2 4 o CLAYS AND CLAY INDUSTRY. 



bottom passes directly into the body of the kiln and up through 

 the wares, escaping from suitable chimneys or openings at the 

 top. In the latter the heat from the fire boxes is conducted first 

 to the top of the kiln chamber by means of suitable flues, and then 

 down through the wares, being carried off through flues in the 

 bottom of the kiln to the stack. The down-draft system is grow- 

 ing in favor, as the burning can be regulated better. Furthermore, 

 since the bricks at the top receive the greatest heat, and those at 

 the bottom the least, there is less danger of the bricks in the lower 

 courses being crushed out of shape. 



Up-draft kilns. — The simplest type of kiln with rising draft is 

 known as the "scove kiln" (PI. XXVIII, Figs, i and 2), which is 

 in use at many yards making common brick, and is of a tem- 

 porary character. The bricks are set in large rectangular masses 

 from 38 to 54 courses high, depending on the kind of clay. In 

 building up the mass a series of parallel arches is left running 

 through the mass from side to side, and with their centres about 

 two feet apart. After the bricks are set up they are surrounded 

 by a wall two courses deep of "double-coal" brick, and the whole 

 outside of the mass daubed with wet clay to prevent the entrance 

 of cold air during burning. The top of the kiln is then closed by 

 a layer of bricks laid close together and termed the platting (PI. 

 XXIX, Fig. 2). Kilns of this type involve little cost except the 

 labor of building. They are, however, adapted only to common 

 brick, and are not capable of being heated to a high temperature, 

 so that in some parts of the State, where they are used to burn 

 bricks made from the sandy Miocene clays, which need a high 

 temperature, the product is not hard. 



The so-called Dutch kilns (PI. XXIX, Fig. 1) are a slight im- 

 provement over the scove kilns, since they have permanent side 

 walls, and so yield somewhat better results, for they heat up better 

 and admit less cold air. 



Many common brick and nearly all front brick, however, are 

 burned in kilns that are walled and roofed, with a door at each 

 end for filling and emptying. They are, therefore, far more 

 reliable, capable of better regulation, attain higher temperatures, 

 and are both up-draft and down-draft. The fuel used is some- 

 times wood, but mostly coal, not a few manufacturers employing 



