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the products of the distillation of highly organized animal tissue, as an effect of the accumulation of sediments, and of metamorphic action upon unaltered sediments, through granite and gneiss to lava and pumice.
20. If we turn from North America to Europe-Asia, the testimony of the most eminent observers seems equally convincing. Daubrée was satisfied that the origin of the bitumen was found in metamorphism. Other French chemical geologists were equally well-grounded in this belief. As early as 1835, M. Rozet read a paper before the Société Geologique de France in which he discussed the occurrence of asphaltic limestone at Pyrimont. He says, "The bituminous matter is found equally in the calcareous rock and the molass that covers it. It is evident the action that introduced it into the two rocks is posterior to the deposition of the latter. The manner in which it is distributed in great masses, which throw their ramifications in all directions, joined in such a manner that the superior portions generally contain less bitumen than the remainder of the mass, indicate that the bitumen has been sublimed from the depths of the globe. . . . . It may be objected that such basaltic rocks do not appear in all the extent of the Jura. To that I reply that they are found in the neighborhood, in Burgundy and in the Vosges and further, that in the changes in the surface of the soil, whether occasioned by fractures or by the disengagement of vapors, the plutonic rocks do not necessarily appear at the surface. Perhaps in the deep valleys of the Jura the basalts are of very slight depth. . . . . In the Val de Travers, near Neufchatel, similar phenomena are observed."1
In 1846, Mr. S. W. Pratt associated the occurrence of bitumen at Bastennes with the eruption of ophite in the Pyrenees. In 1854, M. Parran remarks concerning the occurrence of bitumen in the environs of Alais, "whatever be the origin of these substances, whether they be due to interior emanations from fissures of dislocation or to circumstances exterior and atmospheric, it is evident that there was during the Tertiary period an asphaltic epoch in relation to which it is convenient to recall the numerous eruptions of trachytes and basalts which characterize that period, and have probably acted by distillation upon masses of combustibles hidden in
1 Bull. Geol. Soc. de France (1), vii, 138.
2 Quar. Jour. Geol. Soc., ii, 80.
the bosom of the earth." The anthracites of the Alps offer convincing proof that large amounts of organic matter have been involved in the metamorphic action that has prevailed in that region. In like manner the relation of the bituminous deposits of Galicia and Roumania to the crystalline rocks of those countries show the part that metamorphism has played in their occurrence.
21. No theory that refers the origin of the bitumen to any physical or chemical action that has prevailed on a cosmic scale can satisfactorily explain the differences that exist in crude bitumens. Mr. Phillips has added the testimony of chemistry itself to show the improbability of a chemical origin for bitumens on a cosmic scale. Dr. Day has shown the reasonableness of an hypothesis which regards the bitumens of Pennsylvania as distillates, but his idea that the variation in the petroleums of that region is due to the effect of filtration is, in my judgment, hardly tenable. In Pennsylvania the darkest and heaviest oils are nearest the surface. The sulphur content of bitumen is too wide a subject to discuss here in detail; yet it may be said in general that sulphur enters bitumens by a secondary reaction between the bitumen and the sulphates dissolved in natural waters. The freedom of Pennsylvania petroleum from sulphur has already been shown to be due to the absence of sulphates in the natural waters of the region in which they occur. As has already been stated, Prof. Mabery has shown that the sulphur compounds found in Lima oil are sulpho-paraffines. This would naturally follow the reduction of sulphates by paraffines, the reaction being a double decomposition in which sulphur is substituted for hydrogen in the paraffine. Filtration would not be likely to remove such compounds from solution in the other constituents of the petroleum.
In his discussion of the "Occurrence of Petroleum in the Cavities of Fossils," Mr. Phillips has offered some ingenious but wholly unnecessary suggestions to account for the presence of a nearly solid bitumen in the cells of a coral reef uncovered in a quarry. Petroleum occurs in the rocks of the oil regions filling cavities of every description. Geodes, fossils, sandstones, pebble conglomerates, porous limestones, the Chicago dolomite, gravel, anything and everything that has a cavity or a pore, has been found saturated with it. Why? Simply because the enormous pressure under which the bitumen has accumulated in the crust of the earth has
1Ann. des Mines (5), iv, 334.
forced it there. When it has entered cavities like those in the coral reef described by Mr. Phillips, the diminished pressure and evaporation have resulted in the escape of the most volatile constituents. When the reservoir of the Bradford field was first penetrated, the pressure was estimated at 4000 pounds to the square inch. Whether or not this estimate was approximately correct, the pressure was sufficient to throw the well casing and piping out over the top of a derrick and land it in a meadow near by. A short time after the famous Karg well was struck near Findlay, O., I, myself, saw a pressure gauge register 450 pounds per square inch. Burning gas wells in western Pennsylvania sent streams of flame into the air eighty feet in height. Notwithstanding this accumulation of the facts of experience during many years, writers still ignore the tremendous significance of such phenomena, and speak of these deposits of bitumen as if they resembled a turn-over or an appledumpling laid away by nature. Gas cannot have been held under such tremendous pressure through cycles of geologic time in reservoirs of porous rocks, from which it has been filtering, as suggested by Mr. Phillips.
