352 



NATURE 



'{Feb. lo, r88i 



both to the supplier and to lh8 consumer be so adjusted that ili*' 

 latter, while paying for his illuminating gas an increased price 

 proportionate to the increase of illuminating power, would be 

 furnished with a heating gas at greatly reduced cost ; lor the 

 heating gas could be reduced in price in a much larger propor- 

 tion than the illuminating gas would have to be raised, because 

 it would not require the same ]iurification from sulphur uhich 

 renders illuminating gas comparatively costly. The enormous 

 increase of consumption would moreover enable the gas com- 

 panies to reduce [jrices all round very considerably without 

 interfering with their comfortable revenues. 



For large applications of heating gas to the working of fur- 

 naces and boilers, simpler means than the retort can be found 

 for its produc ion. I constructed a gas producer many years 

 ago in connection with my Regenerative Gas Furnace ; this I 

 need not now describe in detail. In it all the carbonaceous 

 matter of the coal is converted into combustible gas, the solid 

 carbon yi Iding a supply of carbonic oxide ; the resultant mixture 

 of combustible gas contains a very large proportion averaging 

 6l"5 per cent, of nitrogen, which swells its volume without in 

 any way contributing to its heating pnwer. 



It has been my endeavour for some time to construct a gas 

 producer which, without losing the simplicity of the first, should 

 be capable of yielding a heating gas of superior calorific power. 

 This producer consists of a wrought-iron cylindrical chamber, 

 truncated downwards, and lined with brickwork. The fuel to 

 be converted into g.as is introduced through a hopper, and the 

 cinder and ashes work out through the open orifice at the 

 bottom. 



Instead of a grating for the introduction of atmospheric air a 

 current of heated air is brought in, either through the hopper or 

 through the orifice at the bottom, and is discharged into the 

 centre of the mass of fuel ; the effect is the generation of a very 

 intense heat at that point. The fuel, afier its descent through 

 the hopper, arrives gradually at this region of intense heat, and 

 when subjected to it, parts with its gaseous constituents. At 

 the point of maximum heat coke is consumed, producing carbonic 

 anhydride, which, in passing through the considerable thickness 

 of fuel surrounding this portion, takes up a second equivalent of 

 carbon, and becomes changed into carbonic oxide. Here also 

 the earthy constituents are for the most part separated in a fused 

 or .semi-fused condition, and in descending gradually reach the 

 orifice at the bottom, whence they are removed from time to 

 time. Air enters through the bottom orifice to some extent, 

 causing the entire consumption of the carbonaceous matter, 

 which may have got past the zone of greatest heat ; water is 

 also here introduced in a hollow tray, and after evaporation by 

 the heat of the hot clinkers, passes upwards through the incan- 

 descent mass, and is converted by decomposition into cirbonic 

 oxide and hydrogen gas. The exit orifices for the gases .are 

 placed all round, near the circumference of the chamber, ascend- 

 ing upwards into an annular space, whence they are taken through 

 pipes to the furnace or other destination. 



The advantages connected with this modus oferandi con%ht in 

 the intensity of the heat produced within the centre of the mass, 

 whereby the whole of the fuel is converted into combustible 

 gases, with the least amount of nitrogen. The hydrocarbons 

 formed in the upper portion of the apparatus have to descend 

 through the hotter fuel below, and in so doing the tar and other 

 vapours mixed up with them are decomposed, and furnish com- 

 buslible gases of a permanent character. 



The orifice at the bottom of the apparatus may be enlarged, 

 and so arranged that, instead of ashes only being produced, 

 coke may be withdrawn, and in this way a continuous coke oven 

 may be constructed, which is at the same time a gas producer, 

 or in other words an apparatus in which both the solid and 

 gaseous constituents of the coal are fully utilised. 



The intense heat in the very centre of a large mass of fuel has 

 for its result a very rapid distillation, and thus one gas producer 

 does the work of two or three gas producers of the type hitherto 

 employed ; this more concentrated action will moreover allow 

 of the introduction of gaseous fuel, where want of space and 

 considerations of economy have militated hitherto against it, 

 and in favour of the ordinary coal furnace. 



