CLAYS OF SALEM COUNTY. 495 



to the fact that the mottled clay is probably only a weathered 

 phase of the blue, and it is absent from the western end of the 

 pit, because the heavy capping of sand has prevented the weather- 

 ing agents from changing the clay. In working the clay, all por- 

 tions containing the limonite crusts are avoided, as they are 

 difficult to break up by grinding. 



Three samples were tested from this locality, viz., the top clay, 

 the bottom clay and the brick mixture. 



Top clay. (Lab. No. 677.) — This was a somewhat gritty clay 

 and slaked slowly. It worked up with 30.2 per cent, of water to 

 a mass having an air shrinkage of 9.3 per cent, and an average 

 tensile strength of 308 pounds per square inch. In burning the 

 following results were obtained : 



Burning tests of top clay. D. F. Haines, Yorktown. 



Cone 05 Cone 5 Cone 8 



Fire shrinkage, 2.7% 7-7% 7. % 



Color, yellowish red red deep red 



Condition, steel-hard 



Absorption, 12.62% 0.22% 0.34% 



Bottom clay. (Lab. No. 694.) — This was much denser, and 

 was slow slaking. It took 29.9 per cent, water and had an air 

 shrinkage of 8 per cent. Its average tensile strength was 223 

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



Burning tests of bottom clay. D. F. Haines, Yorktown. 



Cone 05 Cone 3 



Fire shrinkage 5-3% 7-3% 



Color, light red red 



Condition, steel-hard 



Absorption, 6.89% 1.07% 



Brick mixture. (Lab. No. 617.) — The brick mixture was very 

 plastic and contained more or less fine grit, as it had some loam 

 added to it. It took only 27 per cent, water and its air shrinkage 

 was 7.6 per cent. The average tensile strength was 229 pounds 

 per square inch. 



