63 



of man, were diminished in quantity to be still later scattered by 

 the Flood to localities where mineral fats are now found. 



Theories on the origing of Petroleum fall into two or three dis- 

 tinct types. I. Cosmical theories, which are almost entirely pure 

 speculation with a very meagre basis of evidence. Sokolow, for 

 instance, stresses the facts that absorption lines characteristic of 

 hydrocarbons occur in the spectra of certain stars and that hydro- 

 carbons occur frequently in meteorites. P. H. Bouligny, of 

 spheroidal state fame, developed a theory in which he went so far 

 as to suppose a sort of downpour of mineral oils in the form of 

 rain. 



II. Inorganic theories as to the origin of oils are chiefly re- 

 presented by that of the great Russian chemist, Mendeleef (J.C.S., 

 Vol. III., p. 28 (1877)), where he assumed the existence of iron 

 carbides at some depth in the earth's crust which generated hydro- 

 carbons in contact with percolating water. Both he and the 

 French chemist, Cloez, who independently came to the same con- 

 clusion, synthesised petroleum-like hydrocarbons by the action of 

 such simple re-agents as superheated steam and weak acids on 

 various iron carbides. This carbide theory had many adherents, 

 especially in the last decade of the 19th century, and much interest- 

 ing laboratory work was done under its stimulus. Moissan pro- 

 duced carbides of practically all known metals with his electrical 

 furnace and studied the action of water on them, obtaining a 

 variety of hydrocarbons — uranium carbide for one yielding a 

 mixture of liquid hydrocarbons. 



Sabatier and Senderens in their classic research on hydro- 

 genation by means of finely divided nickel as catalyst synthesised 

 a petroleum-like substance from acetylene; this varied in com- 

 position, resembling either Pennsylvanian, Caucasian, Galician or 

 Canadian oils, according to conditions of the reaction. 



Another inorganic theory of a distinct type urges the likely 

 origin of oil as a bye product of volcanic or solfataric action, but 

 there being no trace of volcanic or solfataric action in Kimmeridge 

 Glay this theory need not detain the present account. 



III. The Organic theories fall into two sub-classes as the 

 origin is sought among plants or among animals. Even before 

 Racquet's suggestion of the likely animal source of mineral oils 

 Fr. v. Beroldingen, one of the founders of the modern theory of 

 the origin of coal, ascribed the derivation of "earth-fats" to 

 decayed vegetable substance. But while the most stable vegetable 

 substance, cellulose, containing 49 per cent, of oxygen, is slowly 

 converted into coal, the corresponding substance in animals, fat, 

 contains 11 per cent, oxygen, and this would appear the most 

 probable source of the bituminous matter in oil shales, and 

 through this of petroleums. 



The generally accepted theory of the organic origin is that of 

 Engler^ who considers the bodies of abundant fish and reptiles of 

 the ancient seas to have been sufficient to supply the vast stocks 

 of mineral oil and bituminous shale. Engler's experiments took 



