562 



SCIENCE. 



[Vol. VIL, No. 177 



The composition of the limestone gas of north- 

 western Ohio (Findlay gas) is quite different, as 

 appears from the following analysis made by 

 Prof. C. C. Howard of Columbus, for the Ohio 

 survey : — 



Findlay gas. 



Hydrogen 2 18 



Marsh-gas 92.60 



Oleflant gas 0.31 



Nitrogen 3.61 



Carbonic acid 0.50 



Carbonic oxide 0.26 



Oxygen 0.34 



Hydrogen sulphide 20 



There are 125.8 grains of sulphur in 100 cubic 

 feet of this gas. 



Analyses made a year apart show that the 

 constitution of the gas has remained practically 

 unchanged during this interval. 



The reference of the gas or oil of shales to lime- 

 stones, or of the gas or oil of limestones to shales, 

 is seen, in the light of these facts, to be inadmis- 

 sible. The two series are distinct. These facts 

 also furnish an additional argument against the 

 chemical theory of origin of the petroleum series. 

 Such an origin w^ould seem to insure identity of 

 composition to at least the oils of a single district. 



8. Gas and oil are accumulated in more or less 

 porous rocks that act as reservoirs. These reser- 

 voirs may be continuous with the source, or they 

 may be distinct. In the case of limestone oil and 

 gas, the first of these conditions is found. The 

 stocks that are held in sandstones come under the 

 second head. 



While there are many horizons of gas and oil in 

 Ohio rocks, covering the three main elements of 

 the series, — viz., sandstone, limestone, and shale, 

 — there are two of paramount importance; viz., 

 the Trenton limestone and the Berea grit. The 

 Trenton limestone nowhere rises to the surface in 

 Ohio. It was first discovered to be a storehouse 

 of high-pressure gas at Findlay in November, 1884. 

 It is now yielding both gas and oil in large amount 

 in at least three counties of northern Ohio, — viz., 

 Hancock, Allen, and Wood, — and it promises to 

 become by far the most important source of these 

 products in the state. The section by which it 

 is reached in the productive districts is as fol- 

 lows : — 



( Waterlime. 

 20O'-40O' Limestone, upper Silurian. . -j Niagara. 



/ Clinton. 



I Medina. 



hOO'-lCOO' Shale, mainly lower Silurian 4 Hudson River. 



( Utica. 



f Gas and oil accumu- 

 I luted in uppermost 



500' Trenton limestone J bfJ(ls : ofte " at U P.* 



per boundary, and 



I never more than 40 



I leet below. 



The main production of this new horizon has, 

 so far, been limited to points where its upper 

 boundary ranges between three hundred and five 

 hundred feet below^ sea-level. It has been reached 

 in at least a hundred drill-holes within the last year, 

 through a district which would include from eight 

 thousand to ten thousand square miles. The com- 

 position is shown by the following analyses of the 

 gas-rock of Findlay and the oil-rock of Lima, 

 w^hich are one and the same thing. 





Findlay. 



Lima. 





47.05 



52.66 





33.38 



37.53 



Residue, mainly siliceous 



11.73 



4.15 



The rock is highly crystalline and porous, and the 

 greatest porosity seems to belong to the most 

 productive portions. 



The Berea grit becomes petroliferous from the 

 moment that it takes cover. The oil of Mecca 

 and of Grafton is derived almost from the outcrop 

 of the rock. In the first instance, indeed, it has 

 only the bowlder clay for a roof ; and, in the sec- 

 ond, there are but from forty to sixty feet of Berea 

 and Cuyahoga shale above it. It is only where 

 it descends deeper, however, that it holds large 

 stocks of gas or oil. The lightest cover under 

 which large accumulation has been found in 

 Ohio is six hundred feet, while in the Macks- 

 burg field, which is at present the main centre of 

 production from this horizon, the stratum is at 

 least twelve hundred feet below the valley level. 

 The section found here is approximately as fol- 

 lows : — 



Coal-measure strata 5C0'-800' 



Conglomerate measures 200'-300' 



Logan conglomerate (salt-water sand) 200' 



Cuyahoga shale 300' 



Berea shale 30 '-50' 



Berea grit 5'-25' 



There are two distinct oil-sands in the coal-meas- 

 ures, and one in the conglomerate group in this 

 section, in addition to the Berea. 



These reservoirs, whether sandstone or lime- 

 stone, are permeable, and often communicate 

 freely through considerable space. The gas-wells 

 of Findlay are quite unequal in production, ran- 

 ging between one hundred thousand and twelve 

 million cubic feet per day ; but when shut in, all 

 show the same pressure. This pressure is now a 

 little less than four hundred pounds to the square 

 inch. It is called the rock-pressure. A large 

 well, when shut in, comes up to this point quick- 

 ly, and a small well slowly, but all get to the 



