AGRICULTURE WITH CHEMISTRY. 39 



farther supply of oxygen with their peculiar bases, the 

 phosphoric and other acids are formed. These acids, 

 as they are generated, combine with the calcareous mat- 

 ter of the coal, now by full decomposition rendered ca- 

 pable of being afted upon, and form salts that are nearly 

 insoluble. 



Oxygenated coal, when it is not found in that state, 

 may be procured by exposing the smaller refuse coal of 

 a colliery alternately to air and moisture. This process 

 may be much accelerated by previously grinding the 

 coal to a fine powder. 



CHARCOAL, OR THE COKE OF COAL, 



Is a substance in an intermediate state between that of 

 vegetables, wood, or fossile coal ; and that of their re- 

 duction to ashes. The making of charcoal is best 

 performed in close vessels, or by a smothered method of 

 combustion. 



By 



