242 



The Data on whiclt we have to depend 



is less tlian the English proportion. From the want of ex- 

 tended meteorological observations taken in connexion with 

 the Upper Plenty districts^ or, what would have been much 

 more satisfactory, a complete series of stream guagmgs to 

 determine the annual discharge, the available rainfall of the 

 district can only be analogically eliminated from the general 

 data afforded by the most trustworthy English observations 

 on evaporation, corrected for the average differences of tem- 

 perature, for the various months in the year, in London and 

 Melbourne, as given in the Statistical Register for Victoria. 

 Moreover, as wind and the hygrometrical state of the atmo- 

 sphere exercise a marked influence over evaporation, inde- 

 pendently of temperature, and as their action is more intense 

 here than in England, some additional correcitions must be 

 applied to the English data for this increased action. Having 

 made due allowance for all these contingencies, I have 

 arrived at the conclusion that the total annual rainfall and 

 dew at the Upper Plenty may be taken together as equi- 

 valent to thirty-six inches, and that the amount thereof avail- 

 able for the supply of the Plenty, in the present state of the 

 natural surfaces, would be about five inches." 



I entirely concur with the opinions expressed in the above 

 paragraph, but, in adopting for the Upper Plenty district a 

 larger proportion of available rainfall than is relied on for 

 the average surface of England, Mr. Hodgkinson has alto- 

 gether forgotten the principles which he has so ably incul- 

 cated. 



He admits that the proportion of the rainfall in the Upper 

 Plenty district ought to be less than the English proportion : 

 Why does he not, therefore, adopt less than the English 

 proportion ? He admits the want of meteorological obser- 

 vations, and that measurements of the river would have been 

 much more satisfactory : Why does he not base his calcula- 

 tions on the December measurements, making due alloAvance 

 for the winter rains ? 



He tells us that his estimate of the available rainfall of 

 the Upper Plenty District is only analogically eliminated 

 from English data, corrected in a very complicated manner 

 for temperature and dry winds. How is it then that he 

 places such implicit confidence in an estimate so singularly 

 enveloped in difficulties and uncertainties, and applied under 

 novel circumstances to a new country, with a totally different 

 climate ? And after all he has not made the corrections to 

 which he attaches so much importance. He has adopted a 

 less proportion of available rain than Mr, Howard's, which 



