THE MINING AND QUARRY INDUSTRY I9I3 2J 



or combined with the pug mill on a single base. The material from 

 the pug mill is: forced by the auger under great pressure through 

 this tapering barrel and issues from a die at the end in a solid col- 

 umn, the size depending upon the method to be used in cutting. 

 With side-cut bricks the column has a cross-section of about 4J/2 by 

 .10 inches, and with end-cut bricks 4 by 4^2 inches. The column of 

 stiff mud is forced along over a cutting table where it is cut by 

 means of piano wire into bricks of such dimensions that, allowing 

 for repressing, drying and burning, will produce a finished product 

 of a standard size. Twelve bricks are usually made at one cut. 

 From the cutting table the product is taken by a continuous belt 

 either to the represses or direct to the double-deck cars preparatory 

 to drying. Lugs are a necessity on paving bricks and are either 

 formed by the process of repressing or at the time of cutting. 



The product now goes to the drying tunnels where a temperature 

 sufficient to dry the bricks in about 24 hours is secured either by 

 the use of steam, waste heat from the kilns, or by direct heat. The 

 bricks lose in moisture about 20 per cent of their original weight in 

 the process of drying. The cars have a capacity of from 450 to 500 

 bricks and traverse a distance of about 100 feet between the time 

 of entering and leaving the drying tunnels. 



Burning, which is probably the most important branch of the in- 

 dustry, is carried on in down-draft or in continuous kilns, using 

 bituminous or anthracite coal with or without a forced draft. Kilns 

 and methods of burning vary. The kiln in most common use, known 

 as the rectangular down-draft kiln, has inside dimensions of about 

 80 feet in length by 18 feet in width and 12^ feet in height with ten 

 or more fireplaces on each side. The fireplaces are built in such a 

 manner that the heat reaches the top of the kiln first, passes down 

 through the green brick, then through the floor and by a system of 

 flues to the stack. The proper burn is recognized almost entirely by 

 the settle of the brick. Kilns are set about 27 bricks high, the bricks 

 separated from each other by a thin layer of sea sand, and burned 

 from 10 to 12 days until the material settles from 12 to 15 inches. 

 On account of the difference in kiln temperature between the top and 

 bottom it is the usual custom to set the first two to six layers with 

 either common, side-walk, or rough-faced front brick that do not 

 require so high a temperature to burn as do the paving brick. 



A circular down-draft kiln is also used in the burning of paving 

 brick. The kiln, in this case, has an inside diameter of from 20 to 

 30 feet and a height of about 14 feet, and is usually furnished with 

 eight fireplaces having individual stacks or all drawing to one stack. 



