9O THE SCIENTIFIC PAPERS OF 



pass on its way into the air flue G-, as shown by the arrows in 

 Fig. 5 ; by this means the siege is kept comparatively cool, so 

 that no fluid glass can pass through crevices into the regenerators. 

 Any melted glass that may fall from the heating chamber through 

 the apertures at the ends of the siege does not get into the regene- 

 rators, but falls into the pockets M, Fig. 4, whence it can be 

 removed through the opening at the bottom. The passage N, 

 Fig. 5, by which the air enters, affords the means of getting at the 

 regenerators through an opening at the end of each. 



From the air flue G-, Fig. 8, the entering air is directed by the 

 reversing valve H into the air regenerator, as shown by the arrows, 

 and there becomes heated ready for entering the furnace ; at the 

 same time the gas entering from the gas flue I, Fig. 7, is directed 

 by the reversing valve J into the gas regenerator, where it becomes 

 heated to the same temperature as the air. Similarly the products 

 of combustion on leaving the opposite end of the furnace pass 

 down through the second pair of regenerators, as shown by the 

 arrows in Fig. 4, and after being here deprived of their heat are 

 directed by the reversing valves H and J into the chimney flue K. 

 When the second pair of regenerators have become considerably 

 heated by the passage of the hot products of combustion, and the 

 first pair correspondingly cooled by the entering air and gas, the 

 valves H and J are reversed by the hand levers, as shown dotted in 

 Figs. 7 and 8, causing the currents to pass through the regenera- 

 tors and the heating chamber in the contrary direction, whereby 

 the hot pair of regenerators are now made use of for heating the 

 gas and air entering the furnace, while the cool pair abstract the 

 heat from the products of combustion escaping from the furnace. 

 The supply of air and gas to the furnace is regulated by the 

 adjustable stop valves L, whereby the nature and volume of the 

 flame in the furnace may be varied at pleasure ; whilst the chim- 

 ney damper is used to regulate the amount of pressure in the 

 furnace in relation to the atmosphere, so as to allow the opening 

 of working holes. 



The construction of furnace above described may be varied in 

 many ways to suit local circumstances. The regenerators are in 

 some instances not placed immediately under but at the side of 

 the furnace ; but it is important that they should always be placed 

 at a lower level than the furnace, in order that the air and gas 





