74 Analyses of Books. [Jan. 



Como. Wacke is a rock formed by the action of water upon these 

 rocks, and contains calcareous spar, zeolites and piperine. 



There is reason to think that the crystals which are found in bay- 

 salts, have been deposited after the consolidation of the rocks in which 

 they are found, because most of them are altered by a strong heat, 

 and lose their water of crystallization. Fournet attributes the for- 

 mation of zeolites to the transportation of the elements by water from 

 the neighbouring rocks. 



Organic matter. — The mode in which organic matter undergoes 

 decomposition has not been much studied, but a few curious facts 

 have been ascertained. Davy found the manuscripts of Herculaneum 

 converted into a kind of turf, the leaves being united into a single 

 mass by a peculiar substance, formed by the chemical changes of the 

 vegetable matter. The guano in Peru is found in deposits of 50 or 

 60 feet deep, and is formed of the excrement of herons which inhabit 

 the coast. 



Necker de Saussure has observed the teeth of the ursus spil&us 

 in the mines of Carmiola, corroded as if by an acid. Turpin has 

 noticed the egg of the garden snail to be covered on the interior 

 surface of its envelope, with rhombohedral crystals of carbonate of 

 lime. The cellular tissue of the cactus, and the medullary tissue of 

 palms contain oxalate of lime in crystals. 



Nitrification. — When distilled water is placed over plates of 

 iron, lead, zinc, or tin, ammonia is formed in consequence of the 

 combination of the hydrogen of the water with the azote of the air. 



Vanquelin found ammonia in some rusty spots on a sabre, which 

 had been employed by an assassin, and that other traces presented the 

 same substance. Protoxide of iron, yenite, earthy oxide of iron 

 heated in a tube, give out ammonia. Ammonia was detected in the 

 ferruginous water of Passy after evaporation. Boussingault has 

 observed it likewise in oxidized iron by taking a fragment of it, 

 treating it with dilute muriatic acid, evaporating the washings, and 

 heating the residue with quick-lime in a tube, using the precaution 

 to moisten them with water. Faraday obtained ammonia, by heating 

 zinc foil in a glass tube with potash. The experiment succeeded 

 even in hydrogen gas. Potassium, iron, tin, lead, and arsenic like- 

 wise afford much of it, with soda, lime, barytes or potash. The 

 alkalies alone do not yield it. 



The formation of saltpetre has long been a subject of interest. 

 Dumas conceives that the presence of organic matter is not essential. 

 Claubry attributes its production to the action of an acid moisture 

 upon carbonate of lime. 



Fournet thinks that nitric acid may be formed without the pre- 

 sence of organic matter, by the re-action alone of the elements of air 

 and vapour of water. For according to Saussure, oxygen is more 

 condensable by porous bodies than azote, in the proportion of 65 to 

 4'00 ; and Gay Lussac and Humboldt have observed that air dis- 

 engaged from water by boiling, contains more oxygen in proportion 

 to the slowness of its extrication. The result is that oxygen is not 

 only retained with a greater power, but the composition of the last 

 portions of the air approaches protoxide of azote. Fournet has con- 

 cluded, that the united action of porous bodies and of water upon the 



