246 The Data on which we have to depend 
river is correct, he only allows one-seventeenth part to remain, 
and abstracts all the rest for the reservoir. 
In this I feel persuaded that Mr. Hodgkinson has also 
erred, and there can be no doubt that if the Commissioners 
should ever attempt to carry out his recommendation they 
would find themselves overwhelmed with legal actions, and 
would be compelled to make very heavy compensation to all 
those whose interests might be affected by the loss of the 
river. 
In my estimate I allowed 900 gallons per minute, or one- 
third of Mr. Blackburn’s December measurement of the river 
at Yan Yean, and an idea of the smallness of even this 
amount may be got by reflecting on the circumstance, that, 
during the drought of 1851, when the Plenty had very nearly 
ceased to flow, Mr. Blackburn’s measurement in February 
gave 865 gallons per minute. 
I think, therefore, that it will be readily admitted that 
at least six inches must be deducted from Mr. Hodgkinson’s 
estimate on this account, and six inches will supply - 
13,656. 
3. Lhave stated that I have no confidence in theoretical 
estimates, and this is the reason that I preferred my estimate, 
that was based on measurement to that which I computed at 
four and half inches of the rainfall, merely as an approxi- 
mation from English data, hence I allowed the difference 
amounting to one foot five and half a inches in the reservoir, 
as a margin for casualties. 
In my preceding remarks it is, I think, clearly shown that 
I was wrong in assuming four and a half inches, and that I 
ought to have assumed four inches of available rain as the 
best approximation that can be arrived at from the most 
trustworthy English data. There is thus a difference of only 
6-43 inches between the two estimates, and there can be no 
objection to leave this small amount for casualties, and, there- 
fore, it may be deducted from Mr. Hodgkinson’s estimate ; 
but as he has allowed six inches for loss of flood water. and 
from adsorption, I shall regard the 6°43 inches as an equivalent 
for his six inches. 
4, I come now to consider the subject of dew. I explained 
in my former paper that very little dew could be condensed 
on the surface of water, and I allowed two inches only because 
it wa8 my firm conviction that, even without drawing off any 
water from the reservoir, there would often be very little in 
it; and when the water is very shallow, a small quantity of 
dew may possibly be condensed on the surface in very cold 
