!
315
Of the three wells being sunk for the purpose of ascertain-
ort
1903. ing the depth at which a reliable foundation for a dam will be . 64.
met, No. 1 got so far out of plumb by the time it reached a depth of 35 feet below low water that it had to be abandoned.
Well No. 2 was next proceeded with and, after great diffi- culty, principally on account of skin friction, was successfully sunk by the 17th. May to a depth of 46 feet, at which depth rock was reported. The trouble arising from skin friction was over-
come by increasing the load on the well until it ultimately
reached about 200 tons. Pumping operations within such a con-
fined space and from such depths were also a source of great
trouble. The material passed through consisted of clay and
silt intermingled with shells and with occasional layers of
sand and shells. Just before reaching the rock, a later of
beach boulders about 2 feet in depth, was passed through.
boulders were of varying size, down to shingle, consisted of
very hard stone and were densely packed together. The rate at
which water entered the well from the layer of boulders precluded the possibility of pumping it dry in order to admit of an actual
inspection of the bottom.
The
Work was then begun upon Well No. 3 and, after sanking it to a depth of 42 feet through clay silt and sand, the stratum
of beach boulders above described was again encountered.
Sink-
ing operations were continued, and, after passing through about
10 feet of boulders, sand was again met with and it was not
until the well had reached a depth of 58 feet that rock was
finally found. Here also it was found impossible to dry the
bottom by pumping and the extent and nature of the rock were
ascertained by feeling it carefully all over.
Pieces were also
broken