186 GEOLOGY OF OHIO. 



Among all the various types of Round Kilns in the state it is hard 

 to select one which unites the greatest number of favorable points. The 

 kilns of the Hocking Clay Company at L,ogan and the Haydenville Com- 

 pany at Haydenville are probably as uniformly successful as any kilns in 

 the state. Their bottoms are of the best type possible; their fireholes, 

 using inclined grate bars, are not as economical in fuel or labor as the 

 kind fired from above and without grate bars. The stacks are four to a 

 kiln in one case, but merely divide the draft of the well hole into four 

 parts so that no irregularity in the division of the draft is possible. In 

 the other case a single stack is used, on one side of the kiln. The floors 

 are flush with the bottoms of the fire holes. 



Another most successful kiln is that devised and used by H. B. Camp 

 at Cuyahoga Falls. In this case, the floor is raised about twenty or twenty- 

 four inches above the firehole. The latter use no bars, are fed from on 

 top and have their front wall made of a cast iron plate or clamp lined 

 with firebrick — the removal of this clamp allows great saving of time in 

 cleaning out the fireholes after a burn is over. 



The stacks are in all cases separate and outside the kiln. 



At the works of the Cincinnati Sewer Pipe Company at Cincinnati 

 are four kilns built from English designs which have been in operation 

 ior some years. Their novel feature is the use of a central stack running 

 up through the arch roof of the kiln. 



The use of this central stack has some great advantages: 



1st. It enables the greatest economy of construction possible in any 

 form of round kiln. 



2d. It becomes hot as soon as the kiln is lit, and affords a draft at 

 once which makes it the quickest acting kiln in use. 



3d. The central stack, becoming highly heated, radiates its heat 

 powerfully, and assists in bringing the center of the kiln to its final heat 

 as early as the sides are ready. 



4th. The central stack renders a very shallow kiln bottom easy to 

 arrange, so that little or no difference of level of the floor and fire holes 

 is necessary. 



As a means of burning, it is the nearest perfection of any kiln in 

 use. Against it however the following points can be raised. 



1st. The cubic contents of the stack kiln room is lost each burn. 

 This area in a twenty-six foot kiln with a three foot stack is only about 

 1.5 per cent, of its cubic working space, so this loss is not serious. 



2d. The center stack is in the way of drawing and setting, especially 

 when using cars — for bulky articles like sewerpipes th s interference is 

 more serious than in bricks, where less lost space is necessary. 



3rd. There is the possibility of frequent repairs to the cenLral stack, 

 if the bricks used in its construction are not of the best and the work 

 carefully put up. 



The disadvantages do not counter-balance the advantages and it is 

 strange that the virtues of the kiln should have been so long unnoticed 



