FIRE CLAYS. 141 



very porous, of a white, color with a mere tinge of yel- 

 low. At 2400 P. the total shrinkage was 15 per cent. 



In the Deville furnace at cone 27, the clay still re- 

 mained entirely unaffected, but the color was grayish, 

 and the total shrinkage up to this point amounted to 

 26 per cent. 



The composition of the clay is : 



Analysis of Fire Clay, Rock Run, Cherokee Co., No. 4. 



Silica 17.70 



Alumina 59.46 



Ferric oxide ' .36 



Ignition 22.06 



99.58 

 Total fluxes 36 



No. 5. This isi a soft whitish, easy slaking clay, 

 but a very porous one which absorbs 40 per cent, of 

 water in working it up, and even then gave a very 

 lean mass, whose tensile strength, when made into 

 briquettes and air dried, was only 5 pounds per square 

 inch. The air shrinkage is 4 per cent, and at about 

 2250 F. the total shrinkage w T as 17 per cent., but the 

 bricklets, whose color was yellow, were still very 

 porous and could be scratched by a knife without 

 much difficulty ; at 2400 F., the shrinkage showed 

 a total of 22 per cent, and incipient fusion began ; at 

 2500 F., the total shrinkage was 23 per cent, the 

 brick was still porous and faintly yellowish white. 



In the Deville furnace at cone 30, the clay had 

 burned dense, was incipiently fused, but otherwise 

 unaffected, its color was a grayish white and the total 

 shrinkage amounted to 34 per cent., which is really 

 not surprising when we consider the high amount of 



