Ries — Physical Tests of Devonian Shales. 



cent, and in burning, nine per cent. The tensile strength of air-dried 

 briquettes was, on the average, sixty-one pounds per square inch, with a 

 maximum of sixty-two pounds per square inch. 



Incipient fusion occurs at 1,900° F., vitrification at 2,050° F. and 

 viscosity at 2,150° F. 



The composition of the shale according to an analysis furnished by the 

 Celadon Terra Cotta Company, of Alfred Centre, is: 



Silica, 53.20 



Alumina, 23.25 



Ferric oxide, 10.90 



Lime, . 1 .01 



Magnesia, .62 



Alkalies, 2.69 



Sulphuric acid, .41 



Titanic acid, .91 



Water, 6.39 



Manganese oxide, .52 



99.90 



Total mixing impurities, 15.74 



This shale corresponds very closely in composition to that used at 

 Kansas city, Mo.,* for the manufacture of paving brick, but there is a 

 considerable difference in the fusibility, the Missouri shale Weing very tine 

 and consequently more fusible. 



When this factory was first started, both terra- cotta and roofing-tile were 

 produced, but now the Celadon Terra-Cotta Company confines itself entirely 

 to the manufacture of vitrified roofing-tile, which is of a superior quality, and 

 bears an excellent and wide-spread reputation. At first a mixture of clay 

 and shale were used, but now the latter material alone is found sufficient; 

 the shale after grinding and careful tempering is molded either by hand or 

 steam-power machines, and then set aside to dry slowly. The tile is no 

 longer burned in saggars as was formerly done, but is placed in pockets in 

 the kiln. The shale burns to a tough, cherry-red body. 



Hoi-iielhnille, Steuben county. The shale at this locality frequently 

 contains interbedded layers of sandstone, which are separated in mining 

 without much trouble. The shale is rather gritty, and on the addition of 

 twenty per cent, of water gave a lean, workable paste, w hich shrunk 2.7 



* Missouri Geological Survey. XI, p. 565. 



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