FIRE CLAYS. 157 



total shrinkage 10 per cent. Incipient fusion did not 

 occur until heated to cone 27 in the Deville furnace. 

 This is a very refractory clay, and one that has a 

 comparatively low shrinkage, due to the large 

 amount of silica in its composition. 



Vitrification occurs at cone 30 and viscosity at 

 cone 33 in the Deville furnace. 



The composition of this clay is : 



Analysis of Fire Clay, Pearce's Mill, Marion Co. (No. 1). 



Silica 52.95 



Alumina 35.10 



Ferric oxide .80 



Lime tr. 



Magnesia tr. 



Alkalies 93 



Ignition 11.40 



Total fluxes, 



No. 2). 

 FIKE CLAY, 



PEARCE'S MILLS, MARION COUNTY. 



This sample is from a second opening which closely 

 adjoins Pearce's Store, and like the other occurrence 

 in this vicinity, it is very gritty, being even more so 

 than the first, and while the material is very porous, 

 at the same time it slakes very slowly, falling finally 

 to a powdery mass. The fracture of the dry material 

 is hard and angular, the air shrinkage is very low, 

 amounting to only 2 per cent., in the case of sample 

 which had passed through a 30-mesh sieve. 



At 2350 F. the shrinkage is only 6 per cent., and 

 the brickie t was creamy white in color, but still very 

 absorbent. In the Deville furnace incipient fusion 



