WATER SUPPLY TO SYDNEY BY GRAVITATION. 129 



waters by the iron mains should be at the highest point obtain- 

 able, in order to preserve the fullest hydraulic pressure, of so 

 much value, yet I would state, that it would be easy to lead the 

 waters along by an open aqueduct for many miles down the 

 gradual declivities of the Bottle Forest Road, and its marginal 

 eastern slopes on Hacking Creek side, until any other required 

 elevation over Sydney was attained before confining the waters in 

 the closed wrought iron mains. But as such an arrangement 

 would be a violation of my high pressure principle, I do no more 

 than name the feasibility of conducting the waters by open gravi- 

 tation to within 6 miles south of George' s River, where the 

 elevation is 400 feet, and sufficiently high to command the 

 Waverley heights, or the highest point about Sydney. But a 

 proper survey of this part is necessary to determine the feasibility 

 of this part of the conduit. 



Of the George's River waters I wish also to say that should 

 the Illawarra direct railway become a fact, and my gravitation 

 water scheme meet with favour and be adopted, I would like to 

 see that the aqueduct for my proposed wrought-iron mains should 

 be so constructed as to form by it a viaduct over the George 

 River for the railway, if the line crossing there should be practi- 

 cable. I would suggest in this case that such viaduct and 

 aqueduct should be by crossing the river at Kangaroo Point, 

 where it is narrowest, and where embankment materials are 

 inexhaustible — instead of making the railway to pass by the 

 bridgeway and embankments as at present surveyed for the line 

 lower down the river. 



Should this idea meet with favour, I would further suggest 

 that such road and water-way at Kangaroo Point should be con- 

 structed in the simplest possible form of small broken sandstone, 

 sand, and clay, to be thrown into and across the river to the 

 cubical extent or measurement of about 350,000 cubic yards ; 

 and then, by closing the river up altogether (with the protection 

 of an adequate by- wash), and by raising the dam only slightly 

 above high- water spring tides, it would, I think, be shown to be 

 quite possible to keep back the salt w r ater from the inside, by 

 maintaining an almost even pressure on both sides, but giving 

 that of the fresh water the slightest advantage. 



By adopting this course for my proposed over-ground water- 

 mains there w r ould be a saving of quite half a mile of piping, 

 whilst, at the same time, the railway, if the gradients would suit, 

 would be shortened by as much, and the proposed simple embank- 

 ment for the railway would probably cost much less than the 

 intended bridges and railway embankments as surveyed ; whilst 

 by my proposed measure we might prove the possibility of shutting 

 off salt water from fresh, and then leaving it to be a matter of 

 time only for the fresh water floods to clear out the salt and 



