THE CARBONIFEROUS SYSTEM. 137 



Coal 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. It is 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 is the 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. 3 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 lies 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 is 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 ; 



