98 



diaphragms and friction in the piping, and to employ a pressure of 

 4 lbs. to the square inch. The compressor is placed on a bracket 

 fixed to the wall of the pump room outside the laboratory ; the 

 suction pipe being led through the pump room wall to a sheltered 

 place underneath one of the main water storage tanks where a suitable 

 filter is fixed. Both suction and dehverj^ pipes have a short length 

 of rubber hose inserted to prevent the transmission of sound, and the 

 compressor itself is placed on a sheet of rubber. 



Delivery pipes are taken from the compressor to the various 

 parts of the building, wdth valves for shutting off different branches, 

 and regulating valves for each point of delivery. The pipes leading 

 into the main tanks of the aquarium are of Sheradised iron, the 

 nozzles also being of the same material. In all other parts the pipes 

 are of heavily galvanised iron. All the valves are of bronze, heavily 

 tinned, and made to the Admiralty specification. The dehvery 

 end of the valves is made t^o receive either a screwed pipe or rubber 

 tubing. 



This installation has now been running for a considerable time 

 with great regularity, and it has proved itself to be in every way 

 thoroughly effective. On tests being made, it was found that under 

 normal conditions it consumed half an ampere of current at 480 

 volts, or less than J horse-power, and the maximum current con- 

 sumed when delivering 400 cubic feet of air per hour is only | ampere. 



These tests show considerable economy as compared with 

 installations which compress the air to a high pressure in the first 

 instance and require a 2-horse-power motor working from eight to 

 twelve hours per day in regular use. The economy is effected 

 partly by the fine division of air in the water, and also by the fact 

 that the air is not compressed to a greater extent than is actually 

 required. 



