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refuse which accumulated on the farm the refuse 

 of the food consumed by the cultivator, and by 

 the animals which assisted him in tilling the 

 ground, as also the litter and grass which collected 

 on the farm. As these ancient agriculturists culti- 

 vated almost exclusively for their own consump- 

 tion, we may fairly suppose that the refuse of their 

 farms represented nearly all what had been with- 

 drawn from the soil ; this refuse, then, was restored 

 to it, and in this way the fertility of the land 

 was maintained, and may even have increased, 

 crops being raised year after year in rarely 

 diminishing quantities. 



But when arts and manufactures were intro- 

 duced, when fields were deserted for towns, 

 when mankind began to congregate in masses for 

 which the adjoining fields were unable to provide 

 sufficient food, and it had to be supplied from 

 remote districts, when farms thus began to 

 grow their products for exportation and not only 

 for self-consumption from that time the fields 

 commenced to exhibit a gradual decrease in the 

 outturn of the crops an inevitable result ; for 

 thenceforth, year after year, a large quantity of 

 inorganic substances, essential to the successful 

 cultivation of our food-plants, was removed from 

 the soil, and never, or at best but imperfectly, 

 restored in fact, a portion of the soil was 

 exported. 



