THE CARBONIFEROUS SYSTEM. 



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depend. It is impossible to conceive of a greater and more disastrous change than that 

 which an exhaustion of coal would produce. The native-grown timber would furnish no 

 supply of fuel equal to the demand, or would be out of the reach of the mass, from its price. 

 This would speedily be true, likewise, of an imported article; and just in proportion as 

 the former forests of our island were revived to meet the emergency, would the domain 

 of the cereal grasses be invaded, equally necessary to the sustenance of a numerous popu- 

 lation. While the people consisted of a mere handful, scattered over an ample territory, 

 abounding with large tracts of unenclosed timber-ground, they could afford to be ignorant 

 of the ignitable deposits in the bowels of the earth : and it deserves notice, that the dis- 

 covery of these precious stores has not taken place until a very recent date, as if it 

 were an intentional arrangement, to secure from needless waste a material so vital to 

 the maintenance of civilisation in a land replenished with inhabitants. The Greeks and 

 Romans seem to have been quite unacquainted with coal. The earliest mention of it in 

 our own history occurs in a charter granted to the inhabitants of Newcastle, in the year 

 1234, by Henry III. ; but it was not until the reign of Charles I. that it was in common 

 use in the southern part of the kingdom. 



Besides the carboniferous beds, the coal-bearing system comprehends other strata, 

 occurring in the following order of succession: 



Coal Measures Layers of sandstone, shale, ironstone, and clay, alternating with 

 coal, and more rarely with thin layers of limestone : the estimated thickness of the whole 

 mass, 1000 yards. 



Millstone Grit A series of sandstones, composed of sandy and quartoze pebbles, 

 sometimes fine-grained, but generally very coarse. Grit is a provincial name for coarse 

 sandstone, and millstones are obtained from some parts of it. In some localities shale 

 and thin seams of bad coal, with plants of the coal measures, accompany the grit. The 

 estimated thickness is from 500 to 650 feet. 



Mountain Limestone A mass of calcareous rocks, with nodules of chert, several 

 varieties of variegated marbles, layers of red oxide of iron, ores of lead, zinc, and copper, 

 and innumerable remains of crinoidea and marine shells. 



The section exhibits the old red sandstone, o, on the left, the base of the carbon- 

 iferous system ; M the mountain 

 limestone, next occurring ; G the 

 millstone grit ; c the coal measures ; 

 and s the strata of the overlying 

 saliferous system, which cover 

 them in unconformable stratifica- 

 tion. The coal-fields of England 

 usually present the arrangement 

 in the preceding section, the coal 

 lying all above the millstone grit ; 

 but in the north-western parts of 

 Yorkshire the carboniferous sys- 



section of Old Red Sandstone. tern is complicated and varied, the 



coal-measures being interstratified both by the millstone grit and the mountain limestone. 

 The great coal-field of Dudley is also another deviation, for there the old red sandstone is 

 entirely wanting, and the coal rests upon the upper Silurian rocks. 



Mountain Limestone. This formation, a prominent feature of the superficies in 

 England, the north of France, and Belgium, is so called from its mineral character, and 

 frequent development in bold hilly masses, many of which are of considerable magnitude, 

 though it often appears in valleys and flat lands. It is not uniformly calcareous, but has 



