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Sect. VI.] 



GEOLOGY. 



171 



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determined by shells found in the ^^*^me stratum, or 



above it. 



Coal Deposits. — The origin of coal presents a most 



curious and difficult problem in geology, and tliough a 



vast amount of information has been accumulated on the 

 subject, yet good observations in distant countries would 

 be of the highest value. A very brief statement of the 

 most prominent difficulties in the theory of its origin will, 

 perhaps, be the best guide for further inquiries. If we 

 look first to the coal itself, the frequency with which, 

 both in Europe and North America, upright vegetables 

 have been found in and on the coal, and the curious rela- 

 tion between the presence of coal and the nature of the 

 clayey bed (abounding with roots) on w^hich it rests, can 

 leave no doubt that in these so frequent instances the 

 vegetation, whence the coal has been derived, grew on 

 the spot where now embedded. The regularity and 



wide extent of the beds of coal, and especially of certain 



subordinate seams in them, the stratification and fineness 



of the deposits alternating with the coal, aiid the rarity 



of channels (such as would have been formed by a 



^ through the associated strata, 

 all 



') 



seem pretty clearly to indicate that the coal wa.^ 

 not formed on the surface, like a mass of peat, but 

 under water. AVhat, then, was the nature of those 



vast 



of shallow water under which the coal 



was accumulated ? The character of the upright fossil 

 plants, according to our present knowledge, absolutely 

 contradicts the idea of their having lived in the sea; 

 yet occ'-'-ionally strata, 



remains, are r.sociated with the carboniferous series. 



containing undoubted manne 



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