l8o THE SCIENTIFIC PAPERS OF 



from the gas-producer is directed upwards through one of these 

 chambers, and cold air is directed upwards through the adjoining 

 chamber. Both air and gas meet at the entrance of the combus- 

 tion chamber, and if the brickwork contained in the two chambers 

 is heated by any process, the air and gas flowing through it will 

 also be heated to very nearly the temperature of the materials 

 which impart that heat. They will therefore meet in combustion 

 at a high platform, so to speak. If the temperature of the brick- 

 work be at the upper surface, say 1000, the air and gas will 

 be heated practically to 1000 before they combine, and the result 

 of that combustion must be a temperature of at least 1000 higher 

 than it would have been if the gas had not been so heated. The 

 products of combustion flow away at the other side through pas- 

 sages, every alternate passage leading into one or other of the two 

 remaining chambers, and in flowing downwards over the surfaces 

 of the brickwork they impart heat to those surfaces, raising their 

 upper layers to nearly the temperature of the products of combus- 

 tion, which after depositing their heat, reach the chimney compara- 

 tively cool. By reversing the direction of the gases, say every 

 hour, or every half-hour, as the case may be, and admitting gas 

 fuel at the place where one portion of the products of combustion 

 left, and air at the point where the other portion of the products 

 of combustion left, the currents of coal gas and air will pick up, 

 so to speak, the heat which was kept there in deposit, and reach 

 the point where they enter into combustion heated to a higher 

 degree by another 1000 ; and the consequence of this combustion 

 will be the attainment of a still higher degree of heat than was 

 obtained in the previous operation ; and so on, and on, until either 

 there is an equilibrium produced by the fusion of the materials 

 to be heated, at which point, of course, the excess of heat will be 

 absorbed in work done, or it will go on accumulating until com- 

 bustion itself will cease. Such a point will be reached at about 

 2500 Cent., the temperature of dissociation, and in heating one of 

 these furnaces up to the highest point which it would be safe to 

 attain in them, the flame, which at one portion of the operation is 

 a short white flame, becomes gradually extended into a long 

 attenuated flame of somewhat bluish appearance, clearly showing 

 that combustion is earned on under great difficulties. For any 

 temperature exceeding these limits we should have to resort to 



