36 Hitchcock — Petroleum in North America. 



strata ; third, an impervious cover, like the roof of an anticlinal, to 

 have prevented the escape of the fluids in past ages. The best 

 •■' surface indications " generally guide to shallow wells. The best 

 reservoirs have been found at considerable depths. 



5. There are no less than fourteen different formations in North 

 America (not including the West Indies) from which petroleum has 

 been obtained, generally in productive amounts. 



(a) Pliocene Tertiary of California. This has been known for a 



century. 

 (&) In Colorado and Utah, near lignite beds of Cretaceous age — 



not yet explored, 

 (e) In small amount in the Trias of North Carolina and Con- 

 necticut. 

 {d) Near the top of the Carboniferous rocks in W. Va. Most of 



the producing wells of this state are from this horizon, 

 (e) Shallow wells, near Wheeling, W. Va., and Athens, 0., not 



far from the Pittsburg coal. 

 (/) 425 feet lower, near the Pomeroy coal beds. 

 {g) At the base of the Coal-measures, in Conglomerates or Mill- 

 stone grit. 

 Qi) Small wells in the Archimedes limestone (Lower Carboni- 

 ferous) of Kentucky. 

 («') Chemung and Portage groups — certainly three different 

 levels — in W. Penn. and N. Ohio. 

 A careful study of the distribution of the producing wells upon 

 Oil Creek has satisfied me that they are arranged in four groups, with 

 scarcely any intermediate stragglers. These centres are at Titus- 

 ville. Petroleum, Cherry Eun and vicinity, and about Oil City, 

 Those at Pit Hole constitute another group. The quantity and 

 quality of petroleum obtained is proportioned to the depth attained 

 by the bore-holes. Shallow wells yield a small quantity of superior 

 quality, because heavier. The lightest oils generally come from the 

 greatest depths. In the Cherry Kun districts the wells in the valley 

 average 550 feet in depth ; those at Pit Hole average 620 feet. At 

 both these localities attempts have been made successfully to obtain 

 petroleum by boring into the hill-sides ; and that from levels above 

 the average depths of the valleys. 



{j) Black slate of Ohio, Ky., Tenn., or the representatives of 

 the New York formations, from the Genessee to the Mar- 

 cellus slates. This is near the middle of the Devonian. 

 {k) Corniferous limestone, and the overlying Hamilton group 

 in Canada West, extending to Michigan. This is largely 

 productive. 

 ( I ) Lower Helderberg limestone, at Gaspe, C.E. This is Upper 



Silurian, and awaits development. 

 (m) Niagara limestone, near Chicago. Not yet remunerative. 

 («) In the equivalents of the Lorraine and Utica slates and 

 Trenton limestone of the Lower Silurian, in Kentucky 

 and Tennessee. One Avell in Kentucky in these rocks was 

 estimated to have yielded 50,000 barrels. 



