VIII. T. H. HOUGHTO\. 



laid are filled for a portion of the height with small coke breeze 

 so as to prevent the fine sand entering the holes in the pipes. 

 The sludge which will be deposited in the settling tanks will be 

 discharged into a sludge chamber, where, after further settle- 

 ment, it will be forced into a filter press by compressed air, where 

 almost all the remaining moisture will be driven out. Two 

 destructors with a tubular boiler set between them have been 

 provided for burning the matter caught on the screens and 

 the cakes of sludge, but as neither material would burn without 

 the addition of fuel it is intended to mix them with refuse coke 

 from the gas-works. The steam generated in the boiler will drive 

 the air compressor, which is used for elevating the sludge and 

 pressing it. Probably the sludge will have some manurial value 

 and may be disposed of to market gardeners instead of being 

 burned. 



Many districts of Sydney are too low to drain into the main 

 sewers, and in consequence the sewerage will have to be pumped 

 from the low level to the high level sewer. At Marrickville, 

 two large pumping engines, each capable of raising 3000 cubic 

 feet of sewerage per minute, are to be erected, with the necessary 

 steam boilers and buildings. At the Double Bay Station a 

 different system has been adopted. Shone's ejectors are to be 

 used, the air for working them being compressed at the Station 

 containing the ejectors by compressors driven by electric motors, 

 the current being supplied from the Rushcutter Bay power 

 house. Ingenious arrangements for stopping and starting the 

 motor automatically, as the level of sewage in the sump varies, 

 have been provided. At the other low level sewers reciprocating 

 or centrifugal pumps driven direct by electric motors will be 

 used, thus saving both in cost of working and first cost compared 

 to the system adopted at Double Bay. 



The current for driving these motors will be supplied from the 

 Harris Street Generating Station, and, instead of there being an 

 automatic controller at each pumping station, a man will be 

 stationed in some convenient place where dials electrically con- 

 nected to the sumps in which the pumps are to be placed will 



