To Charles Lyell 25 August 
Down. Bromley Kent
Please read this before you go.1 My dear Lyell
This is literally the first day, on which I have had any time to spare; & I will amuse myself by beginning a letter to you, which you can read when you have leisure; for now you must be very busy.— Firstly for the last subject, mentioned between us, viz the radiation of snow, on which you say you are interested: my Brother says I am wrong about colour, but I cannot yet give up a clear impression, I have opposed to the colour-doctrine.— I find from Leslie,2 (in Ure)3 the radiating (& highest) power of Lamp-black being called 100, and gold, silver, copper being 12; writing paper is 98, plumbago 75 and ice is 85. From Wells,4 it appears, that when swan-down (white enough, & the best known radiator) exposed to open sky falls 16o; grass falls 15o; & snow falls between 12o & 13o: gravel & flag-stone (ie naked rock) are inferior to grass, but how much is not said. Dr Wilson,5 however, found on one occasion snow 16o colder than the air two feet above it, & this seems greater than the average coldness of grass on the clearest nights. Therefore I conclude, that a country covered with snow radiates its heat, but little less than the most favourable land.
I was delighted with your letter, in which you touch on slavery; I wish the same feelings had been apparent in your published discussion.—6 But I will not write on this subject; I shd perhaps annoy you & most certainly myself.— I have exhaled myself with a paragraph or two in my Journal on the sin of Brazilian slavery:7 you perhaps will think that it is in answer to you; but such is not the case, I have remarked on nothing, which I did not hear on the coast of S. America. My few sentences, however, are merely an explosion of feeling. How could you relate so placidly that atrocious sentiment about separating children from their parents; & in the next page, speak of being distressed at the Whites not having prospered; I assure you the contrast made me exclaim out.—8 But I have broken my intention, & so no more on this odious deadly subject.—
There is a favourable, but not strong enough review on you, in Gardeners Chron: I am sorry to see, that Lindley abides by the Carbonic-acid-gas theory.9 By the way, I was much pleased by Lindley picking out my Extinction paragraphs & giving them uncurtailed:10 to my mind, putting the comparative rarity of existing species in the same category with extinction has removed a great weight; though of course it does not explain anything, it shows that, until we can explain comparative rarity, we ought not to feel any surprise at not explaining extinction.—
Have you seen Kosmos,11 I think you wd probably find the subject of multiple & single Creations there discussed: at least. H. discussed subject with Hooker & Humbolt is a multiple man.— You speak about Craters of Elevation; I heartily hope your next excursion will be to Sicily: I do not feel at ease on the subject, I cannot swallow, such areas as those of St. Jago in the C. de Verds & Mauritius having been produced by the summit of a volcano having been swallowed up: my suggestion is, perhaps, hardly worth attending to, yet I cannot doubt that the circumferential mountains of St. Jago & Mauritius, have undergone angular elevation of some kind.12
—I am much pleased to hear of the call for a new Edit. of the Principles:13 what glorious good that work has done.— I fear this time you will not be amongst the old rocks;14 how I shd rejoice to live to see you publish & discover another stage below the Silurian; it wd be the grandest step possible, I think.
—I am very glad to hear, what progress Bunbury is making in fossil Botany: there is a fine Hiatus for him to fill up in this country: I will certainly call on him this winter. How I shall miss my break-fast calls on Mrs Lyell & yourself.— From what little I saw of him, I can quite believe anything which you say of his talents.15
I will tell Murray to send the 3d Part of my Journal to you on Monday, though I suppose you
Discusses the power of land covered with snow to radiate heat.
Criticises CL’s discussion of slavery [in Travels in North America (1845)]. A review of CL’s book is in Gardeners’ Chronicle.
Mentions John Lindley’s views on carbonic acid gas and extinction;
refers to the discussion of multiple and single creations in Humboldt’s Kosmos.
The origin of volcanic craters of elevation.
There is a popular demand for a new edition of Principles.
Praises palaeobotanical work of C. J. F. Bunbury.
Please cite as
Darwin Correspondence Project, “Letter no. 905,” accessed on 27 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-905