114. &. F. Peckham—The Origin of Bitumens. 
brought down the Coal-measures nearer the Devonian shales 
and Silurian limestones, first saturated with petroleum, an 
then, through ages of repose, gradually cut down by erosion 
into the cafions of Johnson county, Kentucky, and exhibiting 
heavy beds of black bituminous shales are particularly notice: 
able. These formations lie in folds, the petroleum, which be- 
longs to the third class, occurring under the arches of anticlinals 
ean than in the troughs of synclinals. 
acts to be obtained regarding the occurrence of bitumeD — ' 
‘in Asia are very few. It appears to be generally concluded 
that the formation from which the petroleum in the neighbor 
* A Manual of Coal and its Topography, p. 49. 
Granting that the petroleum of the Niagara limestone at a 
