by its streaming effulgence cheers the dreary nights of
polar regions. It is singular that these beautiful appearances are
nowhere mentioned by the ancients. They seem to be governed by
electricity, are most frequent in frosty weather, and are proved to be
many miles above the surface of the earth, from some of them being
visible over 30 deg. of longitude and 20 deg. of latitude at the same
instant! In colour they vary from yellow to deep red; in form they are
Proteus-like, assuming that of streamers, columns, fans, or arches, with
a quick flitting, and sometimes whizzing noises. The aurora is not vivid
above the 76th degree of north latitude, and is seldom seen before the
end of August. Cook was the first navigator who recorded the southern
lights.

AUSTER. The south wind of the ancients, gusts from which quarter are
called _autan_.

AUSTRAL. Relating to the south.--_Austral signs_, those on the south
side of the equator, or the last six of the zodiac.

AUTHORITY. The legal power or right of commanding.

AUTOMATIC BLOW-OFF APPARATUS. _See_ BLOW-OFF-PIPE.

AUTUMNAL EQUINOX. The time when the sun crosses the equator, under a
southerly motion, and the days and nights are then everywhere equal in
length. (_See_ LIBRA.)

AUTUMNAL POINT. That part of the ecliptic whence the sun descends
southward.

AUTUMNAL SIGNS. Libra, Scorpio, and Sagittarius.

AUXILIARIES. Confederates, an assisting body of allies; or, physically
speaking, vessels using steam as an auxiliary to wind.

AUXILIARY SCREW. A vessel in which the screw is used as an auxiliary
force. Such a vessel is usually fully masted for sailing purposes.

AVANIA. The fine or imposition imposed on Christians residing under
Turkish governors, when they break the laws.

AVANT-FOSSE. In fortification, an advanced ditch without the
counterscarp, and stretching along the foot of the glacis.

AVAST. The order to stop, hold, cease, or stay, in any operation: its
derivation from the Italian _basta_ is more plausible than _have fast_.

AVAST HEAVING! The cry to arrest the capstan when nippers are jammed, or
any other impediment occurs in heaving in the cable, not unfrequently
when a hand, foot, or finger, is jammed;--stop!

AVENTAILE. The movable part of a helmet.

AVENUE. The inlet into a port.

AVERAGE. Whether _general_ or _particular_, is a term of ambiguous
construction, meaning the damage incurred for the safety of the ship and
cargo; the contribution made b