60 AMERICAN MANURES. 



water chemically combined; hence 75.681bs. of 

 quicklime, and 24.321bs. of water will produce 

 100 Ibs. of hydrated or slaked lime. Quicklime 

 has a great tendency to reabsorb carbonic acid, 

 and, if spread on the soil and there slaked 

 by absorbing moisture from the atmosphere, 

 more than half of it would be changed back into 

 limestone. Hence, lime should be slaked in 

 large heaps, and would be still better preserved 

 if these heaps were covered with sods. Lime 

 can be applied to the soil, either in its natural 

 state, as in limestone, or as burnt lime, or as 

 hydrated or slaked lime, with beneficial results. 

 Marls are very rich in carbonate of lime, and 

 some of the best varieties contain from 50 to 75 

 per cent, of it. By appropriate machinery lime- 

 stone could be reduced to a fine powder more 

 cheaply than by burning, where fuel is scarce 

 and dear. Nevertheless, burnt lime is far 

 superior to powdered limestone or marl for the 

 purpose of agriculture ; one of the reasons being 

 that the slaking of lime reduces it to an im- 

 palpable powder, much finer than can be effected 

 by the most perfect machinery. This extreme 

 fineness of division diffuses it more uniformly 

 through the soil, and makes it more readily 

 soluble in water; 1000 Ibs. of water will hold 

 1 Ib. of slaked lime in solution: hence, if the 

 annual rain-fall on an acre of land be seven 



