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Darwin Correspondence Project

From Trenham Reeks   8 February 1845

Museum of Economic Geology

8th. February 1845.

Dear Sir,

I have great pleasure in forwarding the answers to your questions,1 together with the extract upon bones from Liebig.2

You will observe in No. 1313 that there is but a very little Carbonate of Lime, which appears to me strange, as, in No. 1312, a continuation of the same bed, there is an abundance.

I have tested the salts Nos. 759, 762 for Iodine but cannot find a trace of that body or any other which would account for its inefficacy in curing meat.3

If you will direct me how to send the remainder of the Specimens, they shall be forwarded.

I am | Dear Sir | Your obedient Servant | Trenham Reeks

C. Darwin Esqre | &c &c &c


No. 1312. Contains no Carbonate of Soda, but Muriates and Sulphates of Lime & Soda.

* I believe Carbonate of Lime and Muriate of Soda to have no action upon each other. No. 1313. Contains Sulphates and Muriates of Lime and Soda, but very little Carbonate of Lime. No. 763. Is Sulphate of Soda. No. 1633. Contains besides Earthy Matter and Carbonate of lime, Sulphates and Muriates of Soda. 1227. Contains plenty of Muriate of Lime 3052. Contains plenty of Muriate of Lime which may account for its dampness. 3048. Is neither Anhydrite nor Sulphate of Lime but consists of about 64 per cent Earthy Matter, with water & Carbonate of Lime, but no Carbe. of Soda. 1264. The Crust is Gypsum. 759. Contains a little Sulphate of lime & Magnesia with Mechanical Impurities. I can find nothing in it to account for inefficacy in curing meat. 762. Same as 759. 954. Is chiefly Sulphate of Magnesia. 25. Contains about 7 per cent Animal matter and 8 water.

T. Reeks.

One hundred parts of dry bones contain from 32 to 33 per cent of dry gelatine; now supposing this to contain the same quantity of nitrogen as animal glue, viz: 5.28 per cent then 100 parts of bones must be considered as equivalent to 250 parts of human urine.

Bones may be preserved unchanged for thousands of years, in dry or even moist Soils, provided the access of rain is prevented; as is exemplified by the bones of antediluvian animals found in loam or gypsum, the interior parts being protected by the exterior from the action of water. But they become warm when reduced to a fine powder, and moistened bones generate heat and enter into putrefaction; the gelatine which they contain is decomposed, and its nitrogen converted into carbonate of ammonia and other ammoniacal salts, which are retained in a great [measure] by the powder itself. Liebig’s Chemistry of Agriculture and Physiology. Page 194. 2nd. Editn. 4

CD annotations

crossed ink
crossed ink
Top of first page of letter: ‘1845 Gardeners Chronicle p. 93—on salt very [good] for cheese’5 pencil, circled pencil
At end of letter: ‘Gardeners’ Chron. 45 p. 93. on salt for cheese’ ink
Verso last page of letter: ‘Mr Phillips6 (about Patagonian tuff.) | Dela Bech about Muriatic acid’7 pencil, del pencil [Enclosure] *S2 1.1 No… . as 759. 2.15] crossed ink 2.5 No. 763 … Gypsum. 2.12] crossed pencil 2.5 No. 763 … Soda.] ‘Test this for Carbonates’ added pencil, circled pencil 2.6 1633.] ‘Port Desire’ added pencil 2.8 1227.] ‘Nitrate of Soda as quarried’ added pencil 2.12 1264.] ‘Arica’ added pencil 2.15 as 759.] ‘—Chiquitos Salina’ added pencil


See letter to Trenham Reeks, [before 8 February 1845]. For the use CD made of these replies see Journal of researches 2d ed., pp. 66, 155, 370, later elaborated in South America, pp. 52, 69, 72, 74.
Liebig 1842, p. 194. CD possessed an earlier edition of this work (Liebig 1840) in which the cited passage occurs on p. 202. His copy is in the Darwin Library–CUL.
Specimen 759 was a salt, from a salina near the town of Patagones (El Carmen), which CD recorded as being particularly inadequate for preserving meat. For Reeks’s later analysis see letter from Trenham Reeks, 25 February 1845.
CD had apparently requested this reference in connection with his question concerning No. 25 in his letter to Reeks, [before 8 February 1845]. CD cites Reeks and Liebig in his description of the fresh appearance of the fossil bones he found at Banda Oriental (South America, p. 92). The word ‘measure’, which Reeks failed to copy, has been supplied by the editors from Liebig 1842.
Gardeners’ Chronicle and Agricultural Gazette, no. 6, 8 February 1845, p. 93. Cited by CD in Journal of researches 2d ed., p. 66: ‘those salts answer best for preserving cheese which contain most of the deliquescent chlorides’; i.e., they are not pure sodium chloride.
Henry Thomas De la Beche, director of the Geological Survey, at whose request Reeks was answering CD’s queries (see South America, p. 52).


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.

Liebig, Justus von. 1842. Chemistry in its application to agriculture and physiology. Edited by Lyon Playfair. 2d ed., with very numerous additions. London.

South America: Geological observations on South America. Being the third part of the geology of the voyage of the Beagle, under the command of Capt. FitzRoy RN, during the years 1832 to 1836. By Charles Darwin. London: Smith, Elder & Co. 1846.


Sends results of chemical tests on specimens [of salt, see South America, pp. 73–5].

Encloses abstract from Justus Liebig on composition of bones and their ability to withstand decay.

Letter details

Letter no.
Trenham Reeks
Charles Robert Darwin
Sent from
Museum of Economic Geology
Source of text
DAR 39: 43–4, 49–50
Physical description
ALS 3pp, encl 4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 825,” accessed on 22 May 2022,

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