LXXXII. DISCUSSION. 
pumps was that if any stoppage in the main occurred the pump 
would probably be stopped without accident, while in the case of 
a fly-wheel the stored energy might cause a complete wreck of the 
pumping plant. 
Mr. Hoveuton in reply to the discussion said, in answer to 
Mr. Pridham, that he had not mentioned the “air-lift” method of 
raising water as it was not one that could be utilised with economy 
except in very rare cases; it was of no doubt of great benefit for 
the purpose described by Mr. Pridham. Mr. Selfe had made 
several suggestions as to the manner in which the efficiency of 
some of the types of machines described could be increased, but 
it might complicate machines whose great advantage was sim- 
plicity to endeavour to obtain a greater efficiency. Mr. Grimshaw 
and Mr. Selfe both pointed out how the centrifugal pump can be 
adopted for high lift, but in his (Mr. Houghton’s) opinion this 
would not be so economical as ordinary ram or bucket pumps. 
The type of reciprocating pumps advocated by Mr. Selfe, in which 
the water has a continuous upward flow, have already been used ; 
Messrs. Mather & Plott make them for pumping from wells, and 
the Southwark and Vauxhall Water Works Co. have a large plant 
at work on a somewhat similar system. Mr. Selfe introduced the 
question of duty when speaking of the relative merits of rotative 
and direct-acting pumps, the author had purposely left this out 
and referred only to efficiency ; but he is not aware of any pub- 
lished accounts of reliable tests in which the ratio of actual work 
done to indicated power developed was not higher for direct-acting 
pumps than for rotative pumps when working against similar 
pressures of water, no doubt the adoption of roller bearings 
would increase the efficiency of the rotative pumps as suggested 
by Mr. Selfe. 
