214 GEOLOGY OF OHIO 



but it fills up the pores, smoothes over minute cracks and renders the 

 surface of the pipe little liable to offer obstruction to floating solids in 

 the sewage which the pipe is designed to carry. 



The glaze is uniformly obtained by using salt vapors; no instance of 

 any slip glazing has come to notice. The salt glaze is obtained by one 

 or two applications of the coarse salt in the fire holes, the operation 

 lasting from one to two hours. 



Great care has to be observed in setting the pipe to avoid bringing 

 any two pieces too close together, for it frequently happens that the salt 

 vapors are carried through the kiln, only attacking the exposed parts of 

 the ware and two pipe leaning together would both be devoid of glaze 

 from the point of contact downwards. 



The inability to secure a good dark glaze is a source of much loss 

 to the manufacturers; if their clay is difficult to glaze or takes a light 

 clear glaze.the use of oxide of manganese is sometimes resorted to. It 

 is mixed with the salt and burnt in the fire and its effect when vaporized 

 as chloride of manganese is to form a dark, black colored glaze. This 

 is an unsightly color to one who knows what it is, but it has been of 

 great assistance to many manufacturers in getting rid of pipes which 

 would be otherwise rejected on account of their color. 



In fact the system of grading sewer pipe is unnecessarily severe. 

 For any ordinary use, the seconds are as good as the firsts; it is not the 

 consumer who profits by this severity of selection ; it is the middle men 

 or retailers who buy the seconds at low rates, and work them off on the 

 public as first class goods, which, for any matter of service and utility, 

 they are. 



The position of Ohio as a sewer pipe producing state has long been 

 foremost. We not only make by all odds the greatest amount of ware, 

 but we have the three largest factories of this kind in the world. 



The National Sewer Pipe Company at Barberton, Ohio, enjoys the 

 proud distinction of being the finest plant of its kind in the world; it is 

 in reality four complete plants in one. 



It has introduced a number of labor saving economies in its con- 

 struction which are worthy of notice. The clay which is a fairly hard 

 shale is loaded in dumping railroad cars by a steam shovel and hauled by 

 the company's engine to the factory, two miles distant. 



The clay in being dumped is fed to the dry pans by long, steel lined 

 conveyors which are fed by men stationed along its line in the stock 

 house. 



The grinding and tempering offer no special novelties except the 

 great excellence of their .mechanical arrangements. 



Six presses, two on each of the three lower floors are run by four 

 crews, who are changed about somewhat, in qrder to produce the mat- 

 erials where they can be put on the floor to dry with the least cost. 



The drying is novel; it is accomplished by use of the Sturtevant 

 System of heating buildings, using steam coils and a fan for producing 



