308 ANNUAL REPORT 
same substances and probably in the same general manner. For these 
reasons the two will be considered together in this chapter. 
Of the theories propounded that have received serious consideration, 
two classes may be recognized: 
First those which assign to these products an inorganic origin. These 
maintain that oil and gas have been produced by the reactions of inorganic 
substances. In general it may he stated that this class of theories has been 
advocated by chemists, and at the present time some eminent scholars con- 
tend that this is the most reasonable view to take of the subject. This 
class might be called the chemical. 
The second class of theories assigns an organic origin. That is, that 
oil and gas have been formed in some manner from organic matter, either 
animal or vegetable or both. As to how the changes have been produced, 
however, there is much difference of opinion. While this class has been 
advanced by some chemists, it has been most strongly advocated by geol- 
ogists, and might well be called the geological. These theories will now be 
considered with some detail. 
- THE INORGANIC OR CHEMICAL THEORIES. ‘ 
While many theories have been propounded that fall in this class, a few 
only need be considered here. In 1866 Bertholet, a distinguished French 
chemist, argued that petroleum has been produced by the action of water 
containing carbonic acid on alkali metals deeply buried in the earth and 
hence highly heated. He appears to have adopted Daubree’s hypothesis 
that the earth contains in its interior large quantities of these metals, es- 
pecially sodium and potassium. He found by experiment that when car- 
bonic acid acts on hot alka:i metals, acetylides are formed, and that these 
bodies when treated with vapor of water produce hydrocarbons resembling 
petroleum. 
In 1871 Byasson presented a theory maintaining that petroleum has 
. resulted from the action on each other of water vapor, carbonic acid, sul- 
phuretted hydrogen and hot iron. This theory also has some support from 
the laboratory for Byasson claims to have obtained in this manner pro- 
ducts resembling petroleum. The vast repositories of oil found in nature, 
he thought, were produced by sea water containing carbonic acid or lime- 
stone in solution percolating deep into the earth and then acting on metallic 
iron or iron sulphide. . 
The inorganic theories were strengthened in 1877 by Mendelejeff, 
one of the most distinguished chemists of the day. He argued that the in- 
terior of the earth contains metallic carbides, that is metals, especially iron 
combined with carbon. Water coming in contact with these highly heated 
carbides would, he claimed, start reactions which would produce hydrocar- 
bons, and convert the metals into oxides. This theory also is supported 
by laboratory experiments. The manufacture artificially of acetylene gas 
