168 Frank Carney 



tives. As a result, the hydrocarbons are very complex in composi- 

 tion. For over a century, students have been wrestling with the 

 question of their origin, the interest usually centering about oil 

 and gas. Two theories have been advanced; one has many 

 advocates. 



The inorganic theory. This is sometimes referred to as the 

 chemists' theory for the origin of oil and gas. Stated briefly it 

 is this : Steam, in the presence of carbides of iron or other metals, 

 will form hydrocarbons. This is a laboratory demonstration. 

 It is urged, therefore, that percolating ground water, reaching the 

 deeper parts of the earth, produces steam which in the presence of 

 carbides of metals forms hydrocarbons. If this theory operates 

 in nature, both oil and gas, as well as other hydrocarbons, should 

 be very widely distributed. The movement of ground water takes 

 place through all rocks, those of both the continental platforms and 

 the ocean basins. Man, much to his disappointment, has found 

 that these fuels are localized ; not many areas of any one continent 

 have either oil or gas. The theory itself is perfectly tenable. This 

 supposed natural plan for the origin of hydrocarbons is very 

 similar to the artificial method of manufacturing acetylene gas. 

 Only in the last few years has a line of investigation tended to 

 show that hydrocarbons produced by steam and carbides of 

 metals do differ from the hydrocarbons found in nature.^-* This 

 difference I refer to in the next section. 



The organic theory. In nearly every state, rock formations, 

 bearing gas or petroleum, contain fossils of animals or of plants 

 or of both. Some students urge that the hydrocarbons are formed 

 by the slow distillation of this organic material. In the labora- 

 tory, men have made several of the hydrocarbon derivatives by 

 distilling fish oil. Natural gas, too, frequently occurs in coal 

 mines, known as ''fire damp." Practically no oil or gas has 

 been found in the crystalline rocks. Fossils do not occur in 

 these rocks. Furthermore, rocks containing fossils sometimes 

 have a very distinct petroleum odor ; limestones on Kelly's Island 

 is an example. 



The organic theory, then, contemplates the slow distillation of 

 organic remains in the rocks. Along certain tracts of the ocean 

 borders, lakes and rivers to-day, organic remains, plant and ani- 



i» Economic Geology, vol. iv, (1009), pp. 626-27. 



