THE LOWER COAL MEASURES. 149 
our coals than has been charged to them hitherto. The results thus 
obtained can be fairly compared only with each other, or with analyses 
made on the same principle elsewhere. Great injustice would be done 
by setting the composition of nicely selected and exceptional samples 
over against these general averages. But the method has justified itself 
in various ways; especially, it has revealed for the first time, an 
individuality on the part of several of our leading seams, as far as 
chemical constitution is concerned. There is shown to be a normal 
composition for each of these several seams that is as constant and as 
widely extended at least as the physical characters by which it is 
distinguished. For example, the two coals that are known in our 
geological reports as No. 6, viz., the Middle Kittanning and the Upper 
Freeport, are clearly distinguishable from each other throughout Eastern 
and Central Ohio on chemical grounds. The fixed carbon of the former 
seam does not rise to 50 per cent. in a single instance in all the analyses 
that have been made of the seam between Mahoning and Perry coun- 
ties, while the same element in the Upper Freeport coal of the same 
territory does not in one instance fall as low as 50 percent. The 
average of the latter is 53 per cent., and of the former 48 per cent. The 
volatile matter of the Middle Kittanning seam in the same district does 
not in one instance fall below 40 per cent., while in the Upper Free- 
port coal it does not once rise to 40 per cent. 
All of the facts bearing on these points will be made apparent in 
subsequent pages of this report. 
The amount of water in our coals varies between 2 and 9 per cent., 
but a few examples will be found that fall below the smaller limit. 
The largest regular percentage of water is found in the excellent coals 
of Jackson county. There seems to be quite a constant proportion in 
particular coals, making a characteristic feature. 
As to ash and sulphur, but few general statements can be made. 
The details of analysis must be studied to obtain the significance of 
these important elements in our several coals. The percentage of 
sulphur falls below 1 per cent. in our best coals, ranging between .6 and 
1 per cent., but in many seams that are still highly esteemed for varied 
uses, it rises to 3 per cent. and upwards. In comparatively few does the 
average fall below 2 per cent., and some coals are used that contain 
7 per cent. 
There is but little coal in Ohio markets that yields less than 4 per 
