Memm'Jcs on tTie Beport of the Water Commission. 63 



true, but the area of shale is small compared with the area of 

 sandstone and the quality of the water could not be materially- 

 depreciated on that account. Recent investigations in England 

 seem to intimate that extreme purity is not desirable. Moreover 

 it should be remembered that the drainage into the river would 

 be mainly surface drainage. The water will run rapidly off grass 

 lands without having had much time to become contaminated It 

 should be remembered also, that the conduit proposed by the 

 Commissioners runs for a considerable distance through the 

 "Wianamatta tract, and that the great storage reservoir is to be 

 constructed in it. The water their scheme will supply to the 

 city will be stored in this shale prior to its delivery, which will 

 afford the maximum chance of impregnation, and they admit 

 that for some years the water will be so clay-coloured as to be 

 very objectionable in appearance, and the clay will be so fine that 

 the water cannot be effectually refined by filtration. 



The next advantage I wish to mention is, that to construct the 

 reservoir at the mouth of the Greorge's River would require but 

 a comparatively small outlay. To make the reservoir at Prospect 

 would require a dam ; to make the reservoir at G-eorge's River 

 would also require a dam. But the former would be eighty-one 

 feet in height at its deepest part, and a mile and a quarter, or 

 6600 feet in length. A dam at Sans Souci would be only 1850 

 feet long, and the river is only 35 feet at its maximum depth. 

 The former work would have to resist a pressure from water 80 

 feet in depth on its upper side, with nothing to support it on its 

 lower side. The latter would be supported on both sides by 

 water, the relative levels of which would not ordinarily vary 

 more than about six feet. The former work is said to be possible 

 — the latter to be impossible — except at an outlay of £650,000. 

 On this point more hereafter. 



Supposing the dam to be made (and for the present I may be 

 allowed to make the supposition), a reservoir would be con- 

 structed of certainly not less than 3000 acres. This is the rougn 

 estimate of the area made by the Commissioners, supposing the 

 dam to be at Tom Ugly's Poiut, but which I am inclined to think 

 is considerably under the mark. An exact estimate of the area 

 is not possible as there are no accurate surveys on which to base 

 it. But the river is considered to be 27 miles long by its course 

 from Liverpool to Tom Ugly's Point, and the tributary creeks show 

 a large expanse of water at high tide. The Woronora and Salt Pan 

 Creeks are both navigable by boats for several miles. Even sup- 

 posing this to be not under estimated 1000 acres additional would 

 be secured by making the dam at Sans Souci. According to the 

 evidence of Mr. A. K. Smith, C.E., this amount of storage with a 

 depth of only four feet would be equal to 3267 millions of gallons, 

 and one inch of rain on the watershed would give this four feet of 



