ITS ESSENTIAL ELEMENTS. 179 



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 hay. 



Thus in 1102 lbs. of horse-dung, we present to a 

 field the inorganic substances contained in 6612 lbs. 

 of hay, or 9146 lbs. of oats (oats containing 3*1 per 

 cent, ashes according to De Saussure). This is suf- 

 ficient to supply IJ crop of wheat with potash and 

 phosphates. 



The excrements of cows,* black cattle, and sheep, 

 contain phosphate of lime, common salt, and silicate 

 of lime, the weight of which varies from 9 to 28 per 

 cent., according to the fodder which the animal re- 

 ceives ; the fresh excrements of the cow contain from 

 86 to 90 per cent, of water. 



Human faeces have been subjected to an exact 

 analysis by Berzelius. When fresh they contain, be- 

 sides I of their weight of water, nitrogen in very 

 variable quantity, namely, in the minimum 1|, in the 

 maximum 5 per cent. In all cases, however, they 

 were richer in this element than the excrements of 

 other animals. Berzelius obtained by the incinera- 

 tion of 100 parts of dried excrements, 15 parts of 

 ashes, which were principally composed of the phos- 

 phates of lime and magnesia. 



The following quantitative organic analysis has 

 recently been executed for the purpose of ascertain- 



* It has been formerly stated (page 120), that all the potash contained 

 in the food of a cow is again discharged in its excrements. The same 

 also takes place with the other inorganic constituents of food, either 

 when they are not adapted for assimilation, or when present in supera- 

 bundant quantities. The value of manure may thus be artificially in- 

 creased. We lately saw, for example, some cow-dung, sent by a farm- 

 er, who wished to ascertain the cause of its increased value. He had 

 formerly employed this manure for his land, but with so little advan- 

 tage that he found it more profitable to dry it, and use it as fuel. On 

 inquiry, it was found, that his cows had been fed upon oil-cakes. This 

 species of food is particularly rich in phosphates. More of these salts 

 being present than were requisite for the purpose of assimilation, they 

 were removed from the system in the form of excrementitious matter, 

 and in a condition adapted for the uses of plants. The fact that partic- 

 ular kinds of food enrich or impoverish the manure obtained from the 

 cattle fed upon them, has repeatedly been observed. — £d. 



