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Darwin Correspondence Project

To Gardeners’ Chronicle and Agricultural Gazette   [before 14 September 1844]

I should be extremely obliged if any of your chemical readers would inform me whether salt and carbonate of lime (under the form of sea-shells) would, if slightly moistened and left in great masses long together, act in any degree on each other?1 It is, I believe, known that masses of the same substances will act on each other, of which smaller quantities will not. I do not ask this question for agricultural purposes (though possibly the answer might be of some interest in that point of view), but from having found in Peru a great bed of upraised recent shells, mixed with salt, which are decayed and corroded in a singular manner, so that the surfaces of the shells are scaling off and falling into powder.2 I may mention, as explaining one element in the value of sea-shells as manure, that they are dissolved by water with greater facility than apparently any other form of carbonate of lime: one proof of this I observed in a curious rock, from Chili, chiefly composed of small fragments of recent shells, which are all enveloped and cemented together by a pellucid calcareous deposit; but in some parts of this rock the little included fragments are in every stage of decay and disappearance; in other parts they are entirely dissolved, the little calcareous envelopes being left quite empty. Here we see that water, capable of dissolving shelly matter, has penetrated through their thin films or envelopes of carbonate of lime, without having acted on them; these films, moreover, being a deposition from water within quite recent times.—3 C. Darwin.

Footnotes

Only one reader, who signed himself ‘T. P.’, responded to CD’s query (see Gardeners’ Chronicle and Agricultural Gazette, no. 40, 5 October 1844, p. 675), although there was considerable interest in the agricultural use of salt. In 1845 a short comment attributed to Christian Konrad Sprengel carried the discussion further (see Gardeners’ Chronicle and Agricultural Gazette, no. 10, 8 March 1845, p. 157).
See Journal of researches, p. 451, and South America, pp. 47–9, 52–3. CD was interested in the chemical decomposition of sea-shells as further evidence for the existence of elevated beaches on the west coast of South America. See also letters from Trenham Reeks, 8 February 1845 and 25 February 1845.
Described in Volcanic islands, p. 144 n., and South America, pp. 36–7.

Summary

Asks whether salt and carbonate of lime (in the form of seashells) would act upon each other if slightly moistened and left in great quantities together. The question occurs from CD’s having found in Peru a great bed of recent shells that were mixed with salt, decayed and corroded "in a singular manner". Mentions, as relevant to the value of seashells as manure, that they are dissolved more rapidly by water than any other form of carbonate of lime.

Letter details

Letter no.
DCP-LETT-778
From
Charles Robert Darwin
To
Gardeners’ Chronicle
Sent from
unstated
Source of text
Gardeners’ Chronicle and Agricultural Gazette, no. 37, 14 September 1844, pp. 628–9

Please cite as

Darwin Correspondence Project, “Letter no. 778,” accessed on 17 June 2019, http://www.darwinproject.ac.uk/DCP-LETT-778

Also published in The Correspondence of Charles Darwin, vol. 3

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