136 Failure of the Yan Yean Reservoir. 
enormous evaporation in this colony, supposing it to be about 
three feet, only calculated upon a certain supply for 150,000 
individuals, they, admitting nine feet of evaporation, which 
is equal to an annual loss of water that would supply 327,000 
at thirty gallons per head per day, find that there is still 
sufficient left for a population of 666,000, and very gene- 
rously leaving one half of this enormous amount for the use 
of the district, they regard the reservoir scheme as adequate 
to supply 333,000. Had Mr. Blackburn been spared, how 
rejoiced he would have been to find his favourite scheme so- 
singularly developed in so short a time. ‘This appears to be 
another illustration of the wonderful powers of unlimited 
extension attributed to the Yan Yean scheme. 
The proportion of the Committee’s estimate would stand 
thus: 3,000 gallons per minute for the six summer months, 
15,000 gallons per minute for three of the winter months, 
and 48,000 gallons per minute for the other three winter 
months. 
These large amounts are of course intended to include 
floods, but as I have elsewhere shown that in some seasons 
we may have no floods at all, and that the very highest flood, 
supposing it to last seventy-two hours, would only amount to 
three feet in the reservoir, or less than one-eighth of the 
whole, the above figures may be regarded as substantially 
correct. 
It is a source of great regret to me that my estimate is so 
much at variance with that of the Committee appointed by 
the Society, but a thorough conviction that they are in error 
compels me to call in question the result of their investiga- 
tions, and to discuss at some length their mode of reasoning 
on the subject. 
And here it is necessary to state that the Committee at 
present consists of only two members, Mr. Christy, civil. 
engineer, and Mr. Acheson of the Survey Department. . 
As originally appointed, the Committee contained the names 
of Mr. Wekey, the honorary secretary of the Society, and 
Mr. Hodgkinson, of the Survey Department, who, from his 
great practical knowledge, and long experience in the colony, 
and having already devoted much attention to the whole 
subject of the water supply of the city, was peculiarly fitted 
to aid their labours. : 
The former withdrew on finding, after mature deliberation, 
that he could not reconcile his own opinions and calculations 
with those of his colleagues. 
