18 HENRY DEANE. 



working with most satisfactory results for upwards of a year, and 

 now the town council has applied to the Local Government Board 

 for power to treat the whole of the sewage on the same principle. 



At the London outfall works very exhaustive experiments have 

 been made with the effluent after it leaves the precipitating tanks. 

 The liquid is allowed to remain in contact with the filtrant for a 

 given period ; it is next drained off as quickly as possible, so as to 

 induce oxygen to enter the body of the filter, and give the latter 

 a period of rest before fresh sewage is run in. These experiments 

 show that it is possible to purify sewage to a sufficient extent to 

 admit of its being turned into a flowing stream, after pasing it 

 through breeze filters at the rate of 1,000,000 gallons per 

 twenty-four hours per acre of filter. In other words the experi- 

 ments prove that one acre of properly constructed filter beds will 

 treat the sewage from 20,000 persons after it has passed through 

 the septic tank, against say two hundred and fifty persons per 

 acre if passed over land on broad irrigation lines. 



The Minister for Public Works has approved of the Sewerage 

 Branch of the Department of Public Works (on the recommenda- 

 tion of Mr. Davis, the Engineer for sewerage) erecting works for 

 treating the sewage from the Rookwood Asylum on these improved 

 methods. Should they prove to be a success it is intended to 

 adopt them at two other places. The tanks and filters are arranged 

 so that the whole process is practically automatic, the different 

 valves being opened and closed, when required, by the aid of the 

 sewage. 



Low Level Sewerage of Sydney. — The Sewerage Branch of the 

 Public Works Department has also during the last twelve months 

 had to decide the best method of raising the sewage from the low 

 level areas, on the foreshores of the harbour extending from 

 Balmain to Rose Bay, to the gravitation sewers, as the sewerage 

 system could not be deemed complete until this was done. The 

 first area dealt with was the Double Bay valley, and it was decided 

 here to use Shone's compressed air system. It was originally 

 intended to drive the air compressors by steam, but seeing that 



