COAL 



for the accumulation of considerable thicknesses of vegetable mat- 

 ter, some of it nearly free from sediment, and at the same time the 

 conditions which keep it from complete decay. 



Conversion into coal. While the vegetable matter is not de- 

 -troyed, it is not preserved intact. The approximate composition 

 of wood and peat are shown by the following analyses (ash omitted). 



Carbon Hydrogen Oxygen Nitrogen 



Wood 49.66 6.21 43-03 i.io 



Peat 59-5 5-5 33 -o 2.00 



The relative atomic proportions of carbon, hydrogen, and oxy- 

 uen in cellulose are expressed by the formula (CHi<X)*)x< I n the 

 air, the carbon and the hydrogeji of the wood unite with oxygen 

 of the air or of the wood itself, forming carbon dioxide and water, 

 the principal products of the decay of vegetation. But under water 

 e atmospheric oxygen is largely excluded, and the elements of 

 e wood are thought to unite with one another to a larger extent, 

 vhile the oxygen of the air plays but a subordinate part. One of 

 e common products of decay under such circumstances is CHi 

 arsh-gas), which escapes into the air. The formation of this gas 

 xhu usts the hydrogen of the organic matter four times as rapidly 

 as the carbon. If the carbon and oxygen of the wood are given off 

 combined as CO2, the oxygen is consumed twice as fast as the car- 

 bon. If the hydrogen and oxygen of the wood are liberated as 

 ater, the result is to increase the proportion of carbon remaining. 

 While the exact quantitative relations of the reactions which 

 ke place are not known, and are probably not constant, the fol- 

 wing table ! suggests certain changes which might take place, and 

 i- products which would remain at certain stages: 



(,! 1 10 6 (cellulose) 



( ) 2 i (peat) 



(brown coal)- 



(bituminous coal) 



1 Prepared by Rollin T. Chamberlin. 



2oH,0 

 8 CO 2 

 2 CH 4 

 6H 2 O 

 4 C0 2 



CH 4 

 3H-.0 



CO 2 

 2 CH 4 



2 H..O 



: co 2 



(peat). 



(brown coi 



= CM^OS (bitumincnij coal). 



= C48HigO (anthracite coal). 



