THE CARBONIFEROUS SYSTEM. 141 



At Alliance, on the eastern border of Stark county, Coal No. 4 is reached 

 and worked in the Alliance Fire-Clay Company's shaft. This is also the 

 coal which is mined at Atwater, and penetrated in the shaft sunk at 

 Edinburgh. In the former locality it is from four to five feet in thick- 

 ness, with a parting in the middle. It is here an open-burning, semi- 

 cannel coal, much like what it is at Uhrichsville, and in the shaft of 

 the Trumbull Company on the Sandy, below Waynesburg. Its lime- 

 stone is here wanting. 



In the valley of Yellow Creek Coal No. 4 is represented, as I have sup- 

 posed, by the Hammondsville " Strip vein," here as at Atwater without 

 its limestone. 



On the eastern border of the State Coal No. 4 is probably represented 

 by the remarkably pure bituminous coal of Letonia and the cannel of 

 Canfield and Darlington, and hence is identical with the Kittanning 

 coal of Pennsylvania. 



The limestone over Coal No. 4 is that called by Prof. Andrews the 

 Putnam Hill limestone. It is also frequently referred to in our reports 

 as the gray limestone, to distinguish it from that over Coal No. 3, which 

 is designated as the blue limestone. The difference in color indicated by 

 these names prevails over several counties, but is not universal. As has 

 been before stated, both limestones are highly ferriferous. The iron ore 

 which accompanies them is sometimes in the form of tiers of nodules 

 of " kidney ore," which lie just above them ; sometimes as " plate ore," 

 or sheets of calcareous clay, iron stone resting on them ; or, finally, " block 

 ore," a stratified mass of ore, more or less completely replacing the lime- 

 stones. 



It often happens, also, that these limestones become earthy or bitu- 

 minous, and are converted into blue or black calcareous shale, full of the 

 fossil shells which abound in the limestones when purer. 



The Putnam Hill limestone locally assumes still another phase which 

 I have not observed in the lower or Zoar limestone, i. e., it is converted 

 into a hydraulic lime by the addition of a considerable percentage of 

 earthy matter. In such circumstances it becomes somewhat laminated, 

 but retains its hardness, and frequently becomes almost as sonorous as 

 phonolite. Its thickness is usually increased. When freshly broken it 

 is still blue, but when weathered, its lime superficially dissolved out, and 

 its iron oxidized, it becomes brown, or even yellow, and would hardly be 

 recognized as a limestone. When assuming this phase it is sometimes 

 highly fossiliferous, and has then supplied us with by far the largest 

 portion of the Coal Measure mollusks obtained in the prosecution of the 

 Survey. At Flint Ridge, at New Philadelphia where the road to the 



