es for each place must be prepared to answer
for the whole day. If they can only prove that he was not at A in the
morning, and not at B in the afternoon, the evidence of his absence from
both is nil, because he might have been at B in the morning and at A in
the afternoon.

Thus everything depends upon the validity of the second assumption. And
we must proceed to inquire what is the real meaning of the word
"contemporaneous" as employed by geologists. To this end a concrete
example may be taken.

The Lias of England and the Lias of Germany, the Cretaceous rocks of
Britain and the Cretaceous rocks of Southern India, are termed by
geologists "contemporaneous" formations; but whenever any thoughtful
geologist is asked whether he means to say that they were deposited
synchronously, he says, "No,--only within the same great epoch." And if,
in pursuing the inquiry, he is asked what may be the approximate value in
time of a "great epoch"--whether it means a hundred years, or a thousand,
or a million, or ten million years--his reply is, "I cannot tell."

If the further question be put, whether physical geology is in possession
of any method by which the actual synchrony (or the reverse) of any two
distant deposits can be ascertained, no such method can be heard of; it
being admitted by all the best authorities that neither similarity of
mineral composition, nor of physical character, nor even direct
continuity of stratum, are _absolute_ proofs of the synchronism of even
approximated sedimentary strata: while, for distant deposits, there seems
to be no kind of physical evidence attainable of a nature competent to
decide whether such deposits were formed simultaneously, or whether they
possess any given difference of antiquity. To return to an example
already given: All competent authorities will probably assent to the
proposition that physical geology does not enable us in any way to reply
to this question--Were the British Cretaceous rocks deposited at the same
time as those of India, or are they a million of years younger or a
million of years older?

Is palaeontology able to succeed where physical geology fails? Standard
writers on palaeontology, as has been seen, assume that she can. They take
it for granted, that deposits containing similar organic remains are
synchronous--at any rate in a broad sense; and yet, those who will study
the eleventh and twelfth chapters of Sir Henry De La Beche's remarkable
"Researches in T