XL. J. F. FURNISS. 



high efficiency of trials." Now the efficiency of a steam 

 pump is only gauged by a comparison of the fuel or steam 

 used with the results obtained therefrom in a continuous 

 trial of longer or shorter duration. If the pumps are run- 

 ning eight hours and standing sixteen out of the twenty- 

 four afterwards in their actual daily work, and as much 

 coal is used in those sixteen hours by banked fires or other- 

 wise as is consumed in the eight hours work (such things 

 have been reported), that surely is no discredit to the 

 engine's efficiency. Certain it is that no class of engines 

 run with a more uniform load than pumping engines, or 

 afford better opportunities for the adjustment of the steam 

 pressure and grades of expansion necessary to secure the 

 most economic consumption of steam. 



In the fifth paragraph of the paper it is stated that the 

 Eathorn-Davey differential type is allied to the Worthington 

 (High Duty) "in so far as provision is made to store energy 

 at the beginning of the stroke." Now without being 

 captious or hypercritical it must be pointed out that the 

 two systems are entirely and essentially different in their 

 methods of providing constant pressure to overcome con- 

 stant resistance. The Worthington high duty pump does 

 store energy when the pressure on the steam piston is above 

 the mean required by the pump, but instead of storing it 

 in a fly-wheel as a rotative engine does, it stores it in an 

 air-vessel. And here it may be said that so far no accurate 

 investigations appear to have been instituted, and the 

 results of such made available, to show the relative per- 

 centage of the total energy developed which is lost under 

 the two systems. In the Hathorn Davey differential system 

 there is no storage of energy except in the inertia of the 

 reciprocating parts common to all engines ; but, instead of 

 there being a constant relation and correspondence between 

 the velocity of the steam and water pistons, as in the direct 



