IV. T. W. KEELE, 
As no further improvement to the water supply appears 
to have been carried out until the year 1854, when the 
population of the city depending upon it had amounted to 
about 80,000, it will be interesting now to refer to a diagram 
(1) of the rainfall at Sydney, which I have prepared for the 
purpose of illustrating the rise and fall of the rain with 
reference to the mean rainfall. Unfortunately the record 
does not extend further back than 1832; but it shows very 
clearly by the help of the residual mass curve, the accumu- 
lated gain or loss of rain above or below the mean, and 
as this curve has been proved elsewhere to be in general 
agreement with the fluctuating level of the ground water, 
it illustrates in the best possible way the periods of dry 
and wet years, and their cumulative effect upon the ground 
water, upon which the flow of the streams so much depends 
in the absence of rain. 
Professor Smith refers to heavy rains having fallen in 
1811 after a long drought, which continued, with the excep- 
tion of 1814-15, for a number of years, floods being so 
frequent and so destructive, that fears were entertained 
that the cultivation of the alluvial flats of the Hawkesbury, 
on which Sydney then greatly depended, would have to be 
given up. He goes on to say that in 1820 there were 
floods, which probably marked the end of the wet season, 
for he quotes from the Gazette of October 28th, 1820, as 
follows :— 
“The present dry season of the year being indicative of an 
approaching long drought, etc., ete.” 
Reference is again made to drought in 1823-4, and again 
in 1826, when he quotes Captain Sturt as follows :— 
“This year commenced one of those fearful droughts to which 
we have reason to believe the climate of New South Wales is 
periodically subject. It continued the two following years with 
unabated severity.” 
