the apparent necessity of supposing the
past to be widely different from the present has diminished.

The transporting power of the greatest deluge which can be imagined
sinks into insignificance beside that of the slowly floating, slowly
melting iceberg, or the glacier creeping along at its snail's pace of
a yard a day. The study of the deltas of the Nile, the Ganges, and the
Mississippi has taught us how slow is the wearing action of water, how
vast its effects when time is allowed for its operation. The reefs of
the Pacific, the deep-sea soundings of the Atlantic, show that it is to
the slow-growing coral and to the imperceptible animalcule, which lives
its brief space and then adds its tiny shell to the muddy cairn left
by its brethren and ancestors, that we must look as the agents in
the formation of limestone and chalk, and not to hypothetical oceans
saturated with calcareous salts and suddenly depositing them.

And while the inquirer has thus learnt that existing forces--GIVE THEM
TIME--are competent to produce all the physical phenomena we meet with
in the rocks, so, on the other side, the study of the marks left in the
ancient strata by past physical actions shows that these were similar to
those which now obtain. Ancient beaches are met with whose pebbles are
like those found on modern shores; the hardened sea-sands of the oldest
epochs show ripple-marks, such as may now be found on every sandy coast;
nay, more, the pits left by ancient rain-drops prove that even in
the very earliest ages, the "bow in the clouds" must have adorned the
palaeozoic firmament. So that if we could reverse the legend of the
Seven Sleepers,--if we could sleep back through the past, and awake a
million ages before our own epoch, in the midst of the earliest geologic
times,--there is no reason to believe that sea, or sky, or the aspect of
the land would warn us of the marvellous retrospection.

Such are the beliefs which modern physical geologists hold, or, at any
rate, tend towards holding. But, in so doing, it is obvious that they by
no means prejudge the question, as to what the physical condition of the
globe may have been before our chapters of its history begin, in what
may be called (with that licence which is implied in the often-used term
"prehistoric epoch") "pre-geologic time." The views indicated, in fact,
are not only quite consistent with the hypothesis, that, in the
still earlier period referred to, the condition of our