CG4 



PETROLEUM, OE ROCK OIL. 



ores lies in some cases 100 feet thick. The 

 rocks of the valleys here, however, are devo- 

 nian, and are those of the Ohernung and Portage 

 groups. The beds of these rocks lying along 

 and beneath the course of Oil Creek dip at 

 a small angle to southward, but so that they 

 pass 500 to 600 feet below the coal measures. 

 In fact, the outcrop of strata from under the 

 great Pennsylvania coal-basin spreads out tow- 

 ard the west and north somewhat in fan shape ; 

 and the eastern or inner line of the outcrop of 

 the Chemung and Portage sandstones (known 

 in the Ohio reports as the Waverley sandstones) 

 is traced in a general way from Portsmouth, on 

 the Ohio, by Cuyahoga Falls, whence, taking a 

 more easterly course, it passes through the 

 southern part of Crawford County, Pa. Thus, 

 northeastern Ohio and northwestern Pennsyl- 

 vania, north of this line, and a portion of 

 southwestern and southern New York, in some 

 parts as far north as the southern border of 

 Genesee County, have altogether or mainly 

 the Chemung and Portage sandstones as their 

 surface rocks. 



The strata now in question have been de- 

 scribed as " compact, close-grained white and 

 gray flaggy sandstones, alternating with red 

 and olive-colored argillaceous shales." Drillers 

 have for convenience numbered the beds oT 

 sandstones 1, 2, 3, &c., beginning in the bot- 

 tom-land on Oil Creek, below Titusville. Prof. 

 Ridgway estimates the total mass of oil-bearing 

 strata as 1,200 feet in thickness, extending from 

 the overlying conglomerate down to the Gene- 

 see slates. It has already been seen that the 

 outcrop of these rocks to northward extends 

 over all the southern counties of western New 

 York, and to the northwest beyond Trumbull 

 County, Ohio. The Mahoning Valley region, 

 lying to the southward of the limits already 

 named, is in fact within the outcrop of the coal 

 measures; though here the oil is found also 

 in the underlying Chemung and Portage sand- 

 stones. The lowest oil-bearing sand-rock comes 

 to the surface in the town of Waterford, Erie 

 County, Pa. Unlike those of the Ohio River 

 region, these rocks have been but little dis- 

 turbed from their nearly horizontal position ; 

 though, according to Prof. Ridgway, some miles 

 north of Titusville the inclination becomes as 

 great as 10 to the south, while under that town 

 occurs a synclinal trough, farther on near the 

 Stackpole farm, 2J miles down, an anticlinal 

 roll, and from this to the mouth of Oil Creek a 

 series of small undulations and crimps in the 

 strata. 



In the borings along Oil Creek, and generally 

 where the surface strata are similar, the " first 

 .sand-rock," a whitish sandstone, is met with at 

 a depth of from 70 to 200 feet ; and it is stated 

 that the wells penetrating only this bed yield 

 generally a thick oil. From 100 to 200 feet 

 below this, after passing through soap-stone and 

 perhaps slate, lies the " second sand-rock," of 

 similar aspect to the first; and in or beneath 

 . this oil is again obtained, also heavy, though 



less so than the former. From this rock pn- 

 ceed nearly all the wells of the Alleghanj 

 River; while, with few exceptions, the wells 

 of French Creek descend only to the first rock. 

 From 100 to 200 feet again below the second, 

 there is a " third sand-rock ; " and wells pene- 

 trating this more commonly yield a light and 

 purer oil. To this rock descend most of the 

 flowing wells ; and in fact, most of the wells 

 more recently sunk along Oil Creek. Though 

 the wells have thus far been sunk chiefly in the 

 valleys, there appears no reason why oil should 

 not also be reached through the higher land, 

 by boring proportionally deeper. So far as the 

 oil supply of wells is that which slowly collects 

 from porous rocks, or those filled with fine 

 cavities, it should certainly be found under the 

 hills as well as the valleys, and so far as it ex- 

 ists in large fissures or chasms, these too must 

 probably to some extent underlie the hills. To 

 the foregoing statements, and which substan- 

 tially agree with those of a notice in the "Amer- 

 ican Journal of Science " for Jan., 18G5, it should 

 perhaps be added, that to the extent to which 

 fissures of irregular position and height, and 

 penetrating one or several successive layers of 

 rock, serve as the reservoirs of petroleum, it 

 cannot of course be intended to assert that en- 

 tire invariableness of the quality of the oil at 

 different levels, and of the depths ct which 

 it is found, which the statements as made 

 would appear to imply. Further, so far as the 

 wells of the northwestern Pennsylvania re- 

 gion receive then rnpply from such fissures, 

 remarks similar to those already made respect- 

 ing the wells of West Virginia will apply to 

 them. 



In whichever sand-rock the borings terminate, 

 the southern dip of the strata requires that the 

 wells shall go deeper in the same direction. 

 The depth of the early wells of Mecca, Ohio, 

 was from 30 to 200 feet ; while along Oil 

 Creek, from near Shaeffer's to its mouth, wells 

 reaching the third sand-rock are of depths 

 increasing from about 500 feet to 700 feet or 

 more ; and the depth of wells on the Alleghany 

 below Franklin are also quite various, ranging 

 from 360 to Y50 feet. 



As, proceeding northward, the Chemung and 

 Portage groups of sandstones run out, the 

 Hamilton group, next below, comes to or near 

 the surface. The black inflammable shales of 

 the devonian series in western Canada, and 

 which over some parts of it appear highest, are 

 considered as belonging to the base of the 

 former, while the argillaceous shales and lime- 

 stones underlying belong to the Hamilton 

 group. The low broad anticlinal axis running 

 nearly east and west through the peninsula 

 north of Lake Erie, brings these shales and 

 limestones in the township of Enniskillen near- 

 ly to the surface. At the base of the group 

 occur the Marcellus slates or shales, which, 

 as well as those at its summit, contain petro- 

 leum inclosed in very small cavities. Imme- 

 diately below the group in question is the cor- 



