XLII. T. W. KEELE. 
that time, but the Sydney diagram (1) can be relied upon to 
show the general character of the rainfall. On an inspec- 
tion of it, it will be seen that the rainfall for the two first 
years was well above the mean, viz.:—82°81 inches in 
1860, and 58°36 inches in 1861, and the rainfall on the 
catchment area would probably have been greater than 
this. It takes the whole of the rainfall equal to 29 inches 
falling off an area of 50 square miles to fill the Cataract 
reservoir, aud if we assume that it was empty in 1859, and 
Prospect reservoir was drawn down to its safety limit also, 
then with the rainfall above stated, allowing say 40% run- 
off, both reservoirs would have been filled to overflowing, 
and would have remained so probably to the end of 1861. 
During 1862 the Sydney diagram shows a rainfail of only 
23°98 inches, and although the rainfall on the catchment 
area would probably have been a little more, the run-off 
would have been inappreciable. In 1863, 47°08 inches fell, 
and being close to the mean, some contribution to the 
storage might be expected. The rainfall having been 
below the mean, however, for the two years would have 
resulted in a continual draft upon the reservoirs, but not 
to a serious extent. The following year, 1864, had a rain- 
fall of 69°12 inches at Sydney, and probably more than that 
on the catchment area and the reservoirs would have been 
filled again; but it must not be forgotten that the popu- 
lation and rate of consumption would probably have 
increased to 705,000 and 424 million gallons respectively, 
and allowing for loss by evaporation over the surface of 
the two reservoirs, the daily loss therefrom would probably 
have amounted to 51 million gallons. Under these con- 
ditions, and the rate of increase still going on, the next 
two years have to be faced, during which the rainfall at 
Sydney was only a little over 36 inches per year, denoting 
very dry seasons on the catchment area, when there 
