CLAYS OF MERCER COUNTY. 431 



mixed with a certain percentage of sandy surface clay and used 

 in the manufacture of bricks. The clay molds well and easily on 

 a stiff-mud machine, and is also used to some extent for making 

 draintile. The physical properties of a sample taken from the 

 boundary of Clay Marls I and II at this locality are as follows: 

 Clay (Lab. No. 609), tough and fairly plastic, working up with 

 34 per cent of water; air shrinkage, 6.6 per cent. The fire tests 

 were as follows: 



Burning tests of Reed & Bro's. black clay. Hightstown. 



Cone 03 13 5 



Fire shrinkage, 3.4% 5-4% 54% 6.4% 



Absorption, 16.66% 10.59% 



Color, pale red red red ..... 



Condition, not steel-hard steel-hard few small fused 



specks. 



A dry-press tile made from this clay and burned at cone 5 had 

 a fire shrinkage of 5.2 per cent, and was slightly mottled in its 

 color. 



Windsor. — A boring made along the road just by the bridge 

 at Windsor (Loc. 192) showed at least 7 feet of Clay Marl I. 

 The overburden is slight, but the clay appears somewhat sandy 

 in its character, although not burning to a specially porous body. 

 A partial physical test of this material (Lab. No. 602) showed 

 that it required 31 per cent, of water to' temper it, and that its 

 air shrinkage was 8.6 per cent. Its average tensile strength was 

 251 pounds per square inch, but the latter did not seem to be an 

 index of its plasticity, for the material did not feel especially 

 plastic. In burning it gave the following results : 



Burning test of a Clay Marl I, Windsor. {Loc. 192.) 



Cone 05 01 1 



Fire shrinkage, 0% 3-4% 1.4% 



Absorption, 17.09% 10.78% 12.22% 



Color, light red with bright red 



small black specks 



Hardness, not steel-hard not steel-hard 



