14 DEPARTMENT OF AGRICULTURE GEORGIA. [300 



such as limestone, marble, etc. Its most prominent forms 

 are mineral, coal, charcoal, graphite, soot, lamp-black, etc. 



The diamond is pure, crystalized carbon. Coal consists 

 of the remains of vegetable matter which once existed on the 

 earth. It was formed by the agency of heat in the absence 

 of oxygen of the air, in very much the same manner as 

 charcoal is now produced, but on a larger scale. It has 

 been found that to produce a foot of mineral coal requires 

 from five to eight feet of dense vegetable matter, such as 

 peat. 



Bone-black or animal charcoal is made by burning bones 

 in closed vessels, by which the organic matter of the bones 

 is converted into charcoal. It is ground to a powder, and 

 used in sugar refineries to remove the impurities from the 

 sugar. 



The crude sugar is dissolved, and the solution filtered 

 through the bone-black, which absorbs the dark, impure 

 matter, leaving a clear liquid, from which the pure white 

 sugar is crystalized. After the bone-black has been used 

 and " revived" several times it is treated with sulphuric 

 acid, and the phosphate of lime, which it contains, is con- 

 verted into super-phosphate of lime, and sold as a fertilizer. 



The carbon contained in the cellular structure of plants 

 is absorbed, both by the roots and leaves, in the form of 

 carbonic acid, the oxygen of the compound being exhaled, 

 and the carbon retained by the plant, and appropriated to 

 its own use in building up its structure. 



This structure is best seen in vegetable charcoal, in 

 which the contents of the cells are burned out and only 

 the framework left. 



" Peat is an accumulation of half decomposed vegetable 

 matter found in swampy places. It is produced mainly 

 by a kind of moss, which gradually dies below as it grows 

 above, and thus forms beds of great thickness ; sometimes, 

 however, plants may grow in the form of turf and decay, 

 thus collecting a vast amount of vegetable debris. This 



