88 THE MOUNTAIN. 



FORMATION 12. 



On the red shales of No. 11 repose the coarse sandstones 

 and quartzose conglomerates, called generally, "the con- 

 glomerate," as it is considered the floor of the coal measures 

 proper. In the anthracite region it attains the thickness of 

 1400 feet, but in the bituminous region or Alleghany Moun- 

 tain, it is generally not more than from 100 to 250 feet 

 thick ; whilst occasionally, a few coarse-grained, massive 

 strata, are all that stand as its representative. There are 

 occasionally thin layers of dark carbonaceous slate and 

 shale in this formation, the representatives of imperfect coal- 

 seams, the formation being the inauguration of that splen- 

 did group of which it forms the base. 



FORMATION 13 



Is the true carboniferous division of the great sedimentary 

 pile. Upon the conglomerate rests the series of sandstones 

 of all colors, generally gray and white, slates of all colors, 

 and shales of all colors, limestones, and coal-seams, called 

 the coal series or " carboniferous group." In the anthra- 

 cite region, as estimated on the vertical section, it is near 

 6000 feet thick. In the bituminous coal measures, the whole 

 group gives a thickness of some 3000 or 3500 feet of sand- 

 stones, shales and slates, limestones, iron ores, with beds of 

 coal through the whole group. In the whole series there 

 are about twenty coal-seams, many of which are workable ; 

 together with a number of other insignificant layers, the 

 aggregate of coal being about 55 feet in all. 



The true significance of this division of the series of 

 rocks, the carboniferous group, in the great chapter of uses 

 of the world and its connection with the progress and well- 

 being of humanity, it is impossible to estimate. 



The patient toil of centuries has here accumulated 

 reservoirs of power that seem exhaustless, and the genius 

 of the hour having subdued the fire-king, having chained, 

 tamed, and harnessed the most terrible of the brute forces 



