SCIENCE OF AGRICULTURE. 117 



excess or a larger quantity of the acid or of that 

 which possesses acid properties, than exists in neu- 

 tral salts where the acids and the lime or other sub- 

 stances with which they are combined exactly bal- 

 ance or neutralize each other.) Super geates are 

 always more soluble than neutral salts. Soluble 

 geine includes the watery solution; the solid extract 

 caused by the action of the air on the solution, and 

 the combinations of this with alkalies, earths and 

 oxyds. Insoluble includes all the other forms of 

 this substance. 



Geine forms the basis of the nourishing part of all 

 vegetable manures. The relation of soils to heat 

 and moisture depends chiefly on geine. Of all the 

 problems to be solved by agricultural chemistry, 

 none is of so great practical importance, as the de- 

 termination of soluble and insoluble geine in soils. 

 It lies at the foundation of all successful cultivation. 

 Among the few facts best established in chemical 

 agriculture are these; that a soil whose earthy part 

 is composed wholly or chiefly of one earth, or any 

 soil with excess of salts, is always barren ; and that 

 plants will grow in all soils destitute of geine, up to 

 the period of fructification, failing of geine the fruit 

 fails, the plants die. Earth, salts, and geine consti- 

 tute then, all that is essential; and soils will be 

 fertile in proportion of the last is mixed with the 

 first. The salts can be varied but very little in their 

 proportion without injury. The earths admit of a 

 wide variety in their nature and proportions. The 

 earths in our New England soils are chiefly the de- 

 tritus of our primitive rocks, granite, gneiss, mica 

 slate, sienite, and argillite. These earths are in 

 fact all salts, formed by silica, which acts as an acid 

 combined with alkalies, lime, magnesia, alumina, 

 and metallic oxydes as bases. 



In the analysis of soils for agricultural purposes it 

 is not necessary to be more particular than to con- 

 sider all these as one and the same thing, and call it 

 granitic sand or silicates. All our soils, except per- 



