THE LOWER COAL MEASURES. ; 145 
Hence, the bitumen in them, relatively small in quantity, is held in 
cells, and cannot flow together so as to give the mass a pasty, coherent 
character. In Ohio the lowest stratum of this series . . . is gen- 
erally a furnace coal. As it occurs in the Mahoning Valley, it isa type 
and standard of the class to which it belongs, and is one of the best 
furnace fuels known. . . . . Coal No.6 . . . has locally this 
open-burning character.” 
“The second class or cementing coals are such as have few parti- 
tions, but show upon fracture broad surfaces of pitch-like bitumen. 
These, to a greater or less degree, melt or aggultinate by heat, forming 
what blacksmiths term a hollow fire. This property causes them to 
choke up the furnace, and arrest the equal diffusion of the blast through 
the charge; hence, they cannot be used in the raw state for the manu- 
facture of iron, but must be coked. This process of coking consists in 
burning off the bituminous or gaseous portion, which leaves the coal in 
the condition of anthracite, except that as this change is effected with- 
out pressure, the resulting material is cellular and spongy. Coals of 
this character when free from sulphur, their great contaminating im- 
purity, are used for the manufacture of gas, the volatile portion driven 
off in the retorts serving the purpose of illumination, while that which 
yet remains is coke, and may be used as fuel. By far the greater por- 
tion of our coals are of the coking variety. 
“The cannel coals are more compact and homogeneous in texture, 
and contain a larger percentage of volatile matters than the others ; 
also, the gas they furnish has higher illuminating power; hence, they 
would be used to the exclusion of all others for the manufacture of gas, 
but that the coke yielded by them is of inferior quality. They are, 
therefore, chiefly employed as household fuel, for which they are specially 
adapted, and in small portions for enriching the gas from inferior 
varieties.” 
To these statements it may be added that the last-named division 
has but very little economic value in Ohio at the present time. In 
working the regular coal seams, small deposits of cannel are sometimes 
struck, which take the place of a part or even of the whole of the seam 
for a limited extent. When thus situated, an effort is often made to 
dispose of the cannel that is obtained in this way, and a little of it is 
occasionally pushed into the market, but there is no regular and reliable 
10 G. 
