MINEIL\L MATTERS RESTORED BY MAN. 187 



The incombustible elements of cultivated plants do not 

 of themselves return to the soil, as the combustible ele- 

 ments return to the atmosphere from which they spring. 

 The hand of man alone restores to the ground the condi- 

 tions of the life of plants : in farm-yard manure wherein 

 they are contained, the farmer, following a natural law, 

 restores the lost power of production. 



