WATER SUPPLY TO SYDNEY BY GRAVITATION. 103 



country how vast such a supply would be ; but in order to try to 

 convey a practical idea of the expanse and depth of such a lake, I 

 beg to inform you that supposing the great steamships the 

 ""Whampoa" and "St. Osyth," when loaded, were to be floated 

 there, those ships could make a cruise of two and a half miles 

 from the dam and back, and would in that distance never have 

 less than six feet of water under their keels ; whilst such vessels 

 as the " Emu " on the Parramatta River, could cruise for six miles 

 around various arms of the lake forming bays of shallower depths. 



On reference to the appendix of this paper, which exemplifies 

 the construction and cost of another cement concrete dam erected 

 lately in Victoria for Gleelong water supply, it will be observed 

 that it cost £17,306 12s. for conserving 141 million gallons of 

 water, which brings the cost on each million of gallons of water 

 storage equal to £122 15s. By the estimates of the storage 

 capacity of the Loddon reservoir, roughly stated 2,000 million 

 gallons, we could, cceteris paribus, afford to spend £245,500 on the 

 Loddon concrete dam of same nature as the one at Stony Creek, 

 distant twenty miles from Geelong ; but as this is probably a 

 larger sum by more than four times than would be required for the 

 erection of the Loddon dam, sluices, and valve-house, it would give a 

 fair result at such comparative cost of £61,375, and would place the 

 cost of storage of each million gallons at the almost unprecedent- 

 edly low price of £30 13s. 9d., which indicates in a remarkable 

 manner the superiority of the position for the Loddon dam. 



Let us now consider the chances of so large a Teservoir being 

 filled by the adjacent watershed. During the period of one month 

 that I was engaged in my last survey, we estimated that probably 

 enough water passed down those various branches of the Loddon 

 Eiver to be nearly equal to fill the whole of the lake to its full 

 depth of 50 feet at the dam. The floodmark at the narrow pass 

 where I have marked off" the proposed dam showed a perpendicular 

 rise of 14 feet 2 inches and 8 chains wide by the last flood previous 

 to the survey ; and there is reason to believe that on Saturday, the 

 6th of March last, it must have exceeded 16 feet at such pass. I 

 am, therefore, quite satisfied that the watershed of that high dis- 

 trict, close to the sea, is quite ample for all our requirements. 



It has been remarked by several, that probably the country 

 would not present good retaining ground for large reservoirs. 

 This is, however, quite a mistake ; and in satisfaction of this im- 

 portant question, and of the adaptation of the country for such 

 purposes, I desire to adduce evidences in favour of my assertion. 

 First, then, the whole watershed is formed of the coal sandstone 

 as I fully described in my first paper on this subject. The whole 

 formation there is a bare sandstone rock, covered with sand, the 

 debris of itself. Here and there the sands are peaty ; but nearly 

 everywhere the waters are to be seen oozing out of the sides of 



