422 CLAYS AND CLAY INDUSTRY. 



a sample was taken to a depth of 4 feet, but the clay extends below 

 this. The material (Lab. No. 693) is rather free from grit, and 

 quite plastic. It took a very high percentage of water, viz., 47.7 

 per cent, to temper it, but the air shrinkage of 8.3 per cent, is 

 lower than that of some other Alloway clays requiring less water. 

 Its tensile strength was also' very high, averaging 405 pounds 

 per square inch. At cone 1 its fire shrinkage was 5.7 per cent. ; 

 the bricklet steel-hard and light red. A dry-pressed tile burned at 

 cone 8 showed a total shrinkage of 13.3 per cent. 



Bwan Mills. — At locality 174, north of Ewan Mills the most 

 northerly outcrop of Alloway clay was found, but it is probably 

 too thin for economic working, there being not more than 4 or 5 

 feet of light chocolate-colored clay underlain by loose sand and 

 overlain by a heavy burden of sand with pebbles and iron crusts, 

 passing upwards into gravel. 



A bed of clay at least 7 feet in thickness is found along the 

 road on the North Farwell farm (Loc. 175), and in fact under- 

 lies the entire property. Brick made from it many years ago 

 can still be seen in a good state of preservation in the walls of 

 neighboring farmhouses. It is a smooth, light-brown clay with 

 yellow mottlings, few iron crusts and of good plasticity. There 

 is little or no stripping. The following are the physical characters 

 of the material (Lab. No. 687) : Amount of water required, 32.1 

 per cent. ; air shrinkage, 9.3 per cent., this is rather high. Aver- 

 age tensile strength 208 pounds per square inch. 



At cone 1 : fire shrinkage, 2.7 per cent., and absorption, 5.4 

 per cent., bricklet steel-hard and yellowish red. 



At cone 5 : fire shrinkage, 4.7 per cent. ; color, gray brown, and 

 bricklet quite dense, absorbing only 2.21 per cent. 



The clay vitrified at cone 12. On looking at the tabulated tests 

 of Alloway clays (p. 352), it will be seen that only one other 

 had an equally low fire shrinkage, i. e., the brick mixture used at 

 Yorktown. The latter, however, had a lower air shrinkage and 

 required less water for tempering. 



Talc-like Clay. 



Harrisonroille. — At locality 173 a mile due east of Harrison- 

 ville, there is an old pit which shows several feet of the micaceous 



