CLAY WORKING INDUSTRIES. 217 



from the river valleys. The preparation of this class of clays ranges 

 from nothing at all to crushing between rollers and pugging. The 

 Auger mill is almost the universal machine used in manufacturing; the 

 drying is usually in racks protected from sun and rain but unassisted by 

 artificial heat. The burning is usually managed in small round down 

 draft kilns, though some tilemakers retain the old updraft kilns. 



The business is not a large or important one, or one which bids fair 

 to add much wealth to the state for the manufactures are almost wholly 

 for the home consumption of their district. The low values and fragile 

 character of the wares stand in the way of any extensive shipments. 



There is one tile works, that of Messrs. Dennison Bros, at Delaware, 

 Ohio, which has taken a new departure in the business. They have 

 built an entirely new plant, suitable for sewer pipe manufacture, includ- 

 ing dry and wet pans, sewerpipe press, elevators, etc. and devote their 

 special attention to the manufacture of the largest sizes of tiles suitable 

 for county ditches and railroad work. 



The product is not vitrified, but is hard burnt, and will stand ship- 

 ment. They make common drain tile up to twenty four inches in 

 diameter. 



Their clays are derived from a stratum of the Huron Shales, which is 

 of a very high grade clay here, except for the presence of considerable 

 iron pyrites in little nodules. 



The field of operation in this line is not large however, and a long 

 experience in the drain tile business has been the only way to get a trade 

 in this line sufiicient to ensure success. 



IV. THE MANUFACTURE OF REFRACTORY MATERIAL. 



The art of manufactuing refractory material calls into play a know- 

 ledge of the higher qualities of clay; we have considered in the discussion of 

 crude pottery and vitrified wares the kinds of clay suited to each, and have 

 seen that in these cases, a certain degree of fusibility is required. In mak- 

 ing refractory material the whole study is to secure the utmost resistance to 

 the fusing and fluxing action of fire, consistent with a certain physical 

 structure of the material. 



The importance of this form of clay working is hard to justly 

 represent. It does not now occupy the important stand it once did in 

 the business industries of the state or the world; other forms of clay 

 working have easily outstripped it, as far as capital invested and value of 

 output go. Perhaps, however, the best way to picture its importance is 

 to try and imagine what we should do without it. Every ton of iron in 

 the country is smelted inside of firebrick walls; every boiler setting and 

 household grate uses a small quanity of it. No metallurgical industry is 



