d the two red lights prescribed by article 4 (_a_).

ART. 12. Every vessel may, if necessary in order to attract attention,
in addition to the lights which she is by these rules required to carry,
show a flare-up light or use any detonating signal that can not be
mistaken for a distress signal.

ART. 13. Nothing in these rules shall interfere with the operation of
any special rules made by the government of any nation with respect to
additional station and signal lights for two or more ships of war or for
vessels sailing under convoy, or with the exhibition of recognition
signals adopted by shipowners which have been authorized by their
respective governments and duly registered and published.

ART. 14. A steam vessel proceeding under sail only, but having her
funnel up, shall carry in daytime forward, where it can best be seen,
one black ball or shape 2 feet in diameter.

SOUND SIGNALS FOR FOG, ETC.

ART. 15. All signals prescribed by this article for vessels under way
shall be given--

1. By "steam vessels," on the whistle or siren.

2. By "sailing vessels" and "vessels towed," on the fog horn.

The words "prolonged blast" used in this article shall mean a blast of
from four to six seconds' duration.

A steam vessel shall be provided with an efficient whistle or siren,
sounded by steam or by some substitute for steam, so placed that the
sound may not be intercepted by any obstruction, and with an efficient
fog horn, to be sounded by mechanical means, and also with an efficient
bell. (In all cases where the rules require a bell to be used a drum may
be substituted on board Turkish vessels or a gong where such articles
are used on board small seagoing vessels.) A sailing vessel of 20 tons
gross tonnage or upward shall be provided with a similar fog horn and
bell.

In fog, mist, falling snow, or heavy rain storms, whether by day or
night, the signals described in this article shall be used as follows,
viz:

(_a_) A steam vessel having way upon her shall sound at intervals
of not more than two minutes a prolonged blast.

(_b_) A steam vessel under way, but stopped and having no way upon
her, shall sound at intervals of not more than two minutes two prolonged
blasts with an interval of about one second between them.

(_c_) A sailing vessel under way shall sound at intervals of not
more than one minute, when on the starboard tack