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Letter 771

Darwin, C. R. to Horner, Leonard

29 Aug [1844]

    Summary Add

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    Thanks Horner for his letter [about Volcanic islands].

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    Discusses craters of elevation with respect to the views of Leopold von Buch and Élie de Beaumont. Compares Lyell's views to those of continental geologists. Mentions reading A. D. d'Orbigny [Voyage dans l'Amérique méridionale (1835–47)].

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    Encloses note from Emma to Mrs Horner, inviting the Horners to visit Down.

Transcription

Down near Bromley | Kent

Aug 29th

My dear Mr Horner

I am greatly obliged for your kind note & much pleased with its contents. If one third of what you say, be really true & not the verdict of a partial judge (as from pleasant experience I much suspect), then should I be thoroughily well contented with my small volume, which small as it is, cost me much time.— The pleasure of observation amply repays itself; not so that of composition, & it requires the hope of some small degree of utility in the end, to make up for the drudgery of altering bad English into sometimes a little better & sometimes worse.

With respect to Craters of Elevation, I had no sooner printed off the few pages on that subject, than I wished the whole erased.— I utterly disbelieve in Von Buch & de Beaumonts views, but on the other hand in the case of the Mauritius & St Jago, I cannot, perhaps, unphilosophically persuade myself, that they are merely the basal fragments of ordinary volcanoes, & therefore I thought I would suggest the notion of a slow circumferential elevation, the central part being left unelevated, owing to the force from below being spent & relieved in eruptions. On this view, I do not consider these so-called craters-of Elevation, as formed by the ejection of ashes lava &c &c but by a peculiar kind of elevation, acting round & modifyed by a volcanic orifice.—

I wish I had left it all out; I trust that there is in other parts of the volume more facts & less theory.— The more I reflect on volcanoes, the more I appreciate the importance of E. de Beaumont's measurements (even if one does not believe them implicitly) of the natural inclination of lava-streams & even more the importance of his view of the dikes or upfilled fissures in every volcanic mountain being the proofs & measures, of the stretching & consequent elevation which all such mountains must have undergone: I believe he thus unintentionally explains most of his cases of lava-streams being inclined at a greater angle, than that at which they could have flowed.

But excuse this lengthy note & once more let me thank you for the pleasure & encouragement you have given me,—which together with Lyells never-failing kindness, will help me on with S. America, & as my Books will not sell, I sometimes want such aid.—

I have been lately reading with care A. d'Orbigny work on S. America, & I cannot say how forcibly impressed I am with the infinite superiority of the Lyellian school of Geology over the Continental. I always feel as if my books came half out of Lyell's brains & that I never acknowledge this sufficiently, nor do I know how I can, without saying so in so many words—for I have always thought that the great merit of the Principles, was that it altered the whole tone of one's mind & therefore that when seeing a thing never seen by Lyell, one yet saw it partially through his eyes— it would have been in some respects better if I had done this less—but again excuse my long & perhaps you will think presumptuous discussion.

Enclosed is a note from Emma to Mrs Horner to beg you, if you can, to give us the great pleasure of seeing you here— we are necessarily dull here & can offer no amusements, but the weather is delightful & if you could see how brightly the sun now shines you would be tempted to come—

Pray remember me most kindly to all your family & beg of them to accept our proposal & give us the pleasure of seeing them.— Emma will tell how feasible the coming here is by a coach, which puts down by our door at dinner-time.

Believe me | dear Mr Horner | Yours truly obliged | Charles Darwin

    Footnotes Add

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    f1 771.f1
    Volcanic islands was published in March 1844 (The Publishers' Circular).
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    f2 771.f2
    CD discussed ‘craters of elevation’ in Volcanic islands, pp. 93–6. According to Christian Leopold von Buch (1836) and Jean Baptiste Armand Louis Léonce Élie de Beaumont (1838), volcanoes were caused by pressure from below which arched the strata into a dome-like formation until the centre collapsed and a vent was formed. Charles Lyell (1840a, 2: 238–50) argued that volcanoes were formed merely by the expulsion of underground material. CD attempted a compromise position according to which elevation took place only around the circumference of the volcano, requiring no collapse of the crater.
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    f3 771.f3
    Élie de Beaumont had made measurements of the inclination of lava streams that convinced him that lava would cool into thick layers of volcanic rock only on nearly level ground (1838, pp. 173–8), a finding that seemed to exclude Lyell's notion that substantial rock layers would normally be formed by ejected lava on the growing slopes of the volcano. CD's copy of Élie de Beaumont 1838 is in the Darwin Library–CUL.
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    f4 771.f4
    Élie de Beaumont argued that the growth and expansion of internal crevices meant Mount Etna, like other volcanoes, was constantly growing in volume and altitude (1838, pp. 116–21).
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    f5 771.f5
    Probably Géologie, the third part of the third volume of Orbigny 1835–47, which was published in 1842. See letter to Charles Lyell, [1 September 1844]. CD borrowed the book from the Geological Society, see letter to the Geological Society of London, [3 January 1844].
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