LIV. J. F. FURNISS. 



dry saturated steam per indicated horse power. The 

 efficiency of these beam engines when working against a 

 head of 150 to 200 feet is high, being about 84°/°, so that to 

 compare favourably with the older types of pumping engines 

 a centrifugal pumping plant must have a high efficiency, as 

 must also the motor, whether it be steam, electricity, or gas 

 that drives it. The cost of beam engines and the necessary 

 foundations and buildings to house them is much greater 

 than that of high speed machinery of the same capacity, 

 so that for a plant running intermittently, the annual charge 

 for interest will prove whether the advantage of decreased 

 cost of maintenance and depreciation will not enable them 

 to hold their own with high speed pumps. Many horizontal 

 pumping engines have been built with mechanically con- 

 trolled pump valves, the engines being fitted with the most 

 economical type of valve gear running at high speeds and 

 being such as to ensure the efficient use of the steam 

 admitted. These have given good results and although 

 somewhat costly, yet when the maintenance and fuel con- 

 sumption are capitalised, it will be found that they show 

 very favourably; as the author points out it is not only fuel 

 consumption which has to be considered, but the whole 

 question from the handling of coal to the disposal of the 

 ashes, and to this should be added the cost of maintenance, 

 depreciation and supervision. 



The author calls attention to the difficulty of balancing 

 the impellers of centrifugal pumps; I suppose he refers to 

 single suction pumps, as on those pumps the suction inlets 

 are equal on each side I do not see how it is possible for 

 any serious end thrust to occur. In many of the pumps 

 built some years ago we bored holes in the side of the 

 impeller to admit water from the impeller into the space 

 between it and the side of the pump in order to balance 

 the end thrust. This is very similar to what he describes 



