FIRE CLAYS. 153 



The tensile strength is moderate, and varied from 100 

 to 110 pounds per square inch. 

 The ultimate composition is: 



Analysis of Fire Clay, Woodstock, Bibb Co. (No. 111). 



Silica 65.82 



Alumina 24.58 



Ferric oxide 1-25 



Lime ; 



Magnesia tr. 



Alkalies .60 



Ignition 8.165 



100.415 



Total fluxes 1.85 



Specific gravity 2.40 







The rational analysis srave : 



Clay substance (J2.90 



Feldspar ^ 



Quartz } 37 ' 00 



99.90 



(No. B). 

 FIRE CLAY, 



AUXFORD'S, NEAR HULL'S STATION, TUSCALOOSA CO. 







This is a sandy micaceous gray clay, with a slightly 

 reddish tinge, which crumbles to pieces very quickly 

 when immersed in water. When worked up it gives 

 quite a plastic mass, and requires 33 per cent, of 

 water to accomplish it. 



The air shrinkage is from 9 to 10 per cent., and at 

 2000 F. the total shrinkage was only 12 per cent. At 

 this latter temperature the bricklet was hard, grayish 

 red in color, but still somewliat absorbent, while at 

 about 2200 F. vitrification occurred, with a total 

 shrinkage of 14 per cent. The viscosity occurred at 



