GRISWOLD.] 
MODE OF ACCUMULATION OF OIL AND GAS. 
15 
from water. This condition of complete or partial saturation of the 
porous rocks becomes of the greatest importance in the application of 
the anticlinal theory to the accumulation of oil. The natural gas, by 
reason of its less specific gravity than water, oil, or air, will continue 
to rise in a porous rock until stopped by an impervious cover. The 
oil, on the other hand, can continue upward only so long as it has the 
water upon which to climb, and must, therefore, stop at the water line, 
although this may be but part way up a decided slope. The accom- 
panying sketch, representing an imaginary section through folded 
strata of petroleum-bearing shale and a porous sandstone capped with 
an impervious limestone, shows the theoretical method of accumulation 
of the hydrocarbons. 
a4: 
y 
Fig. 1. — Ideal section showing method of accumulation of oil and gas. 
The oil and gas, entering the sand rock all along its base, work their 
way to the roof A, and gradually creep along to the right to the bend 
or crest of the terrace at B, where the strata become so nearly level 
that the horizontal tendency of the oil particles is not sufficient to 
overcome the friction through the sand, Avhile the gas, having more 
buoyancy, and therefore more force of lateral motion, moves on, 
leaving the accumulation of oil, unaccompanied by much gas, at the 
break represented at B. The hydrocarbons entering between C and E 
gradually work upward until a dome, or anticline, is reached at D, 
which completely captures both gas and oil. From E to G the tend- 
ency is to work toward G, but the higher portion of the sand rock is 
not completely saturated with water, and the oil can move only to the 
