AGRICULTURE WITH CHEMISTRY. 



47. 



Lime is cajiablc of being dissolved in water, in six 

 hundred times its own weight. Chalk, ;. e. lime com- 

 bmcd to a certain degree with lixable air, is insoluble ; 

 but chalk is capable of solution by a greater proportion 

 of fixable air, either in consequence of its disengagement 

 from vegetable matters decaying in the soil, or from the 

 changes which the carbonaceous matter therein con- 

 tained may undergo. When chalk in this manner is ren- 

 dered soluble, the solution will sink through the surface 

 mould to a more compa6l stratum, through which it can- 

 not pass: in this situation it will lose the superabundant 

 2)roportion of fixable air by which it previously had be- 

 come soluble, and Avill again return to the state of chalk, 

 ft)rming a stratum infinitely more pure and unadulterated 

 than could possibly have been formed, had the process 

 been merely mechanical : in which case, contrary to the 

 fact, all the argillaceous, magnesian, siliceous, and ferru- 

 ginous matters, of equal degree of attenuation or size of 

 parts, woidd have sunk with the lime. * 



The 



* Chalk and clay arc nearly of the same specific gravity, and sand of greater 

 ipccific gravity than lime. 



