A. von Humboldt (1804) also advocated the emanation. theory, without however expressing an opinion of "how" petroleum is formed. He observed a petroleum well issuing from metamorphic rocks in the bay of Cumana and remarked: "If it may be supposed correct that further eastward near Cariaco, the hot and submarine waters are sufficiently abundant to change the temperature of the gulf at its surface, we cannot doubt that petroleum is the product of distillation at an immense depth, issuing from those primitive rocks beneath which lie the forces of volcanic commotion."

Rozet (1835) also supposes that the asphalt in Pyrmont emanates from a great depth from which it has reached its present deposit by sublimation. He connects this process with basaltic eruptions at a distance (Java, Burgundy, in the Vosges).

S. W. Prott (1846) connects the occurrence of petroleum at Basténes, a village in the south of France, with the ophite eruptions of the Pyrenees. Parran (1854) also asserts "that during the Tertiary period an asphaltic epoch took place 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 the masses of combustibles hidden in the bosom of the earth." He deduces the occurrence of asphalt between Mons and Auzon from the distillation of deeper strata, the inferior cretaceous, or perhaps the carboniferous, formation, which contain combustible substances.

Thoré, in 1872, published a paper on the occurrence of petroleum in the water of St. Boés (Basses-Pyrénées) and arrived at a similar conclusion to Prott. He asserts that the greater part of the deposits of petroleum is related to the eruptive rocks (ophite), which may be considered the principal cause of its formation, or, at least, of the appearance of mineral oil.

The investigators above mentioned supposed that the oilforming process takes place at a great depth, partially in the pyrosphere, that the hydrocarbons formed are forced upwards

through deep-reaching fissures where they condense to fluids and remain either as an accumulation in the fissures, or spread out in the porous rocks they met with in ascending. We have thus to deal here with emanation hypotheses. The occurrence of petroleum together with cavities and hot springs might be referred to as an apparent confirmation of these hypotheses. However, this process would have to take place at the present time also, if the requisite agents have not been exhausted. Hence, according to the emanation hypotheses, it might be expected that an oil territory cannot be exhausted, since it would constantly receive a new influx from a great depth. These sanguine expectations are unfortunately contradicted by experience in many localities, especially in the hitherto most important oil regions, namely those of Pennsylvania.

That, independent of the above-mentioned reason, the emanation and similar hypotheses are untenable, is proved by the following statement:

The oil derived from a very great depth would have to show a higher temperature than can be supposed from the increase in the heat of the earth, which, however, is not the case. On the contrary it might be said that the petroleum, having been imbedded for a long time in the strata traversed by the supplyfissures, has acquired their temperature. But, when this old supply is exhausted, fresh quantities of oil would gush from the deep in consequence of the pressure which forced the oil upward from an extraordinarily great depth, and these fresh quantities of oil would possess a much higher temperature, which, however, does not agree with experience.

To quote the hot springs in proof of the correctness of these hypotheses, as was repeatedly done in the discussion of the conditions prevailing in the Caucasus, is inadmissible in consideration of the low temperature of the petroleum opened up, which scarcely exceeds that of the soil by 20 or 3°. These facts rather prove that the seat of the petroleum formation must be located at a slighter depth. Moreover, the thermal and oil springs of that region are not genetically connected.

According to these emanation hypotheses, petroleum might be expected to occur wherever deep-reaching fissures are shown to exist, the more so since there is no reason to suppose that metallic carbides are evolved locally only in the interior of the earth. However, this supposition is not correct, the Alps, for instance, being traversed by extraordinarily deep-reaching fissures without petroleum occurring in them.

One of the greatest known faults in Europe, outside the Alps, is the Eifel fissure, which is, however, destitute of oil. C. M. Paul and E. Tietze have also referred to the fact that though the petroleum of the Carpathians may occur in fissures, the most important faults are totally destitute of oil. They further lay special stress upon the fact that "in the Caucasus also it is not the region of the great downcast in the south of the mountains which appears to be exclusively distinguished by the occurrence of petroleum, but that, independent of the larger and better known occurrences on both ends of the chain (Baku, Taman), petroleum is frequently found on the northern slope of the same."

