GGG 



PETROLEUM, OK EOCK OIL. 



product of the decomposition of organic mat- 

 ters, and is copiously evolved from rocks 

 which are destitute of bitumen. It is similar 

 to the gas of marshes and to the fire-damp 

 of coal mines." Accepting this view, even 

 an inflammable gas would not show beyond 

 question the existence of petroleum ; and es- 

 pecially in marshy places such a gas may arise 

 only from the bottom of the pools in which it 

 appears. Still further, a well may penetrate a 

 fissure and release from it a large volume of 

 gas, when the oil is contained in a lower one 

 to one side, and is not reached by the same 

 well. But while it is thus always necessary to 

 examine into the character and source of gas- 

 springs, in order to determine their value as a 

 sign of oil, it is well known that in some of the 

 great oil regions of both hemispheres where in- 

 flammable gas-springs are most abundant, there 

 petroleum is likewise so. To the examples of 

 the Alleghany region, and those of "West Vir- 

 ginia and Canada, in this country, it seems that 

 we should add that of western New York. As 

 to the last-named, however, since the surface 

 oil was there long since mainly exhausted, 

 while some of the gas-vents have been kept 

 supplied to a recent date or to the present, the 

 inference would seem warranted that there are 

 supplies of oil in strata deeper than those yet 

 penetrated in or near that region perhaps en- 

 tirely beneath the Chemung and Portage sand- 

 stones. Finally, to quote again from Prof. 

 Andrews : " The great majority of these gas- 

 springs are unknown, since they are seldom dis- 

 covered, except when they appear in streams ; 

 and," he continues, "probably the same may 

 be true of oil-springs, since the soil would ab- 

 sorb the oil, and in only a few cases would it 

 be detected." 



Little further need be said in regard to oil- 

 springs^ with or without water, and the sur- 

 face litumen which shows the former or present 

 place of such springs. These are, indeed, un- 

 questionable signs of the past or present exist- 

 ence, as the case may be, of accumulations of 

 oil somewhere beneath the surface, and usiially 

 not very far removed from the place of outflow. 

 The important questions in these cases are, the 

 direction, and the probable depth, from which 

 the supply may come. A little oil on the sur- 

 face of a spring may prove a deceptive sign ; 

 for the water feeding the spring may have 

 borne the oil to a great distance from its hid- 

 den reservoir; or again, such oil may be the 

 last drainage of long standing oil-cavities. But 

 continued gas-jets, on the other hand, if con- 

 nected with oil supplies, quite certainly indicate 

 that the quantity of oil is large at the time, 

 though it has been suggested that they may 

 show only a greater depth of the oil. 



Surface oil, exuding upon rocks, or in the 

 Foil, or on pools or streams, is a sign quite gen- 

 erally regarded as trustworthy, and one that is 

 much sought. It was one of the marked signs 

 in all the great oil regions of this continent 

 that have, so far, been developed ; as in the 



Oil Creek and surrounding districts, in Etuiw- 

 killen, on Hughes River, and elsewhere; and 

 it is said to be now abundantly met with, at 

 least at some seasons, on the waters of parts 

 of the Great Kanawha and Elk Rivers, and of 

 some of their tributaries. As to the exact 

 promise, however, of particular spots or loca- 

 tions, this sign may prove wholly fallacious. 

 Thus, the oil on pools or streams, where it may 

 appear either as an oily scum or as a thin film 

 of oil, and often reflecting the prismatic colors, 

 may be the slow washings from alluvium or 

 cavities in which little of it finally remains. 

 The Rev. Mr. Eaton states that some of the 

 most unsuccessful operations in the whole 

 Oil Creek valley have been in the midst 

 of the ancient pits there found, though un- 

 doubtedly these were at some past time dug 

 with profit for the oil that then filled the very 

 surface earth where they were made. Again, 

 petroleum on the surface or in crevices of rocks 

 may, as previously seen, indicate no more than 

 its presence in small cavities within the rock, 

 or even simply that the rock is itself bituminous. 

 An instance of the former kind is the oozing 

 of petroleum from broken surfaces of the dark- 

 colored limestone at Black Rock ; and exam- 

 ples of the latter kind, it appears, are found in 

 its appearance upon sandstones quarried in 

 Erie County, Pa,, and limestones in Monroe 

 County, N. Y., and in Canada. 



The "show of oil" sometimes obtained in 

 the course of wells going down, is not so much 

 as formerly considered decisive as to a success- 

 ful result. A good show of oil near the sur- 

 face or still lower may disappoint, since the oil 

 so found may be from small fissures or veins 

 that are not with any certainty in the course 

 to, or connected with, the large collections of 

 it; and on the other hand, productive wells 

 have been obtained with no intermediate 

 "show." The value of this show as a sign, 

 however, according to Prof. Evans, increases 

 with the depth at which it occurs. 



Salt icater, in springs or wells, taken alone, 

 has little value as a sign of petroleum ; since the 

 salt may be from seams or deposits of that ma- 

 terial, and, as in springs and wells, generally, 

 it may emerge or be struck at some distance 

 from its source. One of the earliest facts in 

 the course of discovery of rock oil in this coun- 

 try was its very frequent appearance on the 

 water of wells bored for salt, and often to so 

 great an extent as to be regarded as a nuisance, 

 or even to lead to the abandonment of such 

 borings. It was thus found on the water of salt 

 wells, on the Great Kanawha, and on numer 

 ous tributaries of the Alleghany and Ohio Rivers 

 within and near the limits of the present oil 

 regions. And in any case, salt water becomes 

 a more important sign when it occurs in the 

 vicinity of gas-springs or surface oil. 



Finally, it appears that no infallible criteria 

 or rules as to whether petroleum is or is not 

 present in remunerative quantities in the strata 

 beneath any district, can yet be laid down 



