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nities to expound and enforce his views, insomuch that the conviction has obtained great currency in Canada that this limestone is the principal source of petroleum in that province. Under this conviction, scores of oil wells have been bored throughout the belt of Canadian territory immediately underlaid by the Corniferous limestone. If this formation, say they, is the source of the oil obtained at Enniskillen, where it lies five hundred feet from the surface, let us proceed to some region where this formation approaches nearer the surface, and thus save several hundred feet of boring. Though this reasoning has been put in practice in multitudes of cases, both in Canada and the United States, I am not aware of a single well bored in the Corniferous limestone that has produced sufficiently to pay expenses. I do not regard the inference acted upon as legitimately drawn from Dr. Hunt's views; for he must perceive that, even were this limestone the source of petroleum-supplies, it must have evaporated throughout the regions of surfaceoutcrop of the formation.

But the Corniferous limestone seems not to be the source of petroleum-supplies even in those regions where the superposition of another formation has arrested wastage. If it were the source of such marvelous quantities as have been drawn from the Canadian strata, its own cavities and interstices should certainly be charged with the liquid. To test this precise question, a "test well" was bored at Enniskillen at the joint expense of parties interested, and was continued over two hundred feet in this formation; but from the time of entering it the signs of oil were materially diminished instead of increased. The Corniferous limestone has also been penetrated at St. Clair, in Michigan, under circumstances as favorable as possible for the discovery of any great quantities of oil which may be stored up in its recesses. The salt well at that place extended through the

whole thickness of the Hamilton group and the Corniferous limestone, but with nothing more than continued "signs" of oil. The same was done in the salt well at Port Austin, and in the deep boring at Jackson, in the same state.

In addition to these and other negative evidences that the view of Dr. Hunt is untenable, we have the demonstration of experiment upon the constitution of limestones and black shales. The amount of oil that can be extracted from any sample of the Corniferous limestone is utterly insignificant in comparison with the amount obtainable from the Genesee shale. It is a matter of ocular demonstration that the Genesee shale incloses a vast supply of the material for petroleum-making, while the Corniferous limestone contains almost none of the material, and comparatively little of the generated product. I shall insist, then, with my distinguished friend Dr. Newberry, late President of the American Association for the Advancement of Science, upon the correctness of that view which regards the black shales as the chief generators of supplies of native petroleum. I dissent from the position of Dr. Hunt with the utmost deference to the weight of his authority, and only because I have enjoyed opportunities seldom equaled to examine the geology of all the "oil-regions" east of the Rocky Mountains.

The petroligenous formation may be present in the absence of reservoirs for the reception of the product. There is a well-defined belt along the eastern and the western slopes of the lower peninsula of Michigan which is immediately underlaid by the Genesee shale, capped by a deposit of argillaceous surface materials adequate to prevent wastage; but no oil has accumulated, because no space has been provided for it. In some portions of the Enniskillen region, twenty miles distant, the geological conditions are perfectly identical, except that a bed of gravel lies at the bottom of the drift materials, and immediately upon the

Genesee shale. This bed of gravel is the reservoir, and becomes charged with a supply of thick petroleum called "surface oil." Some wells have yielded thousands of barrels of surface oil. It may be necessary to add that in some portions of Enniskillen the Genesee shale has been removed, and the surface wells are evidently supplied from the lower Marcellus shale, which also stocks the crevices of the Hamilton limestones. In Venango County, Pennsylvania, and Trumbull, and Knox, and contiguous counties in Ohio, the Genesee shale is overlaid by porous sandstones which serve as reservoirs of the oil. In the Glasgow region of Southern Kentucky, the formation overlying the Genesee shale is the Mountain limestone; but this is in places arenaceous, and in others vesicular and cavernous, and thus furnishes the requisite conditions of oil-accumulation. In one instance at least, in that region, the Genesee shale itself affords the reservoir for the storage of its productions. In West Virginia the oil seems to accumulate in the conglomerate at the base of the Coal-measures. The same is the case in Southwestern Pennsylvania, Southeastern Ohio, and Northeastern Kentucky. The reservoir in the Burkesville region of Southern Kentucky is found in the shattered shaly limestones of the Cincinnati group. These are reproduced in physical characters in the shattered shaly limestones of the Hamilton group, which serve as the place of deposit of the oils of Ontario.

I close this sketch of the geological phenomena of petroleum by presenting a synopsis of oil regions and the formations tributary to their supplies.

I. The black shales of the Cincinnati group afford oil which accumulates (1) in the fissured shaly limestones of the same group, and supplies (A) the Burkesville region of Southern Kentucky, and (B) Manitoulin Island in Lake Huron.

II. The Marcellus shale affords most of the petroleum

which accumulates (2) in the fissured shaly limestones of the Hamilton group, and thus supplies (C) the Ontario oil region, locally divided into (a) the Bothwell district, (b) the Oil-Springs district, and (c) the Petrolea district.

The Marcellus shale affords also a large portion of the oil which accumulates (3) in the drift gravel of the Ontario region.

III. The Genesee shale, with perhaps some contributions from the Marcellus shale, affords oil which accumulates (4) in cavities and fissures within itself in (D) some of the Glasgow region of Southern Kentucky.

It affords also the oil which accumulates in (5) the sandstones of the Portage and Chemung groups in (E) Northwestern Pennsylvania and contiguous parts of Ohio.

It affords also the oil which accumulates in (6) the sandstones of the Waverly (Marshall) group, in (F) Central Ohio.

It affords also that which accumulates in (7) the mountain limestone of the Glasgow region of Kentucky and contiguous parts of Tennessee, as also some of that which is found in the drift gravel of the Ontario region.

IV. The shaly coals of the false Coal-measures, aided, perhaps, by the Genesee and Marcellus shales, seem to af ford the oil which assembles in (8) the coal conglomerate as worked in (G) Southwestern Pennsylvania, (H) West Virginia, (I) Southern Ohio, and the contiguous but comparatively barren region of Paint Creek, in Kentucky.

V. The Coal-measures may perhaps be regarded as affording a questionable amount of oil, which may have been found within the limits of (9) the Coal-measures in the West Virginia and neighboring regions.

From this exhibit it appears that the principal supplies of petroleum east of the Rocky Mountains have been generated in four different formations, accumulated in nine different formations, and worked in nine different districts.

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Fig. 90. View of the Salt Works at Mason City, West Virginia.

CHAPTER XXVI.

SOMETHING ABOUT ROCK-SALT AND GYPSUM.

COMMON salt, upon which the chemist has imposed the

more dignified title of chloride of calcium, is a mineral almost universally distributed through the stratified portion of the earth's crust. Like those other substances of universal utility to man-petroleum, coal, iron, water, and lime it is supplied by Nature to every habitable region of the terrestrial surface. Like lime, which is the chief constituent of the bones and teeth of man and the other vertebrates, the shells of molluscous animals, and the mountains of coral accumulations reared in the bottom of the sea, common salt also subserves the necessities not only of man, but of the quadrupeds and various other terrestrial animals, including insects, and is the characteristic constituent of sea-water, the home of two thirds of all the animals now existing, and a much larger proportion of the animals of former geological ages.

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