to the memory, is also of use in his, or but urge that it
enables him to sort and arrange his facts; and that, by converting one
idea into the type and exemplar of many resembling ones, it imparts to
him an ability of carrying not inadequate conceptions of the mighty
whole in his mind? If this were all, you might well ask, Why obtrude
upon us, in connection with your special science, a common
semi-metaphysical idea, equally applicable to all the sciences,--in
especial, for example, to that botany which is the science of existing
plants, and to that zoology which is the science of existing animals?
Nay, I reply, but it is not all. I refer to this classifying principle
because, while it exists in relation to all other sciences as a
principle--to use the words of the metaphysician just quoted--"given to
us by nature,"--as a principle of _the mind within_,--it exists in
Palaeontological science as a principle of nature itself,--as a principle
palpably _external to the mind_. It is a marvellous fact, whose full
meaning we can as yet but imperfectly comprehend, that myriads of ages
ere there existed a human mind, well nigh the same principles of
classification now developed by man's intellect in our better treatises
of zoology and botany, were developed on this earth by the successive
geologic periods; and that the by-past productions of our planet, animal
and vegetable, were chronologically arranged in its history, according
to the same laws of thought which impart regularity and order to the
works of the later naturalist and phytologists.

I need scarce say how slow and interrupted in both provinces the course
of arrangement has been, or how often succeeding writers have had to
undo what their predecessors had done, only to have their own
classifications set aside by _their_ successors in turn. At length,
however, when the work appears to be well nigh completed, a new science
has arisen, which presents us with a very wonderful means of testing it.
Cowley, in his too eulogistic ode to Hobbes,--smit by the singular
ingenuity of the philosophic infidel, and unable to look through his
sophisms to the consequences which they involved,--could say, in
addressing him, that

"only God could know
Whether the fair idea he did show
Agreed entirely with God's own or no."

And he then not very wisely added,--

"This, I dare boldly tell,
'T is so like truth, 't will serve our turn as well."

We now know, howeve