CAPITAL IN FARMING. 9 



contain about the same elements of nutrition, are different in 

 their effects upon the human system, and the same seems to 

 obtain of vegetable life, especially with regard to the stimu- 

 lating qualities of certain manures. And it is upon this 

 ground alone, as I have before hinted, that the efficacy of the 

 manures of commerce may be established as affording that 

 concentration with which is associated stimulating power. 



Again it is found that a stated crop does not follow in rota- 

 tion, with the same result, all crops to which it bears the same 

 chemical relation. 



But to turn from the complexities which the refinements of 

 agriculture open to our view, the most marked effects of the 

 workings of this great principle are to be observed in the 

 crudest attempts at tilling the soil, and it is to nature herself 

 that we look to behold the most striking instance of the law, 

 that when there is no artificial renewal of fertility, change 

 becomes a necessity of long-continued growth. Witness the 

 evergreen forest, which, once levelled by the woodman's axe, 

 turns, or may it not be, returns, to a deciduous growth. 

 2* 



