CARBON. 17 



the crystals a residue of ash has remained in the form of a 

 cellular net work. 



Graphite is a well known and useful mineral which al- 

 though seemingly very soft, its particles are so hard as to 

 wear out with great rapidity the steel saws w r ith which it 

 is cut. It is produced artificially in charcoal iron furnaces 

 and in the manufacture of coal gas. 



Charcoal is the form in which carbon appears of the 

 most interest io the farmer, because it is derived from veg- 

 etable matter, chiefly from wood, although it is made from 

 peat, by charring it in heaps covered with earth and thus 

 protected from the oxygen of the atmosphere which would 

 change it into carbonic acid. It is brittle, black, taste- 

 less, and inodorous; and perfectly insoluble. Its perfect 

 insolubility disproves the common impression that it can 

 be used as a fertilizer or as plant food in any manner ; but 

 its peculiar behavior with other substances does give it an 

 indirect agency in this way. It resists the action of the 

 air a< well as of moisture, hence it is almost indestructi- 

 ble. 



The charred remains of timber, and of wheat and rye 

 grains which have been found in the ruins of Herculaneum 

 where they have remained unchanged for eighteen hun- 

 dred years proves its unchangeable character. This prop- 

 erty of charcoal has been made use of in preparing posts 

 to be set in the ground by charring them, by which they 

 are made exceedingly durable. When pure and dry, 

 charcoal burns without any flame; the light blue flame 

 sometimes seen when it is burned, is caused by the com- 

 bustion cf w T ater of which it absorbs, in the form of vapor 

 from the atmosphere, from ten to twenty per cent, in a sin- 

 gle week's exposure. 



Having the porous structure of the wood or peat from 

 which it may be prepared, charcoal possesses a remarka- 

 ble power of absorbing gases and of condensing them in its 

 pores; hence it becomes at times of much value in the soil, 

 and it is to this fact that its notable effect upon vegetation 

 is due. This effect is the dark green color of the herbage 



