Succession implies time; the lower members of a series of sedimentary
rocks are certainly older than the upper; and when the notion of age
was once introduced as the equivalent of succession, it was no wonder
that correspondence in succession came to be looked upon as a
correspondence in age, or "contemporaneity." And, indeed, so long as
relative age only is spoken of, correspondence in succession 'is'
correspondence in age; it is 'relative' contemporaneity.

But it would have been very much better for geology if so loose and
ambiguous a word as "contemporaneous" had been excluded from her
terminology, and if, in its stead, some term expressing similarity of
serial relation, and excluding the notion of time altogether, had been
employed to denote correspondence in position in two or more series of
strata.

In anatomy, where such correspondence of position has constantly to be
spoken of, it is denoted by the word "homology" and its derivatives;
and for Geology (which after all is only the anatomy and physiology of
the earth) it might be well to invent some single word, such as
"homotaxis" (similarity of order), in order to express an essentially
similar idea. This, however, has not been done, and most probably the
inquiry will at once be made--To what end burden science with a new and
strange term in place of one old, familiar, and part of our common
language?

The reply to this question will become obvious as the inquiry into the
results of paleontology is pushed further.

Those whose business it is to acquaint themselves specially with the
works of paleontologists, in fact, will be fully aware that very few,