I do not remember Humboldt's fact about the heath regions. Very curious the case of the broom; I can tell you something analogous on a small scale. My father, when he built his house, sowed many broom-seeds on a wild bank, which did not come up, owing, as it was thought, to much earth having been thrown over them. About thirty-five years afterwards, in cutting a terrace, all this earth was thrown up, and now the bank is one mass of broom. I see we were in some degree talking to cross-purposes; when I said I did [not] much believe in hybridising to any extent, I did not mean at all to exclude crossing. It has long been a hobby of mine to see in how many flowers such crossing is probable; it was, I believe, Knight's view, originally, that every plant must be occasionally crossed. (19/3. See an article on "The Knight-Darwin law" by Francis Darwin in "Nature," October 27th, 1898, page 630.) I find, however, plenty of difficulty in showing even a vague probability of this; especially in the Leguminosae, though their [structure?] is inimitably adapted to favour crossing, I have never yet met with but one instance of a NATURAL MONGREL (nor mule?) in this family.
I shall be particularly curious to hear some account of the appearance and origin of the Ayrshire Irish Yew. And now for the main object of my letter: it is to ask whether you would just run your eye over the proof of my Galapagos chapter (19/4. In the second edition of the "Naturalist's Voyage."), where I mention the plants, to see that I have made no blunders, or spelt any of the scientific names wrongly. As I daresay you will so far oblige me, will you let me know a few days before, when you leave Edinburgh and how long you stay at Kinnordy, so that my letter might catch you. I am not surprised at my collection from James Island differing from others, as the damp upland district (where I slept two nights) is six miles from the coast, and no naturalist except myself probably ever ascended to it. Cuming had never even heard of it. Cuming tells me that he was on Charles, James, and Albemarle Islands, and that he cannot remember from my description the Scalesia, but thinks he could if he saw a specimen. I have no idea of the origin of the distribution of the Galapagos shells, about which you ask. I presume (after Forbes' excellent remarks on the facilities by which embryo-shells are transported) that the Pacific shells have been borne thither by currents; but the currents all run the other way.
(PLATE: EDWARD FORBES 1844? From a photograph by Hill & Adamson.)
LETTER 20. EDWARD FORBES TO C. DARWIN.
(20/1. Edward Forbes was at work on his celebrated paper in the "Geological Survey Memoirs" for 1846. We have not seen the letter of Darwin's to which this is a reply, nor, indeed, any of his letters to Forbes. The date of the letter is fixed by Forbes's lecture given at the Royal Institution on February 27th, 1846 (according to L. Horner's privately printed "Memoirs," II., page 94.))
Wednesday. 3, Southwark Street, Hyde Park. [1846].
Dear Darwin
To answer your very welcome letter, so far from being a waste of time, is a gain, for it obliges me to make myself clear and understood on matters which I have evidently put forward imperfectly and with obscurity. I have devoted the whole of this week to working and writing out the flora question, for I now feel strong enough to give my promised evening lecture on it at the Royal Institution on Friday, and, moreover, wish to get it in printable form for the Reports of our Survey. Therefore at no time can I receive or answer objections with more benefit than now. From the hurry and pressure which unfortunately attend all my movements and doings I rarely have time to spare, in preparing for publication, to do more than give brief and unsatisfactory abstracts, which I fear are often extremely obscure.
Now for your objections--which have sprung out of my own obscurities.
I do not argue in a circle about the Irish case, but treat the botanical evidence of connection and the geological as distinct.