662 



PETROLEUM, OR ROOK OIL. 



of strata; that of northwestern Pennsylvania, 

 tvhich stands next in order ; and that of Canada 

 West, which has a still lower place; though even 

 the last named is not so low in the entire series 

 as the geological position of certain single springs 

 or limited oil districts. In fact, the three great 

 oil territories of the eastern part of the continent 

 lie, in succession, within the coal measures, and 

 below them as far down as nearly or quite to 

 the lower devonian. Their place in the general 



series of strata is thus seen at a glance [table of 

 stratified rocks, preceding]; but the more spe- 

 cial relations Avhich they severally bear to the 

 strata and groups making up the two series of 

 the carboniferous and devonian, that contain 

 them, will be better understood by aid of the 

 following table, extracted from the more ex- 

 tensive one given in the NEW AMEEICAST CY- 

 CLOPEDIA, and embracing the particular series 

 under consideration : 



PFJMAKY OR PALAEOZOIC ROCKS FROM THE SUMMIT, DOWN THKOTJGH ins DEVONIAN. 



Permian. 



Carboniferous. 



Devonian. 



Magnesian limestone. 

 ( Coal measures. 



\ Millstone grit, or conglomerate. 

 ( Carboniferous limestone. 

 f Grey sandstone. 

 Kcd sandstone. 

 Chemung group. 

 (^ Portage group. 



Found in southeastern Illinois, Iowa, north- 

 eastern Kansas, &c. 



The anthracite and bituminous coal-fields, ex- 

 cept those of Richmond, Va., and N. Carolina. 



The floor of the eastern coal-measures. 



Sub-carboniferous limestone and red shales. 



! Catskill group. 



> [Sandstones and shales.] 



QjHH r 



Hamilton group. 

 Corniferous limestone. 



Schoharie grit. 

 Cauda-galli grit 

 Oriskany sandstone. 



Genesee shale. 

 . Moscow ' 

 Marcellus " 

 [Devonian limestone.] 



[Prof. Eogers'i 

 Series.] 



[ Serai. 



Umbral. 

 j Vespertine. 

 ( Ponent. 



Verjrcnt. 



Cadent. 

 Post-meridian 



Meridian. 



Silurian (upper). Ladlow and Wenlock beds. Nine strata or groups, mostly limestones. Pro-meridian and Scalcnt. 



In "West Virginia and southeastern Ohio, 

 petroleum is found in the carboniferous strata, 

 and, it would appear, to greater or less extent 

 in the coal measures. Upon these, in fact, the 

 oil-producing counties of Ohio are located ; 

 while many parts of the oil region in the former 

 State, show veins of bituminous and of cannel 

 coal. According to Mr. Richardson's state- 

 ments, in Virginia, the coal seams commonly 

 lie above the oil-bearing rocks. The same writer 

 states also that where dry splint coal the bitu- 

 minous constituents of which are partly elim- 

 inated is most abundant below water-level, 

 there, in the shales beneath the coal, oil is most 

 extensively diffused. 



Prof. Andrews, speaking of the oil region 

 now considered, divides its rocks into three 

 classes: those nearly horizontal, those which 

 have a dip of from 15 to 40 feet in a mile, and 

 those which are broken and dislocated by up- 

 heaval. From the Ohio River at Parkersburg, 

 tip the Little Kanawha, to within a few miles 

 of the great oil wells, the strata are nearly hori- 

 zontal, and probably contain few fissures, ex- 

 cept those due to shrinking ; and there appear 

 to be no productive wells in this region. But 

 on the Great Kanawha, and also about Pomeroy 

 and in Washington County, Ohio, as well as in 

 the counties around the latter already named as 

 yielding petroleum, the rocks have more or less 

 dip ; and in these sections they probably also, 

 as a result of the uplifting force, contain many 

 fissures. Prof. Andrews had traced the line 

 of upheaval and dislocation already referred to, 

 from the eastern part of Washington County, 

 Ohio, to beyond the Little Kanawha at Burning 

 Springs, its direction being nearly north and 

 Bouth, and making with the general coiirse of 



the Alleghanies an angle of about 40. IP 

 Ohio, the anticlinal axis is generally well 

 marked. 



The important part which vertical cleavage 

 planes, or fissures in the strata, are likely to play 

 in connection with the oil supply and discover- 

 ies of it, will be understood when it is recollect- 

 ed that, through the variety of their forms, 

 branches, and communications, such openings 

 could receive, and in case of such parts of them 

 as were closed below, so as to act as "pockets," 

 retain the oil, whether it entered them as a 

 liquid at or from above their own level, or 

 whether it ascended as a vapor from strata 

 lower down, and which held the bituminous or 

 organic matters that were its source. But be- 

 sides fissures or rents through strata, there may 

 obviously be cavities of other sorts also, and of 

 greater or less size. Such, in particular cases, 

 could be formed either by the wearing or the 

 solvent action of water, or perhaps in some 

 instances by the greater or less horizontal sepa- 

 ration of disturbed strata; and, as produced 

 through any of these or similar agencies, cavi- 

 ties of the nature of small caverns, such as are 

 known to exist in the rocks in multitudes of 

 cases, can readily be supposed to be among 

 those which are pierced by the successful wells 

 of oil districts. 



Whatever the origin or character of oil-con- 

 taining cavities, it appears that they must often 

 be more or less vertically situated, and that 

 usually they are not of great horizontal extent. 

 For neighboring wells seldom strike oil at the 

 same depth, either in horizontal or inclined 

 strata; while the oil from wells near together 

 may be of very different qualities; and it i.-? 

 only in a certain proportion of cases that even 



