Fog Signals.
A steam vessel must be provided with a whistle operated by steam or air.
A sailing vessel must be provided with a horn.
In fog, mist, falling snow, or heavy rainstorms, whether by day or night, the signals described shall be used:
A steam vessel underway shall sound, at intervals of not more than one minute, a prolonged blast.
A sailing vessel underway 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.
A vessel when at anchor shall, at intervals of not more than one minute, ring the bell rapidly for about five seconds.
A steam vessel when towing shall, instead of the signal prescribed above, at intervals of not more than one minute, 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.
All rafts or other water craft, not herein provided for, navigating by hand power, horse-power, or by the current of the river, shall sound a blast of the fog horn, or equivalent signal, at intervals of not more than one minute.