378 SECTIONMECHANICS. 



No. 1940, which is before me, is a model of Stirling's hot-air engine, 

 but time does not remain to describe it. 



Besides hot-air engines, we have had engines working by the explo- 

 sion of gunpowder, and others working by the explosion of gases. No. 

 1945 is Langen and Crossley's gas engine, from which, I believe, ex- 

 tremely excellent results have been obtained. 



I will now ask you to look at a tabular statement which shows the con- 

 sumption of fuel in agricultural engines when under trial, expressed in 

 pounds per horse-power per hour, and also in millions of pounds raised 

 one foot high by the consumption of one hundredweight of coal. I told 

 you how excellent were the results at which our agricultural engineers 

 had arrived. You will see that one of those machines working with 80 Ibs. 

 steam, and of course without condensation, has developed not a gross 

 indicated horse-power, but an actual dynamometrical horse-power for 

 279 Ibs. of coal per horse per hour, giving a duty of as much as 

 seventy-nine millions. This high result was obtained by the excellence 

 of the boiler and of the combustion, as well as by that of the engine. 

 If you look at the column of evaporation you will find that as much 

 as 1 1 '83 Ibs. of water were converted from the temperature of the 

 boiling-point into steam by the combustion of I Ib. of coal. This was 

 due not to the excellence of the boiler alone, but to the extraordinary 

 ability of the stoker, and to the care and labour bestowed a care and 

 labour far too expensive to be employed in practice. But should not 

 we engineers endeavour to ascertain whether we cannot by mechanical 

 means practically, with certainty and cheapness, procure an accuracy 

 of combustion as great or even greater than that which can be got by 

 the almost superhuman attention of a highly-trained man, who at the 

 end of four hours of such work is utterly exhausted ? Many forms of 

 fire-feeders have been attempted and used with more or less success ; 

 but I cannot help thinking that in order to obtain the accurate pro- 

 portioning of air and fuel by which alone can we get efficient and 

 economical combustion, we shall have to turn our attention in the 

 direction of dealing with the fuel in a comminuted state, either by 

 converting it into gas, as is done by our President, Dr. Siemens, by 

 availing ourselves of liquid fuel, or by employing the process of Mr. 

 Crampton, the making of the fuel into an impalpable powder, which 

 can be driven into the furnace by the air which is to consume it there. 



