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° F., vitrification at 

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

 burns to a white but somewhat porous body. 



Its composition is as foUows : 



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



S'"ca 65 49 



Alumina , 24 84 



Water ; "' ^qq 



Ferric oxide _' (., 



'^'"e ....'. 1.26 



Magnesia tj. 



Alkalies ' ' ^j.' 



Moisture 3q 



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. 



PEAECB^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. > i 



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. 



