Recent Publications on Manures. 89 



added water to the soil, after free exposure to the air for three hours, 

 a brown-coloured matter came off with the water in considerable 

 quantity. This fact he considers of great importance, as giving a 

 clue to the way in which humus may be rendered soluble in soil, 

 and explaining the origin of the dark brown fluid from all dung- 

 hills, &c, which yields ammonia abundantly when treated with 

 caustic potash. The reason why a brown-coloured solution is 

 not obtained by agitating soil with water is, that allowing all the 

 ammonia to be evolved from 30 tons of farm-yard manure to be 

 saturated with humus, still it would at no period form more than 

 xyioo P ar t; a quantity too small to colour solutions made in 

 the usual manner with cold water, without allowing time for the 

 air to act. It was pure ammonia he used above; and as ammonia 

 is generally found in the state of carbonate of ammonia, he tried 

 soil agitated with carbonate of ammonia, and found that it also 

 possessed the power of dissolving humus in the soil, though not 

 nearly to the same extent as the pure alkali. If the 2*016 lb. 

 of ammonia from the 30 tons of manure were pure, it would 

 dissolve, he calculates, 36*288 lb. of humus, which, though only 

 in the state of ulmic acid, would contain 20*684lb. of carbon ; 

 and allowing the ammonia of the manure to be all carbonate, 

 and rating its powers of solution only at one third of the pure 

 alkali, would give carbon for five years' crops, independently of the 

 consideration, that if part of the humus dissolved were apotheme 

 much more carbon would be yielded. In his farther researches 

 on the action of water, he found that pieces of animal substances, 

 as sheep skins, when moistened only with water, and exposed to 

 the action of the air, decomposed much more quickly than when 

 totally under water. In the same way, when carbonate of am- 

 monia was added in solution of water to humus, it produced 

 little effect, only yellowing the water ; and, though allowed to lie 

 a time, it did not get very dark; but when he mixed it moist 

 only, and after a few days' action added water, it came off of an 

 intense brown black, showing the immense difference between 

 wet and moist action. Suspecting, also, that the reason why 

 carbonate of lime, and not humate or ulmate of lime, is found in 

 the stalactites of caverns (as pointed out by the opponents of the 

 humus doctrine, to indicate that that acid did not exist in the soil), 

 was, that it was decomposed in the soil in passing through, the 

 soil exerting partly a chemical action on the humus; he. poured 

 ulmate of ammonia in solution on a dry soil in a flower-pot till 

 it began to flow out at the bottom, when he found that what 

 came through had lost colour to such an extent, that he reckoned 

 it did not contain one half of its original quantity of organic 

 matter. In this manner, he thinks, is the food preserved in soil: 

 when ammonia is extricated, it acts on the organised matter of 

 the soil, producing carbonate and ulmate of ammonia. When 

 rain occurs it renders these substances soluble, and they would 



