188 Report of the Commissioners on the 
only accepted so much of our supply as was warranted by data, 
although apparently larger, so that our results might represent 
the minimum, if not the actual amount. 
Impressed as we are with the difficulty and intricacy of this 
question, in a locality where so many conditions come into 
play, and, consequently not subject to deductions from known 
data, we approach this subject with great diffidence, and hope 
that the mode in which we treat it, to the best of our humble 
abilities, shall receive from your society a candid and con- 
siderate judgment. 
We commenced our investigations on the 24th of January, 
by measuring the discharge of the River Plenty, one mile 
below the reservoir, at the bridge, being the same place alluded 
to in Dr. Wilkie’s paper, as measured by him, and giving 
153°8 cubic feet per minute, and on which he based the supply 
by the Plenty, at 3,000,000 cubic yards per annum; our 
measurement of discharge at this place was only 75:9 cubic 
feet per minute, deduced from a sectional area of thirty-eight 
square feet, and surface velocity of :05 feet per second, or only 
half that of Dr. Wilkie’s discharge. We then followed ‘up 
the river to the reservoir, at which point we found it diverted 
into the puddle trench of the new embankment, and dammed. 
up for the use of a water-wheel, which at once accounted for 
the smallness of discharge at the bridge, as also Dr. Wilkie’s 
previous discharge. Proceeding further up, we came to that 
point of the river where it joins with the aqueduct, or inlet, , 
for supplying the reservoir, here, finding a clear and uniform 
flow, we took two aceurate sections, the mean of which, or, 
13-2 square feet we adopted, also the surface velocity, from a 
number of experiments equal to 8-568 inches per second, the 
mean velocity being obtained by the following formula, 
double the square root of surface velocity, in inches, deducted 
from surface velocity, and one added, gives the velocity at 
bottom, the mean velocity is half the sum of top and bottom 
velocities, was found to be 6:15 inches per second, hence the 
discharge was 406 cubic feet per minute, or more than two 
and half times that of Dr. Wilkie’s discharge at the bridge. 
Further up we crossed the river at Mr. Sherwin’s Bridge, 
at which point it flows out of the swamps, and a little above 
which it divides into two arms, one from the westward, the 
other from the eastward. We followed up the western arm 
two miles, the whole of which distance it was nothing more 
than a swamp, about 100 yards wide, having no defined 
channel, and over the surface of which, the whole flow of the 
water is diffused, and exposed to evaporation nearly equal to 
