632 



GEOLOGY 



plants concerned, intermingled in such manner and proportions as 

 to indicate that the vegetation grew where the coal now is. If 

 the vegetation had been drifted together, these various constituents 

 would hardly have been left commingled as they are. But while 

 it is confidently believed that most of the workable coal represents 

 the growth of vegetation in situ, it is not to be understood that coal 

 was never formed from vegetation which drifted together. 



Fig. 445. Showing a stump standing as it grew in Coal Measures, near Glas- 

 gow, Scotland. 



In the formation of a coal-bed, three things are to be accounted 

 for: (1) The conditions under which the necessary bodies of vege- 

 tation accumulated, often essentially free from the admixture of 

 sediment; (2) how the vegetation was kept from decay; and (3) 

 how it was changed into coal. 



The accumulation of organic matter. Large marshes, or 

 marshes in low surroundings, are the only places where vegetable 

 matter is now accumulating in quantity, with little admixture of 

 sediment. Thus in the marshes along some parts of the Atlantic 

 coast (Fig. 446), there are great quantities of organic matter 

 which, locally, is mixed with little sediment. In Dismal Swamp. 



