FOG-SIGNALS. The chief use of fog-signals is to give facilities 10 apprnaehing vessels when not in sight of one another, to enlble them to continue their respective courses after having first localized the direction and distance of the neighboring ship. In addition, fog-signals are most useful indications of dangers to vessels ap proaching headlands or feeling their way through narrow channels.
In considering the first: mentioneduse of the fog-signals. the International Alarine Conference, held at Washington in 1890, concluded that :ill steam vessels should be provided with au efficient whistle or siren, sounded by steam or suh titute for steam, so placed that the sound is not interrupted by any obstruction, and having an efficient fog-horn to lie sounded by meehanical means, and also an efficient bell. In fog, mist, falling snow, or heavy rainstorms, whether by day or night, the following signals are to be used: A steam vessel having way upon her is to sound a prolonged blast at intervals of not more than two minutes. A steam vessel under way, but stopped and having no way upon her, is to sound at intervals of not more than two minutes, two prolonged blasts, with an interval of about One second between them. A sailing vessel under way sounds at an interval of not more than one minute, one blast when on the starboard tack, two blasts in succession when on the port tack, and three blasts in succession with the wind abaft the beam. A vessel at anchor is to ring her bell rapidly for about five seconds at intervals of not more than one minute. When a vessel anchors in other than ordinary anchorages, and is in danger of being an obstruction to vessels under way, if a steam vessel, she must sound two prolonged blasts with her whistle or siren, with not more than a two minutes' interval, followed by ring ing her bell; if a sailing vessel, at intervals of not more than one minute, two blasts with her fog-ho•n, followed by ringing her bell. A vessel when towing. at intervals of not more than two minutes, sands three blasts in succession, viz. one prolonged blast followed by two short blasts. A vessel towed can give this signal, but she can not give any other. When one steam vessel
wishes to indicate to another that she can feel 4 her way past, she can do sn by sounding a short blast, followed by a long and a short, with inter vals of about one second between them. A cable ship. at work, hearing another vessel's fog-signal, answers it with three prolonged blasts in suc cession.
A vessel under way, but not sufficiently under command to get out of the way of an approaching vessel, answers fog-signals by sounding four short blasts in succession. Sailing vessels and boats of less than twenty tons gross tonnage are not obliged to give the above; but if they do not they are to make some other efficient sound signal at intervals of not more than one minute. Every vessel in foggy, misty weather, or in snow or heavy rainstorms, is obliged by the rules adopted to go at a moderate speed, having careful regard to the existing circumstances and conditions. When a steam vessel hears, forward of her beam, the fog-signal of a vessel, the position of which is not ascertained, she must, as far as the cir cumstances of the ease admit, stop her engines, and then navigate with caution 'until danger of collision is over.
Experiments made in Holland on the force and duration of sound signals show that a steam whistle two inches in diameter requires n pres sure of about two atmospheres in order to make the sound heard at, the distance of one kilomen r (.(12 mile) ; whereas /11 of six inehes diameter, with a pressure of six famosphi••,, makes its sound heard about I I kilometers (8.11)i miles). if, however, the whistle be placed in horizontal position within a reflector, the two inch whistle van lie heard :It four kilometers (2.1 is about the same distance that it Nessel's side-lights are visible. With a bell of 8 inchys diameter sound travels only ti00 meters 11808 feet ), and it requires a bell of a weight of SO kilograms (about 17(1 pounds) to transmit the sound 1500 meters (4920 feet ). The sound of a movable hell (i.e. when ti tongue or clapper is fixed) travels farther than when the revere is the ease.