452 CLAYS AND CLAY INDUSTRY. 



quite porous and showed the presence of many small fused specks. 

 The behavior of the molded material under fire was as follows : 



Burning tests of a red-mottled clay. J. R. Cross'man, Burt Creek. 



Cone 3 5 8 10 



Fire shrinkage, 8.3% 11% 11% 12.6% 



Absorption, 16.85% n.31% 10.02% 7-32% 



Color, yellowish yellowish yellowish white speckled 



white white speckled 



These speckles showed on the fracture even at cone 3, and the 

 clay became steel-hard slightly above this cone. In spite of its 

 red color, which suggests a high per cent, of ferric oxide, it is 

 more refractory than a No. 1 blue fire clay dug in the same pit 

 (p. 457), for it does not become viscous until cone 31. 



Ball Clays. 



Refractory ball clays occur in the South Amboy fire-clay bed, 

 and those dug by C. S. Edgar and J. R. Such were tested with the 

 following results. 



Sayreville. — Washed ball clay from pits of C. S. Edgar, east of 

 Sayreville (PL XLIX, Loc. 268, Lab. No. 723). This is a whit- 

 ish, very fine-grained, soft clay. Its fineness can be judged from 

 the fact that it contains 87 per cent, of clay particles which are 

 under ttwtf inch in diameter. It slaked fast and worked up with 

 39.1 per cent, of water to a plastic-feeling mass whose air shrink- 

 age was 5 per cent., but the clay had a very low tensile strength. 

 Its burning qualities were as follows : 



Burning tests of washed ball clay. C. S. Edgar, Sayreville. 



Cone 5 10 15 



Fire shrinkage, 10.6%' 16.3% 16% 



Absorption, 10.53% 3-98% -63% 



Color, white whitish light gray 



It burned steel-hard at cone 5, but showed many fine cracks. 

 The material is not used alone, but mixed with other white-burn- 

 ing clays. It is refractory, being only vitrified at cone 27. 



Bart Creek. — Another sample of washed ball clay was exam- 

 ined from J. R. Such's pit (Loc. 6y, Lab. No. 389). This is like- 



