WATER SUPPLY TO SYDNEY BY GRAVITATION. 113 



This is the result of three pipes to Waverley, Petersham, and 

 Sydney respectively, whilst the horse power would be : — 



Waverley ... H.P. = 520'32 



Petersham H.P.zz 65170 



Sydney H.P. := 42000 



1,592-02 H.P. 



This is the result of three pipes to the three places as above, 

 and fed from the one 24-inch main from the high-level point of 

 1,062 feet. I think that, after showing such extraordinary results 

 in both the water delivery and water power given from so small a 

 pipe under high pressure, no one can be sceptical enough to doubt 

 the efficacy and economy of such a mode of water supply. 



By my former paper, read here on the 9th of December last, 

 I based all my estimate of water supply to Sydney by the use of 

 two 18" mains from high level. The subsequent surveys having 

 given such extended prospects of an increased supply, and the 

 economy being so greatly in favour of the adoption of larger pipes, 

 as shown by the above notes, it need not be a matter of any sur- 

 prise that I now advocate the use of one 24" main to begin with, 

 in terms of my present paper, and that such one main should be 

 followed by another of similar size as soon as practicable. 



In my proposal for conducting the wrought iron mains over- 

 ground by the easy gradients of the Bottle Forest Road down to 

 the sea level of George's River, I have considered that such 

 gradients for the pipes can be made to be so regular in their 

 declension to the crossing of George's River by the proposed 

 railway bridge for the Illawarra line, that the line of pipes would 

 probably be in almost one continuously straight direction, owing 

 to the gradual depression of the country from the starting point 

 of the mains at 1,062 feet, down to the sea level at George's 

 River, distant about 17 miles. Assuming that a future survey of 

 this line should prove the correctness of this statement, considerable 

 advantages will be given in the construction of the wrought iron 

 overground aqueduct, as compared with a similar work in Nevada 

 from Martella Lake, over hill and dale, to Yirginia City and Gold 

 Hill, a work which has been carried out so successfully in the 

 short space of five months over a distance of more than 10 miles, 

 to cross the waters over a mountain valley that is 1,750 feet deep 

 and 7 miles across, and where the wrought-iron pipes are bearing 

 at the bottom of the deep valley the unprecedented pressure of 

 750 lbs. to the square inch. 



Should this high-gravitation scheme become adopted, the con- 

 struction of the wrought-iron aqueduct could be rapidly dealt 

 with by engineering firms in Sydney; one of which, I am in- 

 formed, could undertake to construct by steam machinery one mile 



