of the site of the proposed entrance or lock, so that
the excavations for the entrance to the dock may be pushed forwards,
and the lock or entrance built under its protection. Sometimes the
lowest portion of the excavation for the dock can be accomplished
economically by dredging, after the dock walls and lock have been
completed and the water admitted.

Where a dock is partially or wholly constructed on reclaimed land, the
reclamation bank for enclosing the site and excluding the tide has to
be undertaken first by tipping an embankment from each end with
wagons, protected and consolidated along its outer toe by rubble stone
or chalk. When the ends of the embankments are approaching one
another, it is essential to connect them by a long low bank of
selected materials brought up gradually in successive layers, and
retaining the water in the enclosure to the level of this bank, so
that the influx and efflux of the tide, filling and emptying the
reclaimed area, may take place over a long length, and in smaller
volume as the low bank is raised. In this way a reduction is effected
of the tidal current in and out, which in the case of a large
enclosure and a considerable tidal range, would create such a scour in
the narrowing gap between two high embankments as to wash away their
ends and prevent the closing of the gap. Occasionally the final
closure is effected by lowering timber panels in grooves between a
series of piles driven down at intervals across the gap. On the
closing of the reclamation bank the water is pumped out; and the
excavation is carried on in the ordinary manner. It is very important
that such an embankment should be carried well above the level of the
highest tide which might be raised by a high wind; and in exposed
sites, the outer slope of the bank should be protected by pitching
from the action of waves, for any overtopping or erosion of the bank
might result in a large breach through it, and the flooding of the
works inside.

Foundations for dock walls.

Docks are generally surrounded by walls retaining the quays, alongside
which vessels lie for discharging and taking in cargoes. In order to
ascertain the nature of the strata upon which these walls have to be
founded, borings are taken at the outset to the requisite depth at
intervals near the line of the walls, but inside the dock area if the
piercing of quicksand is ant