180 FAKM-YARD MANURE. 



no matter what plants he cultivates, or what order of 

 rotation he may adopt. The removal of his crops is 

 nothing else than robbing the ground of the conditions 

 for future harvests. 



A field is not exhausted for corn, clover, tobacco, or 

 turnips, so long as it yields remunerative crops, with- 

 out needing the replacement of those mineral constitu- 

 ents which have been carried away. It is exhausted 

 from the time that the hand of man is needed to restore 

 the failing conditions of its fertility. In this sense 

 most of our cultivated fields are exhausted. 



The life of men, animals, and plants is most inti- 

 mately connected with the restoration of all those con- 

 ditions which cause the vital process to go on. The 

 soil, by its constituents, takes part in the life of the 

 plant ; its permanent fertility is inconceivable and im- 

 possible, without the replacement of those conditions 

 which have made it productive. 



The mightiest river which sets in motion thousands 

 of mills and machines must fail, if the streams and 

 brooks supplying its waters run dry ; so, too, the 

 streams and brooks w r ill run dry if the many little 

 drops of which they consist fail to return in the form 

 of rain to the place whence their sources spring. 



A field which, by the successive cultivation of 

 different plants, has lost its fertility, may recover the 

 power of yielding a new series of crops of the same 

 plants, by the application of manure. 



What is manure, and whence comes it ? All ma- 

 nure comes from the farmer's fields : it consists of 

 straw, which has served as litter ; of remains of plants, 

 of the liquid and solid excrements of men and animals. 

 The excrements are derived from food. 



In his daily bread, man consumes the ash-constitu- 

 ents of the grain from the flour of which bread is 

 made : in meat he consumes the ash-constituents of 

 flesh. 



The flesh of herbivorous animals, and its ash-con- 

 stituents, are derived from plants ; these ash-constitu- 

 ents are identical with those of the seeds in leguminous 



