Hitchcock — Petroleum in North America. 35 



1. Petroleum sometimes occurs in synclinal hasins like the sub- 

 terranean streams of water penetrated by Artesian bore-boles. This 

 is tbe case in Western Pennsylvania, tbe most prolific of all the "oil- 

 regions." It is found beneath three sandstones or sets of impervious 

 strata, called the " first," " second," and " third." In the small -yield 

 wells the oil may constitute the drainage of an inconsiderable thick- 

 ness of saturated layers. The fluid may often require the aid of 

 pumps to bring it to the surface. 



2. Petroleum may occur in cavities and fissures in the strata, either 

 upon synclinal basins or anticlinal slopes. The existence of a cavity 

 is inferred from the prodigious flow of fluid, as of the Grant Well, 

 which at the time of my visit was spouting in a hissing stream 1800 

 barrels of petroleum every day. Many of these wells discharge their 

 products intermittently. Besides petroleum, brine and gas are com- 

 monly, if not universally, discharged from the orifice ; and we may 

 suppose that before the tapping of the cavity they were arranged 

 according to their specific gravities, the gas uppermost and the brine 

 beneath the others. The varying phenomena of discharge may be 

 explained by supposing different parts of the cavity to have been 

 reached by the boring rod in the several instances. When a cavity 

 is large two or more boreholes may penetrate it, as was the case with 

 the celebrated Phillips and Woodford Wells. Generally the wells 

 of one neighbourhood seem to have some connection with one an- 

 other ; for if old and unproductive holes are not closed, the discharge 

 from new and promising wells is impeded. Abandoned holes should 

 always be plugged up ; partly for the benefit of new enterprises, 

 and partly because it has been discovered that by rest they will 

 again become productive. 



The oleiferous reservoirs may be irregular cavities — vertical, 

 horizontal, or inclined fissures ; an enlargement of natural joints, etc. 

 Explorers look for regions where the strata have been much folded 

 and broken, premising that the dislocations may produce cavities in 

 which fluids will collect. 



3. Petroleum may occur along lines of faults. Examples of this 

 nature are in Western Virginia, Cumberland and Barren Counties, 

 Kentucky, and elsewhere. 



4. Petroleum may exist in great quantities beneath anticlinal arches. 

 These run into Ko. 3. Examples of this nature are in Albert Co. 

 N. B., Gaspe C. E., and hi the productive region of Canada West. 

 The roof acts as an impervious cover to confine the fluids until the 

 drill of the workman appears for their liberation. 



These facts show us where to expect petroleum in considerable 

 amount. If we search in that area where the oil-layer comes to the 

 sm^face, or its distribution as represented by the colors of a geological 

 map, we shall find only shallow and small producing wells. Never- 

 theless these may be more permanent than the deeper ones, and may 

 be profitably worked from generation to generation where labour is 

 inexpensive. Tbe great wells involve three essentials — first, plenty 

 of bituminous matter in the petroleum formation, from whence an 

 abundant supply may be drawn ; second, cavities and crevices in the 



