POTTERY OR STONEWARE CLAYS. 161 



desirable flux, but carbonate of lime especially if in 

 greater quantities than two or three per cent, is 

 objectionable, and sulphate of lime is likewise not 

 desired as owing to its dlsassoc : ation at high temper- 

 atures blisters may be formed. 



A clay vitrifying at a low temperature is more 

 desirable as it requires fuel to burn ?t, 



The pottery clays reported on are all from the 

 Tuscaloosa formation of the Lower Cretaceous except 

 No. 204 from Blount county, and No. 192 from near 

 Rock Run, both of which come from the Paleozoic 

 limestone formations. 



(No. 204.) 

 STONEWARE CLAY 



FROM F. S. WHITE, BLOUNT CO. 



A yery finegrained sedimentary clay of grayish white 

 color with occasional spots of yellow. 



It slakes easily when thrown into water and works up 

 to a very plastic mass with 28 per cent, of water. The 

 bricklets made from this had an air shrinkage of 5 per 

 cent. 



Then burned at 2200 F. it is nearly dense, cream gray 

 in color and showed a total shrinkage of 1 7 per cent. 



At 2350 F. was vitrified and showed very light gray 

 color and a total shrinkage of 20 per cent. 



It fused at the time at cone 27 in the Deville furnace. 



The tensile strength of the air dried briquettes was low, 

 ranging from 45 pounds per square inch to 55 pounds 

 per square inch. 



The analysis of the clay yielded : 



