^6 PETKOLEUM AND NATUKAL GAS. [Feb. 5, 



ture. Cloez, in 1877, also obtained petroleum-like hydrocarbons 

 by the action of dilute acids, and even of boiling water, upon the 

 carbides of iron such as exist in spiegeleisen. In the paper of the 

 Russian chemist Mendelejeff, however, published also in 1877, this 

 theory is most fully elaborated. The existence of metallic carbides 

 in the depths of the earth he considers likely from the fact that 

 similar carbides are found in meteorites, and that metallic iron may 

 occur in large deposits in the interior of the earth he considers 

 possible, because the mean specific gravity of the earth, 5.5, is 

 notably higher than that of ordinary rock material. If, then, water 

 be supposed to have infiltrated through fissures in the earth's crust, 

 we have the conditions shown by experiment as capable of yielding 

 petroleum-like hydrocarbons. The same steam which, acting upon 

 the metal or metallic carbide, was capable of forming the petroleum, 

 could also force its vapors when formed through the fissures until 

 on cooling they condensed and were absorbed in strata capable of 

 holding them in liquid form. The eminent geologist Abich, who 

 had made a study of the Caucasian oil field, also joined in the 

 acceptance of this theory of Mendelejeff, and it may be said to be 

 the one of the inorganic theories that has found the most general 

 indorsement. 



The great preponderance of belief is, however, at the present 

 time against this or any other theory based upon purely inorganic 

 materials or reactions. The entire absence of petroleum from the 

 archaic formations, from which traces of fossil life are also absent, 

 and the occurrence of the petroleum in sedimentary formations 

 which have been free from any volcanic or metamorphic disturb- 

 ance, go to render these emanation theories improbable. The fact, 

 moreover, that while the hydrocarbons of petroleum show a range 

 of temperature of condensation from 0° to 300°, which would 

 necessarily distribute them in different strata if they rose from the 

 interior in vapor form, we find them all, from the highest to the 

 lowest, admixed in one and the same oil-bearing formation, also 

 speaks against the probability of the theories stated above. 



Turning now to the theories of the organic origin of petroleum, 

 we note first the belief that it comes essentially from vegetable 

 sources. Thus Prof. Lesquereux considered that the Pennsylvania 

 oil was formed from the remains of marine algae, because the Devo- 

 nian shales which accompany the oil formation contain an abund- 

 ance of fossil fucoids. It is pointed out, however, by Hofer and 



