I have been much pleased and interested by your note. I never actually tried sea-water, but I was very fond of angling when a boy, and as I could not bear to see the worms wriggling on the hook, I dipped them always first in salt water, and this killed them very quickly. I remember, though not very distinctly, seeing several earthworms dead on the beach close to where a little brook entered, and I assumed that they had been brought down by the brook, killed by the sea-water, and cast on shore. With your skill and great knowledge, I have no doubt that you will make out much new about the anatomy of worms, whenever you take up the subject again.
LETTER 551. TO J.H. GILBERT. Down, January, 12th, 1882.
I have been much interested by your letter, for which I thank you heartily. There was not the least cause for you to apologise for not having written sooner, for I attributed it to the right cause, i.e. your hands being full of work.
Your statement about the quantity of nitrogen in the collected castings is most curious, and much exceeds what I should have expected. In lately reading one of your and Mr. Lawes' great papers in the "Philosophical Transactions" (551/1. The first Report on "Agricultural, Botanical, and Chemical Results of Experiments on the Mixed Herbage of Permanent Grassland, conducted for many years in succession on the same land," was published in the "Philosophical Transactions of the Royal Society" in 1880, the second paper appeared in the "Phil. Trans." for 1882, and the third in the "Phil. Trans." of 1900, Volume 192, page 139.) (the value and importance of which cannot, in my opinion, be exaggerated) I was struck with the similarity of your soil with that near here; and anything observed here would apply to your land. Unfortunately I have never made deep sections in this neighbourhood, so as to see how deep the worms burrow, except in one spot, and here there had been left on the surface of the chalk a little very fine ferruginous sand, probably of Tertiary age; into this the worms had burrowed to a depth of 55 and 61 inches. I have never seen here red castings on the surface, but it seems possible (from what I have observed with reddish sand) that much of the red colour of the underlying clay would be discharged in passing through the intestinal canal.
Worms usually work near the surface, but I have noticed that at certain seasons pale-coloured earth is brought up from beneath the outlying blackish mould on my lawn; but from what depth I cannot say. That some must be brought up from a depth of four or five or six feet is certain, as the worms retire to this depth during very dry and very cold weather. As worms devour greedily raw flesh and dead worms, they could devour dead larvae, eggs, etc., etc., in the soil, and thus they might locally add to the amount of nitrogen in the soil, though not of course if the whole country is considered. I saw in your paper something about the difference in the amount of nitrogen at different depths in the superficial mould, and here worms may have played a part. I wish that the problem had been before me when observing, as possibly I might have thrown some little light on it, which would have pleased me greatly.
2.IX.VIII. MISCELLANEOUS, 1846-1878.
(552/1. The following four letters refer to questions connected with the origin of coal.)
LETTER 552. TO J.D. HOOKER. Down, May {1846}.
I am delighted that you are in the field, geologising or palaeontologising. I beg you to read the two Rogers' account of the Coal-fields of N. America; in my opinion they are eminently instructive and suggestive. (552/1. "On the Physical Structure of the Appalachian Chain," by W.B. and H.D. Rogers. Boston, 1843. See also "Geology of Pennsylvania," by H.D. Rogers. 4 volumes. London and Philadelphia, 1843.) I can lend you their resume of their own labours, and, indeed, I do not know that their work is yet published in full. L. Horner gives a capital balance of difficulties on the Coal-theory in his last Anniversary Address, which, if you have not read, will, I think, interest you. (552/2. "Quart. Journ. Geol. Soc." Volume II., 1846, page 170.) In a paper just read an author (552/3. "On the Remarkable Fossil Trees lately discovered near St. Helen's." By E.W. Binney. "Phil. Mag." Volume XXIV., page 165, 1844. On page 173 the author writes: "The Stigmaria or Sigillaria, whichever name is to be retained... was a tree that undoubtedly grew in water.") throws out the idea that the Sigillaria was an aquatic plant (552/4. See "Life and Letters," I., pages 356 et seq.)—I suppose a Cycad-Conifer with the habits of the mangrove. From simple geological reasoning I have for some time been led to suspect that the great (and great and difficult it is) problem of the Coal would be solved on the theory of the upright plants having been aquatic. But even on such, I presume improbable notion, there are, as it strikes me, immense difficulties, and none greater than the width of the coal-fields. On what kind of coast or land could the plants have lived? It is a grand problem, and I trust you will grapple with it. I shall like much to have some discussion with you. When will you come here again? I am very sorry to infer from your letter that your sister has been ill.
LETTER 553. TO J.D. HOOKER. {June 2nd, 1847.}