NORTH SYDNEY AND DOUBLE BAY SEWERAGE SCHEMES. XXIII. 



Indicator diagrams were taken of the compressor and engine 

 under varying conditions, viz. : (1) Full load driving compressor 

 and lime mixer. (2) Light load, engine driving lime mixers and 

 shafting only. 



In each case a constant pressure of 80 lbs. per square inch was 

 maintained in the receiver, and a steam pressure of 80 lbs. per 

 square inch on the boiler. 



DOUBLE BAY LOW LEVEL SEWERAGE. 



Obviously the object to be attained in the construction of the 

 sewerage of Sydney and suburbs has been to provide means of 

 carrying the sewage off quickly and conveniently, and prevent it 

 flowing into the Harbour on the North, and Cook's River on the 

 South. 



A small portion of the country to be drained is below the level 

 of the gravitation sewers which discharge at Ben Buckler, Cook's 

 River, and Arncliffe, and has, therefore, to be lifted by pumping 

 or other means to the higher level. 



Double Bay being one of these low lying areas, the sewage is 

 raised by means of Shone's Hydro-pneumatic Ejectors through 

 delivery mains into the Darling Point branch of the Bondi main 

 sewer. 



These works have just been completed under the supervision 

 of the Author, and they form the subject of this portion of his 

 paper. 



The Double Bay low level zone, which comprises 77*4 acres 

 after roads, reserves, etc., have been deducted, affords facilities 

 for the adoption of the Shone system, as it is flat and sufficiently 

 large to warrant a separate air compressing plant being erected. 



It is 6 or 7 feet above mean high water, and the sub soil is 

 peat and sand heavily water charged. 



It may, therefore, be seen that many difficulties were met with 

 in sinking the ejector chambers, and laying the sewers and mains, 

 but such difficulties would have been magnified had a pumping 

 scheme been adopted. In such a scheme a proper self-cleansing 

 grade in the sewer would only have been obtained at the expense 

 of a deep pump well and a correspondingly high lift to the 



