must therefore be increased in the ratio which 100 bears to 

 80, so that the loss becomes 47 J per cent. 



There is also the loss of fuel in keeping the steam up 

 during the time the engine is inactive. The best stationary 

 engines may be worked at a consumption of 5 lbs. of coal 

 per horse power of 60,000 per hour working constantly, but 

 if the engine be worked only a portion of the time, and re- 

 main inactive during intervals, having the steam still kept 

 up, the expenditure of fuel during the working will be after 

 the rate before stated, 5 lbs. per horse-power per hour; during 

 the intervals, fuel will be required at the rate of 2^ lbs. of 

 coal per horse-power per hour. 



These data are fully confirmed by the evidence of Mr. 

 Bergin, who has part of the management of the Kingstown 

 and Dalkey Atmospheric Railway, both as being the general 

 opinion of engineers, and as confirmed by the results of eleven 

 months' working of the engine there. 



On the basis of the results shown by these calculations, I 

 anticipate considerable advantage may result from the system 

 of exhaustion, which I have patented,* by which the power 

 constantly exerted by comparatively small engines may be 

 accumulated during the intervals between the running of 

 trains, and afterwards made available in assisting the engine 

 in exhausting the tube. 



In addition to the loss of power whilst the engine is work- 

 ing, the Atmospheric system, as hitherto applied, must be 

 charged with a quantity of fuel burnt without producing 

 any power; and unless some method be adopted for accu- 

 mulating power during the intervals, this lost fuel will in 

 some cases amount to more than twice the amount of fuel 

 usefully burnt, and even in very favourable cases, to half the 

 amount of the fuel usefully burnt. 



I, however, hope that my method of accumulating power 



* See specification annexed. 



I 



