50 SYDNEY WATEB SUPPLY BY 'GRAVITATION. 



was computed at £14,600, including its sluices in cast iron, &c. 

 Kow, cceteris paribus, and allowing for the great difference in the 

 price of labour, the Loddon dam of same structure might reach 

 from £20,000 to £25,000, and a similar dam in Port Hacking 

 valley, at 35 feet high, and about 500 feet across, might be 

 estimated at £15,000 at most, with its sluices built in. 



The other and minor dams, with only concrete cores, would be 

 of comparatively very small espense, and the whole set of them 

 might be estimated at £15,000. 



Next to these dams, costing some £65,000, but which may be 

 far short of the cost here, comes the one tunnel of 3 miles and 

 35 chains, which would be all cut out of solid sandstone, and 

 would be available for excavation by shafts at five different spots, 

 besides at the two ends ; hence the advantage of the westerly 

 dip, which reduces depth of sinkings. As the velocity to be given 

 to the waters in the tunnel would be by a gradient of 4^ feet to 

 the mile, besides the head of water at the inlet, there would be no 

 necessity of using cement or masoury anywhere along its course. 

 "What the cost of this work would be I know not, and must leave 

 to others to determine. 



To many this underground work of 3| miles may seem to be 

 very great, therefore it may be desirable to mention that in the 

 Nepean scheme, which was adopted by the Water Commission, 

 they start at 63 miles from Sydney with one tunnel of 4 miles 

 and 49 chains, and have in all ten tunnels aggregating 10 miles 

 and 7 chains, besides 10 miles of 46-inch diameter iron mains and 

 over 3,000 feet of iron aqueducts in the first 17 miles of the total 

 63 miles to Sydney ; whereas, by my short-cut scheme on the high 

 levels, I have only the one tunnel, and do not require a single foot 

 of iron aqueducts in the ranges before the waters enter the long 

 mains of 28 miles to Sydney. 



Following my proposed work comes the open aqueduct for 4 

 miles, to the deKvery mains on the Bottleforest Road,' at 28 

 miles from Sydney. This aqueduct would be constructed like the 

 north-west feeding aqueduct to the great reservoir, and would be 

 all cut out of solid sandstone, with a gradient of 5 feet to the mile. 

 The expenses of this work would be a matter for tender. 



Beyond the above simple works as compared with other water 

 schemes, and viewed as a national undertaking and for such an 

 achievement, there would remain the large and chief cost of the 

 t\N'o high delivery over-ground mains, in wrought-iron or in steel, 

 of 18 inches diameter — these to run side by side as far as Cook's 

 E.iver, on their way to deliver respectively 4,270,891 gallons daily 

 to the Petersham and Canterbury heights, and 4,029,143 galls, 

 daily to Waverley, with the respective heads of water of 850 and 

 750 feet, as computed by Eytelwein's formula ; and these two 

 high delivery mains to be coupled together by union joints above 



