ed by a
circuitous canal, in which it deposits its burden of silt before it is
pumped into the docks.

Equipment on quays.

In order to deal expeditiously with the cargoes and goods brought into
and despatched from docks, numerous sidings communicating with the
railways of the district are arranged along the quays, which are also
provided with steam, hydraulic or electric travelling cranes at
intervals alongside the docks, basins or river, for discharging or
loading vessels, and with sheds and warehouses for the storage of
merchandise, &c., the arrangements depending largely upon the special
trade of the port. Though different sources of power are sometimes made
use of at different parts of the same port, as for example at Hamburg,
where the numerous cranes are worked by steam, hydraulic power or most
recently by electricity, and a few by gas engines, it is generally most
convenient to work the various installations by one form of power from a
central station. Water-pressure has been very commonly used as the
motive power at docks, being generated by a steam-engine and stored up
by one or more accumulators, from which the water is transmitted under
pressure through strong cast-iron pipes to the hydraulic engines which
actuate the cranes, lifts, coal-tips, capstans, swing-bridges and gate
machinery throughout the docks (see POWER TRANSMISSION: _Hydraulic_).
The intermittent working of the machinery in docks results in a
considerable variation in the power needed at different times; but
economical working is secured by arranging that when the accumulators
are full, steam is automatically shut off from the pumping engines, but
is supplied again as soon as water is drawn off. Electricity affords
another means for the economical transmission of power to a distance
suited for intermittent working; as far back as 1902 it was being
adopted at Hamburg as the source of power for the machinery of the
extensive additional basins then recently opened for traffic.

Coal-tips.

At ports where the principal trade is the export of coal from
neighbouring collieries, special provision has to be made for its rapid
shipment. Coal-tips, accordingly, are erected at the sides of the dock
in these ports, with sidings on the quays at the back for receiving the
trains of coal trucks, from which two lines of way diverge to each
coal-tip, one serving for the conveyance of the full wagons one by one
to the tip, after passing over a