THE WATER SUPPLY OF SYDNEY. XCIII. 
so highas this. On the impermeable catchments of Great 
Britain the run off averages only 20%), and in the permeable 
catchments only 74’. Mr. R.T. McKay, in his paper read 
before this Society in September 1906, gives the run off of 
various catchments from 15 years observation as follows:— 
The Murrumbidgee at Gundagai 21°67; the Goulburn at 
Murchison 337; the Ovens 287. The above catchments 
may be classed as impermeable. It was found when con- 
structing the reservoir for the Lloyd Copper Co. at Burraga, 
on impermeable slate country, that the amount of rainfall 
conserved was only 214%. On permeable catchment such 
as the Murray at Morgan, in flood years the run off was 
9%, and in drought years only 1. The Darling at Wilcannia 
shews a mean run off of only 0°65%. 
The author’s reasons for anticipating a large increase in 
consumption of water are perfectly sound. Amongst the 
causes likely to increase consumption is the development 
of manufactures which have only just begun to expand 
under the Federal tariff. The amount of water consumed 
by a city is some indication of its refinement and civilization, 
and the climate of Sydney is such as to encourage a large 
use of water, if it can be obtained in unlimited quantity at 
a reasonable price. Given the latter conditions and the 
consumption might easily go to 120 gallons a day per head. 
Not the least interesting part of the address was the 
analysis of rainfall and its effect on the reservoirs, but lam 
of the opinion that the data regarding the rainfall does not 
extend over a sufficient number of years to make it reliable 
for forecasting. I am prepared to admit the cycle theory, 
but so far we have no proof of the extent or periodicity of 
the cycles, and possibly it may require the meteorological 
study of hundreds of years to arrive at a solution of that 
question. Attention might be directed to ascertaining the 
greatest number of years that the rainfall is above and 
