182 OF MANURE. 



silicate of lime and phosphates of magnesia and lime 

 must be yielded by these excrements, and will in a 

 certain measure compensate for the loss which the 

 corn-land had sustained. The absolute loss in the salts 

 of phosphoric acid, which are not again replaced, is 

 spread over so great an extent of surface, that it 

 scarcely deserves to be taken account of. But the loss 

 of phosphates is again replaced in the pastures by 

 the ashes of the wood used in our houses for fuel. 



We could keep our fields in* a constant state 

 of fertility by replacing every year as much as 

 we remove from them in the form of produce ; 

 but an increase of fertility, and consequent in- 

 crease of crop, can only be obtained when we add 

 more to them than we take away. It will be found, 

 that of two fields placed under conditions otherwise 

 similar, the one will be most fruitful upon which 

 the plants are enabled to appropriate more easily 

 and in greater abundance those contents of the 

 soil which are essential to their growth and de- 

 velopment. 



From the foregoing remarks it will readily be 

 inferred, that for animal excrements, other sub- 

 stances containing their essential constituents may 

 be substituted. In Flanders, the yearly loss of 

 the necessary matters in the soil is completely 

 restored by covering the fields with ashes of 

 wood or bones, which may or may not have been 

 lixiviated, and of which the greatest part consists 

 of phosphates of lime and magnesia. The great 



