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fore, must find in the soil, or by default, in the 

 manure, those matters which they prefer. 



The day is, doubtless, rapidly approaching 

 when, aided by chemistry, we can determine 

 the exact amount of substance removed from 

 the soil by the crops, and then, as Liebig says^ 

 the farmer, as in a well organized manufactory^ 

 may keep his set of books in which to record, 

 according to the crops, the nature and exact 

 quantity of the principles necessary to sustain 

 the fertility of each of his fields. 



Substances contributive to the growth of 

 plants are of two kinds: First, those of the or- 

 ganic kingdom, as nitrogen, oxygen, hydro- 

 gen and carbon : Second, those which consti- 

 tute the ashes of the crops, and consisting of 

 earthy and alkaline salts. The first are ab- 

 sorbed partially from the atmosphere; the se- 

 cond, on the contrary, are furnished to the plant 

 only by the soil or manures. Indeed, Bous- 

 singault has proved, by direct experiments, that 

 the organic matter of plants is always harvested 

 in greater proportion than that introduced 

 through the medium of manures; hence, as this 

 result always occurs, the excess must necessa- 

 rily be furnished by the atmosphere. On the 

 next page is the average of the results of some 



