from that which could have witnessed the
first shaping of our globe.

It is probable that no modern geologist would hesitate to admit the
general validity of these reasonings when applied to the physics of his
subject, whence it is the more remarkable that the moment the question
changes from one of physics and chemistry to one of natural history,
scientific opinions and the popular prejudices, which reflect them in a
distorted form, undergo a sudden metamorphosis. Geologists and
palaeontologists write about the "beginning of life" and the