Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/648

 LIGHTHOUSE Pints : buoy. Pintsch s Gas Illuminated Buoy for Producing a Fixed Light. These buoys are gas and water tight, and are charged to a pressure of ten atmospheres. The buoy is filled with gas sufficient to burn night and day for three or four months ; the burning pressure is kept constant by Pintseh s regulator. These buoys promise to be of great service, and have now been in use for more than a year at several places both in England and Scotland. Automatic Meter for Producing Intermittent Lights by the Flow of the Gas. In order to distinguish one buoy or beacon from another, Mr T. Stevenson has proposed to make the flow of the gas itself produce automatic intermittent action without using clockwork. The full flame continues to burn until the action of the meter reduces the supply, but leaves a small jet still burning in the sockets of the burner till the full ilaine is again produced. This meter has been tried successfully on shore for twenty-eight hours consecutively. Uniform Uniform System of Beacons and Buoys. The first proposal for system of dealing systematically with the colours of beacons and buoys was in beacons. 1828, when Mr R, Stevenson proposed for the navigation of the Auto matic buoy. FIG. 63. Courtney s Automatic Buoy. A, cylinder, 27 ft. 6 in. long ; B, mooring shackle ; C, rudder ; D, buoy ; E, diaphragm ; F, ball valves ; G, air inlet tubes ; H, air (compressed) outlet tube to whistle ; I, compressed air inlet to buoy ; K, manhole ; L, steps ; N, whistle. river Forth that red buoys should be taken on the starboard and black on the port side in going up the river. This system has since been adopted generally in the United Kingdom. In 1857 Admiral E. J. Bedford suggested a uniform system for all the coasts of tho country, which was carried out in Scotland by Mr A. Cuning- ham. A different uniform system has been adopted in England by the Trinity House. In 1859 Mr J. F. Campbell suggested what is undoubtedly the best system, that a buoy shall indicate by its shape and colour the compass direction in which a vessel should sail after seeing the buoy. Courtenaifs Automatic Buoy. This useful form of buoy (fig. 63) first used in America, has a cylindric tube A projecting below the level of the water, on the upper part of which cylinder there is a whistle N and also two inlet valves F, F, so that the rising and falling of the buoy draws in and expels the air alternately which sounds the whistle. It is said that an undulation of even 12 inches is sufficient to sound the whistle. Tolling of Bells by the Hydrostatic Tolling ( Pressure of the Tide. In 1810 Mr R. bulls by Stevenson designed apparatus for tolling tide. a bell on the Carr Rock beacon, which was to have been effected by a float when ascending with the pressure of the flowing tide, when descending with the fall of the ebb tide and by means of a peculiar arrangement of weights for keeping the bell in action during the time of slack water. Illuminants. After Argand s ordinary single-wick oil Illmnin- burner, Fresnel still adheringto Argand s ants. principle of the double air current intro- Oils. ducedtwo, three, and four concentric wick burners, Mr Alan Stevenson, the five, and Mr Douglass the six wick burner. These burners are suitable for the consumption of animal and vegetable oils, which were in use in the various _ lighthouse services of the world till within the last few years. These oils are, however, super seded by hydrocarbons, which at one half the cost give an increased luminous intensity for an equal consumption, but they require a larger supply of air for their combustion, and con sequently an improved form of burner. M. Maris in 1856 devised a single-wick burner for this purpose which gave good results, but many and all attempts to con struct a multiple-wick mineral oil burner failed till 1868, when Captain Doty s form was devised. By a happy choice of proportions in the various parts of his burner (fig. 64), and by the addition of an exterior cylinder sur rounding the outer wick, and a central disk, both placed in such a manner as to throw a current of air into the flame at the right place, Captain Doty succeeded in producing single and multiple-wick hydro carbon burners, which carry a flame of great luminous intensity and regularity. The following table gives the details of these burners, and also the candle power and con sumption, as determined by Dr Stevenson Macadam : 64. Height of Candle Power f Number of AVicks. Mean Dia meter of Outer Wick in Indies. intense part of Flame, excluding Tails, in Inches. in Sperm Candles, each consuming 120 grs. Sperm per Hour. Light from Consumption of 1 Gallon in Ib Sperm. Consumption per Hour in Gallons. 1 82 1 23-65 27-39 0148 2 1-75 li 80-13 2704 0508 3 2-5 if 200-75 27-2 12C2 4 3-2 2 287-62 27-3 -1801 Mr J. N. Douglass has also introduced a mineral oil burner, which, however, Doty claims as similar in principle to his. By igniting only half the number of wicks (the outer in a six-wick for instance) the power of the burner can be diminished by one half. This is Mr Douglass s lamp of single and double power for use in clear and foggy weathers respectively. The mineral oil employed most extensively in lighthouse illumina tion is Scotch paraffin. The specific gravity, which is a test of the relative richness of the oil, should be from 8 to 82 at 60 Fahr., and the flashing point or temperature at which it begins to evolve inflammable vapour should not be lower than 125 nor higher than 135 Fahr. The Board of Northern Lighthouses was the first light house authority in Britain that adopted paraffin and Doty burners, and by doing so an annual saving of between 4500 and 5000 in the maintenance of the lights on the Scotch coast was effected. Single-wick burners are supplied with oil from the cistern by the capillary action of the wick alone. But in the case of multiple- wick burners other methods must be employed to secure a sufficient supply. If the cistern be placed above the level of the top of the burner, the flow of the oil to the wick cases is effected by the direct