1920.] Engineering Survey of Proposed Arapuni Dam Site. 79 
lies inland from the cliff. There was a possibility, if this country was not 
sufficiently water-resisting at and below the level of the crest of the dam, 
of the river scouring its way along the line of the depression after its level 
had been raised. Accordingly these holes were sunk to about the level 
of the crest of the dam ; rock specimens were taken from them and tested 
to determine the degree of their water-resisting power, with quite satis¬ 
factory results. 
Among the minor works which had to be accomplished before the work 
of investigation could be started were the navvying of a wagon-track to 
the camp from the end of the existing road, a mile away ; a walking-track 
down the cliff into the gorge ; and the construction of a suspension bridge 
over the river. 
■ The levels given herein have not been referred to sea-level, but are 
based on the Waihi Company’s datum at Horahora, which assumes a zero 
100 ft. below the level of the head-race there. That zero point is probably 
somewhat above sea-level, so that all the levels given here will be found 
low if closed on to a sea-level datum. The actual fall between the Arapuni 
tail-race and the Horahora head-race will be 60 ft. 
In conclusion, I would refer to the effect the building of the dam will 
have on the Waikato River here as a navigable waterway. The damming- 
back of the river will result in a lake 18J miles long and about 180 ft. deep 
at the lower end. This will provide a fine inland waterway for motor- 
launches and small steamers, into country that is now being rapidly settled 
and brought into farming-land. The Te Awamutu - Putaruru Railway, 
which is being promoted under the provisions of the Local Railways Act, 
proposes to cross the river on a bridge built on top of the dam, thus pro¬ 
viding the up-river farmer with a most convenient access to the outside 
markets. The lake will also afford fishing, shooting, and boating possibili¬ 
ties, and scenic beauties that should prove a decided attraction to the 
future tourist and holiday-maker. 
A MINERAL NEW TO NEW ZEALAND—PILOLITE. 
By J. Henderson, M.A., D.Sc. 
A mile or more north of Mahoenui, a small township in the south-western 
corner of the old Province of Auckland, the Awakino has cut a gorge 
through thick beds of sandy limestone. In a road-cutting in the gorge 
a bank of yellow clayey sand, undoubtedly derived from the decay of the 
limestone, contains parallel veinlets of a white material. These veins dip 
steeply, are up to \ in. thick, and occur in a zone some 2 in. or 3 in. wide. 
They extend down the whole face of clayey sand, 7 ft., and were excavated 
2 ft. into the bank without showing any change in appearance or dis¬ 
tribution. Evidently the veins have been formed from material leached 
from the clayey sand by surface waters. 
The mineral, which is tough and leathery, readily splits into translucent 
flexible sheets as thin as paper, and parallel to the walls of the veins. It 
is white in colour, with a faint yellow tinge, and has a satiny lustre. 
Hydrochloric acid causes the mineral to gelatinize slightly, and readily 
removes the yellowish tint above referred to. Some portion of the material 
collected was less tough and leathery than others, and did not so readily 
split into thin sheets. An analysis was made of this variety by the 
Dominion Analyst, as well as of the more abundant papery material, with 
the following results :— 
