538 Professor Faraday [June 20, 



burn, producing the heat due to tlieir 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 downwards, 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, 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 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 

 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 

 passes upwards through the regenerator, so that they attain a tempera- 

 ture 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 con- 

 sidered that when the furnace is in full order, the heat carried forward 

 to be evolved by the chemical action of combustion is about 4000", 

 whilst that carried back by the regenerators is about 3000^, making an 

 intensity of power which, unless moderated on purpose, would fuze 

 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 regenerators, 

 the advance of the heated medium is governed mainly by the draught 

 in the tall stack, or chimney. 



Great facility is afforded in the management of these furnaces. 

 If, whilst glass is in the course of manufacture, an intense heat is 

 required, an abundant supply of gas and air is given ; when the glass 

 is made, and the condition has to be reduced to working temperature, 

 the quantity of fuel and air is reduced. If the combustion in the fur- 

 nace is required to be gradual from end to end, the inlets of air and 

 gas are placed more or less apart the one from the other. The gas is 

 lighter than the air ; and if a rapid evolution of heat is required as in a 

 short puddling furnace, the mouth of the gas inlet is placed below that 

 of the air inlet ; if the reverse is required, as in the long tube-welding 

 furnace, the contrary arrangement is used. Sometimes, as in the 

 enameller's furnace, which is a long muffle, it is requisite that the heat 

 be greater at the door end of the muffle and furnace, because the 



