Hunter.—On a Change in the Elevation of the Waikato District. 459 
Arr. LIII.—Direct Evidence of a Change in the Elevation of the Waikato 
District. By AsuLey Hunter, C.E. 
| Read before the Auckland Institute, 12th November, 1883.] 
In December, 1875, a paper entitled ** Observations on the Evidence of 
recent Change of Elevation of the Waikato District,” was read before this 
Institute by Mr. James Stewart. In it the author endeavoured to show by 
certain evidence that the Waikato District had at one time a considerably 
greater elevation than it has at present. The following additional evidence 
as bearing on the subject and going to prove most conclusively that such 
has been the case may prove interesting :— 
In designing the present railway bridge ar Hamilton it was originally 
estimated that the cast-iron cylinders would reach a solid foundation at a 
depth not greater than 40 feet below the present surface-bed of the river ; 
subsequent events, however, proved that this was far from being the case. 
The cylinders were sunk by the pneumatic process, and excavated by 
manual labour under air-pressure until a depth of about 60 feet was reached, 
and the air pressure of 832lbs. per square inch being more than the men 
could stand, dredging was resorted to. 
The excavation throughout the cylinder sinking showed nothing but 
layers of pumice and quartz sand until the vations were carried to their 
present depths, when it was shown by the dredge bringing up large lumps 
of hard coarse greensand that the formation of the old river-bed had been 
struck. 
The western pair of cylinders were sunk to a depth of 80 feet, and the 
eastern pair of cylinders to a depth of 55 feet below the present bed of the 
river. The fact of the eastern cylinders resting upon the same forma- 
tion as the western cylinders, but at a level 25 feet higher than the 
latter, proved that they were resting not upon the old river-bed but upon 
the eastern bank of the old river-bed. This is important as showing that 
the old river must have had a very high velocity to have scoured out a 
channel more than 25 feet deep through such a hard formation. Reducing 
the railway levels to high-water mark at Auckland, we find that the forma- 
tion level of the Hamilton Bridge, which is practically the level of the sur- 
rounding district for some miles, is 126 feet above high-water at Auckland, 
while the level of the old bed of the river is 51 feet below high-water at the 
same place. If we assume that in olden times the general inclination of 
- the river from this point towards the sea was the same as now, viz., about 
9 inches to the mile, then the minimum change of elevation which we can 
certainly assign to this portion of the Waikato District at least is about 80 
fe 
