Lesley.] gg - [April 



black slate. Oil issued also from the Mayo Well, bored about 

 100 yards distant. These are the only wells in all that 

 valley. On Shelby Fork, of Sandy, in Pike County, oil 

 flowed from a salt well. 



It is still doubtful whether the Knobstone formation which 

 immediately underlies the Limestone, is the receptacle of this 

 wide-spread petroleum, or whether we must seek the true 

 horizon in the Black slate formation which underlies the 

 Knobstone in its turn. 



No. X Knobstone formation (consisting of two parts, an 

 upper Sandstone division, and a lower shale division) outcrops 

 in a belt overlooking the Blue Grass country, and measures 

 from 350 to 550 feet in thickness. The upper portion is a 

 thin-bedded, olive-colored, generally fine-grained Sandstone, 

 furnishing good grindstones sometimes, and always building- 

 stone. The lower and larger portion is an olive-colored mud- 

 rock, with pretty generally disseminated nodules of earthy 

 iron ore, from which come most of the Chalybeate Springs 

 of Eastern Kentucky. The upper member seems to corres- 

 pond to No. X, and the upper half of No. VIII, in which lie 

 the three oil sandrocks of Venango County, Pennsylvania 

 (No. IX being entirely unrecognizable). But the difference 

 of thickness throws us out of all our calculations ; for these 

 350 to 550 feet in Kentucky stand as the representatives 

 for at least 2000 feet in Northwest Pennsylvania, and for 

 12,000 feet in the Anthracite coal country. The Venango 

 County First, Second, and Third Sandrocks, which have be- 

 come so celebrated, occupy three horizons in the upper, or as 

 perhaps we should rather call it, the middle part of VIII, 

 lying at maximum depths of 200, 400, and 600 feet respec- 

 tively beneath Oil Creek Valley bed, but 700, 900, and 1100 

 beneath the'bottom of the Conglomerate, which there caps the 

 hilltops on each side of the Valley. The section represented 

 in Plate II will show this relationship of distances farther 

 down the Alleghany River, at Brady's Bend, where the Con- 

 glomerate has reached the level of the Valley bed, and is, 

 therefore, in the same relative position as on our Paint Creek 

 waters. But if, as is pretty certain to be the fact, the Shales 



