30 ELEMENTS OF 



soil will be a fruitful one for all the three kinds of pro- 

 duce. If the first plant, for example, be wheat, which 

 consumes the greatest part of the silicate of potash in 

 the soil, the plants which succeed it should be such as 

 require little potash, as turnips or potatoes. The wheat 

 lands may be sown again with wheat, advantageously, 

 after the fourth year. The reason of this is, that dur- 

 ing the interval of three years, the soil will, by the ac- 

 tion of the atmosphere, be rendered capable of again 

 yielding silicate of potash in sufficient quantity for wheat. 

 Whether this process can be artificially anticipated, by 

 supplying the exhausted ingredient to the soil, is a fur- 

 ther, and most interesting inquiry. 



In a four-years' course of cropping, the crops gathered 

 amounted, per acre, to — 



1st year, Tiiniips^ 25 tons of bulbs, and 7 tons of 

 tops. 



2d year, Barletj^ 38 bushels, and a ton of straw. 



3d year, Clover and Rye Grass, 1 ton of each in 

 hay. 



4th year, Wheat, 25 bushels, and 2 tons of straw. 



Supposing none of the crops to be eaten upon the land, 

 the quantity of inorganic matter contained in the above 



would be as follows : — 



making a gross weight of 1240 pounds, or about ele- 

 ven hundred weight. 



A siill clearer idea of the importance and quantities 

 of these organic matters, may be obtained by a consider- 

 ation of the fact, that if we were to carry olf the entire 

 of the above produce, and return none of it again in the 

 shape of manure, (supposing also that we could stop the 



