Page:The New International Encyclopædia 1st ed. v. 07.djvu/875

1'OG-SIGNALS. ( t i FOG-SIGNALS. continue (heir respective courses after having first localized the direction and distance ■>> neighboring .ship. In addition, Eog signal are most useful indications of danger to re ela ap- proaching headlands or feeling their waj through narrow channels. In considering the first mentioned u e of the fog-signals, the International Marine Conference, h.-ld at Washington in L890, concluded thai all steam vessels 3hould be provided with an efficient whistle or siren, sounded by steam or some ub titute for steam, si. placed that the Bound is not interrupted by any obstruction, and having an eilieieni fog-horn to be sounded by mechanical means, and also an efficient bell. Jn fog, mist, falling snow, or heavy rainstorms, whether by day or night, the following signals are to he used: A steam vessel having way upon her is to sound a prolonged blast at intervals of nol 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 aboul one second between them. A sailing vessel under way sounds at an interval of ii"l 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-horn, followed by ringing her bell. A vessel when towing, at intervals of not more than two minutes, sounds three blasts in succession, viz. one prolonged blast followed by two short blasts. A vessel towed can give this signal, but sin- can- not give any other. When one steam vessel wishes to indicate to another that she can feel fc her way past, she can do so 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 shorl 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 ! 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 a | in- nf aboul two in order b Mil' '.I mil' kiln in. I. i i .62 mile) ; w hen i inches ith a pn i mo pheres, makes i1 a ound beard aboul I I kilon miles) . if, however, the whist li .1 in ,i horizontal position within inch « I11-1 le can be beat .1 al foui I ilometi i miles i , v. hi. i. i about i : " ami di tance thai a re .1 i !, lights an- visible. With a bell of 8 diam und i ravels onlj loo metei - i 1868 feel i . and il n quire i a bell of a wei 80 kilograms (aboul 176 i i the sound L500 metei i (4920 feet). I hi of a movable bell (i.e. when tl tongue or clapper i i avele farl her than when the i is t he ' .' i On man] points along the coast, in the light- houses and mi I ighl hip tea m whist 1. horns of great power have been placed, am bells that are rung mechanically, which are sounded whenever the state of the atmosphi n n quires il to be done n» implesl and commonly mosi powerful signal employed by the United state-, Lighthouse Board is the locomotive whistle, operated by a steam boiler with a pres- sure of from 50 to 75 pounds. The sounds from the land are distinguished from those on board . hip by the length of the uotes and the intervals between. The whistles are from eight to ten inches in diamel er, and a re opei ly by an engine supplied with steam from the same boiler. The Daboll trumpet, worked by condensed air, is next in importance. The trum j.et itself provides the resounding cavity, and the vibratory motion of the air is produced bj The reed is aii iron bar, in the larger trumpets being eighteen inches long, two inches wide, and three-quarters of an inch thick, gradually ing toward tin- free end. The siren trumpet is the in. i-t powerful instrument bo far employed. (See Sua n.i The impulse to the air which pro duces the sound is given by a flal drum, or a hollow' cylinder with a short axis, one end of which is perforated to admit steam. other side the drum is perforated with ei_.li! or more holes, in connection with which i- a re- volving disk having a similar number of holes. As the disk revolves these eight holes arc al- ternately open and shut, allowing egress to as many jets of -.team, which provide- a regular and violent motion in the air. giving ri- in. .-I powerful sound, reinforced by the resonance of a trumpet of suitable length. In -till air this sound can be heard from 20 to 30 miles, even during a dense fog. The notes are not all to be heard at the same distance, however, and an opposing or crossing wind seriously interferes with the transmission of sound. The interven- li, n of rain, snow, <r mi-t also disturbs and re (aids, and temperature has a distinct influence. Whistling buoys and bell buoys arc also largely Used to mark dangers or channel-, and arc of iM'i.i i iii ance in determining the v of a vessel in thick e For a thi ion of various forms of il, the ■ i- referred to Johnson, Modern Ligl St n-irr (Washington, 1889). Railway trains depend largely upon toi to indicate the too cl train to another. The torp cases charged with a detonating powder which is