METHOD OF MANUFACTURING BRICK 157 



Hematite is often added to the brick to give it a nice red color. 

 It is either added to the clay while it is being tempered in the 

 pug mill or else the powdered hematite is mixed with the mold- 

 ing sand. The former way is undoubtedly the best, for in the 

 handling and rubbing which a brick gets before it is finally 

 placed in a wall, much of the molding sand is rubbed off and 

 with it the hematite. 



Soalc jpits. — These are the most primitive machines at present 

 used for the preparation of clays. It consists of a rectangular 

 pit about five feet deep and six feet square. The Long Island 

 ones are usually rectangular in shape. Into this the clay and 

 sand are dumped, water poured on and the mass allowed to soak 

 over night, so as to thoroughly soften it. The following morning 

 the softened material is shoveled into the machine. Two men — 

 pit shovelers — do this, and it is highly important that they be 

 men of intelligence and attend to their work, seeing that the 

 right proportions of clay and sand are shoveled into the machine. 

 From one third to one quarter is the amount of sand added. 

 The operation of mixing the clay and sand is called tempering; 

 the addition of sand is in most cases not necessary, as the 

 majority of clays have sufficient of it admixed naturally. The 

 object of the addition of sand is to counteract the effect of the 

 alumina, by preventing a too great and uneven shrinkage of the 

 brick. Coal dust is also added by some manufacturers and the 

 advantage derived by its use will be mentioned under the head 

 of burning. 



When soak pits are used, two men dig the clay in the after- 

 noon at the bank, while a third man levels off the material as it is 

 dumped into the pit and also adds the requisite amount of water. 

 He is called the temperer. In the morning the two diggers of 

 the previous afternoon shovel the clay from the soak pit into 

 the machine. 



In many large brickyards separate gangs of men do the pit 

 shoveling and digging of the clay. 



Ringjpits. — These temper the clay more thoroughly than soak 

 pits, but are not so extensively used, possibly because it costs a 

 trifle more to operate them. A ringpit, as its name implies, is 

 circular, 25 to 30 feet in diameter, three feet deep and lined with 

 boards or brick. In this there revolves an iron wheel, six feet in 



