DOCK WALLS AT LIVERPOOL AND MANCHESTER. 223
ing up to 14 feet below coping, a strike of masons led to the substitution
of Portland cement concrete. The upper part of the wall, 14 feet in
height, was built as designed with ashlar facing, projecting 6 inches to
form a fender, and with granite coping. The weep-holes are at 75 feet
intervals.*
The section of the tidal basin wall at Tilbury Docks, London, is given
in fig. 168. The material used for the bulk of the wall was concrete,
composed of 10 parts of ballast to 1 of Portland cement. The concrete work
was faced above low-water mark with blue bricks, having a stock brick
backing—the whole being 9 inches in thickness, with half brick piers, about
4 feet apart, dovetailing into the concrete.f
The latest type of Liverpool wall (fig. 169) is built entirely of concrete,
with the exception of a granite coping. The hearting is composed of 8 parts
of gravel to 1 of Portland cement, with as many burrs or plums of clean
rubble and old masonry as can conveniently be bedded in. The facing,
12 inches thick, is of 6 to 1 concrete without burrs.
The new wall for the extension of the Manchester Docks is also mainly
composed of concrete (fig. 170). It has a blue brick facing above water
level, surmounting a limestone fender course. The coping is of granite.
* Hurtzig on “ The Alexandra Dock, Hull,” Afin. Proc. Inst. C.E., vol. xoii.
+ Scott on “ The Tilbury Docks, London,” Min. Proc. Inst. C.E., vol. cxx.