FIRE CLAYS AND FIRE-BRICK INDUSTRY. 323 



and composition of the brick being varied to suit the conditions 

 under which it is to be used. The wide and varied use of refrac- 

 tory bricks therefore necessitates the making of many different 

 and special forms and mixtures, some of which are only produced 

 for special orders. The fire bricks made in New Jersey are used 

 for blast furnaces, rolling" mills, pottery and brickkilns, boiler 

 settings, gas houses, heating chambers, cupolas, etc. 



Among the other products of this nature may be mentioned 

 glass pots and glass furnace blocks, zinc muffles and gas retorts. 

 Of these the last mentioned are made to some extent from New 

 Jersey clays, but not as much as formerly. Glass pots require a 

 special dense-burning fire clay, which has not been found in New 

 Jersey. Zinc muffles have to be made from clays similar to those 

 required for glass pots, but a small amount of New Jersey clay 

 can be sometimes used in the mixture. Clay of a semi refractory 

 character is used in the manufacture of emery and carborundum 

 wheels for the purpose of binding the grains of the abrasive 

 together, when the wheels are burned. A semirefractory, or re- 

 fractory grade of sandy fire clay is used for making fire mortar 

 in which to set fire bricks. Quite a little fire clay is also consumed 

 by foundries and blast furnaces, but here sandiness combined with 

 plasticity are of more importance than high refractoriness. Steel 

 manufacturers, also, demand several grades of fire clay for mak- 

 ing mixtures for mold linings. A clay of high-bonding power and 

 dense character, but not necessarily high refractoriness, is called 

 for by graphite manufacturers. The materials used for graphite 

 crucibles are, however, chiefly imported ones. Aside from, their 

 use in making refractory wares, fire clays of either first or second 

 grade are used in the manufacture of front brick, terra cotta, 

 stove linings, saggers, stoneware, floor tiles, etc. 



HISTORY OF THE FIRE-BRICK INDUSTRY. 



The manufacture of fire brick represents one of the oldest 

 branches of the clay-working industry in New Jersey, and is of 

 more importance than is commonly imagined. The New Jersey 

 clays were first used for fire brick after the war of 1812, and one 



