CHINA CLAYS. 129 



The air dried briquettes showed an average tensile 

 strength of 14 pounds per square inch, and a maxi- 

 mum of 16 pounds. 



Incipient fusion occurs at 2300 P., vitrification at 

 2500 F., and viscosity above 2700 F. The clay 

 burns to a white but somewhat porous body. 



Its composition is as follows : 



Analysis of China Clay, Briggs Frederick, Marion Co. (No. 37, S.) 



Silica 65.49 



Alumina 24.84 



Water 7.50 



Ferric oxide tr. 



Lime 1.26 



Magnesia tr. 



Alkalies tr. 



Moisture 30 



99.37 



Total fluxes 1.26 



Specific gravity 1.7 



This clay is very low in iron, and the small per- 

 centage of lime is no detriment. 



(No. 36 S.) 

 CHINA CLAY. 



PEARCE^S MILL,, MARION CO. 



A hard, porous,, coarse grained, gritty clay, which 

 in water breaks up slowly into angular fragments, 

 each of which in turn keeps splitting. 



Twenty-five per cent, of water was required to work 

 it up, but it is very lean. The air shrinkage was 3 

 per cent, and an additional 12 per cent, in burning, 

 making a total of 15 per cent. 



The tensile strength of air dried briquettes varied 

 on the average 12-14 pounds per square inch with a 

 maximum of 20 pounds per square inch. . 



