EXAMPLES OF WALL SECTIONS. 117 



2J inches thick. The timber and planking below the water 

 level was fixed by divers ; for keeping the framework in 

 proper position |-inch wrought-iron tie-rods were used. Previous 

 to the concrete being deposited over them, the rods were 

 protected with A~ sna P e( i covers, formed of two pieces of board 

 nailed together. This arrangement allowed of the rods being 

 drawn after the concrete had set. 



Within the timber casing, a bag of ample dimensions made 

 of several thicknesses of jute cloth, weighing 19J ounces per 

 square yard, was drawn down into position by pulleys secured to 

 the lower tier of the framing. Above the low-water level the 

 sides of the timber casing was lined with jute cloth, weighing 17 

 ounces per square yard, and secured to the wood casing with 

 1-inch clout nails. On depositing the concrete through the 

 water, the jute cloth protected it until it had consolidated. To 

 secure the framing from being washed away by the sea, it was 

 necessary to load it with old iron, until such time as a portion of 

 the concrete had been deposited. 



The moulds and frames for the parapet, tunnel, etc., were 

 made in suitable lengths, so as to admit of their being shifted 

 and re-erected as the work progressed. 



The proportions adopted for the concrete up to low-water 

 level was 4 of stone and sand to 1 of cement; above low- 

 water, in the faces for a thickness of 5 feet the proportions were 

 7i parts of stone to 1 of cement; and for the hearting 12 stone 

 and sand to 1 of cement. 



Alexandra Dock, Hull. 1 The basin walls were designed to be 

 constructed with Ashlar stone faced with rubble chalk, backing 

 up to 14 feet below the coping, and the upper portion of 14 feet 

 with Ashlar facing projecting 6 inches beyond the lower part of 

 the wall, with rubble stone backing and granite coping; the 

 whole set in lias-lime mortar. Iron pipes were built into the 

 walls at two levels, so as to provide warp-holes at intervals of 

 about 75 feet all round the dock, and a rubble drain 2 feet 

 6 inches square was placed along the back of the wall. In some 

 places water was constantly running through these warp-holes 

 after the backing was in to the full height, and thus the walls 

 were preserved from undue pressure at the back. The chalk 

 used for backing was hard and durable when not exposed to 

 frost, but during construction in the winter months it required 



1 M.P.I.C.E., vol. xcii. pp. 148-154 



