NA TURE 



25 



THURSDAY, NOVEMBER 11, 18 



DR. SIEMENS' S NEW CURE FOR SMOKE 

 T^'HE growing obscurity which distinguishes the winter 

 X. atmosphere of London has disposed men to con- 

 sider whether it is an indispensable evil connected with 

 the use of coal in great centres of population, or whether 

 means can be found of providing the warmth and 

 comfort which the copious use of mineral fuel affords 

 us without having to pay the penalty of dispensing 

 with the solar ray, of finding ourselves and everything 

 we touch covered with soot, and of occasionally having, 

 even at midday, to grope our way with a feeling akin to 

 suffocation. 



I am decidedly of opinion that the evil is one which 

 not only admits of remedy, but that its cure would result 

 from a closer attention to the principles of economy in 

 the use of fuel. 



Until within recent years wasteful expenditure was the 

 rule both in the application of fuel to our large manu- 

 facturing operations and for domestic purposes, but great 

 strides have been made within the last twenty years to 

 improve our mode of burning fuel both under our steam 

 boilers and in the metallurgical furnace. The Regene- 

 rative Gas Furnace, which was the subject of Faraday's 

 last discourse at the Royal Institution in 1S62 has contri- 

 buted its share to this result, combining as it does con- 

 siderable economy, with the entire absence of smoke from 

 the chimney. 



Since by the employment of gaseous fuel results such as 

 these are realised, there seems no A -priori reason why 

 analogous results should not attend its application on a 

 smaller scale, even down to the means of heating our 

 apartments, which, although a small application in each 

 individual instance, amounts, in the aggregate, to the 

 largest of all the uses of mineral fuel. 



Gas-grates have been tried by individuals desiring 

 progress, but I know several instances in which on 

 account of the great comparative expense incurred, and 

 objections raised to the smell, and dry heat, as it is called, 

 in the room, the time-honoured smoky but cheerful coal- 

 fires were reinstated. 



A gas-grate that was arranged in my bilHard-room in 

 the usual fashion, consisting of three air-gas-pipes with 

 apertures distributed over the fire-grate, and covered 

 with pumice-stone, presented certainly a cheerless appear- 

 ance, and filled the room (notwithstanding a fair chimney- 

 draught) with fumes, rendering the benefit of the fire a 

 doubtful one. These fumes could not have passed into 

 the room from the upper surface of the pumice-stone 

 owing to its proximity to the chimney ; but a little con- 

 sideration made me come to the conclusion that these 

 gases really proceeded from the ash-pan into the room. 

 The products of combustion set up by the gas flames 

 ascend no doubt so long as they are intensely hot, but in 

 giving off their heat to the inert pumice-stone they rapidly 

 cool, and being heavier than atmospheric air, descend 

 through the grate between the lines of gas flames, and 

 thus reach the apartment. Moreover the gas burnt 

 towards the back of the fireplace takes scarcely any part 

 in providing a red radiating surface in front of the grate, 

 Vol. XXIII. — No. 576 



serving only to baffle the draught passing towards the 

 chimney from the room. 



The first condition to be realised in an efficient gas- 

 grate consists in suppressing all gas orifices except imme- 

 diately behind the bottom front bar, and in substituting 

 for the grate a solid dead plate. Instead of using inert 

 matter such as pumice-stone, I consider it far more 

 economical and efficacious to transfer the heat of the gas 

 flames to gas coke or anthracite, which when once heated 

 helps the gas to increase and maintain a sufficient tempe- 

 rature for radiation through its own slow combustion. 

 The gas should not be mixed in the pipe with atmospheric 

 air to produce a Bunsen flame, as is frequently done, 

 because by using the unmixed gas a rich flame is set up 

 between the pieces of coke near the front of the grate, 

 producing to the eye an appearance similar to a well- 

 ignited ordinary coal fire, and the hot carbonaceous 

 matter through which it percolates ensures its entire 

 combustion before reaching the chimney. Heat will 

 however gradually accumulate towards the back of the 

 fire, notwithstanding the suppression of the grate bars, 

 and in order to obtain the utmost economy this heat 

 should be utilised to increase the temperature of the gas 

 flames and of the coke in front of the grate. 



To accomplish this I have constructed a grate accord- 

 ing to the annexed sketch. The iron dead plate c is 

 riveted to a stout copper plate a facing the back of the 

 fire-grate, and extending five inches both upwards and 

 downwards from the point of junction. The dead plate 

 c stops short about an inch behind the bottom bar of the 

 grate to make room for a half inch gas-pipe f, which is 

 perforated with holes of about one-twentieth of an inch in 

 diameter placed zig-zag at distances of three-quarters of an 

 inch along its upper surface. This pipe rests upon a lower 

 plate (/, which is bent downwards towards the back so as 

 to provide a vertical and horizontal channel of about one 

 inch in breadth between the two plates. A trap-door c, 

 held up by a spring, is provided for ihe discharge of ashes 

 falling into this channel. The vertical portion of this 

 channel is occupied by a strip of sheet copper about four 

 inches deep, bent in and out like a lady' s frill and riveted 

 to the copper back piece. Copper being an excellent 

 conductor of heat, and this piece presenting (if not less 

 than a quarter of an inch thick) a considerable sectional 

 conductive area, transfers the heat from the back of the 

 grate to the frill-work in the vertical channel. An air 

 current is set up by this heat, which, in passing along the 

 horizontal channel, impinges on the line of gas flames 

 and greatly increases their brilliancy. So great is the 

 heat imparted to the air by this simple arrangement that 

 a piece of lead of about half a pound in weight introduced 

 through the trap-door into this channel melted in five 

 minutes, proving a temperature to exist exceeding 619° F. 

 or 326' C. The abstraction of heat from the back has 

 moreover the advantage of retarding the combustion of 

 the coke there while promoting it at the front of the 

 grate. 



The sketch represents a fireplace at my office, in a 

 room of 7,200 cubic feet capacity facing the north. I 

 always found it difficult during cold weather to keep this 

 room at 60" F. with a coal fire, but it has been easily 

 maintained at that temperature since tlie grate has been 

 altered to the gas-coke grate just described. 



