



\m 



MINERALOGY 



[Sect VIII. 



ground 



a slight covering of water, on which the plants, now con- 



verted into coal, have grown. Should these marked de- 

 posits be found, they often form valuable aids in tracing 

 coal-beds, where the outcrop of the latter may not be very 

 apparent, and they are especially serviceable, as in many 

 of the hilly coal-measure districts of the British Islands 

 where these beds throw out springs of water. Whole 

 lines of such springs coinciding with the bottom of coal- 



beds can be traced in 



South 



Wales and Monmouthshire, and often on a hill side 

 faults traversing the general mass can be as well seen, 



where these lines are interrupted, as if a diagram section 

 were before us. 



In some of the beds immediately subjacent to the coal 

 peculiar fossil plants are found. In the pala^^ozoic coal 

 of the British Islands a fossil plant, named Stigmaria 

 ficoid.es, is very characteristic. Peculiar fossil plants, not 

 the one mentioned, are discovered, it is thought, well 

 marking the beds on which the coal-beds rest in the 

 Burdwan coal district in India, and other instances of a 

 similar kind are recorded. It will be obvious that, although 



the conditions for the production of marked accumulations 

 may have preceded the growth of most of the coal-vege- 

 tables themselves, the latter may not have sometimes 



so that no coal rests upon such beds, a fact 

 observed, and according to conditions more in one part 



roM^n, 



of a coal district than in another. Still these beds, when 

 any such occur, are useful to trace, since while we find 

 in one locality no vegetable accumulation to have taken 

 place upon them, or if effected the vegetable matter to 



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