84 THE SCIENTIFIC PAPERS OF 



took up a second equivalent of carbon (forming carbonic oxide) in 

 traversing the second, so that the fuel of the second fire was con- 

 sumed to no purpose. In order to dimmish this loss and also 

 avoid impairing the draught by a double resistance, the ridges of 

 fuel were discontinued and the coal was fed into the furnace from 

 the sides, resting on a solid hearth, to be there volatilised by the 

 heated air passing over it. By frequently stirring the first fire its 

 combustion was favoured until the current was reversed, when it 

 was left undisturbed until the next change, and so on alternately. 

 It was found very difficult however to maintain an active and 

 uniform combustion and to burn the purely carbonaceous substance 

 that was left in the fireplace after the gaseous portion of the fuel 

 had been volatilised ; and it had frequently to be raked out in 

 order to make room for fresh gaseous fuel. This circumstance led 

 to the first step towards the employment of fuel in the form of 

 gas, by providing a small grate below the heap of fuel, through 

 which a gentle current of air was allowed to enter, forming car- 

 bonic oxide, which afterwards further combined with oxygen on 

 meeting with the hot current of air entering the furnace from the 

 regenerator. The two fireplaces of alternating activity were how- 

 ever attended with considerable practical inconvenience : the 

 furnacenien in particular disliked the idea of attending two fire- 

 places instead of one, and being little interested in the saving of 

 fuel, took no pains to work the furnace in a satisfactory manner. 



It therefore became necessary to devise a plan of heating a 

 single chamber continuously by one fireplace, in combination with 

 the alternate reversal of currents through the regenerators, but 

 without reversing the direction of the flame. This was accom- 

 plished by means of double reversing valves, and was practically 

 carried out in a puddling furnace that worked for a considerable 

 length of time at the ironworks of Messrs. K. and W. Johnson 

 near Manchester. The two regenerators were placed longitudinally 

 side by side, with a flue between, underneath the puddling chamber, 

 and the fireplace was put at one end of the puddling chamber, as 

 in an ordinary puddling furnace, and fed with fuel from above. 

 The heated air from the first regenerator was brought up at the 

 back of the fireplace, and meeting there with the fuel produced 

 the required flame in the puddling chamber ; whence the products 

 of combustion passed down at the end of the chamber, and were 



