1888. | NEW YORK ACADEMY OF SCIENCES. 27 
coals have been formed by the solidifying and compacting of 
ancient petroleum in fissures and seams, as at Canajoharie, N. Y. 
(in the Utica shale), and in the grahamite seams in West Vir- 
ginia; while in the Laramie rocks of N. W. Colorado there are 
“< veins ” of albertite several feet thick, evidently resulting from 
the hardening of petroleum derived from the Colorado shales 
beneath. 
All the indications point clearly to organic matter deposited 
in sedimentary rocks, as the source of all these carbonaceous 
materials. Exposed to the atmosphere, such matter rapidly de- 
composes into gaseous products, mainly carbonic dioxide and 
water-vapor. But shut off from the free access of the air, either 
under water or buried in sediment, a series of complicated 
changes sets in, by chemical reaction among the constituent ele- 
ments of the organic matter itself. These form among them- 
selves a variety of products, solid, liquid, and gaseous. The 
latter gradually escape, rising into overlying beds, where they 
often accumulate in cavities, if such there be, and form reser- 
yoirs of natural gas and light oils. The heavier products re- 
main below, blackening the rock with their residual carbon and 
hydrocarbons, which latter are ready to go on with the process of 
further loss of volatile matter, as long as any remains. 
Processes of a similar kind are constantly in progress, and 
may sometimes be witnessed on a small scale. In pools of water, 
where decaying vegetable matter has accumulated at the bottom, 
both oily and volatile products are formed. A thin film of oil may 
be observed on the surface of the water, and marsh-gas (so 
named from this familiar fact) is given off in bubbles upon 
stirring the mud with a stick. 
All these facts point unmistakably to organic matter as the 
source of natural gas-wells and oil-springs, as well as of the coals 
and asphalts in all their forms. Most of the material is doubt- 
less vegetable, though some small amount may be derived from 
animal remains, as, é. g., adipocere is not unfrequently cast up 
on the sea-shore. But these cases are exceptional. 
Such considerations aid us toasolution of the question regard- 
ing the permanence of the oil and gas supply. Three points 
will be clear, viz.: (1.) Such wells and springs will be confined 
to strata underlain by large deposits of organic matter, as coal or 
bituminous limestones and shales. (2.) Oil and gas will escape 
from such strata as long as any organic matter is left. (3.) The 
daily amount produced will be small, and no large accumulations 
can form, save in cases where two conditions are present, viz.: 
fissured or porous rocks, which may serve as reservoirs for the 
distilled hydrocarbons; and impervious beds above, which will 
prevent their escape. In such cases, the slow yield of centuries 
