comprehension of an author's meaning.

We do not speak jestingly in saying that it is Mr. Darwin's misfortune
to know more about the question he has taken up than any man living.
Personally and practically exercised in zoology, in minute anatomy, in
geology; a student of geographical distribution, not on maps and in
museums only, but by long voyages and laborious collection; having
largely advanced each of these branches of science, and having spent
many years in gathering and sifting materials for his present work, the
store of accurately registered facts upon which the author of the
'Origin of Species' is able to draw at will is prodigious.

But this very superabundance of matter must have been embarrassing to a
writer who, for the present, can only put forward an abstract of his
views; and thence it arises, perhaps, that notwithstanding the
clearness of the style, those who attempt fairly to digest the book
find much of it a sort of intellectual pemmican--a mass of facts
crushed and pounded into shape, rather than held together by the
ordinary medium of an obvious logical bond; due attention will, without
doubt, discover this bond, but it is often hard to find.

Again, from sheer want of room, much has to be taken for granted which
might readily enough be proved; and hence, while the adept, who can
supply the missing links in the evidence from his own knowledge,
discovers fresh proof of the singular thoroughness with which all
difficulties have been considered and all unjustifiable suppositions
avoided, at every reperusal of Mr. Darwin's pregnant paragraphs, the
novice in biology is apt to complain of the frequency of what he
fancies is gratuitous assumption.