WATER SUPPLY TO SYDNEY BY GRAVITATION. 107 



ing Sydney permanently with an abundance of the purest water, 

 even without passing on for more supply beyond the position of 

 the main storage dam. But I am happy to inform this Society 

 that my last survey quite confirmed everything that I had before 

 stated as to the practicability of availing ourselves of the favour- 

 able dip of the country for supplying Sydney still more abun- 

 dantly. With reference to the prospective plan of supplying future 

 requirements by securing the waters from the coast range further 

 south, I was at first apprehensive that the indentation of the 

 south coast range at Westmacott's Pass, behind Bulli, might pos- 

 sibly interfere with the requisite levels. The survey, however, 

 dispelled this anxiety, and proved a remarkable fact, namely, that 

 the lowest point of this gap in the coast range would be 10 feet 

 below the surface of the Loddon Lake when full, and that, there- 

 fore, it would be impossible to run the southern waters by a 

 channel into the lake itself, which would be distant from the gap 

 about one mile. Most happily, however, we found that there 

 were 40 feet 2 inches to spare on the relative elevations of such 

 depression at the gap of the range, and of the position of my pro- 

 posed tunnel-mouth, situated just below the intended great dam; 

 for although we could not flow such waters into the storage lake 

 at all, yet 5 feet alone of fall from Westmacott's Pass to the 

 tunnel-mouth below the dam would have insured our being able 

 to supply Sydney by gravitation wholly with the Cataract Biver 

 waters, when supplemented by the other waters just named, 

 without having to draw upon the Loddon Lake at all unless under 

 very severe droughty seasons. 



This was the most interesting part of my work and discovery. 

 My levels were taken from high-water mark at spring-tides by 

 Bulli. The lowest depression in Westmacott's Pass, or gap, 

 proved to be 1,161'H feet over the sea, whilst my proposed tunnel- 

 mouth was 1,12091 feet, which show T ed a balance in favour of the 

 success of my work to the tunnel of 40*20 feet, and a total fall 

 from the gap of just 99 feet to the intake of the wrought-iron 

 mains, which would be north, and 8'i miles from Westmacott's 

 Pass. I trust, therefore, that I may be pardoned for saying here 

 how rejoiced I felt when I found that the instruments proved 

 that we had thus 40 feet to spare for this development ; because 

 I knew that, this Charybdis being passed, I had no Scylla to fear, 

 and that all the southern waters of the upper elevations for miles 

 and miles along the coast range south were or could be completely 

 at our command. I also felt that by the high elevations com- 

 manded, and by the extreme pureness and brightness of the waters 

 from such a poor sterile country that would never be likely to be 

 occupied by man, our city could be insured the fullest supply of 

 the best of naturally filtered water, free from all peaty and from 

 all chalybeate taste, by direct and high gravitation, for ever. 



