More Letters of Charles Darwin, vol 2 | Page 5

rather than leave
so curious a fact unnoticed.")...Do always remember that nothing in the
world gives us so much pleasure as seeing you here whenever you can
come. I chuckle over what you say of And. Murray, but I must grapple
with his book some day.
LETTER 381. TO C. LYELL. Down, October 31st [1867].
Mr. [J.P. Mansel] Weale sent to me from Natal a small packet of dry
locust dung, under 1/2 oz., with the statement that it is believed that
they introduce new plants into a district. (381/1. See Volume I., Letter
221.) This statement, however, must be very doubtful. From this packet
seven plants have germinated, belonging to at least two kinds of grasses.
There is no error, for I dissected some of the seeds out of the middle of
the pellets. It deserves notice that locusts are sometimes blown far out
to sea. I caught one 370 miles from Africa, and I have heard of much

greater distances. You might like to hear the following case, as it
relates to a migratory bird belonging to the most wandering of all
orders--viz. the woodcock. (381/2. "Origin," Edition VI., page 328.)
The tarsus was firmly coated with mud, weighing when dry 9 grains,
and from this the Juncus bufonius, or toad rush, germinated. By the
way, the locust case verifies what I said in the "Origin," that many
possible means of distribution would be hereafter discovered. I quite
agree about the extreme difficulty of the distribution of land mollusca.
You will have seen in the last edition of "Origin" (381/3. "Origin,"
Edition IV., page 429. The reference is to MM. Marten's (381/4. For
Marten's read Martins' [the name is wrongly spelt in the "Origin of
Species."]) experiments on seeds "in a box in the actual sea.") that my
observations on the effects of sea-water have been confirmed. I still
suspect that the legs of birds which roost on the ground may be an
efficient means; but I was interrupted when going to make trials on this
subject, and have never resumed it.
We shall be in London in the middle of latter part of November, when I
shall much enjoy seeing you. Emma sends her love, and many thanks
for Lady Lyell's note.
LETTER 382. TO J.D. HOOKER. Down, Wednesday [1867].
I daresay there is a great deal of truth in your remarks on the glacial
affair, but we are in a muddle, and shall never agree. I am bigoted to
the last inch, and will not yield. I cannot think how you can attach so
much weight to the physicists, seeing how Hopkins, Hennessey,
Haughton, and Thomson have enormously disagreed about the rate of
cooling of the crust; remembering Herschel's speculations about cold
space (382/1. The reader will find some account of Herschel's views in
Lyell's "Principles," 1872, Edition XI., Volume I., page 283.), and
bearing in mind all the recent speculations on change of axis, I will
maintain to the death that your case of Fernando Po and Abyssinia is
worth ten times more than the belief of a dozen physicists. (382/2. See
"Origin," Edition VI., page 337: "Dr. Hooker has also lately shown that
several of the plants living on the upper parts of the lofty island of
Fernando Po and on the neighbouring Cameroon mountains, in the Gulf
of Guinea, are closely related to those in the mountains of Abyssinia,
and likewise to those of temperate Europe." Darwin evidently means
that such facts as these are better evidence of the gigantic periods of

time occupied by evolutionary changes than the discordant conclusions
of the physicists. See "Linn. Soc. Journ." Volume VII., page 180, for
Hooker's general conclusions; also Hooker and Ball's "Marocco,"
Appendix F, page 421. For the case of Fernando Po see Hooker ("Linn.
Soc. Journ." VI., 1861, page 3, where he sums up: "Hence the result of
comparing Clarence Peak flora [Fernando Po] with that of the African
continent is--(1) the intimate relationship with Abyssinia, of whose
flora it is a member, and from which it is separated by 1800 miles of
absolutely unexplored country; (2) the curious relationship with the
East African islands, which are still farther off; (3) the almost total
dissimilarity from the Cape flora." For Sir J.D. Hooker's general
conclusions on the Cameroon plants see "Linn. Soc. Journ." VII., page
180. More recently equally striking cases have come to light: for
instance, the existence of a Mediterranean genus, Adenocarpus, in the
Cameroons and on Kilima Njaro, and nowhere else in Africa; and the
probable migration of South African forms along the highlands from
the Natal District to Abysinnia. See Hooker, "Linn. Soc. Journ." XIV.,
1874, pages 144-5.) Your remarks on my regarding temperate plants
and disregarding the tropical plants made me at first uncomfortable, but
I soon recovered. You say