o the field of geology. He
occasionally attended the Geological Society, and, as we have already
seen, read several papers there during this period. His friend, Dr
Hooker, then acting as botanist to the Geological Survey, was engaged
in studying the Carboniferous flora, and many discussions on Palaezoic
plants and on the origin of coal took place at this period. On this last
subject he felt the deepest interest and told Hooker, "I shall never
rest easy in Down churchyard without the problem be solved by some one
before I die." ("M.L." I. pages 63, 64.)

As at all times, conversations and letters with Lyell on every branch of
geological science continued with unabated vigour, and in spite of the
absorbing character of the work on the Cirripedes, time was found for
all. In 1849 his friend Herschel induced him to supply a chapter of
forty pages on Geology to the Admiralty "Manual of Scientific Inquiry"
which he was editing. This is Darwin's single contribution to books of
an "educational" kind. It is remarkable for its clearness and simplicity
and attention to minute details. It may be read by the student of
Darwin's life with much interest, for the directions he gives to an
explorer are without doubt those which he, as a self-taught geologist,
proved to be serviceable during his life on the "Beagle".

On the completion of the Cirripede volumes, in 1854, Darwin was able to
grapple with the immense pile of MS. notes which he had accumulated
on the species question. The first sketch of 35 pages (1842), had been
enlarged in 1844 into one of 230 pages ([The first draft of the "Origin"
is being prepared for Press by Mr Francis Darwin and will be published
by the Cambridge University Press this year (1909). A.C.S.]); but in
1856 was commenced the work (never to be completed) which was designed
on a scale three or four times more extensive than that on which the
"Origin of Species" was in the end written.

In drawing up those two masterly chapters of the "Origin", "On
the Imperfection of the Geological Record," and "On the Geological
Succession of Organic Beings", Darwin had need of all the experience and
knowledge he had been gathering during thirty years, the first half
of which had been almost wholly devoted to geological study. The most
enlightened geologists of the day found much that was new, and still
more that was startling from the manner of its presentation, in these
wonderful essays. Of Darwin's own sense of the impo