In Pennsylvania the petroleum does not occur in the Apallachians, where the disturbances are greatest and consequently reach most deeply into the interior of the earth, but west of them, where the anticlinals are extraordinarily shallow.

Another objection to these emanation hypotheses is that petroleum very frequently occurs in sedimentary regions destitute of any kind of volcanic action. It may only be mentioned that eruptive rocks are entirely wanting in the oil regions of Pennsylvania, New York, Canada, Galicia, etc. On the other hand considerable quantities of petroleum or exhalations of carburetted hydrogen gases are scarcely ever found in the neighborhood of volcanoes active at the present time. The occurrence of petroleum in eruptive rocks has, on account of its rarity and the small quantities found, been of scientific, but never of industrial interest.

In the Carpathians, the most productive oil regions are situated on the north side-in Galicia-which is free from eruptive

rocks, wide on the south side, where extensive eruptions have taken place petrolemm does not occur in the neighborhood of the eruptive rocks, or at least only in very small quantities.

The erroneousness of the proposition that the origin of petroSelma due to processes which have taken place at a great depth by the reaction of inorganic substances, is also proved By the fact that up to the present time petroleum has nowhere been found in the Archean strata which were formed at a period when no living being inhabited the earth, although they are also suitable for the reception of this fluid and are frequently traversed by faults. However, this fact supports those hypotheses which deduce the petroleum from organisms.

It has been endeavored to strengthen the emanation hypothesis by the fact of the association of mud-volcanoes (salses) with the occurrence of petroleum. These mud-volcanoes, however, are in no way connected with genuine volcanoes, the material thrown out by them being taken only from the underlying, mostly loose strata, as has been shown by thorough microscopical examinations of organic remains by M. von Gümbel.

In the Carpathians one of the occurrences of petroleum is fixed on shale (fish-shale), while the porous sandstones directly beneath it are destitute of oil. If the petroleum had actually sprung from the deep, it would have very likely impregnated the porous sandstone, and not the shale, difficult to penetrate, lying above. Moreover, there is a series of occurrences of petroleum and other bitumens which forces us to the conclusion that these hydrocarbons also have been formed within fixed strata, which will be referred to later on, so that as far as they are concerned the supposition of emanation is inadmissible.

J. L. Piedboeuf points out that the condensing points of the separate combinations of petroleum lie between 0 and 300° C. (32 and 572 F.). Now, if they had ascended in the form of vapors from the deep, they would have been condensed at va

Older observations from two points in South America are very doubtful, especially also whether the oil, even if it occurs in the Archean strata, is a primary deposit.

rious temperatures prevailing there, and hence could not occur as a mixture within one stratum.

Moreover, the absence of carbonic oxide in the gases accompanying petroleum, as shown in several localities, speaks against the supposition of a higher temperature in the evolution of petroleum. The above-mentioned facts regarding the occurrence of petroleum in nature speak so decidedly against its origin from inorganic substances, and against the emanation hypothesis connected therewith, that these suppositions have no ground to stand on.

Closely related to the previously discussed views are those which, though they acknowledge condensed carburetted hydrogen gases in petroleum, do not touch the mode of origin of the latter, and hence do not express themselves either for or against the inorganic origin. Thus only half an explanation is given.

The most conspicuous representative of this theory is M. Coquand, who has so fully written upon the occurrence of bitumen in Roumania and Albania. He is of the opinion that in consequence of chemical reaction, petroleum, mineral tar and asphalt have been formed from marsh gas (CH). He found mud volcanoes associated with the occurrence of petroleum in Sicily, the Apennines, the peninsula of Taman and the plains of Roumania, and concluded that mud volcanoes produced petroleum and other forms of bitumen by converting marsh gas into more condensed hydrocarbons.

Grabowski in an article on the origin of ozocerite advances similar opinions. He says: "Very little is known about the mode of its formation. It appears to me very probable that it is a product of the oxidation and condensation of the petroleum hydrocarbons. * By this hypothesis the formation of petroleum may be reduced to an oxidation of marsh gas, and thus the close connection between ozocerite, petroleum and coal may be explained in the most simple manner."

C. H. Hitchcock has supported similar views.

That mineral tar, ozocerite and asphalt may be formed from