254 METHODS OF GLASS MANUFACTUEING. 



checker work of the regenerative chamber a great 

 amount of heat. As highly heated gases are capable of 

 producing a greater amount of heat on combustion than 

 cold or only moderately heated gases, it was to this end 

 that Dr. Siemans made this application. If the process 

 of supi)lying the gas to the furnace be reversed, that is 

 by regulating the chamber valves, so that the gas and 

 air which unites with it at the opening of the flues into 

 the furnace, will enter into the furnace through the re- 

 generative chambers which have been heated to a high 

 temperature by the escaping gases, the gas and air will 

 become highly heated, and their combustibility greatly 

 increased. 



This reversal of the supply of gas should take place 

 every 20 to 30 minutes, or as often as necessary, so as not 

 to allow the receiving chambers to grow absolutely cold. 

 In this manner it is possible to obtain a far greater 

 efficiency from a ton of coal than by any known process. 

 The operation of this style of furnace is continuous, 

 the batch being supplied at one end, while the pure metal 

 is worked out at the other. The purpose of the bridges is 

 to prevent imperfectly melted material reaching the 

 working-out end. These are constructed with openings 

 near the bottom through which the glass must pass to 

 go from one compartment to another. As the Sp. Gr. of 

 pure glass is greater than that of the imperfectly melted 

 material, it follows that it is only the pure glass that is 

 admitted into the working-out compartment, and the 

 imperfectly melted material is obliged to remain in the 

 heating compartment until it becomes perfectly fused. 



The principal advantages of the tank furnace over 

 pots may be classified as follows : 



Increased production, it being possible to work several 

 gangs of workmen, so that the glass may be blown at 

 night as well as by day. 



Greater economy in working, as the extra cost of melt- 



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