78 AMERICAN MANURES. 



they would lack one of the most essential ele- 

 ments of nutrition, viz., the power of renewing 

 the blood, the nervous tissues and muscular fibre; 

 or, if the plant could grow and the seed ripen 

 without the aid of phosphoric acid, there would 

 be no substance furnished to build up the bones ; 

 or, if it lacked the three elements of nitrogen, 

 lime and phosphoric acid, it would afford scarce- 

 ly anything to the animal body, except carbon, 

 for furnishing animal heat. The wheat and 

 seeds found in the catacombs of Egypt, where 

 they have lain two or three thousand years, 

 have almost an identical composition with those 

 grown at the present time. The wheat grown 

 in this country has very nearly the same com- 

 position as that grown in other parts of the 

 world. Hence, as there can be but very little 

 variation in the composition of each species of 

 plants used for food, while the physical laws of 

 nature remain as they now are, there can, con- 

 sequently, be no variation in the kind and quan- 

 tity of the elements required by plants to enable 

 them to come to maturity. 



When a knowledge of the nature of these 

 elements is acquired, and the quantity necessary 

 for a given crop ascertained, the accumulation 

 of these materials is just as simple as that of 

 furnishing the raw material for any manufacture. 

 Accurate knowledge of those substances in soils 



