28 AMERICAN AGRICULTURE. 



second was a virgin soil, celebrated for its fertility. The 

 third had been unmanured for twelve years, during the last 

 nine of which it had been cropped with beans, barley pota- 

 toes, winter barley and red clover, clover, winter barley, 

 wheat, oats, naked fallow." (Johnston.) 



Bergman found, that one of the most fertile soils in 

 Sweden contained 30 percent, of carbonate of lime. Chap- 

 tal analyzed a very productive soil in France, which gave near 

 25 per cent of the same, and 7 of organic matter. Tillet 

 even found one, and that the most fertile, which yielded 37.5 

 of carbonate of lime. Some of the best in the Mississippi 

 valley, have yielded upon analysis, 20 to 25 per cent, of 

 magnesiaii lime, and of phosphate of lime, 2 to 3 per cent. 

 Many other soils throughout the United States, contain an 

 equal proportion of carbonate of lime. Such are always the 

 last to wear out, and the first to recover by the addition of 

 manures, when suffered to remain uncultivated or in a state 

 of rest. 



