GAS- FURNACE 597 



which, the moBt inferior qualities of fuel, such as slack, coke-dust, lignite, and peat, 

 may be employed, producing a. money saving, in many instances, amounting to 75 per 

 cent. ,t 



2, Increase of work done per day in a furnace of given dimensions amounting 

 to 30 per cent, or more, owing to unlimited command of heat with low chimney- 

 draught. 



3. Great purity and gentleness of flame, which greatly diminishes the oxidation, or 

 deterioration, of the material heated in the furnace. 



4. Increased durability of furnace, owing to the absence of ashes, and a perfect 

 uniformity of heat throughout the furnace. 



5. Saving of space within the works, and great cleanliness of operation, the fuel 

 being converted into gas outside the works. 



6. Complete command of the intensity of the heat, and of the chemical nature of 

 the flame, which may be arrested or changed from a reducing to an oxidising flame, or 

 the reverse, at any one moment, tending to facilitate and improve all metallurgical 

 operations. 



7. Complete absence of smoke from the stack^ which renders this furnace beneficial 

 to the public in large towns. 



The late Professor Faraday, in his last public lecture at the Eoyal Institution, on 

 the 20th June 1862, described these furnaces in the following terms : 



4 The gaseous fuel is obtained by the mutual action of coal, air, and water, at a 

 moderate red heat. A brick chamber, perhaps 6 ft. by 12 ft., and about 10 ft. high, 

 has one of its end walls converted, into a fire-grate, i.e., about half-way down it is a 

 solid plate, and for the rest of the distance consists of strong horizontal plate bars 

 where air enters, the whole being at an inclination such as that which the side of 

 a heap of coals would naturally take. Coals are poured, through openings above, upon 

 this combination of wall and grate, and being fired at the under surface, they burn at 

 the place where the air enters ; but as the layer of coal is from 2 to 3 feet thick, 

 various operations go on in those parts of the fuel which cannot burn for want of air. 

 Thus the upper and cooler part of the coal produces a large body of hydrocarbons ; 

 the cinders or coke which are not volatilised, approach, in descending, towards the 

 grate ; that part which is nearest the grate burns with the entering air into carbonic 

 acid, and the heat evolved ignites the mass above it ; the carbonic acid, passing slowly 

 through the ignited carbon, becomes converted into carbonic oxide, and mingles in the 

 upper part of the chamber (or gas-producer) with the hydrocarbons. The water, 

 which is purposely introduced at the bottom of the arrangement, is first vaporised by 

 the heat, and then decomposed by the ignited fuel, and re-arranged 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 hori- 

 zontally 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 combined gases) find precisely similar outlets down 

 which they pass ; and traversing the two remaining regenerators from above down- 

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

 state to the shaft or chimney. Now the passages between the four regenerators and 

 the gas and air are supplied with valves and deflecting plates, which are like four- way 

 cocks in their action ; so that by the use of a lever those regenerators and air- ways, 

 which were carrying off the expended fuel, can in a moment 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 gases which enter the stack to be cast into the air are not usually 

 above 300 Fahr. of heat On the other hand, the entering gas and air always pass 

 upwards through the regenerators, so that they attain a temperature equal to a 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 evolyed by the chemical action of combustion is about 



