CLAYS, THEIR ORIGIN, COMPOSITION AND VARIETIES. 61 



the only one of its kind, It consists of four to five feet of hard fire clay, 

 immediately underlying the carbonaceous streak which represents the 

 Quakertown coal. The bottom of the fire clay is thirty feet above the 

 Sharon coal, which has been mined in the same territory. This clay re- 

 sembles the hard, or "number one" fire clay of southern Ohio in its general 

 appearance. It contains, as the latter clay does, abundant traces of veg- 

 tation which consist in the main of the rootlets of Stigmaria or old coal 

 plants. This seam has been made the basis of an important fire brick 

 manufactory, though other first class clays are also worked here. 



Overlying the coal streak ten feet of shale are found adapted to 

 coarser clay products, as paving blocks. 



(c) The Lower Mercer Clay and Shale. — We reach in our ascent the 

 best marked horizon of the entire Conglomerate Measures, that, namely, 

 of the blue or Iyower Mercer limestone. This limestone constitutes one 

 of the vital nodes of this series. Above it is found a'n iron ore that often 

 proves valuable. Under it is a coal seam for which not very much can 

 be claimed, but which in three counties in the state supports a few small 

 mines. Below the coal is an argillaceous deposit; sometimes shale, but 

 generally clay, which is worked in a large way and increasingly, for var- 

 ious clay products. This horizon is the basis of important manufactures 

 in Stark, Tuscarawas, Muskingum- and Hocking counties and particularly 

 in the latter. The Columbus Brick and Terra Cotta Works, located at 

 Union Furnace, is a large and well-established enterprise. There is con- 

 siderable range in the quality of the formation throughout the state, but 

 it nowhere yields clays of especially high character. The average com- 

 position would be without meaning or significance of any sort. A single 

 analysis from the Union Furnace field is here introduced as showing as 

 well as any one analysis can, the general type of clay that belongs here. 

 The figures are as follows. (E. Lovejoy, E. M) 



Water 3.72 



Silica, combined 34.27 



Alumina .' ...27.64 



Si'ica, free 23.92 



Iron ....'? -• 1-39 



Lime 50 



Magnesia 64 



Potash 2.70 



Moisture ••• U6 



The shale or clay that immediately overlies the Iyower Mercer lime- 

 stone gives promise, in its appearance, of adaptation to economic uses. At 

 the bottom of it, the place of the i/ower Mercer ore is found, and for three 

 or four feet directly above the ore the clay is exceptionally light colored. 

 The stratum is nowhere thick, however, and no instance is known of its 

 being brought into use. 



