448 CLAYS AND CLAY INDUSTRY. 



gritty clay, mottled red, and feels plastic, but has a low tensile 

 strength of 35 pounds per square inch. It worked up with 34 

 per cent, of water and the air shrinkage was 6.6 per cent. In 

 burning it behaved as follows : 



Burning test of a mottled red clay. R. N. & H. Valentine, Sand Hills. 



Cone ,3 5 10 15 



Fire shrinkage, 5.4% 9% H-4% 12% 



Absorption, 16.62% 11.09% 6.45% 3-01% 



Color, whitish cream light buff gray buff 



The crude clay, when burned to cone 10, did not become quite 

 SO' dense as the molded material. The clay is a fire clay, but not 

 as refractory as the No. 1 blue, since it fuses at cone 30. 



In the Ostrander pit (Loo. 54, P'l. XLVIII, Fig. 2), to the 

 south of the Sand Hills, there is a sandy clay (Lab. No. 397), 

 also in the Woodbridge bed, which in some respects resembles 

 some of those of the Woodbridge district in its very low tensile 

 strength. The material is a hard, yellowish-mottled clay, which 

 slakes rapidly but has a low plasticity. It worked up with 28 

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

 average tensile strength was 20 pounds per square inch. 



At cone 5, the fire shrinkage was 1 per cent. ; absorption, 17.75 

 per cent. ; color, yellowish white. At cone 8 : fire shrinkage, 2 

 per cent.; absorption, 15.82 per cent.; color, yellowish white. It 

 did not become steel-hard until cone 10. 



Another sample from this property was a black clay, called 

 "steel clay," from the southern pit (Loc. 54, Lab. No. 407). In 

 texture it resembles the top-sandy clay found in the Woodbridge 

 district. The clay worked up with 30 per cent, water, and had 

 an air shrinkage of 6 per cent. Its tensile strength was only 36 

 pounds per square inch. In burning it behaved as follows : 



Burning tests of a black clay, Ostrander Co., Sand Hills. 



Cone 3 5 8 10 



Fire shrinkage, 4.6 % 6% 7% 9.3 % 



Absorption, 20.05% 15.00% 13.36% n.31% 



Color, yellowish white yellow yellow deep cream 



