1890.] Geology and Paleontology. 661 
GEOLOGY AND PALEONTOLOGY. 
The Origin of Petroleum and Gas. — The following state- 
ments bring before us the principal views as to the origin of petroleum, 
viz: 
1. Petroleum is produced by the primary decomposition of organic 
matter, and mainly in the rocks that contained the organic matter. Of 
this view, Hunt is one of the chief advocates. 
2. Petroleum results from the distillation of organic hydrocarbons 
contained in the rocks, and has generally been transferred to strata 
higher than those in which it was formed. Newberry and Peck 
have been quoted at length in support of this general theory. New- 
berry holds that a slow and constant distillation is in progress at low 
temperatures. Peckham refers the distillation of the petroleum of the 
great American fields to the heat connected with the elevation and 
metamorphism of the Appalachian mountain system. 
These views as to the date of the origin of petroleum and gas are 
seen to cover almost all the possibilities in regard to the subject. Hunt 
believes petroleum to have been reduced at the time that the rocks that 
contain it were formed, once for all. Newberry believes it to have been 
in process of formation, slowly and constantly, since the strata were 
deposited. Peckham refers it toa definite and distant time in the 
past, but long subsequent to the formation of the petroliferous strata, 
e supposes it to have been stored in its subterranean reservoirs from 
that time to the present. 
In these several statements as to origin, two questions are seen to be 
especially prominent, viz: What particular kinds or classes of rocks 
‘are the sources of petroleum? and, What is the value of the chemical 
processes involved in its production ? 
In answering the first question, we find the views of Hunt and New- 
berry distinctly opposed to each other. Hunt counts limestones the 
principal source of petroleum, and denies that it has been produced by 
distillation from bituminous shales; while Newberry finds in these 
shales the main source of both oil and gas, and vigorously opposes the 
view that limestones are ever an important source of either.! 
It is not necessary to follow the discussion in relation to these points 
further. It is enough to say thatin the light of present knowledge 
each statement is sustained as to its particular affirmations and incon- 
clusive as to its general denials. Petroleum is undoubtedly indigen- 
1 Rept. Geol. Survey Ohio, Vol. I., p. 159. 
