For our Water Supply, 



235 



towns, we may adopt sucli measures as are really calculated 

 to attain these ends. 



But the question of evaporation Is especially important in 

 relation to the subject of this paper, as upon its decision 

 depends at this moment the very important question, whether 

 the Legislative Council ought to permit the Yan Yean works 

 to be proceeded withj or to abandon them as a hopeless failure. 



It is to be regretted, however, that the subject of evapora- 

 tion is very little understood, and its importance very little 

 appreciated in this colony ; and it is not a little singular that 

 Dr. Davey's experiments and observations, which in any 

 other country Avould be deemed sufficient to determine the 

 rate of evaporation, are here regarded with distrust, and are 

 thought to possess little practical value. 



If those, therefore, whose duty it is to proclaim the truths 

 of science, and to vindicate their paramount claim to con- 

 sideration in the conduct of our great public works, hesitate 

 to do so, can we wonder that the members of the Legislative 

 Council should hesitate to interfere with matters involving 

 scientijSc questions which they cannot themselves resolve ? 



But, independently of the great public importance of 

 having this question of evaporation satisfactorily settled, there 

 are other 'reasons which induce me again to bring this subject 

 before you. The different papers that have been read on 

 this subject contain opinions, observations, and experiments 

 of so opposite and conflicting a nature, that it is altogether 

 hopeless to expect that the public will arrive at correct 

 conclusions, unless the members of the Society can first agree 

 among themselves. 



Surely it must be possible for a body of scientific men to 

 determine the rate of evaporation in this country, and this is 

 really all that is wanted, in order to determine the success or 

 failure of our water supply, derivable from Yan Yean. 



It is not too much to expect from the Philosophical Society 

 that they should be able to inform the Legislative Council 

 what loss will be sustained from evaporation in the Yan Yean 

 Reservoir, and I should be sorry to think that a problem of 

 so easy solution elsewhere should be deemed either difficult 

 or impossible here. I trust, therefore, that it will not again 

 be said of us that we are unable to decide this question. It 

 surely will not be regarded as very complimentary to this 

 colony, that one of our dally newspapers should have pub- 

 lished in its summary for England, that scientific men here 

 were divided on the subject of evaporation, and on the defi- 

 ciency that might result therefrom in the water supply of 

 the city. 



