1886.] on the Principles of Domestic Fireplace Construction. 343 



second point was that this boxing up rendered the chamber hotter, 

 and this increased temperature beneath the fire-grate, i. e. under the 

 fuel, added so materially to the temperature of the whole, even of 

 the cinders coming into contact with the iron grid, that the very 

 moderate supply of oxygen reaching the front and upper surface of 

 the fuel was sufficient to maintain every portion in a state of incan- 

 descence. Moreover, I observed that combustion was going on at an 

 orange, not at a icliite, heat. 



Let us contrast a white with the orange heat. A icliite heat in a 

 fire means rapid combustion, oiduij to the strong current of air, oxyjen, 

 which passes under the grate, through the centre of the fire, and up the 

 chimney. As soon as the heart of the fire has been rapidly burnt 

 away at a white heat, the fuel cools ; the iron grid cools also ; and 

 the cinders in contact with the grid are chilled below combustion 

 point. They then cease to burn, and the bottom of the fire becomes 

 dead and choked. The poker must now be brought into play to 

 clear away the dead cinders, and to re-open the slits in the choked 

 grid. New coal is added to the feeble remnant of burning embers, 

 with no reserve of heat in the iron surroundings ; and in time, and 

 perhaps very slowly, the fire revives, and rapid combustion sets in 

 afresh under the influence of the renewed current of oxygen passing 

 through the heart of the fire. An orange heat means that the coke, 

 i. e. the red-hot cinder, is burning with a slowly applied stream of 

 oxygen, a degree of combustion which is only possible ivhen the coal is 

 kept w-arm by the hot chamber beneath, and by a reasonable limitation 

 of loss of heat at the back and sides by firebrick, either in contact 

 with the fuel, or at least close behind the iron surrounding it. This 

 effect is seen, partially, in the grates with solid firebrick bottom, but 

 far more perfectly in the grates with the chamber closed by the 

 " Economiser." 



This hot chamber has the following effects: — The incandescent 

 coal remains red-hot from end to end of the grate, until nearly all is 

 consumed, thus maintaining a larger body of the fuel in a state to 

 radiate effective heat into a room. The cinders on coming into 

 contact w^th the iron grid also remain red-hot, and so continue to 

 burn away until they fall through the grid as a fine powder. This 

 allows the fire to burn clearly all day long almost without poking. 

 When the fire is low, and new coal is added, the reserve of heat in 

 the hot chamber is such that the addition of cold fresh fuel does not 

 temporarily quench the embers, and the fire is very quickly in a 

 blaze after being mended. 



Having made the discovery by the observation of a grate supplied 

 to me with an " Economiser," the value of which, I suspect, was 

 hardly appreciated by the makers, I applied " Economisers " one by 

 one to all my grates, kitchen included. The result surpassed my 

 expectations. There was a saving of at least a fourth of my coal. 

 The experience of many friends, who at my advice adopted the 

 system, confirmed my own results. It was therefore clear to me that 



