TEMPERED GLASS. 



557 



bath almost without being touchetl. Then came another difficulty 

 that of preventing an already highly-heated combustible liquid taking 

 fire upon the entrance of the still more highly-heated glass. The lat- 

 ter difficulty was met by placing the tempering bath in direct com- 

 munication with the heating oven, and inclosing it so as to prevent 

 access of air ; and the former by allowing the heated glass articles to 

 descend quickly by gravitation, from the oven to the bath. 



The apparatus used by M. de la Bastie is shown in the accom- 

 panying illustrations, in which Fig. 1 is a front vieAv, and Fig. 2 a ver- 

 tical section, of furnace for annealing glass objects; Fig. 3 a sectional 

 plan of the oven for annealing flat plates. The working oven, a, is 

 heated by a furnace, h. The bottom of the oven, c, and the slope to 

 the bath, are made in one piece of refractory material, and are very 

 smooth on the surface. At the side of the oven is a j^reparatory oven, 

 communicating by a passage in the sepai'ating wall. In this oven the 

 glass is partially heated before being placed in the main oven, a. 

 The products of combustion are carried away in the direction of the 

 arrows through the chimney. When the oven, a, is sufficiently heated, 

 the ash-pit and fire-doors are closed, and rendered air-tight by luting, 



Fig. 2. 



and the fire is maintained by small pieces of fuel introduced by a hole 

 in the fire-door. The draught is then stopped by lowering the chim- 

 ney-cap, or closing the damper. The vertical damper, /, is then raised, 

 so that the flame passes by the flue, g, to a second chimney, passing 

 thus along the slope and heating it, and also opening communication 

 from the oven, a, to the bath, A, which is filled with the oleaginous 

 compound. It is covered from the external air by a lid, and within it 

 is a basket of fine wire gauze, A-, hung from brackets. A tube, I, con- 

 tains a thermometer, w,to indicate the temperature; and by this tube 

 the contents of the bath may be added to, or any excess may overflow 

 by the discharge-pipe, n. A plug, o, on the cover may be removed to 



