LXVI. T. H. HOUGHTON. 
pump is naturally that one which turns the greatest amount of 
the power put into it into effective work, and in Figure 1, are 
shewn the efficiency curves of various types for different lifts, from 
this it will be seen that although the reciprocating pumps are 
very economical as regards power wasted at lifts greater than 30’, 
yet at lower lifts the centrifugal pump gives better results, and 
for lifts up to 15’, a well designed scoop wheel has about the same 
efficiency, as the centrifugal pump. The first three types are not 
suited for places where there isa very great variation in the levels 
of either the suction water or of that in the delivery channel such — 
as occur in most of the Australian rivers, but there are probably 
many places in which they could be used, and the author has con- 
sequently included them in the paper. 
Scoop wheels are largely used in the Fen lands of England, and 
in Holland for low lifts, but are going out of favour. Figure 2 
shews the form first used, this has been superseded by those with 
the improved form of bucket shewn in Figure 3. 
The defects of the wheel are the liability for a large waste of 
water by leakage at the sides, and if straight buckets as in Figure 
2, are used, the water is raised much higher than necessary, 
and as frequently erected, a considerable loss is incurred owing to 
defective construction of the races for the ingress and egress of 
the water, a wheel constructed asin Figure 3 and properly installed 
will utilize about 70% of the power developed by the engine, 
whereas those of the older make rarely give more than an efficiency 
of about 467%, and in Figure 1 is shewn at H, the efficiency 
obtained on four tests of a wheel 33’ 6” diameter with a width of 
25”, raising 714 tons of water per minute 9-8’ high, few of the 
wheels are giving this efliciency, but there is no reason why 
properly constructed wheels should not be used, where the lift 
-does not exceed 15’, and the lower water level is fairly constant. 
Archimedean screws if made on Mr. Wilfred Airey’s system 
give good results, but owing to the angle at which they have to 
be fixed,are not suitable for a lift of more than 20’, as the length 
— -and ceri the _— sah cost mount up very rapidly. 
