678 NEW YOKK STATE MUSEUM 



are called, before tliej are allowed to escape into the kiln. The 

 fire then passes downward through the product and out through 

 the openings in the floor of the kiln to the flues, and from these to 

 the stack, or chimneys. The hight of the bags on the inside wall 

 of the kiln varies, and depends partly on the type of kiln, and 

 largely on the individual opinion of the manufacturer. 



There may be one main stack or, sometimes, there are several 

 small ones on each kiln. The down-draft kilns are either rect- 

 angular or round in shape. The average capacity of the former is 

 about 150,000 brick, while that of the latter varies with the diam- 

 eter, which is from 15 to 25 feet. 



The percentage of salmon brick is much smaller in a down- 

 draft than in an up-draft kiln, and seldom exceeds 15^. Those 

 bricks which are on the top of the kiln receive the greatest 

 amount of heat, but as there is no pressure on them they do not 

 become misshapen, and consequently on account of their great 

 hardness and density are often sold under the name of " rough 

 hard " and serve excellently for use in damp situations and for 

 sewer work. 



Several types of down-draft kiln are illustrated in the report. 



Down-draft kilns sometimes have two sets of fireplaces, the 

 one connecting with the bags on the inside of the kiln and the other 

 leading directly into the interior. The kiln may thus be worked 

 either as an up or a down-draft, the former being used during 

 the water-smoking and the latter during the burning. 



Continuous kilns. These consist of a series of chambersi separated 

 by either temporary or permanent walls. The fire is started in the 

 first, and as the burning proceeds the heat from the burning cham- 

 ber is conducted through the succeeding ones either through flues in 

 the wall or pipes connecting the openings in the roof of the kiln. In 

 this way, by means of the exhaust heat, the temperature of the suc- 

 ceeding chambers is raised, so that less fuel is required. The heat 

 from a burning chamber can not as a rule be carried safely through 



