LOCALITIES AND CONDITIONS OF OIL-FORMATIONS.
The same arguments hold good in relation to the existence of rock-oil as to coal, viz.: certain conditions of position, lithological structure, and topographical feature are required for the one as well as the other, since oil produces coal. We have seen that both petroleum and coal are produced in and from granitic formations, as well as from and - in the Palmozoic,—in volcanic re gions and in the stratified fossilifer ous. But in the former the coal and oil are both limited: first, because condensation could only take place when the temperature of volcanic regions was reduced to the proper standard, or below the boiling-point; and second, because neither the _ lithological structure nor the physical features of such regions admits of their retention or formation in ex tensive fields. We find petroleum existing abundantly in Cuba, which is a volcanic region of late activity, and we find coal in the crater of an extinct volcano, as the Richmond coal-field, in Virginia, which was of much older activity, and yet much more recent than the true Carbon iferous formations.
In volcanic regions the tempera ture is naturally high, and it re mained high even when it became low in the centre of the Great Basin. The volcanoes of the East continued to vent their lava until the highest sandrocks in our coal measures were formed; and the fact of a con tinual increase of bitumen from the East towards the West proves that the temperature decreased in the same proportion in that direction. We find that the hydro-carbons were produced in greater abundance in the East than the West; but we find, too, that nearly all their volatile matter was expelled on the Lehigh, less on the Susquehanna, and still less on the waters of the Juniata: yet our coal-beds are of an immense thick ness, individually or as an aggregate, in the East, and very limited in the West. Though more than half the volume of the oil was expelled in the East by the higher temperature, we still have a greater residue left than in the West, where the low tem perature admitted of the solidification of the oil with half its volatile matter remaining. This is proved by the fact that anthracite coal in the Lehigh basins contains scarce a trace of hydrogen or other volatile matter than water ; while the cannel coal of Kanawha and some of the rich bituminous coals of the West contain more than half their weight in volatile substances. Between these extremes of temperature exists every grade of coal,
from the pure carbon of the hard anthracites to the bitumen of the most volatile cannel.
The causes of this are evident: first, a gradual removal from the volcanic regions of heat; and second, a gradual elevation from the internal heat of the earth, by the con stant accumulation of the Palaeozoic strata in the waters of the Great Basin. The same causes, of course, affect the present existence of oil, as they affected the production of coal. We see that the quantity of coal decreases in a westward direction, as all the stratified rocks decrease : consequently, the volumes of gas arising and the oil and bitumen resulting must have been in relative proportion. That is, the oil was limited then, as the coal is limited now, and the same may be said of the proportions to-day. Much of the bitumen, however, of the West is taken up by the rocks through which it arose to the surface, because the condensation took place at a lower point there than farther east in the Allegheny coal-field. But it is against all reason and the laws of chemistry to expect the bitumen of the rocks to produce oil. It requires heat to effect this ; and that which did not produce it during early ages cannot produce it now. If the rocks now holding bitumen obtained their bitumen from the ascending oils or organic remains, as they must have done, because they were cool enough to condense it, can it be possible for them to yield it again in oil or gas if they continue to grow colder? It is evident that heat alone can produce oil or gas from the bituminous rocks; and since they certainly are not accumulating heat, even if they do not grow colder, they can never give up their bitumen as oil in nature. The Corniferous limestone will yield its bitumen in the sun, as may be seen at the celebrated "oil-stone" church in Chicago ; but if left in the earth the oil would never be disturbed. This is a plain statement of fact ; there is no theory about it, and, therefore, it upsets entirely the doc trine which accounts for the production of rock-oil from the organic remains of the fossiliferous Devonian strata.