LXXVIII. DISCUSSION. 
Discussion. 
Mr. Pripuam said that the method of raising water by means 
of the “air lift” had not been touched upon by the author. 
Although the efficiency is small compared with any of the pumps 
and lifts mentioned, being only about 50% with a lift of 10, 
diminishing to 20% with a lift of 200’ (as pointed out by Mr. 
E. E. Johnston, M. Am. Soc. M.E.), yet this plan might be used with 
great success for increasing the yield of some of our flowing 
artesian wells. At Asbury Park, New York, the yield of two 
wells, about 1000’ in depth, was stated to have been increased by 
about 24 times the natural flow by the “air lift,” but in these 
cases the air pipe was extended to a depth of 200’, necessitating 
a pressure of nearly 90 Ibs. per square inch. 
Mr. Norman SELFeE said that he considered the diagram illus- 
trating the falling off in efficiency of centrifugal pumps as the lift 
increased, was of special value; and he had only recently had 
occasion to ask the author for data similar to that now furnished. 
The scoop wheel, shewn in Fig. 2, could only have a low efficiency 
because the wave of water was raised so much above the level of 
the head race as to cause a waste of power. He was of opinion 
that a practical scoop wheel could be made with feathering or 
folding buckets, that would lie close against the drum of the 
wheel as they approached guide vanes, so fixed and curved as to 
deflect the water horizontally at the delivery level, and that 4 
wheel so constructed would reduce the loss by at least one-half, 
or, in other words, increase the efficiency to say 759. The loss 
of efficiency in the Archimedean screw through the delivery not 
being adapted to variable heads could be got rid of by making 
the whole screw adjustable in the direction of its axis, so that 
while the lower end was more or less immersed the delivery would 
be always at the exact height required. The efficiency of 557, 
set down for the chain pump seemed extremely low, certainly 
some of the Melbourne makers of this class of machinery claimed 
a very much more effective result, and the rotary pump giving 
_ only 57% efficiency, did not seem of the highest type. 
