For our Water Supply. 235 
towns, we may adopt such 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 with, 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 would 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 inthe 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 
scientific 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 daily 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. 
