200 OF MANURE. 



cent, of solid matter, and in that quantity only 0.7 

 of urea; whilst 100 parts of the urine of man 

 contain more than four times as much. 



The urine of a cow is particularly rich in salts 

 of potash ; but according to Rouelle and Brande, it 

 is almost destitute of salts of soda. The urine of 

 swine contains a large quantity of the phosphate of 

 magnesia and ammonia; and hence it is that 

 concretions of this salt are so frequently found in 

 the urinary bladders of these animals. 



It is evident that if we place the solid or 

 liquid excrements of man, or the liquid excre- 

 ments of animals, on our land, in equal propor- 

 tion to the quantity of nitrogen removed from 

 it in the form of plants, the sum of this element 

 in the soil must increase every year ; for the 

 quantity which we thus supply, another portion 

 is added from the atmosphere. The nitrogen 

 whichjwe export as corn and cattle, and which is 

 thus absorbed by large towns, serves only to benefit 

 other farms, if we do not replace it. A farm 

 which possesses no pastures, and not fields suffi- 

 cient for the cultivation of fodder, requires manure 

 containing nitrogen to be imported from else- 

 where, if it is desired to produce a full crop. In 

 large farms, the annual expenditure of nitrogen is 

 completely replaced by means of the pastures. 



The only absolute loss of nitrogen, therefore, is 

 limited to the quantity which man carries with him 

 to his grave ; but this at the utmost cannot amount 



