Failure of the Yan Yean Reservoir. 147 
Ft. In. 
Total - - = - 24 8 
Deduct one-half for district - : eet? 4 
Balance for reservoir . : Shale, 4 
Rain in reservoir - = - - 2 a 
42-4 per cent. of rain over drainage 
area of ditto - - 2 4 
Total in reservoir - = - Si willis 3 
Deduct evaporation - - - - 9 (0) 
Total for the use of the city - is LSPs 
This amount will exactly supply, at thirty gallons per 
head, 333,000; at 100 gallons per head, 100,000. 
Now, let us contrast twenty-three feet six inches, with two 
feet two and two-third inches, the discharge for eight months 
according to the measurement of the Committee. Thus they 
make the Plenty for the eight winter months contain ten 
times the volume of water that it does in January, or, accord- 
ing to Mr. Blackburn’s measurement, in December. 
It will perhaps be said that this actually takes place in 
the Merri Creek; but such reasoning, if it proves anything, 
proves too much. This creek is not a river, and only runs 
after wet weather, and does not always run in winter; or the 
_ stream is so small that it can scarcely be said to run in very 
dry winters. After a heavy fall of rain, the creek is flooded 
for two or three days, but if the flood water were divided 
over 365 days, it would be a miserably small amount. 
If any argument could be extracted from this, it would 
prove that, because the Merri Creek is at one season many 
million times larger than it is at another, therefore the Plenty 
may be so also, which is absurd; besides, this sort of reason- 
ing has its inconveniences as well as its advantages. If we 
take the highest flood in the Plenty, and reduce it by a few 
million times, it would cease running altogether like the 
Merri Creek, and the City would stand a poor chance of a 
permanent supply of water from this source. 
Perhaps it may be thought that the Yarra is an analagous 
ease, and if it can be shown that it contains ten times the 
volume of water during the eight winter months that it does 
in December, so may the Plenty. The Yarra differs in many 
essential points from the Plenty, and chiefly in this important 
particular, that it takes its rise in very high mountains 
