BRIOK CLAYS. 193 



(No. 129, Stevens.) 

 BRICK CLAY. 



BIRMINGHAM. 



This is a very dense hard clay, which required con- 

 siderable grinding to break it up. The different lots were 

 mixed up, and the one, A, being composed of two-fifths of 

 the clay which was passed through 20 mesh sieve, and 

 thee-fifths of particles greater than 20 mesh. 



The second lot, B, was made up entirely of that which 

 had passed through the 20 mesh sieve. 



Both lots gave a rather lean mass, but A required 19 

 per cent, of water and B 16 per cent, to work up. The 

 average tensile strength of A is 12 pounds, and that of B 

 35 pounds. The air shrinkage of both was 4 per cent. 



In burning to 2300 F. the shrinkage of A was 3 per 

 cent, the color of the bricklet a full yellow, and the body 

 very absorbent. At 2400 F. incipient fusion occurred in 

 both cases, and the color of the bricklet was a brownish 

 gray, and the total shrinkage 10 per cent. 



At 2500 F. the clay was vitrified, of a dull brownish 

 gray color, and showed a very homogeneous fracture. 



Viscosity occurred at 2700 F. 



The chemical composition of the clay is : 



Analysis of Brick Clay, Birmingham. (No. J9 Stevens.) 



Silica 67.30 



Alumina 16.10 



Ferric oxide 7.77 



Lime tr. 



Magnesia tr. 



Alkalies tr. 



Ignition 9.25 



Total fluxes ... 100.42 



