338 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
given in the location of this line of complete saturation had the unsuc- 
cessful test wells of the past been divided into two classes, as salt- 
water wells and dusters, instead of calling them all dry holes, as has 
generally been done. 
The question of saturation does not assume the same prominence 
when searching for gas, though had it been noted and reasoned 
from, it would have saved many thousands of dollars expended in 
searching for oil near large gas wells. 
In territory where the anticlinal folds are entirely below the satu- 
rated area the water-line theory is of no value, as the accumulations 
of gas are in the anticlinal arches, with the oil immediately below. 
Under this condition the crest of the anticline should be followed to 
find productive territory and the extent of the gas accumulation 
determined by test wells. 
AREA SURVEYED. 
The area selected for investigation in 1901 was the Cadiz quadran- 
gle, an area containing about 240 square miles in Harrison and 
Jefferson counties, Ohio, and lying east and norch of the town of 
Cadiz. The surface forms a plateau, which has been dissected by the 
streams to a depth of nearly 300 feet, exposing in outcrops six or 
seven easily distinguished beds of limestone and coal. The geologic 
section extends upward from near the base of the Conemaugh (Lower 
Barren) Measures to about the middle of the Monongahela (Upper 
Productive) Measures. The Pittsburg coal outcrops in the lowest 
valleys in the southeast corner and tops the highest hills in the 
northwest corner of the quadrangle. 
Parallelism of strata. — As these beds are of sedimentary origin it is 
evident that there must be a certain degree of parallelism between 
the strata, hence a stratum lying 1,000 or 1,500 feet below the surface 
may be platted by data obtained from deep. wells and from the out- 
cropping strata with the same degree of accuracy as one but a couple 
of hundred feet below. The distance between two prominent strata, 
such as an outcropping coal at the surface and an oil sand below, 
maybe increasing or decreasing. In the Cadiz quadrangle the dis- 
tance from the top of the Pittsburg coal to the cap of the Berea grit 
sand is 1,481 feet at tin' Bricker oil pool, 1,490 feet at Hopedale, 1,527 
feet at Bloomfield, and 1,564 feet at Smithfield. 
The rate of variation of the interval between two strata can be 
determined only by actual boring tests. Over the Appalachian oil 
fields such tests have been made in great numbers by the "wild cat" 
wells searching for oil. There is hardly a portion of the country lying 
within the now producing oil fields where the record of such a well 
can not be obtained within a distance of 5 miles from a given point. 
In extending the platting of substrata into entirely new territory 
a rate of increase or decrease must be assumed, which introduces a 
degree of uncertainty into the results. 
