Geological Contemporaniety and Persistent Types of Life | Page 7

discovery, let us double the lesser number
and suppose that 60 per cent. of the species are common to the North
American and the British Silurians. Sixty per cent. of species in
common is, then, proof of contemporaneity.
Now suppose that, a million or two of years hence, when Britain has
made another dip beneath the sea and has come up again, some
geologist applies this doctrine, in comparing the strata laid bare by the

upheaval of the bottom, say, of St. George's Channel with what may
then remain of the Suffolk Crag. Reasoning in the same way, he will at
once decide the Suffolk Crag and the St. George's Channel beds to be
contemporaneous; although we happen to know that a vast period (even
in the geological sense) of time, and physical changes of almost
unprecedented extent, separate the two.
But if it be a demonstrable fact that strata containing more than 60 or
70 per cent. of species of Mollusca in common, and comparatively
close together, may yet be separated by an amount of geological time
sufficient to allow of some of the greatest physical changes the world
has seen, what becomes of that sort of contemporaneity the sole
evidence of which is a similarity of facies, or the identity of half a
dozen species, or of a good many genera?
And yet there is no better evidence for the contemporaneity assumed by
all who adopt the hypothesis of universal faunae and florae, of a
universally uniform climate, and of a sensible cooling of the globe
during geological time.
There seems, then, no escape from the admission that neither physical
geology, nor paleontology, possesses any method by which the
absolute synchronism of two strata can be demonstrated. All that
geology can prove is local order of succession. It is mathematically
certain that, in any given vertical linear section of an undisturbed series
of sedimentary deposits, the bed which lies lowest is the oldest. In
many other vertical linear sections of the same series, of course,
corresponding beds will occur in a similar order; but, however great
may be the probability, no man can say with absolute certainty that the
beds in the two sections were synchronously deposited. For areas of
moderate extent, it is doubtless true that no practical evil is likely to
result from assuming the corresponding beds to be synchronous or
strictly contemporaneous; and there are multitudes of accessory
circumstances which may fully justify the assumption of such
synchrony. But the moment the geologist has to deal with large areas,
or with completely separated deposits, the mischief of confounding that
"homotaxis" or "similarity of arrangement," which 'can' be
demonstrated, with "synchrony" or "identity of date," for which there is
not a shadow of proof, under the one common term of
"contemporaneity" becomes incalculable, and proves the constant

source of gratuitous speculations.
For anything that geology or paleontology are able to show to the
contrary, a Devonian fauna and flora in the British Islands may have
been contemporaneous with Silurian life in North America, and with a
Carboniferous fauna and flora in Africa. Geographical provinces and
zones may have been as distinctly marked in the Paleozoic epoch as at
present, and those seemingly sudden appearances of new genera and
species, which we ascribe to new creation, may be simple results of
migration.
It may be so; it may be otherwise. In the present condition of our
knowledge and of our methods, one verdict--"not proven, and not
provable"--must be recorded against all the grand hypotheses of the
paleontologist respecting the general succession of life on the globe.
The order and nature of terrestrial life, as a whole, are open questions.
Geology at present provides us with most valuable topographical
records, but she has not the means of working them into a universal
history. Is such a universal history, then, to be regarded as unattainable?
Are all the grandest and most interesting problems which offer
themselves to the geological student essentially insoluble? Is he in the
position of a scientific Tantalus--doomed always to thirst for a
knowledge which he cannot obtain? The reverse is to be hoped; nay, it
may not be impossible to indicate the source whence help will come.
In commencing these remarks, mention was made of the great
obligations under which the naturalist lies to the geologist and
paleontologist. Assuredly the time will come when these obligations
will be repaid tenfold, and when the maze of the world's past history,
through which the pure geologist and the pure paleontologist find no
guidance, will be securely threaded by the clue furnished by the
naturalist.
All who are competent to express an opinion on the subject are, at
present, agreed that the manifold varieties of animal and vegetable form
have not either come into existence by chance, nor result from