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To Robert Mallet   26 August [1846]1

Down Farnborough Kent

Aug. 26th.

Sir

I take the liberty of writing to thank you for your most obliging present of the Dynamics of Earthquakes, & for the much too honourable mention you make of my name.—2 I have read your memoir with the greatest interest & it has much cleared my ideas, though undulations of all kinds will ever be of difficult comprehension to non-mathematical heads.—

During writing the first Edition of my Journal, I consulted Mr. Whewell,3 & soon perceived how difficult a subject that of waves was. In the Col. Library Edit, I condensed what I had said, & now heartily wish I had said nothing for I felt at the time that I was out of my depth.4

I beg to send you a paper of mine, which perhaps you may never seen & may be scarcely worth your reading; my chief object in writing it, was to show the intimate connection & indeed identity of the forces, which pour forth lava & elevate continents: this to my mind is an important conclusion.—5 At p. 621. you will see an indirect argument against Earthquakes being undulations in an underlying fluid mass & in favour, (of what your memoir will never again allow to be doubtful) of their being a vibration or oscillation in the solid crust.—6

Have you seen the Mrs. Rogers of N. America papers on earthquakes,7 they push the doctrine of fluid undulations to a monstrous extent, & if I might take the liberty to suggest, it would be adviseable to send a copy of your memoir to them; for they are excellent geologists.

How wonderfully interesting it would be, if you could have your instrument8 worked in Chile: in Lima, there was or is a merchant Mr Maclean9 with a strong taste for Natural History, & earthquakes are frequent there.

I have some intentions of being at Southampton,10 & I trust, you will allow me to introduce myself to you.

With my sincere thanks | I beg to remain dear Sir | Yours faithfully | C. Darwin

It has often occurred to me that a faithful record of earthquakes in Chile, would perhaps afford curious results from coincidences with the moon or state of tides.—11

1
The date is based on the reference to the September 1846 meeting of the British Association in Southampton.
2
Mallet 1846. CD received pre-publication copies of this work and Mallet 1848b, which were read at the Royal Irish Academy on 9 February and 22 June 1846, respectively. CD’s copies are dated 1846, bear an abbreviated title, and are separately paginated. They are in the Darwin Pamphlet Collection–CUL. The following references are to the later published version. In the paper Robert Mallet cites CD on the twisting displacement of building stones and ornaments (Mallet 1846, pp. 54–5), notes CD’s use of the term ‘undulation’ to describe earthquake motion (pp. 57–8), and quotes at length from CD’s description of tidal waves associated with earthquakes (pp. 65–6).
3
See Correspondence vol. 2, letter to William Whewell, 18 June [1837].
4
CD described the Concepción earthquake in Journal of researches, pp. 368–81, and 2d ed., pp. 301–12. However, Mallet explained the twisting displacement of building stones as due to different centres of gravity and adhesion in the affected stones (Mallet 1848a, pp. 54–7). Mallet also explained numerous aspects of tidal waves as the result of the different velocities of wave propagation in the rock of the sea-bed, the water, and the air above (Mallet 1846, pp. 65–74).
5
‘On the connexion of certain volcanic phenomena in South America’, Collected papers 1: 53–86. The passage cited by CD appears on pp. 72–3.
6
Mallet argued that the primary motion of earthquakes had to occur in the crust since any motion imparted to the crust by the underlying fluid would be transmitted more rapidly in the crust than in the fluid itself.
7
Rogers and Rogers 1843.
8
Mallet 1848b describes an experimental seismograph. Though his invention was never used, elements of his design were incorporated into later instruments (DSB 9: 60–1).
10
See n. 1, above.
11
CD referred to this idea in Notebook A: 137, 153.

Manuscript Alterations and Comments

2.1 writing] interl
2.2 that of waves] above del ‘it’
2.3 what I had said,] ‘had’ interl
3.4 elevate] altered from ‘elevates’

Please cite as “DCP-LETT-992,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-992