56 REroRT — 18G6. 



On account of its economic importance, therefore, this commodity demands a 

 passing notice of its geological relations. 



1. Petroleum sometimes occurs in si/iich'/ial basins, like the subterranean streams 

 of water penetrated by Artesian bore-holes. This is the case in Western Pemisyl- 

 vania, the most prolific of all the " oil-regions." It is found beneath each of three 

 sandstones, or sets of impervious strata, designated by tlie workmen as the "first,'' 

 " second," and " third." In the small-yield wells the oil may constitute the drain- 

 age of an inconsiderable thickness of saturated Layers. The aid of pumps is often 

 required to bring the fluid to the surface. 



2. Petroleum may occm- in cuvities andjissnres in the strata, either upon synclinal 

 basins or anticlinal slopes. The existence of a cavity is inferred from the prodigious 

 amount of fluid spouting out of the ground, as of the Grant Well at Pitt Hole, 

 which at the time of my visit was producing 1800 barrels of petroleum every day. 

 Manj' of these wells discharge their products intemiittently. Besides petroleum, 

 brine and gas are commonly, perhaps universally, discharged from the orifice ; and 

 we may suppose that, before the tapping of the cavity, they were an-anged according 

 to their respective gravities, the gas xippermost and the brine at the bottom. 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 bore-holes may penetrate it, as was the case with 

 the celebrated Phillips and Woodford Wells. Generally the wells of one neigh- 

 bourhood seem to have some connection with one another ; for if old and unpro- 

 ductive holes are not closed, the discharge from new and promising wells is im- 

 peded. Abandoned holes should always be plugged up, partly for the benefit of 

 new entei-prises, and partly because it has been discovered that by rest they will 

 again become productive. The oleiferoiis reser\oirs may be iiTegular cavities, ver- 

 tical, hoi-izontal, or inclined fissures, an enlargement of natural joints, &c. Ex- 

 plorers look for regions where the strata have been much folded and broken, pro- 

 mising that the di.slocatious may produce cavities in which fluids will accumulate. 



.3. Petroleum may occur along lines of fniiUs. Examples of this nature are in 

 Western "S'irginia, Southern Kentucky, and elsewhere. 



4. Petroleum may exist in c/reat quantities beneath anticlinal arches. A fault 

 may change into an anticlinal along the strike. Examples of this nature are in 

 Albert Co., N. B., Gaspe, C. E., and in Canada West. The roof acts as an impervi- 

 ous cover to confine the fluids until the drill of the workman appears for their 

 liberation. 



These facts show us where to expect petrolemn in considerable amount. If we 

 search in that tarea where the oil-layer comes to the surface, or its distribution is 

 represented by the colours of a geological map, we shall find only shallow and 

 small-produciiig wells. Nevertheless these may be more permanent than the 

 deeper ones, and may be worked profitably from generation to generation, where 

 labour is inexpensive. The great wells involve three essentials ; first, plenty of 

 bituminous matter in the petroleum formation, from which an abundant supply 

 may be drawn ; second, cavities and crevices in the strata ; third, an impenious 

 cover, like the roof of an anticlinal, to have prevented the escape of the fluid in 



East ages. The best " surface-indications " generally guide to shallow wells. The 

 est reservoirs have been found at considerable depths. 



5. There are no less than fourteen different fonnations in North America (not 

 including the A^'est Indies) from which petroleum has been obtained, generally in 

 productive amount. 



(a). Pliocene Tertiary of California. This has been known for a century. 



(6). In Colorado and Utah, near lignite beds of Cretaceous age. Not yet 

 explored. 



(c). In small amount in the Trias of Connecticut and North Carolina. 



((?). Near the top of the Carboniferous rocks in W. Va., including many of the 

 best producing wells in the .state. 



(e). Shallow wells near Wheeling, W. Va., and Athens, O., not far from the 

 Pittsburg coal. 



(/). 475 feet lower, near the Pomevoy ccal-bed. 



