well-known fact that wells sunk into the black shale yield no considerable quantity of oil, unless from strata resting upon it.
The foregoing statements, it will be seen, go to substantiate the theory upheld by Newberry, in common with other geologists, that the strata yielding much oil have only served to store the oil which comes from other strata below. T. S. Hunt holds that the petroleum of the limestone of Ontario, Canada, and other localities is largely the result of decomposition of the organic matters in these same rocks, and not of distillation from below. This view Newberry opposes on the following grounds: The Corniferous limestone, from his very extended observations, contains little hydrocarbons; oil and gas springs are rare where it underlies the surface; no considerable quantity of petroleum has been derived from wells in the Corniferous, Niagara, or any other limestone; even at Chicago there are no paying wells. Borings have been unsuccessful in Ohio wherever the Corniferous is the surface rock; and, further, there is no Corniferous limestone where Hunt cites it in Kentucky. There is positive proof that part of the oil comes from a lower horizon, and probably the Canada oil comes from underlying Silurian Collingwood shale. On Oil Creek are the argillaceous shales of the Waverley and Chemung strata, forming the sides and bottom of the valley, and below are several beds of sandstone, with the black shales of the Portage and Genesee still lower. In Ohio these favorable conditions are wanting; the sand-rocks of Oil Creek thin out and give place to fine, impervious, argillaceous shales; the strata become more homogeneous and free from crevices, and hence the oil cannot penetrate them so well. In Cuyahoga County, Ohio, the wells reach down through carboniferous rocks to the Huron shale, but there are no good wells, because the sandstone reservoirs are lacking, and only close-grained shales are present.
Hunt, on the other hand, holds that the petroleum of Southwest Ontario, and probably in other localities, is to be sought in the oliferous limestones of the Corniferous and Niagara formations, both of which abound in indigenous petroleum (American Journal of Science, III., ii., 369), which, in the case of the Ontario limestone, he shows cannot have come from overlying strata. He also mentions a well sunk at Terre Haute, Indiana, 1,900 feet deep, which yields two barrels of oil daily; and a second one, very near, which yields 25 barrels. This one is 1,625 feet deep, and passes through 700 feet of coal-measures, 700 feet of carboniferous limestone, with underlying sandstone and shales, 50 feet of Genesee slate (or its equivalent), and at a depth of 25 feet below this the oil-vein was met with in Corniferous limestone. A third well, a mile east, at a depth of 2,000 feet showed no oil.
The truth seems to be, that these limestones may contain a little petroleum indigenous to them, but they have not furnished the grand supplies of very productive regions. Before leaving this part of the
