178 OF MANURE. 



animal. The urine of a milch-cow contains less 

 nitrogen than that of one which does not yield 

 milk ; and as long as a cow yields a plentiful supply 

 of milk, it cannot be fattened. We must search 

 for the nitrogen of the food assimilated not in the 

 solid, but in the liquid excrements. The influence 

 which the former exercise on the growth of vege- 

 tables does not depend upon the quantity of nitro- 

 gen which they contain. For if this were the 

 case, hay should possess the same influence ; that 

 is, from 20 to 25 Ibs. ought to have the same power 

 as 100 Ibs. of fresh cow-dung. But this is quite 

 opposed to all experience. 



Which then are the substances in the excrements 

 of the cow and horse which exert an influence on 

 vegetation ? 



When horse's-dung is treated with water, a por- 

 tion of it to the amount of 3 or 3^ per cent, is 

 dissolved, and the water is coloured yellow. The 

 solution is found to contain phosphate of magnesia, 

 and salts of soda, besides small quantities of organic 

 matters. The portion of the dung undissolved by 

 the water yields to alcohol a resinous substance pos- 

 sessing all the characters of gall which has under- 

 gone some change ; while the residue possesses the 

 properties of sawdust, from which all soluble matter 

 has been extracted by water, and burns without 

 any smell. 100 parts of the fresh dung of a horse 

 being dried at 100 C. (212 F.) leave from 25 to 30 

 or 31 parts of solid substances, and contained, ac- 



