106 Asphaltic Coal. 



tage group of the New York geologists, contains throughout 

 from 10 to 25 per cent, of carbonaceous matter, and is the 

 source whence most of the oil is derived, both in Pennsyl- 

 vania and Ohio. These rocks are lower than any in which 

 true coal has ever been found ; and this material, moreover, 

 occurs not in beds like true coal, but in fissures and crevices 

 intersecting the layers of the rock. The mineral examined 

 by Prof. Leeds should therefore be regarded as an asphaltic 

 coal, originally derived from the spontaneous distillation of 

 petroleum, like the Albertite of New Brunswick and the 

 Grahamite of West Virginia. 



The white scales which till the cracks of this coal, as found 

 in Huron and Lorain counties, in Ohio, have probably been 

 derived from deep-seated sources, coming up, perhaps as 

 chloride of barium, through the fissures which contain the 

 asphaltic coal. 



The region where this mineral occurs is occupied exclu- 

 sively by unchanged sedimentary rocks, Devonian and Upper 

 Silurian. These contain, so far as known, no disseminated 

 sulphate of baryta ; but the Water Lime group of the Upper 

 Silurian, which lies some distance below the Huron shale, 

 and comes to the surface a few miles west, on the Islands of 

 Lake Erie, is much shattered, probably in connection with 

 an uplift along the line of the Ohio anticlinal : and the cav- 

 ities and crevices, once existing in this rock, are frequently 

 filled with sulphate of strontia and sulphate of baryta, or 

 with native sulphur. These minerals, occurring thus, should 

 probably be regarded as deposits from thermal waters ; and 

 it is quite possible that the fissures in the Huron shale, con- 

 taining this asphaltic coal, have derived their sulphate of 

 barvta from a similar source. 



