60 CHYMISTRY APPLIED TO AGRICULTURE, 



employed are the results of decomposed vegetable sub- 

 stances, and some animal matters. 



The salts, which likewise serve for manures, are im- 

 bibed by the pores of plants, and serve to stimulate vege- 

 tation. 



By comprehending all these substances under the gene- 

 ric name of manures, too extensive a signification is given 

 to the word. I divide manures into two classes ; and in 

 order to deviate as little as possible from the customary 

 mode of expression, I shall call those nutritive manures, 

 which supply plants with nourishment, and all those 

 which excite the organs of digestion stimulating manures. 

 These last are, strictly speaking, the seasoning; the 

 spices, rather than the food. 



ARTICLE I. 



Of Nutritive Manures. 



The nutritive manures are those which contain juices 

 or other substances, which, being dissolved in water, or 

 otherwise divided to the most minute degree, are capable 

 of being drawn into the organs of plants. All the vege- 

 table and animal juices are of this description. 



These substances are rarely employed in their natural 

 state for the aliment of plants. It is generally considered 

 preferable to allow them to putrify or ferment ; the rea- 

 son of this is simple. Besides the decomposition resulting 

 from this operation, whicfi renders the substances more 

 soluble in water, the gases produced by it, such as the 

 carbonic acid, the carburetted hydrogen, azote, and am- 

 monia, furnish food for plants, or stimulants for their 

 organs of digestion. It is not, however, well to prolong 

 this decomposition too far ; for if it be completed, there 

 will remain only some fixed salts, mixed with those earths 

 and juices which have resisted its action. Besides, the 

 effect of manures, which have been entirely decomposed, 

 is almost momentary, lasting but for a single season ; 

 whilst those which are employed before arriving at this 

 state, continue to exert an influence for several years. In 

 this last case, the decomposition, retarded by the separa- 

 tion of the manures into small portions, continues to go 



