84 MANURES. 



Organic manures comprise all animal and vige 

 table matters wliicli are used to fertilize :lie soil, such 

 as dung, swamp-muck, etc. 



Mineral manures are those which are of a purely 

 mineral character, such as lime, ashes, etc. 



Atmospheric manures consist of those organic 

 manures which exist in the form of gases in the at- 

 mosphere, and which are absorbed by rains and car- 

 ried to the soil. These are of the greatest impor- 

 tance. The ammonia and carbonic acid in the air 

 are atmospheric manures. 



CHAPTER II. 



animal excrement 



The first organic manure which we shall examine, 

 is animal excrement. 



This is composed of those matters which have 

 "been eaten by the animal as food, and have been 

 thrown off as solid or liquid manure. In order that 

 we may know of what they consist, we must refer to 

 the composition of food and examine the process of 

 digestion. 



The food of animals, we have seen to consist of 

 both atmospheric and earthy matters. The atmos- 

 pheric part may be divided into two classes, i. e., 

 that portion which contains nitrogen — such as glu- 



