GooDALL.-- Water Supply for Auckland. 37 
obtained from Mount Eden, it wil be necessary to prove the depth of the 
basin or floor of the volcano, its shape, height of the rim of the basin at its 
lowest part, probable direction of the flow of water from it, summer level 
(minimum) of water, and inclination of the water from the rim of the basin to 
its outlet at the springs. 
A part of these questions may be answered by a survey of the ground, and 
by obtaining levels—that is, by surface examination ; and the entire question 
would be solved by adding to the above a series of bores. A survey of the 
ground would determine the probable shape of the rim of the basin, also the 
course of the water travelling beyond the rim. The lava streams having run 
in the old valleys formed by the tertiary rocks, indications may yet be obtained 
of the course of the bottom of that valley by the run of the lava and other 
indications, such as the outcropping tertiary formation ; and, as the overlaying 
lava rocks are of a very porous nature and abounding in large cracks and 
cavities, any water pouring from the hills above (after rain) would undoubtedly 
flow through the ancient valley, but would occupy more space, have a greater 
inclination, and would take more time to flow than were it unimpeded. 
Having completed the survey, it will then be advisable to put down a 
series of bores between the site of the reservoir at Gilfillan’s corner and Mount 
Eden. These bores, put down between the limit of the scoria and half way to 
the centre of the hill, would probably be sufficient to give the depth and shape 
of the basin. This will be important to ascertain accurately, as on that side 
the necessary shaft would be sunk, and a correct knowledge alone could be a 
guide as to the depth of shaft and distance of а drive to tap the water. Then, 
at a point to the westward of the hill facing the lava flow, another series of 
bores should be started, beginning at about half-way down the hill, over the 
rim of the basin, and thence along the probable course of the subterranean 
stream to its outlet at the springs. These bores would determine the depth of 
the basin, the permanent level of water, and the inclination of the water 
towards the springs. Having all these data, it can now be calculated, without 
much trouble, what available water there is; and by the height of the rim of 
the basin may be determined how much extra supply can be obtained from 
the outward flowing stream ; for the lower the rim is, the better will it be, as 
then, by pumping at Mount Eden, any insufficiency of water in the basin 
would be supplied by infiltration. Having arrived at this stage, it can be 
positively ascertained if there be an adequate supply or not ; and, if there be, 
a shaft will have to be sunk, and pumping machinery erected for supplying 
the reservoir. 
There are two available sites for a shaft, one being at the proposed 
reservoir. If this be fixed upon, the shaft should be sunk to the level of the 
bottom of the basin under Mount Eden, unless that exceeds high-water mark, 
