Skertchly, who is examining such districts. Pray forgive me for writing so long a letter, and again thanking you for the great pleasure derived from your book,
I remain yours very faithfully, CH. DARWIN.
P.S....I am glad that you have read Blytt (Axel Blytt.--'Essay on the Immigration of the Norwegian Flora during alternate rainy and dry Seasons.' Christiania, 1876.); his paper seemed to me a most important contribution to Botanical Geography. How curious that the same conclusions should have been arrived at by Mr. Skertchly, who seems to be a first-rate observer; and this implies, as I always think, a sound theoriser.
I have told my publisher to send you in two or three days a copy (second edition) of my geological work during the voyage of the "Beagle". The sole point which would perhaps interest you is about the steppe-like plains of Patagonia.
For many years past I have had fearful misgivings that it must have been the level of the sea, and not that of the land which has changed.
I read a few months ago your [brother's] very interesting life of Murchison. (By Mr. Archibald Geikie.) Though I have always thought that he ranked next to W. Smith in the classification of formations, and though I knew how kind-hearted [he was], yet the book has raised him greatly in my respect, notwithstanding his foibles and want of broad philosophical views.
[The only other geological work of his later years was embodied in his book on earthworms (1881), which may therefore be conveniently considered in this place. This subject was one which had interested him many years before this date, and in 1838 a paper on the formation of mould was published in the Proceedings of the Geological Society (see volume i.).
Here he showed that "fragments of burnt marl, cinders, etc., which had been thickly strewed over the surface of several meadows were found after a few years lying at a depth of some inches beneath the turf, but still forming a layer." For the explanation of this fact, which forms the central idea of the geological part of the book, he was indebted to his uncle Josiah Wedgwood, who suggested that worms, by bringing earth to the surface in their castings, must undermine any objects lying on the surface and cause an apparent sinking.
In the book of 1881 he extended his observations on this burying action, and devised a number of different ways of checking his estimates as to the amount of work done. (He received much valuable help from Dr. King, of the Botanical Gardens, Calcutta. The following passage is from a letter to Dr. King, dated January 18, 1873:--
"I really do not know how to thank you enough for the immense trouble which you have taken. You have attended EXACTLY and FULLY to the points about which I was most anxious. If I had been each evening by your side, I could not have suggested anything else.") He also added a mass of observations on the habits, natural history and intelligence of worms, a part of the work which added greatly to its popularity.
In 1877 Sir Thomas Farrer had discovered close to his garden the remains of a building of Roman-British times, and thus gave my father the opportunity of seeing for himself the effects produced by earthworms' work on the old concrete-floors, walls, etc. On his return he wrote to Sir Thomas Farrer:
"I cannot remember a more delightful week than the last. I know very well that E. will not believe me, but the worms were by no means the sole charm."
In the autumn of 1880, when the 'Power of Movement in Plants' was nearly finished, he began once more on the subject. He wrote to Professor Carus (September 21):--
"In the intervals of correcting the press, I am writing a very little book, and have done nearly half of it. Its title will be (as at present designed) 'The Formation of Vegetable Mould through the Action of Worms.' (The full title is 'The Formation of Vegetable Mould through the Action of Worms with Observations on their Habits,' 1881.) As far as I can judge it will be a curious little book."
The manuscript was sent to the printers in April, 1881, and when the proof- sheets were coming in he wrote to Professor Carus: "The subject has been to me a hobby-horse, and I have perhaps treated it in foolish detail."
It was published on October 10, and 2000 copies were sold at once.