178 THE SCIENTIFIC PAPERS OF 



preferred that the choice had fallen on a gentleman who could 

 have given more time to the actual preparation of such a paper 

 than I have been able to bestow upon it, yet having for nearly 

 thirty years given much attention to the subject of combustion, 

 and the utilization of gaseous fuel, it was perhaps natural thnt 

 your President called upon me to open out the subject before this 

 new Society. 



The fuel at our disposal, generally speaking, is coal, and in 

 most applications coal, in its raw condition, is still used for the 

 production of heat. I have put a table before you, showing the 

 amount of heat energy residing in a pound of fuel. If that fuel 

 is pure carbon, 14,544 units of heat are producible. If coke were 

 used, and burnt entirely to carbonic acid, 12,500 heat units would 

 be produced. If coal of the average quality is employed, 11,000 

 heat units may be obtained. But, if instead of using solid fuel 

 we should employ gaseous fuel, we immediately jump to much 

 higher figures. Olefiant gas gives in its combustion 21,344 heat 

 units ; marsh gas, 23,500 ; and hydrogen, 62,000 units, or very 

 nearly six times as much as raw coal. Then carbonic oxide, not 

 counting the oxygen already taken up, but simply the carbon in 

 the carbonic oxide, gives 10,100. These figures may serve to 

 show the great advantage in the use of gaseous fuel ; and if by 

 some means or other we could impart to the fuel as it is consumed 

 the greatest possible power for the production of heat energy, it 

 would be clearly to the advantage of the user, because not only 

 does this better fuel produce for the same weight of material a 

 greater result, but it produces that result with a smaller expendi- 

 ture of oxygen, that is, with less draught. 



The principal reason why gaseous fuel, especially hydrogen, 

 produces such a large amount of heat energy, consists in the heat 

 energy already expended in expanding it to its volume, and the 

 ultimate result, therefore, depends less upon combustion than it 

 would do in the case of coal where a large proportion of the heat 

 produced is expended in converting the solid into gaseous fuel to 

 begin with. But gaseous fuel, when used instead of solid fuel, 

 possesses several other advantages. It is much easier to produce 

 perfect combustion in using gaseous than in using solid fuel. 

 Solid fuel, when first heated, flies off to a great extent into 

 products of distillation, and the supply of oxygen can hardly keep 



