16 BEREA GRIT OIL SAND IN CADIZ QUADRANGLE, OHIO. [bull. 198. 
upper surface of the water, while the gas passes on to the highest 
attainable point, leaving what may be a considerable distance between 
the accumulations of gas and oil. 
In the second sketch the same forces have acted, forming an accu- 
mulation at H. At I the sand rock has become impervious, and an 
obstruction is formed that nullifies all calculations from the geologic 
structure, for it is evident that the oil and gas accumulations will take 
place at the bottom of the barrier opposed to its movement, though it 
be near the bottom of a decided slope. 
The factors in the problem. — It is evident, therefore, that three impor- 
tant unknown factors affect the accumulation of oil, in addition to the 
fundamental conditions of a petroleum-yielding shale in juxtaposition 
to a porous stratum suitably capped with an impervious layer. 
First and most important is the internal condition of the sand, which 
must be such as to allow the passage of the fluid between its particles. 
Second is the amount of water in the porous stratum, a knowledge of 
which is necessaiy for determining at what point with reference to the 
structure the accumulation of oil may be expected. Third is the geo- 
logic structure, or the slopes of the porous stratum. If the strata have 
a gradual and regular slope over a considerable area, the probabilities 
are that there have been no accumulations of oil of economic value, but 
that the supply which has entered the porous stratum is evenly distrib- 
uted along its upper surface. 
The first two factors, relating to the porosity of the rock and the 
degree of saturation, can be determined only by the expensive method 
of the drill. The third, however, in certain localities may be to a great 
extent elucidated by careful geologic work. It is evident that if the 
cap of the oil-bearing formation formed the present land .surface, so 
that its slopes with its high and low points could be seen, the most 
probable locations for the collection of oil and gas could be readily 
selected. This condition is represented in the accompanying map of 
the Cadiz quadrangle. The surface drainage and the culture, with the 
Government land-survey lines, are represented as a base, upon which 
are shown, by means of 10-foot contours in red, the position, slopes, 
and grades of the top of the cap of the Berea grit oil sand. The pres- 
ent land surface with its hills and valleys is entirety disregarded, and 
the surface represented by the contours is that which the region would 
have if all the rocks above the Berea grit were completely removed. 
THE CADIZ QUADRANGLE OIL FIELDS. 
Location and topography. — The Cadiz quadrangle, Ohio, is bounded 
by parallels 40° 15' and 40° 30', and by meridians 80° 45' and 81° 00'. 
It includes parts of Jefferson, Harrison, and Carroll counties, Cadiz 
being the principal town. Near the western side of the quadrangle is a 
