CLAY WORKING INDUSTRIES. 187 



In square kilns the arrangement of the flues or bottoms is much less 

 thorougly worked out than in the round. 



There are several types in use however. 1st. A solid floor with a 

 deep flue from end to end of the kiln down the center. In the Hallwood 

 Kiln the flue communicates with a stack at one end. In the Thomas 

 Kiln a stack at both ends is provided. In the Griswold Kiln a stack at 

 one end is used with a horizontal partition in the flue, dividing it into an 

 upper and lower half in the two-thirds of its length nearest the stack. 

 By the use of a damper the heat can be made to escape all from the front 

 end of the kiln or all from the back, or in any ratio between, that is desired. 



This principle has been applied to the other kinds mentioned, though 

 in different ways of manipulation. 



In the Eudaly kiln, which is nearly always built in the rectangular 

 form, the floor is a checker bottom which is divided up into sections by 

 dead walls from end to end and crossways. Each section is drained by a 

 small stack, built up in the sidewalls of the kilns. The claim is that by 

 the regulation of the drait of these stacks the most perfect uniformity 

 can be obtained. This theory certainly looks plausible, but in practice 

 it is nearly always found that the heat takes the shortest course toward 

 the outlet and that the portions of the bottom near the dead walls and 

 partitions suffer from lack of draft. 



The Excelsior kiln is practically the same as the Eudaly in form, 

 but its bottom is made of pigeon work partitions so that the currents 

 freely circulate from one part of the kiln to another in response to move- 

 ments ot the dampers in the stacks. In addition the furnaces of the 

 Eudaly are replaced by incline grate bar fireholes, which make no smoke 

 when firing. The kiln is a great step ahead of the Eudaly in its opera- 

 tion while embodying all of the structural advantages and shape of the 

 latter. 



The Yates Kiln is another kiln very much like the last two; the 

 stacks, instead of issuing from the sidewalls of the kiln, run up the out- 

 side of the crown in pairs and meet in a line of low stacks along the 

 centers of the crown. The fireholes are of good type; the dimensions 

 and shape and structural points are almost identical with the former two. 

 The patentee claims great advantage from the use of one stack in the cen- 

 ter of his kiln instead of two on each side. The reason for any great 

 superiority by virtue of this point is not apparent, but the use of the 

 improved fireholes is certainly commendable. Nearly all of the patented 

 kilns in the market are of the square form — only one or two round kilns 

 being in use which are operated under patents. 



The value and utility of any of these patented kilns have received a 

 severe check in the last few years in the fact that the results attained 

 in several forms of the common round down draft and two forms of the 

 square downdraft have been continuously and steadily of a very much 

 higher grade than any of the patented kilns have been able to attan; 

 under these circumstances, the advantage of paying a large royalty or 



