3.
feet, to obtain some idea of the nature of the immediately underlying strata.
After the above information had been plotted and examined, positions for testing the strength of the harbour bed were selected and this work was commenced.
For this purpose twelve solid concrete dumny pipes were cast 131⁄2" in dia., 12'0" long and weighing exactly 100 lbs. per foot run in air, and three old blocks, two 6'6" x 4'6" x 4'0" and one 5'6" x 4'6" x 4'0" weighing approx. 8 and 6 tons in air respectively were obtained.
P
The procedure adopted was to set one concrete block and have it carefully examined by the diver for initial subsidence, then set a second block on top of the first, and have a further examination made. The two boîcks were then left for forty eight hours when a final examina-
tion was made and the subsidence recorded. At the same time as the blocks were being set a dummy pipe was laid
on the harbour bottom, examined and left for future
examination, while in the soft mud section near Queen's
Pier a foundation of broken granite was dumped and trimmed
and a second dummy pipe was laid on this foundation
and left for further examination.
The average unit pressure on the harbour bottom
with a single block was 0.28 tons per sq. ft. and 0.55
tons per sq. ft. when the second block was in position.
The general results of the survey and the examina-
tion of the harbour bottom are shown on the small scale Cross
Section and in greater detail on the larger scale Cross
Section.
Nature of Harbour Bed.
It will be seen from the Cross Sections that after
leaving the pell mell rubble of Queen's Pier the proposed