230 The American Geologist. -^i'"'' ^^os. 
figure. Farther south in Hocking county similar conditions 
are found. It appears that these small reservoirs are separ- 
ated by strata that are practically impermeable, and conse- 
quently that one may be drawn on or even exhausted without 
materially affecting the adjacent reservoir. . This is a marked 
contrast with the results experienced in the Trenton limestone 
territory of northwestern Ohio. 
Composition of the Gas. 
Below is given an analysis of gas from the Thurston field, 
the work having been done by professor C. C. Howard of 
Starling Medical College. 
Carbon dioxide 
.25 per cent. 
Oxygen 
.15 " " 
defines 
.30 ••' " 
Carbon monoxide 
■15 " 
Nitrogen 
8.12 " •• 
Jriyclrogen 
Paraffines (Marsh 
gas 
etc.) 
■ 55 
90.48 " 
For comparison there is given an analysis, made by the 
same chemist, of natural gas from the Trenton limestone at 
Findlav.* 
Marsh gas 
92.61 per cent 
Olefiant gas 
.30 " " 
Hydrogen 
2.18 " " 
Nitrogen 
3.61 " " 
Oxygen 
■34 " " 
Carbonic acid 
.26 " " 
Carbonic oxide 
■ 50 " " 
Sulphuretted hydi 
■ogen 
.20 " " 
Search for the Clinton in Eastern Ohio. 
Many wells have been drilled within the past few years in 
the eastern part of the state, especially in the counties border- 
ing on the Ohio river, for an oil or gas rock below the Berea 
grit. The object has been to find one of the deeper sands 
known in Pennsylvania and West Virginia, and if not success- 
ful in this to proceed until the Clinton is reached. 
These trials have disclosed an interesting fact with reference 
to the thickness of the Ohio shales, lying between the Berea 
grit and the Corniferous limestone. Thus at Lancaster these 
shales have a thickness of 702 feet, near New Lexington, 
t Vol. vi.. p. 136. 
