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. Naval lights and recognition signals. 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. Steam vessel under sail by day. ART. 14. A steam vessel proceeding under sail only, but having her funnel up, may carry in daytime, forward, where it can best be seen, one black ball or shape two feet in diameter. INLAND RULES: III. SOUND SIGNALS FOR FOG, AND SO FORTH Preliminary. 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; also with an efficient bell. A sailing vessel of twenty 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, namely: Steam vessel under way. (_a_) A steam vessel under way shall sound, at intervals of not more than one minute, a prolonged blast. Sail vessel under way. (_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. Vessels at anchor or not under way. (_d_) A vessel when at anchor shall, at intervals of not more than one minute, ring the bell rapidly for about five seconds. Vessels towing or towed. (_e_) A steam vessel when towing, shall, instead of the signals prescribed in subdivision (_a_) of this article, 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. Rafts, or other craft not provided for. (_f_) 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. Speed in fog.