equently. Their use is too well known to need explanation. They are
conveyed by flags, semaphores, balls, guns, lights, rockets, bells,
horns, whistles, &c., and half a century since were carried on with
incredible ability. It may be also observed that signal officers of
those days became subsequently the elite of the navy; _signal-officer_
being then a proud term of distinction.--_Fog-signals_, certain
operations which emit sound.--_Night-signals_, either lanterns disposed
in certain figures, flashes, or false fires, &c.

SIGNIFER. The zodiac.

SIGNING OFFICERS. The captain, senior lieutenant, master, and purser
(now paymaster); but where the document relates to the stores in charge
of any stated officer, that officer is to sign it instead of the purser.

SIGNS OF THE ZODIAC. The emblems of the twelve divisions, into which the
ancients divided the zodiac.

SILL. A northern term for the young of a herring.

SILLOCK. The podling, or young of the coal-fish, affording food and oil
on the Scottish coasts; they are grayish, and are taken when somewhat
less than a herring.

SILL OF A DOCK. The timber at the base against which the gates shut; and
the depth of water which will float a vessel in or out of it, is
measured from it to the surface.

SILLON. An old word for envelope. In fortification, formerly, a
counterguard.

SILLS. The upper and lower parts of the framing of the ports. The bottom
pieces of any ports, docks, scuttles, or hatches.

SILT. Sediment; ooze in a harbour, or at a lock-gate.

SILT-GROUNDS. Deep-water banks off Jamaica, where _silt-snappers_ are
fished for.

SILT-UP, TO. To be choked with mud or sand, so as to obstruct vessels.

SILVER-CAEDUA. A statute term for wood under twenty years' growth.

SILVER-OAR. One of the badges of the civil court afloat, conferring the
power to arrest for debt if not less than L20.

SILVER-THAW. The term for ice falling in large flakes from the sails and
rigging, consequent on a frost followed suddenly by a thaw.

SIMOOM. The Arabian name for the _sirocco_ (which see). The simoom,
sirocco, samiel, and kamsin seem to be modifications of the same wind
from the desert.

SIMULATION. The vice of counterfeiting illness or defect, for the
purpose of being invalided.

SINE. A right sine in geometry, is a right line drawn from one end of an
arc perpendicularly upon the radius from the centre to the other end of
the arc; or it is half the chord of twice the arc.