108 EEPOET— 1878. 



Report on the best Means for the Development of Light from 

 Goal-Gas of different qualities, by a Committee consisting of 

 Dr. William Wallace (Secretary), Professor Dittmar, and Mr. 

 Thomas Wills, F.G.S., F.I.G. 



Part I. — Drawn up by Dr. Wallace. 



The fact has long been recognised that the illumination afforded by the 

 combustion of coal-gas depends, to a large extent, upon the way in which it 

 is burned. Setting aside, for the present, all reference to the different 

 theories of Davy, Frankland, Heumann, and others, as to the source of the 

 illumination, whether from solid highly-heated particles of carbon or from 

 incandescent gases, the fact is patent that a given quantity of gas may be 

 burned under different conditions, so as to yield widely different illumi- 

 nating effects. For example, a gas made from bituminous coal gave, when 

 burned by Sugg's Improved London Argand at the rate of 5 cubic feet 

 per hour, the light of 14'81 candles. The same quantity burned by a 

 union jet at -5 inch (water) pressure gave 11-46 candles ; and by a union 

 jet at 1'5 inch pressure 3"66 candles ; these quantities corresponding to 

 100, 77, and 25. Pattinson states that burners are in extensive use in 

 Newcastle which, for 5 cubic feet of gas, give a light equal to only 3£ 

 candles, which gas, burned in a good Argand, gives for the same consump- 

 tion 17| candles, and in good union or fishtail burners 12±- candles. 

 In the case of cannel-gas, the variations are not so extensive"; but the 

 following illustrates the effect of pressure alone in influencing the light 

 obtained, the burners being of the same kind in each case, but with orifices 

 suited to deliver 5 cubic feet of gas at the different pressures : at i-inch pres- 

 sure a union jet of the best construction gave a light equal to 28~47 candles, 

 while at 1^-inch pressure the light from an equally good union jet was 

 21T4 candles ; these numbers being in the proportion of 100 to 74. In 

 these instances the quantities of gas were the same (5 cubic feet per hour) ; 

 but if we take smaller quantities of gas, and calculate the results to 

 5 feet, the numbers obtained are still more startling. The following cases 

 are quoted from Wallace's paper on the " Economic Combustion of Coal- 

 Gas," * all the burners used being Bray's " adam as-tipped " union jets for 

 cannel-gas. A No. at 1^-inch pressure burned 2 cubic feet per hour, and 

 gave a light of 35 candles, or for 5 cubic feet per hour, 88 candles ; a 

 No. 8 at 1-inch pressure burned 7T cubic feet per hour, and gave 45-4 

 candles, or for 5 cubic feet, 32 candles. Between ordinary working 

 limits of pressure and with equally good burners, we have, therefore, a 

 given quantity of gas (5 cubic feet per hour) giving, in the one case, 32 

 candles, and in the other 8'8 ; or in the proportion of 100 to 27^. The 

 loss of light here shown, amounting to 72^ per cent, of the whole, is ex- 

 ceededwhen still higher pressures are used,"and it is greater with common 

 than with cannel-gas. A remarkable effect is obtained with a mixture of 

 cannel-gas with about twice its bulk of air. At a low pressure in an 

 Argand jet with large holes it gives a fairly luminous flame, while, at a 

 high pressure (3 or 4 inches), although the quantity of gas consumed is 

 three times as great, the flame is almost totally non-luminous, and has a 

 greenish tint. The gas, used somewhat extensively in the United States, 



* Transactions of the Philosophical Society of Glasgow, 1873-4. Journal of Gas 

 Lighting, 1874. 



