Ohio Natural Gas Fields.- — ■ Bowiwckcr. 227 
quantity of carbonate of lime, this being most abvindant in the 
thirty-five feet above the gas rock. Well drillings strongly in- 
dicate that the green and chocolate colored shales are inter- 
stratified with calcareous ones. 
The gas rock is a light colored sandstone of moderate grain. 
It drills hard, suggesting that the parts are well cemented. 
The thickness of the stratum is not definitely known ; espec- 
ially is this true in the Sugar Grove field, where it has rarely 
been drilled through. The maximum reported from that ter- 
ritory is thirty-four feet, and the average is perhaps one-half of 
that. Around Homer the sand is drilled through ; five wells 
selected at random showing thicknesses of 10, 28, 8, 12 and 18 
feet, an average of 15 feet. 
Below the gas sand there is found a thin bed of shales com- 
monly ranging from ten to thirty-five feet in thickness. This 
has a dark color and is succeeded below by dark red shales. 
Since work nearly always stops before the latter are reached, 
or when they have been penetrated a few feet, thus making 
certain that the horizon of the gas sand has been passed, data 
bearing on their thickness are meager. The record of the Mc- 
Nichols well, previously given, credits 100 feet to the form- 
ation. The top of this red rock is regarded as the summit of 
the Medina. 
Life of Wells. — This depends on several factors, such as 
nature of gas rock, closed pressure, initial flow, acreage per 
well, rapidity with which the gas is used, salt water, care taken 
of wells, etc. The short life of the Thurston field has already 
been noted. That of the territory around Newark was longer 
because the demands made on the wells were not so heavy. 
The following table was compiled from wells in the Sugar 
Grove field. It shows the original rock-pressure and open 
flow, the decrease of these, and to some extent the life of the 
wells. The data are taken from wells that have been prac- 
tically in continuous use. Doubtless records could be secured 
from this teritory that would show a greater period of pro- 
duction than any wells contained in this table. 
