WATER SUPPLY TO SYDNEY BY GRAVITATION. 99 



before you that should savour more of abstract science, as befits 

 these meetings perhaps more than such a subject as that of 

 water supply can well give rise to ; at the same time I trust that 

 we may claim its adaptation to our Society, by reason of its being 

 a subject for so called " social science," which term seems to me 

 to imply the application of the valuable principles of abstract 

 science to the practical benefits of mankind. 



Eeverting to the former work of my survey in last October, I 

 may say that the sudden illness of my surveying assistant, as 

 well as of myself, obliged me to disband my party when my survey 

 was incomplete, and that I was compelled afterwards to finish the 

 remainder of the work hurriedly by means of a prismatic compass 

 and of an aneroid only, in lieu of the proper instruments which I 

 had returned to Sydney. But not being satisfied with the sup- 

 posed elevations taken, I resolved, later on, to renew my survey, 

 and to take complete and true elevations which should all be 

 connected with the sea level at high-water spring tides. The 

 second survey, I am happy to say, was most satisfactory, and has 

 led to very improved results, although we found that the former 

 aneroid observations had betrayed me into serious mistakes as to 

 the extent of area available for water reservoirs. Happily, how- 

 ever, these aneroid deceptions told both ways, because my cor- 

 rected survey showed 6 feet more depth in my intended lake for 

 some 60 chains up the main valley fronting the proposed dam. 

 My further work also disclosed the uselessness of trying to 

 impound so large a body of water as 2,000 acres thereabouts, as 

 before named by me, partly because the true levels proved that 

 such a large impoundage would be impossible ; and because I 

 could see that such vast bodies of stagnant water, if obtainable, 

 would be undesirable, and would only lead to excessive waste by 

 evaporation, and to vegetable growth over the extended outer and 

 shallower surfaces. 



I saw also that by making subsidiary dams up each of the four 

 main and permanently-running creeks, I could multiply the storage 

 of water very considerably, but to no good end, inasmuch as I found 

 that by confining the expense of dam-making mainly to the one 

 great storage dam in the mountain valley of the Loddon, which 

 should be suitably built to be capable of being added to when 

 required, we could impound about 2,000 million gallons of water 

 by raising the one dam across a very narrow gorge of sandstone 

 rocky hills 50 feet only ; and that as that amount of impounded 

 water would alone represent quite 400 days' supply for all 

 Sydney, at the rate of its present extreme delivery of 5,000,000 

 gallons per day by the Botany pumps, so I thought that a pro- 

 posal for any further expense for impounding more water, unless 

 by small storm-water embankments, would imply a total waste of 

 money until the extension of the city should make it necessary 



