460 CLAYS AND CLAY INDUSTRY. 



with limonite. The underlying sand was called kaolin by the 

 workmen, and had been sold for mixing with asphalt in making 

 pavements. 



The pipe clay is used for mixing with some Pleistocene clays in 

 another State to make sewer pipe, and has also been mixed with 

 fire clay for making stove linings. It (Lab. No. 387) is a very- 

 fine-grained, gritty clay of low plasticity and low tensile strength,, 

 the latter not exceeding 20 pounds per square inch. It worked up 

 with 35 per cent, of water, and its air shrinkage was 5 per cent. 

 When fired it behaved as follows : 



Burning tests of pipe clay, J. R. Crossman's, Burt Creek. 



Cone 5 8 10 



Fire shrinkage, 11% 11% 12% 



Absorption, 15-45% 16.65% 11.49%- 



Color, yellowish white cream buff 



The reason for the slight increase in absorption at cone 8 was. 

 probably due to some slight irregularity in the bricklet. 



Miscellaneous. 



The "blue top" clay from Maurer's pit (Loc. 24, Lab. No.. 

 374, layer 8 o{ section on p. 436) contains less sand than the fire- 

 mortar clay described on p. 458. It is a moderately fast-slaking 

 clay, which works up to a sticky mass. It went through a 

 100-mesh sieve without leaving any residue, and worked up with 

 33 per cent, of water. Its air shrinkage was 5.5 per cent., and its 

 average tensile strength 122 pounds per square inch. Its burning- 

 qualities were as follows : 



Burning tests of blue top clay, Henry Maurer & Son, Woodbridge. 

 Cone 3 5 8 15 



Fire shrinkage, 4.5% 5.1% 5-6% 7-i% 



Absorption, 9.80% 7.86% 6.17% 1.86% 



Color, very light yellow light buff buff gray buff 



The clay burned steel-hard between cones 3 and 5, and warped 

 slightly at cone 8. When tested in the Deville furnace it was. 



