PALEOZOIC TIME — LOWER SILURIAN. 523 



at the rate of 20 to 25 millions of cubic feet of gas per day, and half the 

 whole amount came from a single well, the Karg well. One boring in the 

 vicinity, at Bairdstown, yielded 4,000,000 cubic feet per day when 9 feet 

 down in the limestone, and 12,400,000 when 17 feet down; and the tools 

 " refused to descend deeper, dancing in the well like rubber balls." (Orton, 

 Rep. Econ. G. Ohio, 1888.) 



The rock pressure in some parts has been found to equal 650 pounds to 

 the square inch; in the Findlay field it is about 450 pounds ; in the Indiana 

 field about 320 pounds. Owing to the pressure, the gas, as it is confined in 

 the Trenton limestone, is greatly condensed, — its volume, if the pressure 

 equals 320 pounds to the square inch, being about -j^th of that after escape. 



The productive limestone, as stated by Orton, is in all cases dolomyte. 

 In the Findlay region the composition was found to vary from a ratio, for the 

 calcium and magnesium, of 1 : 1 to that of 2 : 1. The marsh conditions under 

 which dolomyte is formed are favorable for the gentle trituration or mace- 

 ration of organic materials, and their inclusion in the deposits so made. It 

 is found, also, by Professor Orton, that the limestone is porous, and is thus 

 enabled to contain the oil or gas. Since the conversion of calcyte to dolomyte 

 causes a diminution in bulk of yL to -|- (page 134), the pores, which are a 

 result of the change, should give the rock great containing capacity — equal, 

 says Orton, to the actual amount afforded. 



The amount of marsh gas (ordinary illuminating gas) in the mineral 

 gas of Findlay is about 92-5 per cent ; and with this are 2 per cent of hydro- 

 gen, 0-3 of olefiant gas, 3*5 of nitrogen, and about 0-5 per cent each, of oxy- 

 gen, carbonic acid, and carbonic oxide, and 0-2 of hydrogen sulphide. In 

 the region of Lima, Ohio, the limestone yields oil. Salt water, also, comes 

 up in some borings. In the borings water is excluded by tubing. The pro- 

 duction of the wells is often greatly increased by lowering torpedoes con- 

 taining from 20 to 160 quarts of nitro-glycerine to the bottom of the well 

 and exploding them by means of a piece of iron called a " go-devil," which 

 is dropped down the hole and strikes a fulminating cap on the torpedo. The 

 whole process is termed " shooting " a well. The explosion shatters the 

 rock and opens fissures. Thus the area of supply is extended and the yield 

 of oil or gas increased. 



In Indiana the natural gas territory adjoins the eastern, or Ohio, 

 boundary for about 65 miles, and has an average width of 50 miles. The 

 porous layer, according to A. J. Phinney, is 1 to 20 feet thick, and lies 

 beneath a non-porous outer layer of the limestone, 1 to 15 feet thick ; and 

 the rock is sometimes so open-textured that air may be freely blown through 

 it, and it will absorb -^ or even i- of its weight of water. In 1890, the 

 aggregate daily flow of the Indiana gas wells was 779,525,000 cubic feet. 

 (Phinney, U. S. G. S. Rep.) The Trenton limestone has afforded no gas or 

 oil in Kentucky or Pennsylvania. 



Marbles. — The Chazy affords black marble in the vicinity of Lake Cham- 

 plain. The Taconic crystalline limestone yields white and clouded statuary 



