CLAYS OF MIDDLESEX COUNTY. 447 



the pits around Sand Hills, where the following- succession of 

 layers was exposed in 1902 in the pit of R. N. & H. Valentine 

 Company (Loc. 86, PI. XLVIII, Fig. 1). 



Section in R. N. & H. Valentine's clay bank, Sand Hills. 



1. Pensauken sand and gravel, 



2. Brick clay, 0-7 ft. 



3. Dark-blue clay, buff -burning, 6-IO " 



4. Gray-burning, terra-cotta clay, 3-4 " 



5. Black clay, 1 " 



6. Sand for masonry, 3-4 " 



7. Black clay, 6 " 



8. Gray-black sand, 2-4 " 



9. Fine fire clay, 8 " 



10. Mottled red clay, 8 " 



11. Bottom-sandy clay, 4 " 



Several samples were collected from the Woodbridge fire-clay 

 bed in this vicinity. The first of these w T as a so-called No. 1 blue 

 fire clay (Lab. No. 404) from the pit just described. This was 

 an easily-slaking clay, which required 33 per cent, of water for 

 tempering. Its air shrinkage was 4.4 per cent., and its tensile 

 strength from 45-50 pounds per square inch. It burned fairly 

 dense, as can be seen from the firing tests given below. 



Burning test of a No. 1 blue fire clay. R. N. & H. Valentine, Sand Hills. 



Cone. 5 10 



Fire shrinkage, 13.6% 13-8% 



Absorption, 7-07% 6.47% 



Color, streaky yellow yellow 



It burned steel-hard at cone 5, and fused at cone 32. This is 

 used in making fire brick, but it cracks in burning and has to> be 

 mixed with other clays of better bonding qualities. Comparing 

 this with a No. 1 clay from the Woodbridge fire-clay bed, near 

 Woodbridge, we see that it fuses nearly three cones lower. 



Another layer found in the same bank is interesting to com- 

 pare with the first one, as it produces an equally dense brick at 

 cone 10, with lower fire shrinkage. This* material represents the 

 layer 10 (Lab. No. 410), of the above section. It is a very 



