58 



FORMATION OF COAL. 



aYSSr. wide > and u P wards of 400 yards long is interposed in the 

 Waii^se4i. measureS? S radua % cutting out bed after bed of the coal. 



" This mass of sandstone was very fine-grained, rather soft 



slightly argillaceous, not 



at all differing from 



the usual 



argillaceous sandstones of the neighbourhood, which pass 

 under the name of " rock " or "-rock-binds." It was not 

 only interstratified with the coal en masse, but at or near 

 the junction of the two, they each split up into many beds 

 that interlaced with the utmost regularity. Beds of sand- 

 stone 2 or 3 feet thick, extended many yards into the coal 

 gradually thinning out and splitting up, so that hand speci- 

 mens could be procured of alternations of bright coai and 

 pale sandstone, each little bed not being more than one 

 tenth of an inch in thickness. Similarly, did small beds and 

 thin laminae of coal stretch into the mass of the sandstone ; a 

 few separate masses also, a foot or so in thickness, sometimes 

 occuring suddenly, not as detached fragrants, but as little 

 independent beds in the sandstone. (See " Records of 



Mines 



Jukes.) 



of the occurrence of C< 

 which it was form 



Though coal occurs of different geological ages in various 

 parts of the world,— in Europe, North America, and most 

 other countries, — by far the greater proportion of valuable 

 workable coal occurs in the carboniferous (Coal Measure) 

 series. In other formations, as in the Oolites of Yorkshire 

 and Scotland, it is exceptional, and of little value. In 

 Wales and the South of England the coal bearing strata lie 

 above the Carboniferous or 

 North of England and in Scotland, beds equivalent to the 

 Carboniferous limestone of the south, become interstratified 

 with strata of sandstone, shale, and coal. 



It is easy to trace every possible gradation from common 

 shale into true coal, by the gradual admixture of carbonaceous 



matter with ordinary muddy sediment j for coal is a truly 



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