PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 427 



Alleghany, and tlie upper is known as the Uncertain coal, because 

 it is sometimes found, and sometimes is not. There is a regular 

 dip of eight or ten feet to the mile, and the Uncertain coal will 

 appear on the tops of hills which come within the range, while 

 it may be wanting on intermediate but lower hills. The whole 

 country from the western edge of the Alleghany mountains to the 

 Rocky mountains, seems once to have been a level plain. The 

 rocks, which ha\e never been disturbed, have all a general dip 

 in a different direction. There is no appearance of volcanic 

 action. It is a country of valleys rather than of hills ; for it 

 seems as if the valleys had been formed by washing the surface 

 away, leaving the hills. Upon a branch of the Tuscarawas river, in 

 Ohio, is a bed of cannel coal, in a basin of clay ; and in Coshocton, 

 thirty or thirty-five miles distant, there is a similar basin. 

 Above the cannel coal is a bed of blue limestone, containing 

 certain fossils by which it may be identified. They are all per- 

 fect and beautiful sea shells, entirely diflerent from any now 

 found in any of our waters. Just beneath that limestone is a 

 little layer of four to six inches of bituminous coal. The dif- 

 ference between bituminous and cannel coal is merely in the 

 amount of bitumen. Cannel coal makes good kerosene ; but 

 bituminous shale will make good paraphine. 



To take up the relations of the inflammable oils: There are 

 oil wells from which a natural oil flows at the rate of 500 

 barrels per day ; and it is sometimes supposed that that must be 

 the drainage from coal. The oil is found from 300 to 1,200 feet 

 beneath the coal. I suppose it to be a chemical formation, con- 

 stantly going on in the bowels of the earth. Bitumen contains a 

 percentage of hydrogen, and a certain percentage of carbon. A 

 very slight change in the relative amount of hydrogen and carbon 

 will give you all the products from diamond, on the one hand, 

 which is pure carbon, to the gas which we burn, which is a 

 hydro-carbon. 



Mr. Nash. — Have you never seen the conglomerate rock above 

 the anthracite coal ? 



Dr. Stevens. — There are two conglomerate strata which may 

 be confounded with each other ; but the lower contains sea 

 shells and never bits of wood, and the upper bits of wood and 

 never sea shells. There is still another, above these, containing 

 nuts resembling butternuts, but dividing into three instead of 

 , two parts. But even the three low^er conglomerate may be found 



