December 29, 1910] 



NATURE 



293 





in the same proportion, although the air may feel warm 

 the walls will remain cold, so that the heat of the body 

 would pass by radiation to the walls and give rise to a 

 chill. 



If, therefore, one can retain the chief characteristic of 

 the open-fire heating by radiation, and eliminate the 

 smoke production and excessive waste of heat up the 

 chimney, we should have the ideal conditions for house- 

 warming. 



Enormous improvements have been made in the domestic 

 grate during the last fifteen years both from the artistic 

 and economic point of view, and whilst with the older 

 forms it was not unusual to find a coal consumption of 

 7 to 8 lb. of coal per hour, this quantity has been re- 

 duced in the more modern forms to about one half, and 

 this in itself has been an important step in smoke reduc- 

 tion ; but grates have long lives, and the capital outlay 

 of putting in new ones results in the modern forms being 

 chiefly found in new houses. There have been many 

 attempts made to construct grates for the smokeless con- 

 sumption of coal, but it is found in practice that when 

 once the heavy carbonaceous smoke is produced it is very 

 difficult again to burn the carbon particles completely, as 

 the dilution caused by the large volumes of nitrogen pre- 

 sent prevents their easy combination with the oxygen of 

 the air ; and there is no doubt that the best methods of 

 preventing smoke from bituminous coal is to feed on the 

 fresh coal only in very small quanties, and to supply the 

 top of the fire with a sharp draught of hot air. Under 

 these conditions complete combustion of escaping hydro- 

 carbons is ensured, and very little carbon is allowed to be 

 liberated in the solid form. In order to do this, how- 

 ever, the stove has to be to a certain extent closed in, 

 which is a drawback, and it is also found that no grate 

 for bituminous coal is absolutely smokeless. 



Stoves have been constructed in which the coal should 

 be supplied to the bottom of the fire, so as to keep the 

 top bright and clear, all the smoke having to pass through 

 the clear fire above, where it is decomposed. Such grates 

 are by no means novel, as one of the best was the 

 "Arnott," and must be more than sixty years old; but 

 for some reason they have never been popular with stove 

 manufacturers, with the result that they have never 

 reached the public, otherwise they are efficient and 

 economical. 



The great factor in making special forms of grate an 

 ineffective solution of the smoke problem is that it involves 

 large capital outlay on the part of the consumer, and my 

 own experience is that unless the consumer can become 

 a reformer without expense or extra trouble, the majority 

 will talk but never act, and it is for this reason that the 

 use of solid smokeless fuel, which can be used in all 

 ^sting grates, appears the most likely solution of the 

 great question. 



Smokeless solid fuels may be classified as : — 



(i) Coal which has been carbonised at a high tempera- 

 ture, so as to drive out practically all the volatile matter, 

 and this class is represented by gas coke and Coalexld. 



(2) Coal which has been partially carbonised so as to 

 distil out the smoke-forming constituents, but to leave 

 enough volatile matter to give a non-luminous flame and 

 easy ignition, as seen in coalite and carbo. 



(3) Non-bituminous coal, such as anthracite. 



~ Coke, the solid product of high-temperature distilla- 

 ''n, has never found favour with the middle and upper 

 isses as a domestic fuel, owing to prejudice against it 

 ^ause of its being somewhat difficult to ignite and not 

 rning freely, and its chief market has been for steam- 

 sing and other manufacturing purposes, verv little find- 

 :: its way into the householder's grate. The result is 

 It, had not carburetted water gas offered a convenient 

 d economical way of using it in the gas works, manv 

 ■npanies would have found great difficulty in keeping 



the price during the years that coal was cheap. 



It must be remembered, however, that during the past 



ee years the great gas industry has been in a transi- 



^" stage, and England is slowly following the lead of 



^ Continent in recognising the fact that great economies 



to be found in carbonising coal for gas-making in 



T^\, ^^^""^^^ ^^^" J^^ve ever before been attempted, 



a the introduction of vertical and oven retorts is un- 



-ibtedly a step in the direction of making a coke which 



NO. 2148. VOL. 85] 



shall be more fitted for a domestic fuel than the over- 

 heated product made in the horizontal retorts of late 

 years. 