It has been already proved that steam boilers can be worked 

 economically on laiicl with gaseous fuel, and there is no reason 

 that I know of why the same mode of working should not also 

 be api)lied to marine boilers. The marine engine has, within 

 the last fifteen years, been improved to an extent which is 

 truly surprising : the consumption of coal, which at the com- 



mencement of that period was never less than 8 lbs. per IIP., 

 has been reduced by expansive working in compound cylinders 

 to 2 lbs., or even less, per actual IIP. The mode of firing marine 

 boilers has, however, remained the same as it was in the days 

 of Watt and Fulton. In crossing the Atlantic one may see a 

 con-iderable number t.f men incessantly employed in the close 

 stoke-hole of the vessel opening the fire-doors and throning 

 in fuel. Each charge gives rise to the development of great 

 clouds of black smoiie issuing from the chimney, to the great 

 annoyance and discomfort of the passengers on deck. If, 

 instead of this, the fuel could be discharged mechanically into 

 one or more gas jiroducers, the gaseous fuel produced would 

 maintain the I oilers at a very uniform heat, without necessi- 

 tating the almost superhuman toil of the fireman ; no smoke or 

 dust would be emited from the chimney, and a large saving of 

 fuel would be effected. 



This cha ge would be specially appreciated by the numerous 

 tourists visiting the Western Highlands. Speaking from my 

 own experience on one occasion, I may say that the pleasure of 

 a trip on the beautiful Loch Lomond was very seriously marred 

 in consequence of the fumigation which my fellow passengers 

 and myself had to endure. 



The change from the u<e of solid to gaseous fuel would be 

 the prelude probably to another, and still more important change, 

 namely the entire suppres-ion of the steam boiler. We are 

 already in posse-sion of gas-engines working at moderate ex- 

 pense as compared with small steam-engines, even when supplied 

 with the comparatively expen-ive gas from our town gas-mains, 

 and all that will be required is an extension of the principle of 

 operation already established. The realisation of .such a plan 

 would of course involve many important considerations, and 

 may be looked upon as one of those subjects the accomplish- 

 ment of which may be left for the energy and inventive power of 

 the rising generation of engineers. 



Before le.aving this branch of the subject I wish to call atten- 

 tion to a favourite sugge-tion which I had occasion to make 

 some years ago. It consists in placing gas-producers at the 

 bottom of the coal mines themselves, so that in-tead of having 

 to raise the coal V>y mechanical power, the combustible gases 

 ascending from the depth of the mine to the surface would 

 acquire by virtue of their low specific gravity such an onward 

 pressure that they could be conducted in tulies to distances of 

 many miles, thus saving the cost of raising and transporting the 

 solid fuel. 



Glasgow v\ith its adjoining coal-fields appears to me a parti- 

 cularly favourable locality for putting such a plan to a practical 

 trial, and the well-known enterprise of its inh.ibitants makes me 

 sanguine of its accomplishment. When thus applied with 

 gaseous fuel, the town would not only be able to boast of a 

 clear atmosphere, but the streets would be relieved of the most 

 objectionable portion of the daily traffic. 



I now approach another and the last portion of my address, 

 the attainment of very intense degrees of heat either for effect- 

 ing fusion or chemical decomposition. Althciugh by means of 

 the combustion of either solid or gaseous fuel heats are pro- 

 duced which suffice for all ordinary purposes, there is a limit 

 imposed upon the degree of temperature attainable by any 

 furnace depending upon combustion. It has been shown by 

 Bunsen and by St. Claire-Deville, that at certain temperatures 

 the chemic.ll affinity b'^tween oxygen on the one hand and 

 carbon and hydrogen on the other ab^oluteIy ceases, and that 

 if the products of combustion CO2 and H.fi be exposed to such 

 a degree uf temj^erature they would fall to pieces into their 

 constituent elements. This point of dissociation, as it is called, 

 is influenced by pressure, but has been found for CO^ under 

 atmospheric pressure to be 2600° C. {or 4700° Fahr.). But 

 long before this extreme point has been arrived at, combustion 

 is greatly retarded, and the limit is reached when the losses of 

 heat by radiatio 1 from the furnace balance its production by 

 combustion. 



To electricity we must look for the attainment of a tempera- 

 ture above that of dissociation, and we have evidence of the 

 early application of the electric arc to such a purpose. In 1807 

 Sir Humphry Davy succeeded in decomposing potash liy means 

 of an electric current from a Wollaston battery of 400 elements, 

 and in 1810 he surprised the members of the Royal Institution 

 by the brilliant electric arc produced between carbon point."; 

 through the same agency. 



Magneto-electric and dynamo-electric currents allow of the 

 production of the electric arc much more readily and eeono- 



