22 



NITROGEN. — CARBON. 



deposites, and gushing forth to fertilize and beautify 

 the surface of the globe, again to be evaporated and 

 again to fall, constitutes no small item in the aggre- 

 gate amount. 



The amount of hydrogen contained in coal, lig- 

 nite, and peat, is by no means inconsiderable. Some 

 varieties of coal, as the Cannel and others, contain 

 as much as 21 per cent, of hydrogen ; this, com- 

 bined with carbon, forms the gas used for lighting 

 cities. 



In many places, especially where coal and rock- 

 salt are found, hydrogen issues in a constant stream 

 from the earth, as at Bristol, Honeoye, &c. ; and 

 many places in the western part of New-York, and a 

 village on Lake Erie, are lighted by this means. The 

 phenomenon of burning springs, of which almost 

 every country, particularly China, furnishes numer- 

 ous examples, is owing to the same cause. 



Nitrogen gas, or azote, is chiefly important as con- 

 stituting 80 per cent, of the atmosphere. It neither 

 supports combustion nor animal life. It abounds in 

 animals and vegetables, being obtained, doubtless, 

 from the atmosphere ; some have supposed that it 

 also exists in rocks which contain animal organic 

 remains. Some species of bituminous coal contain 

 15 per cent, of nitrogen. 



Carbon abounds not only in living animal and ve- 

 getable substances, but also in fossil vegetables and 

 limestone. It forms the largest proportion of every 

 species of coal, bituminous coal containing from 50 

 to 75 per cent., and anthracite often as much as 90 

 per cent, of carbon. Diamond is pure carbon. It 

 also enters into the composition of many of the me- 

 tallic minerals, as iron, lead, zinc, and copper. De 

 la Beche remarks, that if carbonic acid be compo- 

 sed of equal volumes of the vapour of carbon and 

 oxygen, the volume of the vapour of carbon con- 

 densed in the calcareous strata must be very great. 

 Taking the specific gravity of pure limestone at 2.7 



