Failure of the Van Yean Reservoir, 



137 



The latter writes to the Society, " that although precluded^ 

 from want of time, from affording his assistance in the calcu- 

 lations of the Committee, yet, if he could have agreed with 

 the conclusions aiTived at by them, he would have appended 

 his name to their report, but he differed very materially from 

 some of their views." 



It is much to be regretted, that the Committee thus lost 

 the co-operation of two of the members, and especially on 

 the grounds above stated, as it is evident, that they, as ori- 

 ginally constituted, would have arrived at very different 

 conclusions, and although I entertain the highest opinion of 

 the professional abilities of Messrs. Christy and Acheson, I 

 have to state, on public grounds, that however competent 

 they may be to draw up a report on the watershed of Eng- 

 lish rivers, with the aid of English tables, they cannot be 

 supposed to have much practical knowledge of the rivers of 

 this country, from their comparatively short colonial expe- 

 rience, and they have never actually seen the river Plenty 

 in the winter months, although their calculations show that 

 they expect nine-tenths of the whole supply from the winter 

 rains. The report, therefore, has lost much of that practical 

 value that would otherwise have attached to any document 

 emanating from a Committee of the Philosophical Society. 



Finding such an enormous difference between my esti- 

 mate of the watershed of the Plenty basin, and that ar- 

 rived at by the Committee, Mr.Hodgkinson w^as induced to 

 read a very interesting and valuable paper on the subject be- 

 fore the Society ; and the result at which he has arrived 

 strongly corroborates all my calculations and conclusions 

 with respect to the watershed, which is the fulcrum upon 

 which the sufficiency of the supply for a rapidly increasing 

 population will depend. At forty gallons, per head, per day, 

 Mr. Hodgkinson calculates that there will be water for 

 190,000, so long as there is no drought like that of 1837-38 ; 

 in such a contingency he thinks the supply of water would 

 fail. 



But, it is to be noticed, that this estimate for 190,000 is 

 based on a very important consideration, about which there 

 is at present some difference of opinion. He has taken mea- 

 surements of the evaporation from a pond Avhich supplies his 

 house, and calculates that it does not amount to more than 

 five feet six inches in the year. Dr. Davy, on the other 

 hand, who is our highest meteorological authority, regards 

 ten feet as the probable evaporation. Now, at forty gallons 

 p 



