48 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
have produced gas ; and those in black were either dry or the product 
has not been reported. Persons familiar with the region will observe 
that in the Washington field and hi general over the northern and 
western portions of the quadrangle the data are very incomplete; 
many wells are omitted, and in others the product is not known. The 
wells shown on the map include only those of which the exact positions 
were noted by the geologists in the field, no attempt being made to 
give any of which the location is doubtful. In portions of the Wash- 
ington field the wells are bunched so close together that their repre- 
sentation on the general map is impossible. In this field, therefore, 
only those wells are mapped of which the records have been obtain el 
and published in this report. The remaining wells and those not accu- 
rately located are omitted, but the approximate limits of the oil fields 
are represented on the map by the green shading. 
DEPTH OF WELLS. 
In the Washington field the wells are only 2,200 to 2,900 feet deep, 
and this is about the average throughout the quadrangle. In the 
Zollarsville field the depth is somewhat greater, averaging 2,700 to 
3,100 feet. The deepest section in the quadrangle is that of the Mrs. 
A. L. Hawkins No. 1 well (31) in the borough of Deemston. This well 
extends 3,611 feet below the surface, or over 3,100 feet below the low- 
est exposed horizon in the quadrangle. 
MODE OF OCCURRENCE OF OIL AND GAS. 
The three requisites for the occurrence of oil and gas are, first, a 
sufficient supply from some source; second, a bed of porous rock in 
which the oil and gas can accumulate; and third, suitable impervious 
confining beds — clays or shales — to prevent the escape of the oil and 
gas into surrounding strata. 
OIL AND GAS SANDS. 
Drillers' names. — In western Pennsylvania all the oil and gas yet 
discovered have been produced from beds of sandstone, or "sands," 
as they are called. The various sands penetrated by the drill have 
been given common or fanciful names by the drillers, and these names 
have come into common usage as descriptive of the various beds. 
Their relations are shown in the following table, which gives the 
driller's name, the depth above or below the Pittsburg coal, and 
the geologic formation to which the sand belongs. 
