XCIV. DISCUSSION. 
below mean respectively, and the total amount of rainfall 
for various periods above and below mean in order to deter- 
mine the periods of greatest plenty and greatest scarcity. 
The Sydney records seems to show a proportion of 41% of 
the whole above, and 59% of the whole below the mean. 
This disparity is greater in Australia than on the continent. 
of Europe, India, or Africa. In Europe the range is about 
45% to 557+ respectively; in India 48% to 52%; and in Africa 
46% to 53%. The subject is such a complex one that it is. 
difficult to discuss it off hand, but it is one that requires to 
be continually watched and studied by the authorities. It. 
is greatly to be deplored that such an expert as Mr. 
Keele should bave been removed from a sphere of usefulness. 
where technical knowledge and vigilant administration are 
so valuable to the public, and where he would have brought 
his professional experience to bear on the question of pro- 
viding Sydney with an extended supply of high pressure 
water. 
Iam not at all satisfied that the method adopted by our 
late Chairman of presenting the aspect of the rainfall by 
the residual mass curve is the best for the engineer to 
adopt for a study of the question. It appears to me that 
the varying accumulations of rainfall over a long period of 
years as shewn by the residual mass curve, except on such 
a catchment as Botany or Long Island, might be deceptive, 
without some knowledge of the maximum and minimum 
and the intensity of the rainfall. Another element in the 
question is the nature of the catchment and its capacity 
for holding the accumulation of rainfall over a series of 
years. Its physical features may be such that the surplus. 
rainfall might flow rapidly off, and after filling the reservoirs. 
the balance would escape to the sea, leaving little or no 
accumulation in the ground for future delivery. On the 
other hand the catchment may be of such an absorptive 
