Prof. Faraday on Gas Furnaces, fyc. 163 



at the bottom of the arrangement, is first vaporized by the heat, and 

 then decomposed by the ignited fuel and rearranged as hydrogen 

 and carbonic oxide ; and only the ashes of the coal are removed as 

 solid matter from the chamber at the bottom of the fire-bars. 



These mixed gases form the gaseous fuel. The nitrogen which 

 entered with the air at the grate is mingled with them, constituting 

 about a third of the whole volume. The gas rises up a large vertical 

 tube for 12 or 15 feet, after which it proceeds horizontally for any 

 required distance, and then descends to the heat-regenerator, through 

 which it passes before it enters the furnaces. A regenerator is a 

 chamber packed with fire-bricks, separated so as to allow of the free 

 passage of air or gas between them. There are four placed under a 

 furnace. The gas ascends through one of these chambers, whilst 

 air ascends through the neighbouring chamber, and both are con- 

 ducted through passage outlets at one end of the furnace, where 

 mingling they burn, producing the heat due to their chemical action. 

 Passing onwards to the other end of the furnace, they (i. e. the com- 

 bined gases) find precisely similar outlets down which they pass ; and 

 traversing the two remaining regenerators from above downwards, 

 heat them intensely, especially the upper part, and so travel on in 

 their cooled state to the shaft or chimney. Now the passages be- 

 tween the four regenerators and the gas and air are supplied w r ith 

 valves and deflecting-plates, some of which are like four- way cocks 

 in their action ; so that by the use of a lever these regenerators and 

 air- ways, which were carrying off the expended fuel, can in a mo- 

 ment be used for conducting air and gas into the furnace ; and those 

 which just before had served to carry air and gas into the furnace, 

 now take the burnt fuel away to the stack. It is to be observed 

 that the intensely-heated flame which leaves the furnace for the stack 

 always proceeds downwards through the regenerators ; so that the 

 upper part of them is most intensely ignited, keeping back, as it 

 does, the intense heat ; and so effectual are they in this action, that 

 the gas which enters the stack to be cast into the air is not usually 

 above 300° F. of heat. On the other hand, the entering gas and air 

 always pass upwards through the regenerator ; so that they attain 

 a temperature equal to white heat before they meet in the furnace, 

 and there add to the carried heat that due to their mutual chemical 

 action. It is considered that, when the furnace is in full order, the 

 heat carried forward to be evolved by the chemical action of combus- 

 tion is about 4000°, whilst that carried back by the regenerators is 

 about 3000°, making an intensity of power which, unless moderated 

 on purpose, would fuse furnace and all exposed to its action. 



Thus the regenerators are alternately heated and cooled by the 

 outgoing and entering gas and air ; and the time for the alternation 

 is from half an hour to an hour, as observation may indicate. The 

 motive power on the gas is of two kinds — a slight excess of pressure 

 within is kept up from the gas-producer to the bottom of the rege- 

 nerator to prevent air entering and mingling with the fuel before it 

 is burnt ; but from the furnace, downwards through the regenera- 

 tors, the advance of the heated medium is governed mainly by the 

 draught in the tall stack, or chimney. 



