your attention to another point which formerly perplexed me much--viz. the presence of basaltic dikes in most great granitic areas. I cannot but think the explanation given at page 123 of my "Volcanic Islands" is the true one. (495/5. On page 123 of the "Geological Observations on the Volcanic Islands visited during the Voyage of H.M.S. 'Beagle,'" 1844, Darwin quotes several instances of greenstone and basaltic dikes intersecting granitic and allied metamorphic rocks. He suggests that these dikes "have been formed by fissures penetrating into partially cooled rocks of the granitic and metamorphic series, and by their more fluid parts, consisting chiefly of hornblende oozing out, and being sucked into such fissures.") LETTER 496. TO VICTOR CARUS. Down, March 21st, 1876. The very kind expressions in your letter have gratified me deeply. I quite forget what I said about my geological works, but the papers referred to in your letter are the right ones. I enclose a list with those which are certainly not worth translating marked with a red line; but whether those which are not thus marked with a red line are worth translation you will have to decide. I think much more highly of my book on "Volcanic Islands" since Mr. Judd, by far the best judge on the subject in England, has, as I hear, learnt much from it. I think the short paper on the "formation of mould" is worth translating, though, if I have time and strength, I hope to write another and longer paper on the subject. I can assure you that the idea of any one translating my books better than you never even momentarily crossed my mind. I am glad that you can give a fairly good account of your health, or at least that it is not worse. LETTER 497. TO T. MELLARD READE. London, December 9th, 1880. I am sorry to say that I do not return home till the middle of next week, and as I order no pamphlets to be forwarded to me by post, I cannot return the "Geolog. Mag." until my return home, nor could my servants pick it out of the multitude which come by the post. (497/1. Article on "Oceanic Islands," by T. Mellard Reade, "Geol. Mag." Volume VIII., page 75, 1881.)