For our Water Supply, 



255 



This is a very important deduction from Mr. Hodgklnson's 

 premises^ as it proves one of two things. If his evaporation 

 is right, then the 3 '2 6 inches must be supplied from a spring, 

 or from some distant and higher level beyond the limits of the 

 nine acres. If, on the other hand, the rainfall of the nine 

 acres is the only source of supply, then the evaporation for 

 our three hottest months cannot exceed 6' 91 inches. Either 

 alternative would be sufficiently embarassing. 



Dr. Davey has shown that the temperature of our three 

 summer months, during last season, exceeded the temperature 

 of the corresponding months in London, according to the 

 meteorological tables of the Royal Society, by 10*^ of Pahr., 

 and also that our dryness exceeded that of London by two and 

 one-fourth to one. From these data we are warranted, ac- 

 cording to the tables of Dr. Dalton, to compute our evapora- 

 tion at nearly three times the English evaporation ; but, if we 

 are to trust Mr. Ilodgkinson's experiments in the pond, our 

 evaporation will only exceed Dr. Dalton's estimate for June 

 by less than half an inch for each of the three months. And, 

 if we further deduct one inch of dew, which Mr Hodgkinson 

 has allowed for the three summer months, his estimate of the 

 evaporation accurately deduced from his own premises, will 

 almost exactly equal the Enghsh evaporation. 



The watershed of the nine acres for twelve months, cal- 

 culated at fifteen per cent, of the rainfall, is equal to 27 "7 6 

 inches, which, added to the rainfall of 30*85 inches, gives four 

 feet 10*61 inches, as the available supply for the pond, but 

 Mr. Ilodgkinson's evaporation is five feet 6*6 inches. How is 

 it then that the pond does not dry up ? And how shall we 

 account for a depth of ten feet of water in the summer 

 months? It only receives four feet 10'61 inches, and it eva- 

 porates five feet 6.6 inches, the difference amounting to 7*99 

 inches. 



The conclusion is inevitable that the balance is made up 

 from a spring, or some other source independent of the 

 rainfall. 



And, this being proved, who is to compute the amount of 

 water thus supplied ? or what confidence can be placed in an 

 estimate of the evaporation based on such uncertain data? 

 Thus, to determine the amount of this lateral supply is purely 

 an impossibihty, and to assume the amount is to beg the whole 

 question. 



After the explanation given above respecting dew, it will 

 be of no use to allege that the balance is made up in this way. 

 If nine inches of dew are assumed to be condensed on the 



