Probable Evaporation at Yan Yean. 175 
winds from the interior and the winds from the ocean. Sup- 
posing the wind to blow continuously in either one of these 
directions we should certainly have no rain. The dry north 
wind cannot deposit the wet which it does not contain. The 
sea breeze, coming from the south, has its tendency to absorb 
moisture increased as it proceeds northward, and will conse- 
quently give no rain. 
If, therefore, we suppose that from whatever cause, at 
any time, there may be a more than usually steady current 
and uniform pressure in the ocean winds, off the Australian 
coast, we find at once, an adequate proximate cause for a 
drought on the land. As to the ultimate or remote cause, 
we have at present no data even for probable surmise, unless 
indeed we ascend another link in the chain of causes, and 
attribute the circumstance to the accidental absence of storms 
in the adjacent regions. On this subject at least a point is 
gained when a fallacy is cleared away. It is to be hoped 
that the result of simultaneous observations, which, under 
the patronage of the Board of Trade, are now about to be 
made at sea, in all parts of the world, will in due time throw 
a light upon this subject: I now conclude by recommending 
a co-operation in this important investigation, as one of the 
most legitimate objects to which the attention of the 
Philosophical Society could be directed. 
Art. XIV.—On the Probable Influence of Evaporation on the 
Quantity of Water to be supplied by the Reservoir at Yan 
Yean. By CiementT Hopecxinson, C. E., Survey De- 
partment. 
At the last Meeting of the Philosophical Society, after 
Dy. Wilkie’s Paper on the anticipated failure of the Plenty 
Scheme of Water Supply had been read, and your Committee’s 
Report received, the President, in the course of a few terse 
and apposite observations, directed the attention of the 
members of the Society to the necessity of further elucidation 
of the phenomena connected with evaporation. 
I quite concur in the President’s opinion that the excessive 
difference in the estimated effects of evaporation on the 
surface of the Upper Plenty District by Dr. Wilkie and 
your Committee, calls for further investigation. 
For Dr. Wilkie, on the authority of Thompson’s computa- 
