Failure of the Van Yean Reservoir. 



145 



Table III. — Showing the Mean Rain and the amount of Rain 

 evaporated, and the Watershed, or that portion of the Eain 

 that escapes evaporation in Victoria, deduced from Mr. Demp- 

 sey's Tables : — 



MEAK RAIN. EVAPORATION. WATERSHED. 



January . 1-36 1-34 002 



February . 0*95 0-93 0*02 



March . . 1'60 1-57 0*03 



April . . 3-13 307 0*06 



May . . 3-67 3-45 022 



June . . 2-41 1-90 0*51 



July . , 2-18 1-71 0-47 



August . . 3-61 2-85 0-76 



September . 3*27 3-08 0*19 



October . 2*54 . 2*36 O'lS 



November . 4-27 4*21 0'06 



December . 1'86 1-83 0'03 



Total 30-85 28*30 2-51 



In illustration of this method I shall take our month of 

 January^ which has a mean temperature of 67« 94. On re- 

 ferring to Mr. Dempsey's tables I find that August in Eng- 

 land has a mean temperature of 61*^ 6. Now, what can be 

 more just or more in accordance with scientific accuracy, 

 than to conclude that the proportion of the rain evaporated 

 in our January is at least as great as that in the August of 

 England ? 



In the same way I shall take our July, which has a mean 

 temperature of 49*^ 34, and I find that April in England has 

 a mean temperature of 49^- 9. Am I not then warranted 

 on scientific groimds to assume that the proportion of the 

 rain evaporated here in July is equal to that of April in 

 England ? Now it is precisely in this way that I have de- 

 duced from Mr. Dempsey's tables that 2-51 inches, or one- 

 twelfth of the rainfall adopted by the Committee, represents 

 the proportion that reaches the Plenty. 



I do not insist that Mr. Dempsey's tables are correct ; but 

 if they are so, then it would appear that the watershed of 

 the Plenty is much less than I made it. His tables give 

 2*51 inches; I estimated 4*50 inches as the nearest approxi- 

 mation, and there is a vast difference between 2*51 inches 

 and 10*69 inches when multiplied by sixty square miles of 

 surface; and this is the watershed adopted by your Com- 

 mittee for eight months of the year. And as every point is 



n 



