206 FORMATION OF COAL. 



brought down by the rivers which submerged the coal forming 

 vegetation, would have upon it. The plants would be in a dying 

 state 5 they would be composed for the most part of Carbon, 

 Hydrogen, and Oxygen. The Carbon would naturally tend to com- 

 bine with other elements, but there would only be a limited number of 

 atoms of Oxygen and Hydrogen available from the decomposing 

 mass ; it would therefore unite, if possible, with any available 

 constituents which might be brought down by the water. Now 

 suppose the water to contain sulphates (as all river waters do) say 

 sulphate of Lime, the result would be that a certain amount of 

 Carbon would leave the coal-forming mass, reduce the sulphate to 

 sulphide by depriving it of its oxygen, and form Carbonic acid. 

 Then the Carbonic acid would act on the sulphide, forming 

 carbonate of lime (so abundant in the strata associated with coal) 

 and sulphuretted Hydrogen gas would be liberated. 



The soil carried down by the rivers would contain oxides of 

 iron, some more than others ; in fact there is little doubt that vast 

 quantities existed in some of the Carboniferous rivers as shown by 

 the deposits of iron bands. 



The result of Ferric oxide coming into contact with decom- 

 posing vegetation, would be similar to the last reactions ; Carbon 

 would be taken, and carbonic acid formed by the reduction of 

 Ferric oxide into Ferrous oxide. — The Ferrous oxide being 

 soluble would be carried away, or more probably form a carbonate. 



Again the carbonate would be decomposed by sulphuretted 

 Hydrogen with the formation of iron Pyrites and carbonic acid. 

 This last re-action accounts for the occurrence of Pyrites in coal. 



Now what I contend for, is that if vegetation sufficient to form 

 a bed of coal was submerged by water containing certain 

 sulphates and Ferric oxide, even in moderate quantities, a seam 

 of coal with a decreased per centage of Carbon would be formed, 

 containing Pyrites 3 while on the other hand, were these com- 

 pounds absent, the coal would have a larger percentage of Carbon, 

 and little cr no Pyrites, in fact, be more of an Anthracitic nature, 

 while the former would be more Bituminous. 



