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 J anuary, 

 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 follo\yed ^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 accurate 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 bi:idge. 



Further up we crossed the river at Mr. Sherwm's Bridge, 

 at which point it flows out of the swamps, and a little above 

 Avhich 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, havmg no defined 

 channel, and over the surface of which, the whole flow of the 

 water is diffused, and exposed to evaporation nearly equal to 



