geiswold.] RELATION OF OIL POOLS TO GEOLOGIC STRUCTURE. 13 
located upon or near the lines of anticlinal arches. This important 
deduction has been expounded and developed by Prof. I. C. White, of 
Morgantown, W. Va., who has published his conclusions, and has suc- 
cessfully located both gas and oil wells by means of the so-called anti- 
clinal theory. 
Relation of oil pools to geologic structure. — Petroleum, being of less 
specific gravity than the saline waters found in the porous strata 
beneath the surface, is undoubtedly affected by the slope of the rocks 
in which it is contained, and tends to collect along lines of nearly 
equal elevation which parallel the folds of the strata. With this fact 
in mind, it becomes very easy to account for the 45° and 22° lines 
which occupied so prominent a place in the early development of the 
Pennsylvania field. The Appalachian oil field occupies the western 
flanks of the Appalachian Mountains, the axes of its minor folds having 
a general parallelism with the folds of that mountain system. Where 
oil was first discovered these folds have a nearly northeast-southwest 
direction, but in extending southwest their divergence from true 
north and south became less, as does that of the major folds of the 
mountains themselves. 
In looking over maps of the oil and gas producing territory, notably 
those published by the geological surveys of Pennsylvania and West 
Virginia, and comparing them with maps showing the geologic struc- 
ture, the gas and oil producing belts and folds are seen to have the same 
general direction. But there are some notable exceptions to this 
general statement, if the published information as to the direction of 
the structure axes is correct. The mapping of the structural lines, 
however, has been but meagerly and imperfectly done. The minor 
antivlinal arches have been represented as extending for long distances 
in straight parallel lines. More detailed work will probably show 
that their axes are not straight and parallel, but meander with more 
or less irregularity. This is indicated by the recent work of Marius 
R. Campbell in Armstrong and Butler counties, Pennsylvania, where 
the Bradys Bend anticline, instead of continuing in a northeast-south- 
west direction, makes a sharp bend due west and passes out of Arm- 
strong into Butler County. a 
It may be assumed in general, therefore, that the minor anticlines 
do not have anything like the regularity shown on most of the maps 
now published. They are probably curved and irregular, even much 
more so than are the larger folds which occur in the mountainous belt 
to the cast. Hence, it would be unsafe to consider any seeming dis- 
crepancy between the lines of oil development and the axes of the an- 
ticlinal arches as now published as evidence against a theory until very 
careful geologic work has been done to actually locate the folds. 
aEng. and Min. Jyur., February 15, 1<J02. 
