CLAYS, THEIR ORIGIN, COMPOSITIONS AND VARIETIES. 63 



Silica 33.42 



Alumina., : 25.80 



Free Silica 28.39 



Oxide of Iron 1.39 



Lime '. 51 



Magnesia 64 



Alkalies ., 2.70 



Water 6.51 



The description of this stratum completes the list of the principal 

 clay and shale beds of the Conglomerate Coal Measure group. It remains 

 to enumerate the beds of like composition and character in the Coal 

 Measures proper. This great series embraces the following elements, 

 viz.: 



Upper Barren Coal Measures. 

 Upper Productive Coal Measures. 

 Lower Barren Coal Measures, 

 Lower Productive Coal Measures. 

 The list of principal clay deposits of the Lower Coal Measures is as 

 follows, viz.: 



Upper Freeport clay and shales. 

 Lower Freeport clay and shales. 

 Middle Kittanning clay and shales, 

 Kittanning clay. 

 Freeport limestone clay. 

 Putnam Hill limestone clay and shales: 

 These deposits are named in descending order. 



1. The Putnam Hill Limestone Horizon. 



The Putnam Hill limestene covers a coal seam which is designated 

 in Geology ot Ohio, Volume 5, as the Brookville coal. This identification 

 is called in question, though not positively denied, by some geologists who 

 have written upon the question, but for want of a better title, the desig- 

 nation can still be maintained. A valuable deposit of clay is found in 

 the central Coal Measure counties at the level herein named. It is espec- 

 ially well-developed in Muskingum county, where it is worked on the 

 large scale. But it extends in good volume and good character through 

 Coshocton, Tuscarawas and Stark counties, where it is also worked quite 

 largely; and, further, it is found in promising condition in Perry, Hocking 

 and Vinton counties to the southward. Like the Lower Mercer clay of 

 the Union Furnace section, it yields on calcination, at least as it is found 

 in the vicinity of Zanesville, a buff or cream-colored product. This clay 

 is the main reliance of the great tile manufactory of Zanesville. In its 

 chemical and in its physical structure it meets the demands of this very 

 important industry better than any other deposit that has been found. 



