240 The Data on wldch roe have to depend 



Ft. In. 



1. Diiference between 5 inch of rain over 62J square 



miles and 4 J in. over 60 sq. m. ... 17 



2. „ between 500 gallons and 900 gallons ... 6 



3. „ between my two estimates and not relied 



on 1 



4. „ between 2 and 10 inches of dew ... 8 



5. „ between 5 feet G*6 inches of evaporation 



and 9 feet 3 4 



Total 7 6^ 



Deduct loss of flood water, and loss from 



absorption ... ... ... ... 6 



Balance to supply 191,500 7 Oj 



This table, then, exhibits the data on which depend all our 

 hopes of an adequate supply of water from Yan Yean. 



If Mr. Hodgklnson Is right In assuming these data, we 

 shall have a very abundant supply, at least for our present 

 wants. If, on the other hand, I shall succeed in showing 

 that he Is wrong, then, assuredly, the Yan Yean scheme will 

 prove a failure, and wc shall have to look elsewhere for our 

 water supply. 



Having been induced, on public grounds, to investigate 

 the points upon which Mr. Hodgklnson differs from myself, 

 I trust that. In freely expressing my opinions on our points 

 of difference, he will give me credit for simply wishing to 

 arrive at the truth, and, as the question at issue is a most 

 momentous one for the public interests, both in a pecuniary 

 and in a sanitary point of view, I trust that he will see no 

 impropriety in my calling In question his opinions on subjects 

 which he himself admits require further elucidation. 



1. What reason does Mr. Hodgklnson assign for assuming 

 5 inches of the rainfall, instead of 4 inches or 6 Inches ? 



This is a very important question, as one inch over 

 square miles will supply 62,500, at 40 gallons per head, 

 per day. 



The evaporation tables of Mr. Charnock, the Vice-Presi- 

 dent of the Meteorological Society, and Mr. Howard, have, 

 according to Mr. Hodgklnson, been chiefly relied on of late 

 years, in estimating the proportion of the rain that is avail- 

 able for water siq)ply in England. 



The available rain, according to Mr. Charnock, is 4*88 

 inches out of a rainfall of 24 '6 inches, and according to 

 Mr. Howard the proportion is 6*53 inches out of 36 inches. 

 Mr. Charnock's observations have reference to a previous 



