62 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
PRESSURE OF NATURAL GAS. 
The original pressure of gas in the Washington County district was 
about 500 pounds to the square inch, minute pressure. Since its dis- 
covery every gas field in the State has exhibited a constantly dimin- 
ishing pressure. The pressure is different for the different sands and 
also varies for a given sand in various parts of the field. Few pres- 
sure records are available for publication. 
THEORY OF OIL AND GAS. 
Early in the history of oil and gas development attempts were 
made to discover some means of predicting their occurrence. Since 
is,")«) various geologists and others have published papers attempting 
to solve this problem. Among others T. Sterry Hunt (1859 and 
1863), E. B. Andrews (1861), and 11. Hoefer (1876) long ago recog- 
nized certain general relations of oil and gas pools to the anticlinal 
structure of the region. It remained for I. C. White and Edward 
Orton to bring the occurrence before the public in such a way as to 
force a measure of belief in the theory which they advanced. 
THE "ANTICLINAL THEORY." 
In an article on the geology of natural gas, published in 1885/ 
White first formulated the "anticlinal theory," in which he showed 
that nearly all the great gas wells and pools are situated near the 
crests of anticlinal folds; while wells bored in the synclines on one 
side or the other of the anticlines more often obtained little or no 
gas but in many cases large quantities of salt water, hi 1892 the 
same writer published a paper, 6 in which he extended the theory to 
include the occurrence of oil as well as gas, and stated how he had 
located the Washington, Mannington, and other large fields by means 
of the principles involved in the theory. 
The view is, in brief, that when the rocks are gentl} tilted the oil, 
gas, and salt water contained in them are caused to separate out in 
the order of their densities; water (if present) in the synclines, oil 
next above, and gas nearest the crests of the anticlines. In western 
Pennsylvania and northern West Virginia these accumulations take 
the form of belts approximately parallel with the axes, in a general 
nort heast-southwest direction. White states various apparent excep- 
tions, but in reality modifications, of the theory, due to the nonpar- 
allelism of surface beds with the oil and gas rocks, etc. 
Considerable has been written, pro and con, about this theory by 
various geologists and others, and some have seriously doubted 
whether it is true. By most geologists the theory is now accepted, 
not, however, as absolute in its limitation of the occurrence of oil 
a Science, June 26, 1885. While .^ives credit to W. A. Earseman, an operator of Pittsburg, who had 
previously noted the relations of oil and gas to geologic structure. 
I he Mannington oil field and the history of its development : Hull. Geol. Soc. America, vol. 3, 1892, 
pp. 187-216; reprinted in part in West Virginia Geol. Survey, vol. 1 (a), Oil and gas, 1904. pp. 54-59. 
