From Trenham Reeks 8 February 1845
Museum of Economic Geology
8th February 1845.
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.
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
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.
Please cite as
Darwin Correspondence Project, “Letter no. 825,” accessed on 28 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-825