THE WATER SUPPLY OF SYDNEY. CXVII. 
observations of the rainfall had been continued sufficiently 
long on the Melbourne catchment areas, viz: the Watts’ 
River, or Wallaby and Silver Creeks, the curves constructed 
therefrom, would no doubt be found not to compare any 
closer than those of Sydney and the Cordeaux; but the 
distance between them is so short, being not greater than 
30 miles or so, it is reasonable to assume that, the drought 
which has affected Melbourne since 1875, resulting from 
the persistent decline in the rainfall for the following 23 
years, which has brought the curve down to day lower than 
ever previously experienced, will be found to show a some- 
what similar decline on the catchment areas named. That 
this is not an incorrect assumption, is shown by the returns 
published by Mr. Ritchie on July ist. 
While making an investigation of the Australian rainfall, 
the necessity of taking into consideration the cumulative 
effect of the rainfall was impressed upon me, and my views 
were confirmed on reading the report of the Commission 
on Additional Water Supply for the City of New York (1904) 
in which I found that Mr. Walter EH. Spear, one of the 
Department Engineers, had proved that the fluctuations 
of the water table agreed with the mass curve. The 
following is an extract from his report :— 
“Since the height of the water table—on which depends the 
delivery of the ground water on Long Island—represents the 
cumulative effect of the rainfall for many years, it was appreciated 
that the ordinary method of considering the maximum delivery of 
a watershed, to depend upon the rainfall during the dryest season 
or during the dryest year, would not necessarily give the lowest 
yield ; for if the season or year of drought followed a period of 
heavy rainfall, the water table, having been raised during the rainy 
years, would still deliver during the period of drought, a large 
amount of water that had fallen during the previous years. Con- 
sequently the residual mass curves were worked up. The general 
agreement between these mass curves and the fluctuations in the 
elevations of the ground water justify their computations.” 
