To Leonard Horner 18 [March 1855]1
Down Farnborough Kent
My dear Mr Horner
I daresay I am going to trouble you quite uselessly, but as you seem, (or give the impression) in your Nile Paper2 to quite believe Russegger’s statement about the baked upper sandstone deposit,3 I thought I would just state that from what I have seen myself at the C. of Good Hope & Australia4 (& from what I know has been observed in India & the Malayan archipelago) I cannot avoid a total disbelief of the whole account. But please let me premise that if Russegger shows by his observations that he is a mineralogist as well as a geologist,—if in his baked rocks he has measured any crystals of feldspar or augite &c or even tryed the rock under the blowpipe, or examined the grains of quartz & seen their edges under the microscope fused I withdraw with humble apologies to you & him, my doubts. But if he has not, I would not in my own case quote his observations as in the least trustworthy.
In the countries above specified I have seen great areas coated with from 1 or 2 to (I think) 10 or 12 feet of dark brown, & black & angularly vesicular rock, having a most curious vitrified appearance, but which certainly was owing to a curious modification of the oxides of iron contained in it. Certainly there had been no heat from below, & certainly the whole deposit is simply superficial, & alluvial: I cannot explain its origin. To show its appearance, a most intelligent young officer in the Beagle, who had read Lyell & had seen plenty of real lavas, came rushing to me to say that he had found a most splendid stream of recent lava in the mountains near False Bay:5 I knew what it wd. turn out, & so it did.—
I had the greatest doubt whether I wd trouble you with this; but I felt sure you would forgive me, & wd. perhaps like to hear of the possibility of a very great blunder being quoted as worthy of consideration in a memoir which will have value for the next, no one can tell, how many centuries.
I will be still more presumptuous, & say that I think a little shortening in the purely geological introduction would not injure the Paper.— As you will be surprised at all this, I may as well say that I have had to Report on your paper; but have of course made none of these remarks in the Report.6 Indeed I wish I had not just said that the geological introduction wd not be injured by being shortened, for it only just occurred to me as a passing suggestion.— In 50 years, the Geology will probably be all passè, whereas the whole rest of the Paper will be permanent: is not this putting new wine in old Bottles?7
How very curious your account (p. 58)8 of the non-lamination of the mud: it interests me, as I feel sure that the great upheaved Pampean mud deposit9 was formed by slow deposition of mud in an estuary, & yet it is not in the least laminated; & rarely, when splendid sections are exhibited, the slightest variations in bands of colour can be most obscurely be distinguished: Al. d’orbigny has argued from this want of lamination that the whole vast Pampean deposit was thrown down all at once by a debacle.10
Will you forgive my presumption & believe | My dear Mr Horner | Your’s very sincerely & humbly | Ch. Darwin
at p. 25 of your M.S. wd. it not be well to insert some one word instead of “Thus” to show that, you do not suppose the difference of the rise of the Nile at Rhoda & Rosetta is a measure of the amount of evaporation, as the width of the Nile & current are not the same at the two places.—11
CD has been a referee for LH’s Nile geology paper [Philos. Trans. R. Soc. Lond. 145 (1855): 105–38]. Praises the work but offers criticism not in his report: Joseph Russegger’s statement about the baked Upper Sandstone deposit cannot be believed; LH’s paper is too long.
Please cite as
Darwin Correspondence Project, “Letter no. 1649,” accessed on 27 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-1649