The Origin of Bitumen — Morgan 47 
tion, hardly any scientific question has been debated more 
vigorously than that as to the origin of bitumens. Now 
that the industry has assumed such commercial importance 
the interest has not lessened. Natural gas, liquid petroleum 
and solid asphalt are universally admitted to have been de- 
rived from a common source, their existence in these varied 
forms to-day being due partly to a process of natural separa- 
tion based on different degrees of volatility and specific grav- 
ity, and partly due to chemical changes wrought by water, 
air, heat and pressure. While each of these substances was 
formerly thought to be of fairly simple composition, extend- 
ed investigation has demonstrated that each is in reality a 
very complex mixture of many individual compounds often 
of widely dififerent chemical nature. 
The various theories that have been put forth to explain 
their origin may be conveniently classed as mineral, veget- 
able and animal, since in each of these "three kingdoms" it is 
believed that a sufficient cause may be found. 
Berthellot first started the mineral theory by announc- 
ing the possibility of deriving certain constituents of natural 
gas and oil by the action of steam and carbon dioxide on 
various metals hypothetically existing in the interior of the 
earth. This hypothesis was later elaborated by Mendeleefif 
and Moissan and made to include carbides of various metals 
which, according to the nebular hypothesis, must have been 
a very characteristic class of compounds at one stage of the 
earth's cooling process. Although these carbides are found 
nowhere in the earth to-day, their existence in meteorites 
in small quantities is supposed to give support to the theory 
and the laboratory production by this means of gaseous and 
oily products that will burn demonstrated this possibilitv as 
suggestively as does the generation of acetylene from cal- 
cium carbide. The fact that the natural products have quite 
a different chemical nature from the artificial product is ac- 
counted for as a modification due to ages of "storing away" 
in the earth's crust. 
The possibility of such an origin cannot be denied. Its 
probability is not great. It is not a question of what might 
have happened but of what has actually taken place that 
primarily interests investigators in this field, and scarcely a 
