Failure of the Yan Yean Reservoir. 135 
This estimate is of great importance, as showing the exact 
amount that may be saved by effectually withdrawing the 
tributaries from the evaporation, and it may be absorption, of 
the swamps. 
If the two feet five inches, therefore, can be saved, it may 
be added to the five feet four and a half inches. 
The highest ordinary discharge may be computed thus— 
the six summer months being taken at 2,537 gallons per 
minute, or three feet four inches, as measured by the com- 
mittee in January. 
ft. in. 
Six summer months - - - - 1 8 
Six winter months - : 5 x 
Amount lost in swamps - - - 2 5 
Total - - = 9 BL 
Deduct 900 gallons for district - - ae) | 2 
Highest discharge of river - - = 8 33 
First estimate  - - - - - 6 vf 
Balance in favour of 2nd estimate - - 1 84 
Thus my first estimate amounted to six feet seven inches 
as the ordinary discharge of the river, so that this second or 
highest estimate has an advantage of one foot eight and a 
half inches over the first. It will therefore be seen that, 
even allowing the river to be level with its banks for six 
months in the year, for which we have no measurements to 
guide us, still the result is very little more favourable than 
the first, and cannot with any certainty be depended on; and 
if one-third of the whole, instead of the scanty allowance of 
900 gallons per minute, were left for the use of the district, 
this highest average discharge would be reduced below my 
former estimate. 
The Committee, who were appointed by the Society to 
investigate the subject in a scientific manner, have arrived at 
results very different from my own. They do not base their 
conclusions on the measurements at all, which they profess to 
disregard, but on theoretical principles, and on certain 
calculations quite original, and apparently adapted to supply 
any amount of water that may be required in this dry climate; 
and they have determined that the discharge is three times 
greater than my estimate of eight feet. 
Thus, although Mr. Blackburn, who was ignorant of the 
