472 NEW YORK STATE MUSEUM 



felt quite encouraged in his Stillwater well, already described, 

 when chips were brought up showing the presence of abundant 

 fossils. These chips agreed perfectly in appearance with frag- 

 ments of the Orthis testudinaria beds from Trenton Falls and 

 other well known horizons of the limestone. 



On grounds like these it seems necessary to class the Bald- 

 winsville gas fields with the Pulaski and Sandy Creek fields. 

 The gas lies much deeper and there is a much larger production, 

 but it is essentially of the same character. The difference be- 

 tween the two varieties has already been pointed out on the 

 preceding page, but in respect both to volume and rock pressure 

 the Baldwinsville wells are far in advance of all the rest that 

 are referred to the same division. A few hundred thousand feet 

 of gas a day and a few hundred pounds of rock pressure make 

 the record of the largest shale gas wells hitherto observed and 

 recorded. 



In regard to this last element, viz, rock pressure, the facts of 

 the Baldwinsville field oblige us to extend the explanation that 

 has thus far been counted sufficient for shale gas wells far 

 beyond the limits heretofore recognized. The pressure in shale 

 gas fields has long been counted due to the expansive force of 

 the gas as it is generated. No other force adequate to the pro- 

 duction of the result has been discovered. 



The case is entirely different in the matter of reservoir gas, 

 i. e. of gas stored in porous rocks that are also occupied by other 

 fluids. The facts derived from the new fields of Ohio and 

 Indiana brought to light another cause at once true, real and 

 efficient, that gave a rational and intelligible explanation of all 

 the phenomena involved. 



It was observed that when salt water was struck in the Tren- 

 ton dolomite it rose throughout the field to a fairly uniform hight 

 of 600 feet above tide. Its ascent was obviously referable to 

 artesian pressure. No other explanation is worth a moment's 

 consideration. But the artesian pressure that forces water to 

 rise in the porous rocks, would exert an equal pressure on any 

 other fluid, as oil or gas, inclosed in the same porous rock. It 

 was farther found that by taking account of the specific gravity 

 of the salt water, the pressure, which is apparently due to 600 

 feet of the water, could be measured in pounds. The weight of 



