Geology of the Monongahela Valley. 61 



7. Bituminous coal — the main deposit — sometimes twelve feet in 

 thickness. This coal is generally of the finest quality, and is found 

 in exhaustless beds, near the Monongahela river, from this place to 

 Pittsburgh. The specific gravity of this coal is 1.22; it contains a 

 little over fifty per cent of charcoal. Twenty four grains, when 

 heated in a crucible, decompose one hundred of nitrate of potash, 

 and it leaves twenty two grains out of forty, in the state of coak. — 

 10 feet. 



8. Slate, bituminous shale, &c. containing in great numbers, small 

 shells of the family of Pecten. — 6 feet. 



9. Limestone rock — breaking easily into fragments, and containing 

 fossil shells of the genera Gryphea, Spirifer, Producta and Terebra- 

 tula, similar to those found near Zanesville, and figured and descri- 

 bed within the section of " Putnam hill" strata. — 10 feet. 



10. Sandstone — upper part coarse and compact — lower portion 

 in thin beds. — 140 feet. 



11. Rich argillaceous soil, crowning the tops of the hills, and 

 bearing a heavy growth of forest trees. — 20 feet. 



The thickness of the whole series of strata, is three hundred and 

 ninety three feet, which is nearly the average height of the hills in 

 this part of the valley ; they continue of this elevation for the distance 

 of many miles, to the vicinity of Brownsville. 



As we ascend the Valley river, the deposits of sandstone rock be- 

 come of much greater thickness, and the deposits of coal more thin, 

 and of an inferior quality. At the head of this river we ascend the 

 Cheat mountains, and passing over the Greenbrier range, descend 

 into the valley of the Greenbrier river. The summits of these 

 ridges, especially the peaks of the Cheat, are the most elevated lands 

 of any west of the Alleghany range, as has been already observed 

 when we were speaking of the numerous rivers that rise near this 

 spot, and take many different directions, as may be seen by looking 

 on the map of the coal region. The stratification of these moun- 

 tains, is in the following order. 



1. The summit stratum is a coarse conglomerate sandstone, com- 

 posed of water worn silicious pebbles, of various colors, generally 

 white, loosely cemented by an argillaceous, sandy material, of slight 

 cohesive power, easily decomposing. Some of the lower beds are 

 more compact, having a silicious cement, and of a quality suitable 

 for millstones, to which use this species of rock has been largely 

 applied and are known over the valley as the " Laurel hill stone." 



