90 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



still flowed through the concrete. The injured concrete in the 

 vicinity of the pipe was covered with brickwork set in Portland 

 cement, space being left between the bricks for the escape of the 

 water flowing from the concrete. This water was gradually 

 collected into one channel, and conducted through a 6-inch pipe, 

 9 feet long, laid horizontally and set in bricks and cement ; but 

 the combined capacity of the pumps was not sufficient at the 

 time of high water to take all the water, which found outlets 

 through several weak places in the brickwork and concrete. 



Two chain-pumps were kept constantly at work during the 

 time of high water. On one of these breaking down, it was 

 quickly sanded up ; about 20 cubic yards of clean sand were 

 deposited in the foundation in the course of twelve hours. 

 Short lengths were added to the vertical pipe until the total 

 length above the casting amounted to 22 feet. The top of the 

 upper length terminated at sill-level; at this height the water 

 still flowed, but gradually diminished in quantity, latterly bring- 

 ing up tine mud instead of sand. When the water ceased to 

 flow which it did sooner, probably, from boils having broken 

 out in the cutting to the westward the pipe was filled with 

 Portland cement, and the horizontal pipe was with difficulty 

 plugged up at the low level. 



During the time occupied in forming the foundations 

 to the extent just described at the east end of the lock, the 

 cutting throughout the remaining portion had been gradually 

 re-excavated and filled with concrete. A row of sheet-piling had 

 been driven along the south side to sustain the river bank, but 

 as the upper clay had not been removed on the north side, the 

 cofler-dam piling was then considered sufficient. The concrete 

 had been placed on the bottom clay when the upper bed had 

 been removed, excepting for about 50 feet west of the row of 

 piles bounding the compartments. The piles forming this row, 

 of which the tops had been cut off at a uniform level of 4 feet 

 6 inches below the sill level, had settled, especially towards the 

 south side and the centre of the lock, to the extent in the latter 

 place of 5 feet. As the bottom clay had also sank, the sand 

 and silt overlaying it were only removed to a depth of from 4-7 

 to 40 feet below quay level, and the concreting proceeded with. 

 The foundations at this part gave much trouble, and several 

 boils were dealt with. Two of the castings above described 

 were used, to which lengths of horizontal pipes feet long were 



