206 I. C. WHITE — THE MANNINGTOS OIL FIELD. 



or four general rules (which include practically all the limitations known to me. 

 up to tin' present time that should be placed on the statement that large gas wells 

 may be obtained on anticlinal folds), viz: 



a) "The arch in the rocks must l>e one of considerable magnitude. 

 (b) "A coarse or porous sandstone of considerable thickness, or. if a tine-grained 

 rock, one that would have extensive fissures, and thus in either case rendered 

 capable of acting as a reservoir for the gas, must underlie the surface at a depth of 

 several hundred fret (500 to 2,500). 



c " Probably very few or none of the grand arches along mountain ranges will 

 be found holding gas in large quantity, since in such cases the disturbance of the 

 stratification has been so profound that all the natural gas generated in the past 

 would long ago have escaped into the air through fissures that traverse all the l>eds. 

 [•It "Another limitation might possibly he added, which would confine the areas 

 where great gas flows may be obtained to those underlain by a considerable thick- 

 ness of bituminous shah'. 



(e) " Very fair gas wells may also be obtained for a considerable distance down 

 the slopes from the crests of the anticlinals, provided the dip he sufficiently rapid, 

 and especially if it he irregular orinterrupted with slight crumples. And even in 

 regions where there are no well marked anticlinals, if the dip he somewhat rapid 

 and irregular, rather large gas wells may occasionally be found, if all other condi- 

 . tions are favorable. 



'"The reason why natural gas should collect under the arches of the rocks is 

 sufficiently plain, from a consideration of its volatile nature. Then, to.,, the exten- 

 sive Assuring of the rock, which appears necessary to form a capacious reservoir 

 for a large ,^as well, would take place most readily along the anticlinals where the 

 tension in bending would he greatest. 



" The geological horizon that furnishes the best gas reservoir in western Penn- 

 sylvania seems to he identical with the first Venango oil sand, and hence is one of 

 the Catskill conglomerates. This is the gas rock at Murraysville, Tarentum, Wash- 

 ington, Wellsburg, and many other points. Some large gas wells have been obtained 

 in tin- Sul .carboniferous sandstone (Pocono), however, and others down in the third 

 Venango oil sand (Chemung). 



" In Ohio, gas flows of considerable size have been obtained deep down in the 

 Cincinnati limestone, while in West Virginia they have been found in the Potts- 

 ville conglomerate: hence natural gas, like oil. has a wide range through the geo- 

 logical column, though it is a significant fact that it is most abundant above the 

 black slates of the Devonian." 



The conclusions announced in the foregoing article were criticised by Mr. Charles 

 A. Ashburner, geologist in charge of the geological survey of Pennsylvania, who 

 claimed, in effect, that the relation between gas wells and anticlinals was one of 

 coincidence merely, or of the same nature as Angell's " belt theory " of oil. and also 

 that large gas wells could he found in synclines. 



To this criticism the writer published the following reply in Science, of July 17. 

 1 885 : 



■" In reply to .Mr. Ashburner's criticism of the view- advanced in my article on 

 natural gas, I would say that the necessary brevity of the paper in question pre- 

 vented the mention of many facts that might have rendered the conclusion- clearer 

 and less open to challenge. < >ne of these is that my communication had especial 

 reference to the natural gas regions proper, L . .. where the gas is unconnected with 



