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 wdl 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 Austrahan 

 coast, Ave 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 storrns 

 in the adjacent regions. On this subject at least a pomt 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 tune throw 

 a licvht 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 ol the 

 Philosophical Society could be directed. 



Art XIV— the Probable Influence of Evaporation on the 

 Quantity of Water to be supplied by the Reservoir at Yan 

 Yean. By Clement Hodgkinson, C. E., Survey De- 

 partment. 



At the last Meeting of the Philosophical Society, after 

 Dr 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. 



Por Dr. Wilkie, on the authority of Thompsons computa- 



