LXXIV. T. H. HOUGHTON. 
works, requiring more than 20 to 25 horse power, as the additional 
_ boiler power required, would almost equal the difference in price 
between a compound, and a non-compound engine. 
Flywheel reciprocating pumps do not give as good a result, 
in water lifted per indicated horse power, as direct acting pumps, 
owing to the friction of the greater number of moving parts, they 
are besides rather more expensive for moderate powers. One of 
the principal losses in reciprocating pumps, beyond those due to 
the friction of the engine, arises from the friction of the water 
passing through the valves, and as this is constant, other things 
being equal for all heads, it follows that the lower the head the 
less the efficiency, and it is to the improvements in the valves 
that any increase in efficiency is to be looked for. 
Professor Reidler has for some years been using both for water 
pumps, and air compressors mechanically moved valves, and has 
found a great improvement from their use, being able to increase 
the speed of the pump piston to as muchas 420’, or 60 revolutions 
per minute, without any shock occurring on the closing of the valves. 
The first cost and working expenses of the various pumps differ 
considerably as may be expected, and the following table con- 
densed from a paper by Mr. Cuppari, “On the practical results 
obtained from various water raising machines in Holland,” is 
interesting. 
TABLE LI. : 
ee perH.P. | perH.P. — 
Sie and Engines, average of : 
ven pumping stations . ; £46 £46 £92 
Centrifugal pumps, one of five 
pumping stations : £34 £37 £91 
Archimedean secede average of two 
£37 £42 £79 
Piston amps, average of three 
statio: £72 
The conclusions arrived at by Mr. Soe are, that no general 
rule can be given as to the adoption of any one type, but that 
1 Proceedings Inst. C.E., Vol. pxxv. 