The large amount of attention centred upon the pro- 

 duction of a smokeless fuel during the past three years 

 has led to the introduction of several processes for 

 improving the coke during gas manufacture, which, 

 although leading to little or no improvement, have enabled 

 the product to be sold under a fancy name, and have done 

 a certain amount of good by inducing consumers to try 

 under another name the coke which prejudice would have 

 damned untried. 



The second class of smokeless fuel, and the one which 

 many scientific men look upon as the most promising 

 solution to the smoke problem, owes its inception to 

 Colonel Scott Moncrieff, who many years ago suggested 

 the use of a half-coked coal as a fuel supply, and tried 

 to make a commercial article by carbonising coal at the 

 ordinary gas-retort temperature, drawing the charge when 

 half the usual volume of gas had been distilled out from 

 it. Two factors, however, led to failure, the one being 

 that the time was not ripe, and the second that the means 

 by which he proposed to carry out his entirely admirable 

 idea, being dependent upon the ordinary gas-works prac- 

 tice, had to be carried out under certain conditions which 

 led to a want of uniformity in the fuel, and to certain 

 difficulties which those who tried to make it failed to 

 overcome. 



The idea, however, of a semi-carbonised coke which 

 should still contain enough volatile matter to give easy 

 ignition and a cheerful flame without any smoke, was 

 independently revived under the name of " Coalite." 



This differs from the fuel proposed by Colonel Scott 

 Moncrieff in that, instead of shortening the period of 

 carbonisation at a high temperature, the temperature is 

 reduced to one half the ordinary, and is continued in suit- 

 able retorts until a uniform coke, containing 12 to 15 per 

 cent, of volatile matter, is formed. In both processes 

 there is the fatal defect — from a gas manufacturer's point 

 of view — that less than one half the volume of gas is 

 obtained per ton of coal, and as the all-conquering career 

 of the incandescent mantle has rendered a high candle- 

 power gas unnecessary, the rich gas yielded is not looked 

 upon as an equivalent attraction. 



The coalite process has the great advantages over the 

 older process that the fuel is of greater uniformity, and 

 that tlie yield of tar is doubled instead of being decreased, 

 and is greatly enhanced in value. 



Coalite has created so much interest that, as was onlv 

 natural, the Moncrieff process was revived, and the pro- 

 duct is well known under the name of " Carbo." 



Coalite appears at present to be labouring under difficul- 

 ties, but I am convinced now, as I was when I first 

 examined the process, that when its manufacture is 

 properly handled coalite will be the ideal fuel, and will 

 not only solve the smoke problem in the easiest possible 

 way, but will also be an important economic advance in 

 our treatment of coal. 



The use of a non-bituminous coal like anthracite would 

 result in smokeless and very hot combustion, but here 

 again the objection is that stoves with a special draught 

 would have to be used, and the initial cost would prevent 

 its use ever being adopted, besides which any great demand 

 for this kind of fuel would at once send up the price to 

 a prohibitive figure. 



If the consumer can be induced to take the trouble, a 

 very good semi-smokeless fuel can be made by using a 

 mixture of two-thirds coke to one-third coal, and instead 

 of piling up the grate with cold fuel when the fire burns 

 low, to add the fresh fuel frequently in small quantities, 

 so as to prevent the deadening of the top heat of the fire : 

 but this is diminishing, not killing, the evil. 



Leaving the smokeless solid fuels, which I believe will 

 in the future play a very big part in the cleansing of 

 town air, we now come to the gaseous fuels, and here at 

 once we have ready to hand a solution of the difficultv 

 in the use of coal gas. Gas fires, gas cookers, gas water- 

 heaters, gas engines, have all been developed to a point 

 which leaves no valid excuse for overlooking their claims, 

 and ever since Bunsen in the early 'fifties gave us the 

 atmospheric burner, in which non-luminous combustion is 

 obtained and smoke rendered impossible, coal gas has 



