Page:Popular Science Monthly Volume 9.djvu/166

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Counties, between thirty-five and forty miles. No oil is found in the horizontal rocks, but it occurs along the disturbed and broken, tilted strata on the edges of the line of uplift. This same belt runs north into Ohio, through Washington and Morgan Counties into Noble County. Volcano, White Oak, and Burning Springs are the principal points in West Virginia. The oil is found in subcarboniferous rocks, ascending to them from the underlying Devonian.

In Ohio there is another oil-belt, west of the above, beginning in Perry and Morgan Counties on the north, and running south through Athens into Meigs County; and in Cuyahoga and Trumbull Counties are oil-regions closely related to those of Western Pennsylvania. The "Mecca" oil, a valuable lubricating oil, occurs in the Mecca Oil Rocks (Berea grit and Bedford shales) of Trumbull County, Ohio. The total production of Ohio and West Virginia is not over 500 barrels daily (Wrigley).

The Kentucky oil-district is mainly in Barren and Cumberland Counties, with a small adjoining tract south of it in Overton County, Tennessee. A well in Cumberland County, 191 feet deep, produced 300 barrels daily. The abundant supply from Pennsylvania and the difficulty of transportation have prevented these regions from becoming well known.

Origin and Source of Petroleum.—At first it was held by many that petroleum was a result of distillation from the bituminous coals, which were found in its vicinity, and this belief was strengthened by the fact that some of the very bituminous coals, such as Cannel and Boghead coal, afforded large quantities of similar oils on being distilled; but, although this is very probably the source of a small amount of oil, yet the larger part of it is now believed to derive its origin from rocks lying below the coal-measures, since the oil-bearing rocks are mostly older than the carboniferous formations.

Some investigators have ascribed a vegetable origin to petroleum, but most authorities agree in attributing it to animal as well as vegetable agencies. Shales are the most common oil-bearing rocks, and in their formation the organic materials would be finely divided and protected from oxidation. The oil-bearing shales commonly show few vegetable remains, and Dana observes that the absence of distinct fossil animal and vegetable remains points to an abundance of delicate water-plants or infusorial or microscopic vegetable life as the source of the organic material contained in them. Limestones, on the other hand, are frequently full of animal fossil remains, showing an animal origin for the oil in them, although it is by no means agreed that the petroleum in certain limestones was derived from organic remains in the limestones and not from other strata below them. In whatever shape the finely-divided material was originally present, it would be finely diffused through the mud, and protected from atmospheric agencies, and subsequently the hydrocarbons would be formed from them,