The complete inadequacy of all these arguments was never more fully set forth than in the language used by Mr. Phillips: "The movement of the oil through the rock displaced from the interstices in which it had originally collected would have been accelerated as the transition from solid organic tissues to liquid had been advanced." The decomposition of organic matter in situ could never have occurred under any conditions of accelerated pressure of even moderate amount. The rocks must have been consolidated and capable of resisting pressure before, action and reaction being equal, the pressure could accumulate. These facts are themselves the strongest reason for belief that the bitumens were never formed in situ in the porous rocks that contain them, but were gradually accumulated in those porous rocks that had been previously overlaid with impervious strata capable of resisting the enormous pressure until the reservoirs were penetrated by the drill. The fact that in the limestone some fossil cavities are filled while others are empty lies in the further fact, that the lines of shrinkage and other fractures penetrated some of the fossil cavities while others remained intact.
22. Upon this hypothesis, that bitumens are distillates, all of the variations observed in bitumens of different geological ages are
easily explained. The earliest forms of animal and vegetable life are admitted to have been nearly destitute of nitrogen; hence when these forms accumulated in sediments, which, borne down by deposits above them, invaded an isothermal that admitted of their distillation, they must have been distilled, in the presence of steam, at the lowest possible temperature; they must have been distilled under a gradually increasing pressure, the extent of which depended upon the porosity of the sediments above them, up to the surface. They must also have been distilled under a gradually increasing temperature which would have been largely controlled by the pressure. While the temperature and the pressure would have in every instance been the least possible, with steam always present, these physical conditions would on account of the varying porosity and consequent varying resistance of the overlying mass have produced very great effects in some instances and very slight effects in others. As a consequence, we have in natural bitumens, as in artificial distillates, materials varying in density from natural gas to solid asphaltum.
If these distillates proceeded from materials that would yield paraffine, these permanent and stable compounds, from marsh gas to solid paraffine, remained in the receptacles that nature had provided for them until they were released by the drill. If, however, the distillates proceeded from sediments of a different geological age, containing animal and vegetable remains more highly organized, that would yield different series of hydrocarbons, with compounds of nitrogen, then a very different bitumen would be stored in these receptacles. Secondary reactions would convert these primary distillates into a great variety of substances. The contents of the original reservoirs, borne down and invaded by heat, might become involved in a second distillation at an increased pressure and temperature. Fractures of these reservoirs from excessive pressure might lead their contents to the surface along lines of contact of strata or with water containing sulphates by which an originally pure hydrocarbon would be converted into a sulphur bitumen. A nitro hydrocarbon, reaching the surface under these conditions, might, by the combined action of evaporation and reaction with sulphates, pass through all the varying degrees of density from petroleum to maltha and become finally solid asphaltum, and this through the lapse of time and abundance of material on a scale of vast magnitude.
23. Such, then, is the "Testimony of the Rocks," along a line which spans the western continent. Nearly the whole of this line has been brought under my own personal observation. There is also reason for believing that a line might be followed in the eastern continent from the North sea to Java that would furnish equally convincing proof. To this testimony is added that of chemistry, technology, mineralogy, and the chemistry of the cooling earth. Each supports and corroborates the other. We have no need to search for coke until we know that coke was formed. We have no need to assume, that in the laboratory of Nature high temperatures and rapid action were necessary to produce results, for which infinite periods of time and the lowest possible temperature were fully adequate.
24. Since this paper was written I am in receipt of the annual address of the President of the Geological Society of America-Dr. Edward Orton-read at Montreal, December 28, 1897; from which exhales the exquisite aroma of fine literature, as from all the other productions of its accomplished author. In this address I note two very important observations. He says, in speaking of Mendelejeff's chemical hypothesis, "It is hard, therefore, to see why, the whole world over, petroleum is entirely wanting in the Archean and exclusively confined to the stratified rocks. There is not an oil field in the world in rocks of Archean time.” I pass this by without comment to notice his observation upon the gas wells drilled in Oswego and Onondaga counties, N. Y., one of which penetrated a limestone that was found between the Pottsdam sandstone and granite, and furnished a gas pressure of 340 pounds; the other at a depth of 120 feet, in the Trenton limestone, gave the gas pressure of 1525 pounds. Dr. Orton well says, "A rock pressure of 1500 pounds to the square inch stands for, nay demands, a hermetic seal." Speaking of the Pottsdam sandstone and the dark limestone beneath it, he says, "The drillings brought from these horizons. seem normal in every respect. Certainly there is no hint of any transformation by heat. The smell of fire has not passed on them.' There is no carbon residue. The bituminous products found in them cannot owe their origin to the usual form of destructive distillation." It is not likely, that the usual form of destructive distillation as illustrated in a gas retort has obtained anywhere in the operations of nature. I regard the penetration of granite
1 Bull. Geol. Soc. America, ix, 93.