92 



NATURE 



[Nov. 25, 1880 



comparison with a good Abbotsford grate with solid clay bottom, 

 back and sides, the figures would have appeared seriously the 

 other way. 



In a room of exactly half the cubic area of the one referred to 

 by Dr. Siemens we have an Abbotsford grate a little over ird 

 cubic foot capacity, the actual measurement of the fire space being 

 5i inches deep, S inches back to front, 14 inches wide. This 

 is"lighted at 7 o'clock every morning and at 10 o'clock the grate 

 is filled (not piled high). This fire burns until 10 or II o'clock 

 every night untouched, practically smokeless, making the room 

 pleasantly warm all over in the severest weather, and without 

 making a handful of cinders in a month. One ordinary boxful 

 of coals lasts two days. We have five, sometimes six, fires going 

 daily at an average cost for coal for the winter season of five 

 shillings weekly, or less than twopence per day per fire. That 

 Dr. Siemens is correct so far as the old style of firegrate is con- 

 cerned, I know to my cost, but taking any good grate with clay 

 sides and back and a solid clay bottom, his fire at its best «ill 

 not compare either for cleanliness, economy, or comfort. 



Gas fires are wanted where absolutely no attention and dust 

 can be permitted. Allowing either of these as possible, no 

 substitute I know will approach a well-constructed open fire with 

 a solid clay bottom and fire-box. 



With regard to the waste heat, it is no greater than absolutely 

 necessary to take away the products of combustion, as, with our 

 grates, it is utilised for warming the upper rooms. At this moment, 

 with five good fires, there is visible from the tops of our chimneys 

 nothing except a clear transparent current of warm air ; any one 

 at a cursory glance would say there were no fires in the house. 



It must be borne in mind when I refer to cost that we cook 

 entirely by gas, and the price of good coal here is 14J. 2.d. per 

 ton, coke being about half this price. What is required in a gas 

 fire is a perfectly clean source'of radiant heat, without trouble, and 

 quickly available : these conditions are not in any way fulfilled 

 by Dr. Siemens' arrangement. With the exception of two or 

 three minutes expended in lighting, all he has attained can be 

 found in a more perfect form in many of the fire-grates which 

 have been in common use for the last ten years. Amongst our 

 many attempts at gas fires one, although not absolutely the same 

 as Dr. Siemens', was practically so, and was condemned because 

 it required as much trouble as our present fires, and was much 

 slower in lighting. It would be botli interesting and instructive 

 if Dr. Siemens would test an Abbotsford grate under the same 

 conditions as his'cokegas fire, and supplement his report with 

 one from the individual who has to do the cleaning up and 

 dusting, a department w hich it is more than probable he ignores. 



Another important matter is that I believe the cost of making 

 and fixing Dr. Siemens' grate would be not less than that of a 

 good modern fire-grate. Thos. Fletcher 



Warrington 



Through your courtesy I am enabled to reply to the 

 objections raised by three correspondents against my proposed 

 gas-coke grate, before they have actually appeared in your 

 columns. 



Mr. D. A. Stevenson considers that the use of coke is 

 objectionable on account of the gases evolved in its combustion, 

 and especially the carbonic oxide gas, which would poison the 

 atmosphere. In reply I have to say that in burning coke with a 

 supply of hot air, and in contact in front of the grate with the 

 atmosphere, its entire combustion is insured, resulting in car- 

 bonic acid, which is a necessary constituent of our atmosphere. 

 In obtaining the same amount of heat through the perfect com- 

 bustion of gas, products of combustion at least equally objection- 

 able from a sanitary point of view will be evolved. 



The gas-asbestos grate which he describes appears to be judi- 

 ciously contrived, but its power of heating the room depends 

 entirely upon the combustion of gas unaided by hot air or solid 

 fuel. Now 1000 cubic feet of gas weigh about 34 lbs., and the 

 heat developed in the combustion cannot exceed 34 X 22,000 = 

 748,000 units of heat. 



The heat units produced in burning a pound of coke may be 

 taken at 13,400 (assuming it to contain about 8 per cent, of 

 incombustible admixture, the heat equivalent of pure carbon 



being 14,500 units), and it requires 7 48.000 _ ,g ^Oi., or just 



13,400 

 half ;a hundredweight of this coke, to produce the heating effect 

 of 1030 cubic feet of gas. 



Taking gas coke at iSj-. per ton (which is an excessive price), 

 the 56 lbs. of coke represent a cost of 5 ■41/., as compared with 

 y. (>d. for the 1000 cubic feet of gas producing the same amount 



of heat. This great difference of cost at once shows the advan- 

 tage of making coke do as much of the work as possible. With- 

 out it a gas grate will consume y> to 70 cubic feet of gas per 

 hour, whereas my experiments prove that an average consump- 

 tion of 8 cubic feet suffices to heat a large room when combined 

 with a moderate consumption of coke, and with the use of the 

 heating arrangement, to which I attach great importance. Another 

 imi ortant consideration in favour of the joint use of coke and gas 

 is that the existing gas companies produce both these constituents 

 very much in the proportion in w'hich they would be required, 

 and could therefore provide the means of supplying an enormous 

 number of coke-gas grates, whereas their plant and mains would 

 be quite inadequateSto supply a demand upon them for an extended 

 application of purely gas stoves. 



Mr. Cosmo Innes describes a gas grate of his construction, 

 having the closed grate and single gas pipe behind the lower 

 front bar which I advocate ; he proposes to fill the grate with 

 common coal, using the gas only as a means of kindling the fire. 

 My objections to his pioposal are that in using coal he must 

 continue to make smoke, which we are desirous to prevent, and 

 that the hot back to his fire means rapid distillation of the fuel 

 up the chimney in the form of hydrocarbons and carbonic oxide. 

 The gas arrangement as shown by him will be efficacious, no 

 doubt, as a means of kindling a bright and cheerful fire, but he 



would do better in that case to use a few logs of wood instead of 

 coals. A blight but short-lived fire may thus be raised quickly 

 at a cheap rate in a dining-room or in a parlour. 



Mr. Thomas Fletcher admits that my grate has the advantage 

 of economy over a common coal grate, but thinks the Abbotsford 

 grate the best of all. This grate is according to him practically 

 smokeless, and produces only a handful of cinders in a month, 

 although common coal is used. Now I have no desire to 

 detract from the merits of the Abbotsford grate, but I fail to see 

 why it should be smokeless, considering that raw coal is used ; 

 and the extremely small production of ashes or cinder seems to 

 imply that Mr. Fletcher uses an extremely pure and probably a 

 smokeless coal, very different from the fuel we are usually supplied 

 with in London. 



He also objects to the cost of my arrangement, and his opinion 

 in this respect, coming from a practical grate-builder, is entitled 

 to every consideration. In first describing my plan I did not go 

 into the question of cost of application ; but having been since 

 asked by grate-builders to advise them regarding the cheapest 

 form of niy grate and the easiest mode of applying it to existing 

 fire-places, I have devised a form of application which leaves 

 little to be desired, I think, as regards first cost. 



The arrangement is shown by the accompanying sketch,, and 

 consists of two parts which are simply added to the existing 



