186 DETAILED REPORT ON ALABAMA CLAYS. 



age of ferric oxide and fuses very easily, while the gray 

 shale contains several per cent, less, and is much better 

 adapted to the manufacture of vitrified wares. The com- 

 position and physical characters of the two are given side 

 by side for the purposes of comparison. 



Light or gray shale, No. 108. 



Plasticity, quite good. The shale takes 25 per cent, of 

 water to work it up. 



Air shrinkage 2 per cent. 



Shrinkage at 2000 F., 9 per cent. Brick good red 

 color not, very porous. 



Shrinkage at 2200 F., 12 per cent. Brick reddish 

 brown, and just about vitrified. 



Fusion a 2500 F. 



Tensile strength average 105 pouuds, minimum 85 

 pounds per square inch. 



Dark or yellow shale, No. 107. 



Plasticity moderate; shale gritty, requires 20 per cent, 

 of water to work it up. 



Air shrinkage 1 \ per cent. 



Shrinkage at 2000 F., 5 per cent. Brick good red 

 color. Somewhat porous. 



Shrinkage at 2150 F., 6J per cent, Brick nearly 

 dense, reddish towards brown. 



At 2250 F., nearly vitrified. 



Fusion at 2500 F. 



Tensile strength only 40 pounds to square inch. 



Analysis of shales, Birmingham, Jefferson Co. (No. Iffl and 108.) 



(108) (107) 



Silica 57.80 61.55 



Alumina 25.00 20.25 



Ferric oxide 4.00 7.23 



Lime 2.10 tr. 



Magnesia 80 .988 



Ignition 7.50 6.19 



Alkalies 1.80 2.25 



99.00 98.466 



Total fluxes 8.70 8.45 



Specific gravity . 2.12 2.23 



