A typical letter handwritten by author in English and signed by author.
An original MS
Pages with text: 7
Transcriber: Cooper, Rod
Transcription date: December 6, 2012
Scrutiny: 15/01/2013 - Catchpole, Caroline;
Signed off: no
9, St Mark’s Crescent
March 13th. 1869
Dear Sir Charles
Many thanks for your kindness in again speaking to Earl de Grey2 about me. I can quite understand that with the immense amount of Government business now on hand, and especially the new Education bill which he & Mr Forster will especially have to attend to, they can give no time to such a comparatively small matter as the East London Museum.
I should think that in[?] consideration & enquiry the Duke of Argyll will give up his idea of an Indian Nat[ural]. History Mus[eum]. Our Indian Empire is now so extensive that any thing [sic] like a Complete Indian Museum would be a very large affair; -- & an [] incomplete & stationary one would be of very little use or interest.
I shall be glad to hear what answer Mr. Croll3 makes you, as I feel sure that in one of his papers he alludes to the erect trees[?] as being "certainly since the glacial epoch".
I read Canon Moseley’s4 article about glaciers & Mr. Croll’s explanation, which I think a very poor & unsatisfactory one. It seems to me that Canon Moseley’s reasoning is quite inapplicable & his premises unsound. His experiment to determine the "shearing" resistance of ice, seems to me to have no application whatever to the actual conditions of a glacier or of glacier motion. His experiment only shows the force required to rend asunder by a lateral sliding motion the entire section of a glacier at the same [] instant , -- quite ignoring the fact that the ice of a glacier must be in varying states of tension, & the whole weight of a large portion of it may be concentrated to produce rupture at one determinate point in time. This rupture too, will be more or less successive, each simultaneous through the entire thickness or mass of the glacier.
Fig. I. shows Canon Moseley’s experiment. force [sic] being applied to slide the two blocks of wood A & B over each other and rupture the ice, at the line a. To do [Figures I and II are illustrated to the left of the preceding text, commencing at "Fig. I"] which the cohesion of the whole sectional area must be overcome simultaneously. But if we take the same cylinder of ice and supporting it on a curved surface as at A. fig. II and then apply pressure [] on each side so as to produce a fracture at a. the force required even with a very short leverage will be only a fraction of that necessary in the other experiment. Now owing to the irregular surfaces of the ground at the under side of glaciers and the constant melting away of the ice at its under surface, vast masses must often be rest on saddles or bridge over hollows, and the whole weight of the mass will cause a fracture on one determinate line of least resistance. A slight release to the tension being thus given, a new line becomes that of least resistance & in turn gives way, and thus the glacier moves regularly downward.
Canon Moseley goes on the principle that each sectional inch or[?] foot of the glacier, can only be moved by a column of ice of the same sectional area behind it, and that [] 419 2/5 the "shearing" must take place over the whole sectional surface [word illeg.] ice[?], -- but it is clear that horizontal no less than vertical fracture, would occur, but over whole miles[?] of the glacier at once, but in certain limited areas where unequal tension had reached its maximum, and the weight of [word illeg. crossed out] larger areas of the glacier might act to produce successive fractures of a few feet or a few hundred feet at a time. If the whole glacier were at any moment as compact and uniform in its molecular condition as the square inch of ice on which Canon Moseley experimented, and everywhere in close contact with its bed & sides, his calculations might be available to some extent, though even then, owing to unequal slope and lateral irregularities, the weight would [] bear most unequally on different portions, and a number of lines and surfaces of tension & least resistance be immediately formed. The numerous crevasses on every glacier are the proof and the result of such tensions.
I have no doubt Tyndall6 will answer Canon Moseley in due time. Croll’s theory of molecular motions seems to me equivalent to Forbes7 viscosity, -- & if true there ought to be few or no crevasses.
We have made arrangements for a cheap edition of my [] book as soon as this one is out. I could have put[?] a score more illustrations, but of course was obliged to have a limit. The one you suggest would be very effective, but I am afraid people would complain if there was more in the cheap than in the dear edition.
Believe me | Yours very faithfully | Alfred R. Wallace [signature]
Sir Charles Lyell, Bart.
1. The page / catalogue number, "419", appears at the top left of the page.
2. George Robinson, 1st Marquess of Ripon (1827 - 1909). He was Lord President of the Council at the time of this correspondence.
3. James Croll (1821 - 1890). Scottish scientist who developed a theory of climate change based on changes in the Earth’s orbit.
4. Canon Henry Moseley (1801 - 1872). First Professor of Natural Philosophy at King’s College, London, FRS and Canon of Bristol
5. The page / catalogue number "419", appears at the top left of the page, and ARW has numbered the top of the page with an encircled "2".
6. John Tyndall (1820 - 1893). Irish born physicist, glaciologist and pioneering alpinist.
7. James David Forbes (1809 - 1868). Scottish physicist and glaciolgist.
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