POTTERY OR STONEWARE CLAYS. 177 



The composition of this clay is: 



Analysis of Clay, Henry Co., Mo. 



Silica 67.49 



Alumina 21.11 



Water 5.95 



Ferric oxide 2.45 



Lime 17 



Magnesia .63 



Alkalies 2.83 



100.63 



Total fluxes 6.08 



Specific gravity 2.23 



The shrinkage in both drying and burning is s'x per 

 cent, and the tensile strength in 110 on the average, with 

 a maximum of 127. Incipient fusion begins at 2000 F. 

 complete vitrifi- ation at 2300F., and viscosity at 2400 F. 



(No. 68 S.) 

 POTTEKY CLAY (REFRACTORY). 



SHIRLEY S MILL, FAYETTE CO. 



A fine grained, compact clay, with lit'le coarse grit, but 

 considerable fine sand. Color drab. It slakes very 

 slowly to scaly grains. 



Three per cent, of water were required to irake a work- 

 able paste which was quite plastic. This paste shrunk 

 10 per cent, in drying and 4 per cent, in burning, giving 

 a total shrinkage of 14 per cent. 



The tensile strength of the air dried briquettes showed 

 an average of 106 Ibs. per square inch, and a maximum 

 of 123 Ibs. 



The clay burns to a yellowish white body. Incipient 

 fusion. occurs at 2000 F., vitrification at 2200 F., and 

 viscosity at 2400 F., The composition of the clay is as 

 given below: 



