Fan Yean Water Works, 



199 



This supply is equal to 101^ gallons per head per day, for 

 a population of 100,000 persons. 



In thus laying before you, Mr. President and gentlemen, 

 the results of our investigations, as also the several modes by 

 which Ave have arrived at those results, we do so with 

 much diffidence, being fully impressed with the difficulty in 

 obtammg accurate results, under constantly varying condi- 

 tions, resulting from meteorological changes, configuration 

 and character of surfece, &c. We believe that refined scien- 

 tific deductions, relative to surface absorption and evapora- 

 tion, however true under certain circumstances, are liable to 

 many sources of error, where so many conflicting conditions 

 have to be meted out, adjusted, and balanced with each 

 other, so that each shall have a consideration consistent with 

 scientific facts. We have not, therefore, attempted to solve 

 this, the most important part of the problem, by such means, 

 but viewing it more as a practical question due to this parti- 

 cular locality, we have, in the absence of local evidence^ 

 applied the data for surface evaporation of another country 

 to this particular case ; in the hope that its falsity or truth 

 would be shown in the results it gave, when checked by 

 legitimate deductions, we have shown how those results have 

 been confirmed by the mean discharge on the eastern arm, 

 and the other deduced therefrom. This result of mean dis- 

 charge on the eastern arm was founded on accurate measure- 

 ments, and most minute information as to summer and winter 

 levels, furnished by a most intelligent farmer, in the imme- 

 diete neighbourhood, who told us that the summer level was 

 not lower than what we then saw it, and that the ordinary 

 winter level was at the place of measurement up to the top 

 of the banks, which exactly measured three feet above the 

 summer level, and that the floods were over this ao*ain. 



In calculating the mean discharge, we have made no allow- 

 ance for increase of fall with the increase of volume, but, in 

 ignorance of its amount, have taken it upon the known summer 

 fall of 8 inches in two miles. We have also taken the discharge 

 at such a point, near the head of the swamp, as to exclude at 

 least six square miles of the drainage basin from the calcula- 

 tion. Taking all these circumstances into consideration, we 

 believe our result of mean discharge is under the actual amount. 



Our deduction of the mean discharge of the western arm 

 from that of the eastern must appear obviously sound, 

 when we consider that their conditions are precisely similar' 

 their basins being both in the same formation, havino« the 

 same soil and character, and therefore having the sam^ per 



