its bearing from the ship, and the observer's head from the theodolite.

SWINGING-BOOM. The spar which stretches the foot of a lower
studding-sail; in large ships they have goose-necks in one end which
hook to the foremost part of the fore-chains to iron strops fitted for
the purpose. In port they are hooked to bolts at the bends, which, by
bringing them lower down, enables the boats to ride easier by them as
guest-warp booms.

SWIPES. The weak beer supplied to ships on the home station. A swipe is
an implement for drawing water for a brewery, the name of which has thus
been transferred to the beer.

SWIRL. An eddying blast of wind; a whirling wavy motion. Also, a knot in
timber.

SWISH. An old term for the light driving spray of the sea.

SWIVEL. A pivot working freely round in a socket. They are fitted in
boats' bows, ships' tops and bulwarks, &c., for bearing small cannon of
1/2 lb. or 1 lb. calibre, which are worked by hand, and called swivels.
Also, a strong link of iron used in mooring chains, &c., which permits
the bridles to be turned repeatedly round, as occasion requires. Also, a
swivel-link in chain-cables, made so as to turn upon an axis, and keep
the turns out of the chain.

SWONA WELLS. Whirlpools much dreaded by the sailors of the Pentland
Firth. They seem to be caused by the rapidity of the tide and the
position of Swona, which exactly crosses the stream.

SWORD-FISH. A large fish of the family _Scombridae_, remarkable for the
prolongation of the nose into a straight, pointed, sword-like weapon.
The European species, common in the Mediterranean, is the _Xiphias
gladius_ of naturalists.

SWORD-MAT. A mat made with shoulders to protect the laniards of the
lower rigging, boats' gripes, &c., and worked by a piece of wood
somewhat resembling a sword in shape, to drive home the roving threads.

SYKE [from the Anglo-Saxon _sych_]. A streamlet of water that flows in
winter and dries up in summer.

SYMPIESOMETER, OR OIL-BAROMETER. A convenient portable instrument for
measuring the weight of the atmosphere by the compression of a gaseous
column; capital for small cabins.

SYNODICAL MONTH. The period in which the moon goes through every variety
of phase, as from one conjunction to another.

SYNODICAL PERIOD OR REVOLUTION. If the interval of periodic time of a
planet, or comet, be taken in reference to its passages through either
of the nodes, its circuit is called synodical.

SYPHERED. One edge of