SYDNEY WATER SUPPLY BY GRAVITATION. 



By James Manning, Esq. 



ISead before the Hoyal Society, 9 December, 1874.] 



In coming before this Society with a paper having the above 

 designation, I beg to say that the origination of this subject 

 occurred vi'hen I was engaged twelve months ago with the railway 

 engineer, Mr. Stephens, in making a reconnaissance survey of the 

 Port Hacking valley and rivulet for a railway route to the southern, 

 coal mines and to Illawarra. Ou passing up the higher parts of that 

 rivulet I was struck with the natural facilities which presented 

 themselves in the neighbourhood of Bulgo to avail of the great 

 geological north-westerly dip of the country, for the benefit of a 

 water supply for Sydney by gravitation. I perceived that the 

 waters of this rivulet could be supplemented with extra waters 

 from the western slopes of the south coast and coal range, by 

 reason of the great facilities that would be afforded by the 

 northerly dip of 40 to 41 feet to the mile, and by the westerly dip 

 of 60 feet to the mile along the whole of the coast range south 

 of Bulgo and Coalcliff for twenty miles and more. 



By the natural facilities produced through such gradients I 

 foresaw that it would be a simple matter to divert all the upper 

 waters of the great south coast range from their present courses 

 down the Cataract and the Cordeaux Elvers into the Nepean, and 

 to bring them all out north, towards Sydney, by an open aqueduct 

 to the head of the Loddon Eiver, and on through the obstructing 

 cross range by means of a tunnel of no formidable nature, and 

 to lead them, if required, into the Port Hacking Eiver, which runs 

 north throughout its main course. - 



The barometrical elevations of the countries all along and about 

 the south coastrange, behind Stanwell Park, BuUi, Wonona, Mount 

 Kiera, and Mount Kembla, were known to me through the valua- 

 ble researches in 1845, 1846, &c., of the Eev. W. B. Clarke, our 

 venerated V. -President, and partly also through my own aneroid 

 measurements on the south and east side of Maddens Plains, which 

 I made during each of my two journeys there when in quest of 

 the Illawarra Eailroad. By these I made reasonable deductions 

 of what could be done by caualling and tunnelling. The more 

 I dwelt upon the subject the more firmly was I convinced of the 



