ovided 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 one blast, when on the
port tack two blasts in succession, and when with the wind abaft the
beam three blasts in succession.

(_d_) A vessel when at anchor shall at intervals of not more than
one minute ring the bell rapidly for about five seconds.

(_e_) A vessel at anchor at sea, when not in ordinary anchorage
ground and when in such a position as to be an obstruction to vessels
under way, shall sound, if a steam vessel, at intervals of not more than
two minutes, two prolonged blasts with her whistle or siren, followed by
ringing her bell, or if a sailing vessel, at intervals of not more than
one minute, two blasts with her fog horn, followed by ringing her bell.

(_f_) A vessel when towing shall, instead of the signals prescribed
in subdivisions (_a_) and (_c_) of this article, at intervals
of not more than two minutes sound three blasts in succession, namely,
one prolonged blast followed by two short blasts. A vessel towed may
give this signal, and she shall not give any other.

(_g_) A steam vessel wishing to indicate to another "The way is off
my vessel; you may feel your way past me" may sound three blasts in
succession--namely, short, long, short--with intervals of about one
second between them.

(_h_) A vessel employed in laying