123 5 GEOLOGY OF OHIO. 
in coals for producing gas. For instance, one coal will produce 4 feet of 
14.5 candle gas, another 4.40 feet of 16 candle gas. Now, if the two 
coals produce about the same weight and character of coke, it is quite 
a common error to rate the second coal as about 10 per cent. better than 
the first. As the object to be attained in the decomposition of coal is 
light, a simple calculation will show the fallacy of such rating: 
440 x 16= 70.40 candle feet. 
4,00 « 14.5 = 58.00 candle feet. 
Difference, 12.40 candle feet. 
Or, 17.61 per cent. 
In most mines of this State driven in on coal No. 6, or the great vein, 
there are found three members of the seam, the lower member being 
the softest and apparently the best part of the vein. The second mem- 
ber is much the thickest and usually of good quality. The third or 
upper member is sometimes missing, and often of poor quality, con- 
taining a large per cent. of ash. In the Hocking Valley district this 
member is often left to form the roof of the mine. 
Sometimes this member is found to be a fair cannel coal, very rich 
in light-producing gas, as is shown by test numbers XIV and XVI; the 
yield of gas is quite good, and the quality of the gas most excellent, 
being of higher illuminating power than was obtained from a test of the 
justly celebrated cannel coal of the Kanawha Valley. Whether there 
is sufficient quantity of this coal that partakes of the cannel charac- 
teristics to make it of economic value, the writer is not prepared to say. 
The question is one, however, worthy of thorough investigation. 
The coke made from this coal or cannel is very inferior, containing 
a large per cent. of ash. 
The presence or absence of this cannel in coal purchased by gas- 
works will in a measure account for the very different results obtained 
by the different works of the State that have used Hocking coal. 
With a proper admixture of the lower members of the seam with 
the cannel, very fair results may be obtained. 
Assuming that a mizture of the two lower members of the seam 
will produce four feet to the pound, or 8,000 feet to the net ton of 14 
candle gas, and that the cannel will produce four and a half feet or 9,000 
