CLAYS OF MIDDLESEX COUNTY. 451 



A sample of the crude clay (Lab. No. 391) showed it to be a 

 very plastic feeling clay of fine grain and fast-slaking qualities. 

 It required 39 per cent, of water to> temper it to a mass of the 

 proper consistency for molding. The air shrinkage of the brick- 

 lets was 5 to 6 per cent., but when air dried they did not feel very 

 hard or dense, and on the contrary were rather soft and pulveru- 

 lent. The tensile strength of the air-dried bricks was 59 pounds 

 per square inch. 



Burning tests of a No. I blue fire clay. J. R. Such, Burt Creek. 



Cone 3 8 10 



Fire shrinkage, . . 5.1% 12% 12.6 % 



Absorption, 10.84% 5-93% 



Condition, not steel-hard, containing porous 



fine cracks 



Color, white white with yellowish white 



yellowish tinge 



Inasmuch as the washed ball clay, which is purer than the 

 crude, was well vitrified at cone 27 (see below), it seems proper 

 to classify this clay as refractory, although its fusibility was not 

 tested in the Deville furnace. 



Several grades of clay are mined in the pits of J. R. Crossman 

 (Loc. 65 and 66), near Burt Creek. A good grade of fire clay 

 from locality 66, was viscous at cone 33. This is known as No. 

 1 blue. At times it is found sufficiently free from impurities to 

 wash for a ball clay, although this is not commonly done. Some 

 of the buff fire clays from this pit are used by wall-plaster manu- 

 facturers, while other grades are sold for saggers, and enamel ed- 

 brick manufacture. 



A red-mottled clay 1 from another of Crossman' s pits (Loc. 65, 

 Lab. No. 386) was also tested. It was a clay of rather low 

 plasticity but rapid-slaking qualities, working up to a plastic mass 

 with 30 per cent, of water. Its air shrinkage was low, being 4 

 per cent., and its tensile strength of 15 pounds per square inch 

 was equally low. A lump of the crude clay burned to cone 10 was 



1 No. 7 of the section given on page 457. 



