To Gardeners’ Chronicle and Agricultural Gazette [before 6 March 1847]
Your correspondent “W. B. N”1 must, I think, have seen salt from other salinas than those described by me;2 probably (as I infer from his statement that the salt is brought into Buenos Ayres in ox-waggons), from the salinas north of S. Ventana. The salt from the Rio Negro, from the S. Chiquitas and from San Julian, instead of being an “amorphous mass,” yielding “a soft powder,” is coarsely crystallized, some of the cubes being even 3 or 4 inches square. Instead of being mixed with much earth, the salt presents an expanse as white as newly fallen snow, which, viewed from a distance, as I well remember to my cost, might readily be mistaken for a lake.3 Your correspondent seems to think that by the term purity, I imply freedom from dirt, but in my work I explain that I mean, “the absence of those other saline bodies found in all sea-water,”—a remarkable fact, which I state after the careful analysis of Mr. T. Reeks of the Museum of Econom. Geology.4 The salt consists entirely of chloride of sodium, with the exception of only 0.26 of sulphate of lime, and 0.22 of earthy matter. This fact having been ascertained, and the mass being well crystallised, it still appears to me that its lesser value for curing meat is probably owing to its purity, in the sense in which I have perhaps inappropriately used the term, that is, to the absence of those other saline substances found in sea-salt. I should not, however, have ventured on this opinion, had not Prof. Johnston5 come to the conclusion “that those salts answer best for preserving cheese which contain most of the deliquescent chlorides.”6 I must yet think that the experiment of adding some of the muriates of lime and magnesia to the salt from the Rio Negro, would be very well worth trial by the owners of the Saladeros near Buenos Ayres.7 — C. Darwin.
Footnotes
Bibliography
Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.
Journal of researches 2d ed.: Journal of researches into the natural history and geology of the countries visited during the voyage of HMS Beagle round the world, under the command of Capt. FitzRoy RN. 2d edition, corrected, with additions. By Charles Darwin. London: John Murray. 1845.
Summary
Corrects a misunderstanding of his description of salt deposits [in South America, pp. 74–5]. The salt referred to was from Rio Negro, and was coarsely crystallised and free of other saline substances found in sea-salt. CD believes its lesser value in curing meat is owing to the absence of muriates of lime and magnesia and suggests that it might be worth while to add them to the Rio Negro salt.
Letter details
- Letter no.
- DCP-LETT-1069
- From
- Charles Robert Darwin
- To
- Gardeners’ Chronicle
- Sent from
- unstated
- Source of text
- Gardeners’ Chronicle and Agricultural Gazette, no. 10, 6 March 1847, pp. 157–8
Please cite as
Darwin Correspondence Project, “Letter no. 1069,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-1069.xml
Also published in The Correspondence of Charles Darwin, vol. 4