PETROLEUM AND NATURAL GAS. 
43 
with its producing areas, is shown near the southwest corner of 
Pennsylvania. 
While oil and gas wells are widely scattered over the territory, 
the great majority of them are limited to certain groups or fields, 
in which the oil and gas appear to occur in so-called pools or reser- 
voirs of some extent. The term field, as used in this report, means 
Yj 
Gas Oil 
Fig. 2.— Map of oil- and gas-producing areas in the northern Appalachians. 
simply a group of producing wells, or wells which have produced 
in the past, and it is not implied that outside of the field the terri- 
tory is unproductive. It is probable that in time other sections of 
the region will be found to contain more or less oil and gas. 
In this quadrangle oil is much more limited in its occurrence than 
gas, and so far as known it occurs almost entirely in one area — the 
