PETROLEUM, OK ROCK OIL. 



mferous limestone, also specially named "de- 

 vonian limestone." The wells of the Enniskil- 

 len region, which reach oil at the depth of 120 

 feet and more, would appear to pass below the 

 Hamilton group toward or into the devonian, 

 limestone, in which latter, in such case, the 

 supply, of oil in this region must be considered 

 to be found. The devonian or corniferoua 

 limestones, in fact, at points where they come 

 to the surface, both in Canada and Xe\v York, 

 are found to be very generally impregnated 

 with petroleum, or to contain it in small cavi- 

 ties (as is the case at " Black Rock," on the 

 Xiagara River), and sometimes also, it appears, 

 to be charged with bituminous matter in the 

 solid state. To reach these limestones, or the 

 equivalent slates or shales, south of Lake Erie 

 and in northwestern Pennsylvania, supposing 

 such strata to be there continued, and to be as 

 at many other points charged with petroleum, 

 would of course require wells of far greater 

 depth than any yet attempted in the last- 

 named region, though probably not greater 

 than that of some artesian wells already in ex- 

 istence. It is questionable, however, whether 

 the corniferous limestone is continued beneath 

 the regions mentioned ; and if it be so, or not, 

 whether in that part of its distribution also pe- 

 troleum would still be found. The producing 

 wc41s of the Bothwell (Canada) district are of a 

 depth of 270 feet and upward; and some that 

 were in process of being sunk in 1864 had al- 

 ready reached depths of from 350 to 500 feet. 



In the cliff limestone (devonian) of Ohio, as 

 well as in the corniferous limestone at Black 

 Rock, petroleum occurs in cavities, generally in 

 the cells of fossil corals. The Xiagara limestone 

 (silurian) in Monroe County, Xevr York, con- 

 tains bitumen. Still farther down in the series, 

 almost all the lower silurian rocks are found, 

 where exposed, to contain petroleum. The oil 

 is either infiltrated in small quantity through the 

 rock, or fills small cavities in it, as is seen in 

 parts of Canada ; or it makes its appearance at 

 certain points in springs, as in case of the long 

 known petroleum spring of the town of Guilder- 

 land, near Albany, and that on Great Manitou- 

 lin Island. 



In respect to the origin of petroleum, space 

 vrill here allow of nothing further than the 

 statement that, undoubtedly, like all the varie- 

 ties of coal, the oil has in all cases had its 

 source in the bituminous transformation of col- 

 lections of preexisting organic matters these, in 

 i'the oil, having usually been of vegetable, 

 but sometimes, perhaps, of animal character ; 

 while the direct production of the oil has prob- 

 ably taken place sometimes from the resulting 

 bitumen as appearing in coal-beds, and some- 

 tunes from the allied bitumen infiltrated through 

 or collected in certain rock strata. 



Indications of Petroleum. As the most im- 

 portant of the natural indications or " signs," in 

 any section, of the existence of rock oil beneath 

 the surface should be named the following : 

 gas-springs; oil-springs, the oil either flowing 



pure or mixed with water ; appearance of oil 

 on the surface of the ground, of rocks, or of 

 pools, creeks, etc.; surface collections of litu- 

 men; the so-called "show of oil,' 1 ' 1 from strata 

 through which wells are being sunk, or on the 

 water raised from them; salt-water wells or 

 springs, in some cases perhaps, and especially 

 where oil or gas also appears ; and in a geologi- 

 cal point of view, the fact of lines of disturb- 

 ance in strata not far below the surface, afford- 

 ing increased probability of numerous cavities 

 within the rocks, as well as also, in certain in- 

 stances, the nature of the strata that come next 

 below the surface as, whether they are such 

 as have elsewhere yielded oil, or such as are 

 in immediate proximity to bituminous strata, 

 which appear at some other points to have 

 been the source of oil in large quantity. Among 

 the indications named, the least fallacious of all, 

 it would appear, should be those of free-yield- 

 ing oil-springs and the surface bitumen which 

 they sometimes deposit, as the former was 

 shown in the early history of the western 

 Xew York and northwestern Pennsylvania 

 regions, and as both have appeared in those 

 of Canada and California. 



One among the surest signs of subterranean 

 collections of oil, nevertheless, is afforded by 

 gas-springs or jets, the gas coming up from an 

 opening in the surface, or through the water 

 of a spring, or escaping from fissures in rocks. 

 Springs oif uninflammable gas, however, as car- 

 bonic acid and Mr. Richardson states that 

 such are numerous in the boggy bottom-lands 

 which he examined in TVest Virginia could 

 so seldom be supposed to have their origin in 

 connection with supplies of oil, if even they 

 ever did so, that they would be of no real value 

 as indications. An inflammable gas will doubt- 

 less invariably consist of or contain marsh-gas ; 

 and this, from its intimate relation in compo- 

 sition and in origin with petroleum (as pre- 

 viously shown), is the valuable criterion. Prof. 

 Andrews states that, in our bituminous coal- 

 measures, a gas-spring without doubt indicates 

 petroleum, and he adds, "in the rocks below ; " 

 but Mr. Richardson argues that gas may some- 

 times travel to a considerable distance laterally, 

 along horizontal or irregular fissures. ^Vhen 

 it does so, the gas-spring can show no more 

 than that oil is somewhere in the vicinity. 

 Hence, instead of sinking a well directly at or 

 near the vent, the explorer should endeavor 

 first to ascertain the nature, position and pecu- 

 liarities of the subjacent and surrounding rocks, 

 so as to determine the probable place of the 

 oil fissures or basins. The greater buoyancy 

 of the gas, however, and its elasticity and con- 

 sequent upward pressure, while the oil can or.ly 

 flow at its level, render the former the less 

 likely of the two to wander very far laterally 

 before finding an exit to the surface. But again, 

 Prof. Hunt, speaking of the Enniskillen wells, 

 says : " The inflammable gas which issues from 

 the wells is not necessarily connected w!th the 

 petroleum, inasmuch as it is an almost c<mstaut 



