126 WATER SUPPLY TO SYDNEY BY GRAVITATION. 



This is the head and front of my whole scheme for bringing the 

 waters in an almost direct northerly course to Sydney from as far 

 south towards Shoalhaven as we might choose to go with our 

 aqueduct, ditch, or canal, to supplement the water supply to any 

 extent that might be required. The Kev. W. B. Clarke, our 

 Chairman, then said that such dip from the south equalled 42 

 feet to the mile, whereas I had only stated it to be 40 to 41 feet. 

 This being the leading point of the whole value of my discovery 

 and scheme, I desire to lay stress on this fact, as it is probable 

 that this interesting geological truth was not known to many even 

 of this Society, before this late proposed application of the 

 valuable dip of the coal formation for our uses was made known. 



The practical result of this application is, as we all knew be- 

 fore, that it is quite easy to lead luater down hill, especially wdien 

 the broken interruptions of the average downward dip of the 

 country to the north, can be so easily overcome by taking further 

 advantage of the westerly dip of 60 feet to the mile all the way, 

 whereby the waters can be made to contour the obstructing ranges 

 almost everywhere without the necessity of tunnelling through 

 the hills, excepting through that region which constitutes the 

 apex of the dividing watersheds of the Cataract River, the 

 G-eorge's Eiver, the Waranora, and the Port Hacking Creek 

 waters, where my proposed tunnel of 3^ miles would be to unite 

 the head and permanently running sources of all these waters. 



It was on the southern lower levels of these dividing ranges 

 that I found the grand basin for the accumulation and storage 

 of an immense supply of water, as shown by my map, and as de- 

 scribed in my late paper. By or into this basin, and by or into 

 the tunnel and open canal that lie west and north of my proposed 

 dam, and which reach the intake of my proposed wrought-iron 

 mains for direct gravitation to Sydney, I estimate that we can 

 command a watershed on this highest ground, close to the sea, of 

 not less than 15 square miles of a swampy country ; and as the 

 rains in this region are even more abundant than they are lower 

 down, so I can see no reason to doubt that the rainfall there 

 might be set down to average 60 inches per annum as against the 

 average fall for the last sixteen years in Sydney, of 52| inches ; 

 and that as this upper country is so peculiarly and favourably 

 formed for the delivery and catchment of this great rainfall, so I 

 think that we might safely count on being able to secure for 

 Sydney use the one-half of all that is supplied up there by 

 nature. 



Assuming that this estimate may be correct, we should in such 



case still show from this small watershed of 15 square miles, no 



ess a catchment and delivery for the year for Sydney than 



^6,534,000,000 gallons, which would be equal to a delivery of no 



less than 17,901,000 gallons per day, or a quantity from thence 



