THE CARBONIFEROUS SYSTEM. 137 
Coat No. 3. 
This coal underlies the lower of the two limestones which I have 
spoken of as remarkably constant features in the sections of our Lower 
Coal Measures in different parts of the State. Itis more generally found 
directly beneath the limestone, but is sometimes separated from it by as 
much as twenty feet of shale. Like the second limestone coal, this is a 
very variable seam, prone to become a cannel, and exhibiting marked 
changes of thickness within limited areas. Near the eastern border of 
the State it is usually a coking bituminous coal, from two to four feet in 
thickness, of fair quality, but containing considerable sulphur. In Col- 
umbiana county it lies near the bottom of the valley of the Little Bea- 
ver, dipping to the south-east with the fall of the stream. It is quite 
extensively worked in the vicinity of New Lisbon. At the latter local- 
ity it is also coked, and the fire-clay beneath it is used for the manufac- 
ture of fire-brick. 
In the valley of Yellow Creek this isthe lowest workable seam, known as 
the “Creek vein.” It is here from three to four feet thick, a bituminous, 
coking coal, containing somewhat more sulphur than the seams which 
overlie it. Along the Ohio in this vicinity it is opened in many places, 
but in value it is completely overshadowed by the important bed of fire- 
clay that underlies it, and which is the basis of a very extensive manu- 
facture of pottery and fire-brick. This fire-clay is one of the most im- 
portant in the series, and one which at its different outcrops supplies the 
material from which stone-ware, fire-brick, etc., are manufactured to the 
value of more than a million dollars per annum. 
In the Mahoning valley Coal No. 8 is thin and of no value; but the 
limestone over it is visible at a great number of localities, and is a useful 
guide in searching for Coal No. 1, as it les at an average height of about 
160 feet above it. It also furnishes a considerable portion of the lime- 
stone used as flux in the furnaces of the valley. Though nowhere show- 
ing a single bed of greater thickness than three or four feet, this lime- 
stone 1s sometimes doubled, and it is probably the equivalent of the 
“Ferriferous limestone” of the Pennsylvania geologists. In all parts of. 
Ohio more or less iron ore is found associated with the limestone over 
Coal No. 3, and the deposit frequently has great economic value. 
In Summit county this coal, with its limestone and iron ore, is found 
in the south-eastern townships. The coal is here thin, and has no prac- 
tical importance; but the underlying fire-clay is largely worked, and 
supplies some forty potteries. 
Through Stark and Tuscarawas counties Coal No. 3 lies for the most 
part below the surface. It is exposed, however, in the valley of the 
Nimishillen, below Canton ; in the valley of the Tuscarawas, at Zoar; 
