204 REVIEW OF PRECEDING THEORIES. 



knowledge of the quantities of all the constituents removed from 

 the soil by different crops. 



The farmer will thus be enabled, like a systematic manufac- 

 turer, to have a book attached to each field, in which he will 

 note the amount of the various ingredients removed from the land 

 in the form of crops, and therefore how much he must restore to 

 bring it to its original state of fertility. He will also be able to 

 express in pounds weight, how much of one or of another ingre- 

 dient of soils he must add to his own land, in order to increase its 

 fertility for certain kinds of plants. 



These investigations are a necessity of the times in which we 

 live ; but in a few years, by the united diligence of chemists of 

 all countries, we may expect to see the realization of these views ; 

 and by the aid of intelligent farmers, we may confidently expect 

 to see established, on an immovable foundation, a rational system 

 of farming for all countries and for all soils. 



98-980 98-13 



