ITS ESSENTIAL ELEMENTS. 179 



eordingly,from 69 to 75 parts of water. From the 

 dried excrements, we obtain, by incineration, varia- 

 ble quantities of salts and earthy matters according 

 to the nature of the food which has been taken by 

 the animal. Macaire and Marcet found 27 per cent, 

 in the dung analysed by them ; I obtained only 10 

 per cent, from that of a horse fed with chopped 

 straw, oats, and hay. It results then that with 

 from 3600 to 4000 Ibs of fresh horse's-dung, cor- 

 responding to 1000 Ibs of dry dung, we place on 

 the land from 2484 to 3000 Ibs. of water, and from 

 730 to 900 Ibs. of vegetable and altered gall, and 

 also from 100 to 270 Ibs of salts and other inor- 

 ganic substances. 



The latter are evidently the substances to which 

 our attention should be directed, for they are the 

 same which formed the component parts of the hay 5 

 straw, and oats, with which the horse was fed. 

 Their principal constituents are the phosphates of 

 lime and magnesia, carbonate of lime and silicate 

 of potash ; the first three of these preponderated in 

 the corn, the latter in the hay. 



Thus in 1000 Ibs. of horse's-dung, we present to 

 a field the inorganic substances contained in 6000 

 Ibs. of hay, or 8300 Ibs. of oats, (oats containing 

 3*1 per cent, ashes according to De Saussure). 

 This is sufficient to supply 1^ crop of wheat with 

 potash and phosphates. 



The excrements of cows, black cattle and sheep, 

 contain phosphate of lime, common salt, and silicate 



N 2 



