XVlll. ABSTRACT OP PROCEEDINGS. 



Upper Mohawk 60%. It is a dangerous practice to rely 

 on the comparative yields of other catchments whose 

 physical characteristics would not bear comparison with 

 the one we have under review. 



Mr. Garde w believed the higher parts of the Sydney 

 catchment would give a larger rainfall and run-off than 

 adopted by the author. It is surely necessary that a scien- 

 tific exploration should be made of the whole of the Sydney 

 catchment area embracing the question of rainfall, evapor- 

 ation, porosity, volume of the streams, etc., to determine 

 the amount of water the surface contributes to the rivers,, 

 and the amount of underground water contributed to the 

 rivers, of the water table, of the soil, the chemical examin- 

 ation of the water, filters, observations of storage in the 

 reservoirs, plan of reservoirs, bores, surveys with plans at 

 ten feet intervals, a delineation of the various drainage 

 areas on the catchment, geological survey, borings, and so 

 on. Consideration of the foregoing seems to point to a 

 higher percentage, as in the case of the Oroton and Sudbury 

 water sheds of the New York water supply, which amounts 

 to about 50% of the rainfall. He mentioned with the pro- 

 posed tunnel scheme, the fire stream would reach a height 

 of 165 feet, which is greater than the City Council's build- 

 ing limit, and consequently no fire engine would be required. 

 His computation showed that the tunnel from the Cataract 

 to Bankstown would have to be 9 feet 2 inches in diameter, 

 to give the necessary head to supply the branch tunnel from 

 Bankstown, which would be 6 feet in diameter and carried 

 to a point beyond Ryde, and would require a 24 inch main 

 delivering 4J million gallons per day thence to the Wah- 

 roonga elevated tank, and at the same time to supply the 

 outer branch. He estimated the cost of the main tunnel 

 and branches to be £4,033,000; the cost of the whole 

 scheme, embracing tunnels on the catchment with the 



