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 paleontology able to succeed where physical geology fails? Standard
writers on paleontology, 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 Theoretical Geology', published now nearly
thirty years ago, and will carry out the arguments there most
luminously stated, to their logical consequences, may very easily
convince themselves that even absolute identity of organic contents is
no proof of the synchrony of deposits, while absolute diversity is no
proof of difference of date. Sir Henry De La Beche goes even further,
and adduces conclusive evidence to show that the different parts of one
and the same stratum, having a similar composition throughout,
containing the same organic remains, and having similar beds above and