60 Dr Fyfe on (he Prevention of Smoke^ Sfc, 



economy of fuel by the use of the steam. When the furnace 

 was in action without the admission of steam, the fuel con- 

 sumed amounted to 812 lb. in 5 J hours ; and when steam was 

 admitted, the consumpt, for the same time, amounted on an 

 average to 537 lb. Now, as the same work was done by 

 the engine with the consumpt of 537 lb. of coal when the 

 steam was admitted, as was done by 812 lb. without it, the 

 saving by these trials amounted to 34 per cent. ; for, as 

 812 : 537 : : 100 : 66, and 100 — 66 = 34. 



Considering the amount of evaporation obtained by the ap- 

 plication of steam as now described, and keeping in view the 

 results of the experiments which I have given, and also those 

 recorded by others, it is evident that the evaporative power of 

 coal is by this means greatly increased ; but this is done by 

 an expenditure of part of the steam generated in the boiler ; 

 it therefore still remains to be proved what the actual amount 

 of saving is, after deducting the loss occasioned by the trans- 

 mission of steam into the furnace. Different processes were 

 followed, with the view of ascertaining the quantity of steam 

 projected into the furnace. One of these was by comparing 

 the area of the apertures in the distributor with that of the 

 steam-pipe leading to the engine ; but this was found liable to 

 fallacy, owing to the difference in the escape of steam, which 

 is not always in proportion to the area of the tubes or aper- 

 tures through which it is transmitted, and owing also to the 

 escape through the safety-valve. Another method was, to 

 connect a tube with that leading to the furnace, and convey 

 it through a refrigeratory, so as to cause the condensation of 

 the steam, which, when condensed, was collected, and its weight 

 ascertained. When this was in use, the supply of steam from 

 the boiler to the furnace was cut off by means of a stop-cock, 

 and the steam was then allowed to flow through the tube in 

 the refrigeratory — the stop-cock by which the supply to the 

 furnace was regulated being kept at the same degree as for- 

 merly. By this mode I found that the quantity of condensed 

 steam varied considerably, — indeed, so much so, that though 

 several trials were made, the results were so discordant, that 

 I could place no reliance in them. This was owing most 

 likely to the flow of steam into the furnace, through the mi- 



