92 Recent Publications on Manures. 



particles of soil act on the liquid, by absorbing the ulmate of 

 ammonia from its solution in water, retaining it, and letting the 

 water pass, without being decomposed into humus and am- 

 monia? If the oxygen passed through the soil had been moist, 

 not dry, would more not have been absorbed? Liebig says 

 there is an atmosphere of carbonic acid formed in the soil 

 around all the decaying portions of humus. There is much 

 to convince us of the value of humus, and of its derivative, 

 ulmate of ammonia; but it is surely carrying the matter too far, 

 to assume it as the sole source of carbon and ammonia from the 

 soil. Chemists seem too apt to deal in exclusives. Nature is 

 seldom confined to one particular method of producing results ; 

 and nutritious substances will undoubtedly be exhibited in 

 many different forms to the absorbent vessels of plants : Dr. 

 Madden himself seems to be of that opinion. Carbonate of 

 ammonia is the state in which it is principally found in urine, 

 and the most valuable of manures : it is as soluble as the other 

 in water, and as likely to be absorbed. There are, also, as ob- 

 served before, the carbonic acid carried down by rain into the 

 soil from the atmosphere, and that absorbed by the water of the 

 soil from the carbonic acid produced by the decomposition of 

 humus by oxygen, stated by Liebig to be in constant action; 

 also, the carbon produced from the soluble organic substances 

 absorbed by the roots, and from the carbonic or ulmic acid 

 absorbed in union with potash and other alkaline substances. 

 From the much slighter affinity of ammonia for acids than the 

 other alkalies, from the large quantity above stated held in 

 solution by potash, 360 gr. to 48 gr., and from the soda being a 

 more powerful solvent still than potash, it is likely that much of 

 the ulmic acid may go to plants in this form. Professor Thorn- 

 son describes ulmin as it is found in the elm, being always here 

 dissolved in carbonate of potash. The nitrogen, also, cannot 

 always be from ulmate of ammonia; it is undoubtedly furnished 

 from the nitric acid of the nitrates, as they are found to increase 

 the gluten in wheat, in the same way as ammonia does; the 

 small quantity of that of the atmosphere soluble in water will 

 likely also give a part; and the carbonate of ammonia from the 

 rain of the atmosphere, and of manures, may be absorbed as 

 such : the possibility only, not the necessity, of its being con- 

 verted into ulmate of ammonia, has been proved. Professor 

 Dumas says, all the ammonia got from thunder-storms is in the 

 form of nitrate of ammonia. It is, perhaps, not easy to say 

 whether one twelfth part of the plant only is required of nitrogen. 

 Professor Dumas says, M. Payen's researches teach us, that all 

 the organs of the plant, without exception, begin by being 

 formed of an azotated matter, analogous to fibrin ; with which, 

 at a later period, the cellular, ligneous, and amylaceous tissues 

 are associated. This concrete fibrinous substance, he says, 



