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200
HARBOUR ENGINEERING.
avoid forming anything of the nature of a projection likely to produce
damage.
Other adjuncts of a quay are life-chains, mooring-rings, and moor-
ing-posts. The firstnamed are suspended at intervals and festooned, so as
to enable persons accidentally immersed to support themselves until succoured.
The last two are for the purpose of holding vessels close against a quay wall.
Mooring-rings, useful chiefly for very small craft, are now fairly obsolete,
as they are awkward of access and difficult to maintain in order. The
most conveniently arranged of them are recessed within the quay face, so
as to acquire a certain amount of cover. The hest type of mooring-post
has a lip arranged on the side furthest removed from the quay edge, so as
to hold the rope well and keep it from slipping upwards.
A good sloping beach is very desirable in the immediate proximity of a
harbour. If situated at the entrance, it forms a very useful spending-ground
whereon waves may dissipate a very large proportion of their activity. A
beach is also desirable in that small craft may ground thereon for repairs.
When formed artificially, as is sometimes necessary in rocky localities where
the shore descends abruptly, quarry refuse and débris may be used for the
purpose. A. slope of 1 in 10 or 12 will be found most serviceable.
Booms.—Inner basins, or harbours of the smaller class, may be still
further protected from the effects of sea swell by means of a temporary
closure or boom across the entrance, which would naturally, in such a case, be
narrow. Booms take the form of a log partition, set in horizontal layers one
above another, with their ends engaging in grooves specially constructed at
each side of the entrance. It is necessary to observe that unless the logs
extend to the very base or bottom of the passage-way, wave motion will be
transmitted beneath them, and they will prove ineffective for the purpose
in view.
Mooring-Buoys and Stages.—In addition to the facilities afforded by
posts, rings, and bollards on the quays for securing vessels, in large basins and
in rivers floating and fixed moorings are also provided. The former consist
of buoys of various shapes anchored to the bottom of the basin or the bed of
the river, and the latter of piled stages suitably braced. These last are some-
times known on the Continent as “ Ducs d’Albe.”
Landing-stages.
In all his operations the maritime engineer is more or less in touch with
the requirements of the naval architect, and the boundary line between the
two professions is by no means easy to define; indeed there is oftentimes a
zone within which both practitioners find a common field of action, and where
it would be difficult, if not absolutely impossible, to lay down any limitations
for one or the other. Thus, in the case of entrance caissons, floating docks,
and buoyant structures generally, there are presented to the engineer all the
processes and features characteristic of ship design and calculation, and so,
too, in connection with the subject of the present chapter, the laws governing