.S7A' WILLIAM SIEMENS, F.R.S. 131 



to coal, which, if you analyze it, contains very often not more than 

 <; |> r cent, of foreign matter. I think an explanation maybe 

 attempted in this way, that in burning coal we feed the furnace in 

 an exceedingly irregular manner, charging the grate at one time 

 with an excess of hydro-carbon, which flies off" and finds an in- 

 sufficient amount of oxygen in the atmospheric air that enters the 

 L r nu<- to burn it ; and at other times the air that rushes through 

 the grate has not time to take up its equivalent of carbon to pro- 

 duce carbonic acid. The result is, that in examining the products 

 of combustion of an ordinary furnace, we find as much as 25 or 

 30 per cent, of pure oxygen on one hand, and we find a consider- 

 able amount of unconsumed carbonaceous matter going into the 

 chimney along with it. This must be attributed not only to the 

 unequal feeding of the coal into the grate, but it must also be 

 attributed to the cooling effect exercised by the boiler, in checking 

 combustion before the chemical action is completed. The first 

 consideration in constructing a suitable grate ought to be to main- 

 tain the. temperature of the flame for a sufficient length of time 

 to complete the chemical action between the oxygen and car- 

 bonaceous matter. That, no doubt, can be obtained in a much 

 more perfect manner in dealing with a liquid fuel like oil. This 

 liquid in itself would be rather difficult to deal with, inasmuch as 

 the surface it presents in the liquid state to the oxygen of the 

 atmosphere would be very limited ; but in blowing in it, as Captain 

 Selwyn does, by a jet, you get an extreme subdivision of the oil, 

 and in consequence you may obtain a perfect combustion. From 

 the results brought before us by Captain Selwyn that seems to be 

 the case ; we get an extremely perfect combustion, and, therefore, 

 we get an extremely great duty performed. The practical question 

 then arises, what are the sources of supply of this oil ? I do not 

 know whether the author of the paper has gone into that point, but 

 it is a question of very great practical importance. As long as we 

 have liquid fuel, there can be no doubt that, weight for weight, it 

 is superior to solid fuel. These heavy oils are free from the great 

 objections that apply to light hydro-carbons, on account of their 

 volatile qualities. But the question with me is, whether we can 

 obtain such a supply of heavy oils at a moderate cost as will 

 justify their employment upon a large scale ; for instance, will 

 justify their application to our marine boilers. 



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