228 ' GEOLOGY OF OHIO 



holes deliver into the kiln at a point just about level with the floor, the 

 height of the floor level above the bottom of the fire holes, being about 

 twenty-four inches. The kiln is entered through a narrow wicket at each 

 end, just wide enough to let a man come in with a brick barrow. 



In setting these kilns, they adjust the arches carefully in front of the 

 fire holes, so that each arch is filled with the heat from the fire holes at 

 each side of the kiln. The bricks were burned very satisfactorily in these 

 kilns but at a rather high expenditure of fuel; the top course of firebrick 

 were commonly left on edge and in open order, to promote a strong draft 

 of air through the kiln .while drying it off. When the red heat had 

 worked its way upwards to this course, so that it could be seen red at 

 night through the cracks, then men were sent out to tighten the platting. 

 This they did by putting the top cour. e down fiat and as close together as 

 possible and sprinkling sand or ashes or slack coal on the surface. 

 This acts as a seal to the rising draft and prevents the waste of fuel and 

 the formation of uneven drafts up through the bricks. The heat being 

 compressed under the tight course is carried by conduction to every part 

 t f the kiln equally. 



With a well equipped up draft of this description, the burning can 

 be managed with great precision and excellence though it is undoubtedly 

 somewhat more extravagant in fuel. 



In making this kiln into a down draft kiln, but few alterations were 

 necessary. The crown was sprung from wall to wall at a height of nine 

 or ten feet from its centre to the floor. The heat was carried to the top 

 of the kiln by a fire wall on either side of the kiln, tied to the main 

 wall by distance brick at frequent intervals' to keep it from falling into 

 the kiln. The draft was provided by a small stack at each end of the 

 kiln and a continuous flue from end to end down the centre connected 

 the two stacks. 



This flue was divided into an upper and lower section which was 

 made to draw from separate portions of the kilns' length so as to get an 

 equal draft at all points. 



Simple and cheap as such a kiln is, it meets as many of the essential 

 constituents of success as any square kiln in use. The burning which 

 was exhibited from this kiln cannot be surpassed by any appliance now 

 in use. 



The burning of fire bricks is not in any way as delicate or skillful an 

 operat on as the burning of almost all other clay wares is, for the reason 

 that the material, being made to endure high heats, cannot easily be over 

 burned and if burned less strongly than is desirable there exists no difficulty 

 in disposing of the product without sacrifice of the price. In short, the 

 customers of the fire brick trade are about divided in their preference for 

 hard and soft bricks, so whatever the kind of burn, the product will be 

 acceptable to one or the other class of customers. 



