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vided the funds for that purpose. The results of these tests are given in its Annual Reports for 1879 and for 1880.

None of the various lighthouse establishments have as yet succeeded in producing a light that can be identified as to kind, or located as to site, at any considerable distance, through a fog, or even through a snow-storm. But earnest effort is made to guide the mariner by sound when sight will not avail, and fogsignals of various kinds have been applied to this purpose.

In the course of his researches as head of the board's committee on experiments, Professor Henry developed two theories, stating them to be good working hypotheses: one relative to the effect of the wind on the direction of sound, and the other on the failure of sound to make itself heard at irregular intervals. The effect of the publication on the first has been to cause seamen, wishing to hear a fog-signal against which the wind is blowing, to go aloft as they would to see a distant light, and to go as near to the surface of the water as possible to catch the sound, if the wind is wafting the sound toward them.

As to the interval in the audibility of a continuous sound, it is now accepted that a fog-signal may be in full blast and audible for a long distance, and inaudible at varying points within that distance, and that the sound may shade off from audibility to inaudibility, and back to audibility, several times in passing from the fog signal to that point farthest distant from it where it is clearly heard. Hence mariners understand that, though they may not hear it, still they may be within earshot of a fog-signal in operation. They also fully realize the fact that they may, while sailing toward the sound already caught, lose it, and that by continuing their course they may pick it up again. They also understand that, while sailing away from the fog-signal, they may lose its sound and hear it again several times before passing entirely beyond its range of audibility. Therefore, they now make allowances for the variations of the sound of the fog-signal as they do for the variations of the mariner's compass, although the law of the variations of its sound has not yet been fully deduced or completely formulated. The board's annual reports show something of its gradual but effective labors to wrest from Nature her carefully guarded secrets, and to utilize the results of this work as rapidly as they are obtained.

It was within its plans to have continued its researches into the laws of sound by a grand attack with all its available forces. Professor Henry was to have been assisted by several scientists, in addition to those officially connected with the board, who were to be stationed in steamers and in captive balloons above, at various heights, all to note simultaneously the degree of audibility in numerical scale of the sound of a powerful fog-signal in full

blast on a light-ship more than twenty miles from land, so that they would not be puzzled by shore echoes, on which all the various phenomena that could be registered by the thermometer, the hygrometer, and the anemometer, were also to be noted, on charts previously prepared, and it was expected, when all this field work had been plotted, to deduce something of the law of these variations of audibility, and to show what allowance may be made for them. The death of Professor Henry caused the postponement rather than the abandonment of these experiments. Professor Morton, his successor as the scientific adviser of the board, in doing that duty which laid nearest his hand, has brought out the photophone, an instrument by which the mariner, when puzzled as to the location of the fogsignal, which, when heard in snow-storm or in fog, seems to come from anywhere, may determine its direction to within a point of the compass

And at this time, although the board has not brought its fog-signal service up to its own standard, it is of large service to commerce, and has been made the subject of study by commissions sent hither by other countries, especially by Brazil and Great Britain; and it is not too much to say that it is in advance of that of any other lighthouse establishment.

The principal fog-signals now used by the board are the trumpet, the siren, the steamwhistle, the whistling-buoy, the bell-boat, the bell-buoy, and bells rung by machinery impelled by clock-work.

The board, in 1854, employed Professor J. H. Alexander, of the University of Maryland, to make a series of researches as to the audibility of sound in fog and as to the action of fog-signals, and it published the Professor's report and circulated it among scientific mechanics. During this time, Mr. C. L. Daboll, of New London, Connecticut, had been experimenting on his own account. Under the encouragement of the board, he brought out his trumpet fog-signal. His plan was to employ a reed trumpet, made somewhat like a clarionet, and sounded by air condensed in a reservoir by machinery driven first by horse-power, and, later, by a hot-air engine. In it the trumpet is the resounding cavity, and the necessary agitation of the air is produced by the vibration of the tongue-like reed. The trumpet is vertical, curved at the upper part. A firstclass trumpet is 17 feet long, including the curvature, has a flaring mouth 38 inches across, while its throat is 34 inches in diameter. The reed is of steel, 10 inches long, 24 inches wide, 1 inch thick at the fixed, and half that at the free end. It is driven by an Ericsson hot-air engine, having a 32-inch cylinder with an air chamber 43 feet across and 6 feet long, which, at a pressure of from 15 to 20 pounds, could make a five-second blast every minute. the trumpet is not as far-reaching as some other fog-signals, it has been preferred for

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rock stations where there was a scarcity of fresh water, and where fuel was difficult of access. But it is now losing favor because of its liability to accident and the difficulty of its repair.

ranged for that purpose. When the slits in the revolving plate coincide with those in the fixed disk, as they must, say twelve times in each revolution, a jet of steam or air is forced through each opening under great pressure into the The siren, originally invented by Cagniard de trumpet, and the interruption of these jets La Tour, and used by physicists in comparing causes the song of the siren. The rotating sounds and in measuring the number of vibra- plate is directly connected with and supported tions in different musical notes, was largely by the shaft, which is so geared to a steam or changed by A. & F. Brown, of the New York hot-air engine as to make 2,400 revolutions per City Progress Works, under the direction of minute, and as each revolution allows the escape the Lighthouse Board, and adopted for use as and interruption of twelve jets through the a fog-signal. It can be sounded with either coinciding openings, there are 28,800 shrieks steam or compressed air driven through a fixed given, creating, as the vibrations are taken up flat disk, placed in the throat of a trumpet, to by the trumpet, a condensed beam of sound of which is attached the pipe conveying the mo- great intensity and of surpassing power. tive power. The disk has from eight to twelve radial slits. Back of the fixed disk is a revolving plate with a like number of similar openings, which is rotated by power specially ar

The siren is used on shore, as shown in the following cut, and on light-ships, as shown in the cut of Pollock Rip Light-Ship, on page 450. The first-class steam siren, when working

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with a pressure of seventy-two pounds of steam, consumes about one hundred and eighty pounds of coal and one hundred and twentysix gallons of water per hour, and can be heard under usual circumstances at a distance of twenty miles, and in still air thirty miles, even in a dense fog. Its range of sound, however, is not deemed of so much importance as its quality and its power of domination over local noises, such as that of the surf, the whistling of the wind through a ship's rigging, that of paddle-wheels, or the working of an engine. This it has to such extent that it has been well said that "its density, quality, pitch, and penetration render it dominant over such noises after all other signal sounds have succumbed." The committee sent in 1872 by the British lighthouse establishment, Trinity

House, to this country, headed by Sir Frederick Arrow and Captain Webb, of H. M. Navy, reported so favorably upon it that, since then, "twenty-two sirens have been placed at the most salient lighthouses on the British coasts, and sixteen on lightships moored in positions where a guiding signal is of the greatest service to passing navigation." While the siren is the best fog-signal yet invented, it is also the most expensive to build and to run, is the most complicated in its parts, and requires more attention and skill in its management than any other signal, and is adapted only to such stations as are amply supplied with water and have machine-shops in the vicinity where necessary repairs can be promptly made.

The steam-whistle is largely used as a fogsignal, and with satisfactory results, in places

not requiring the greatest intensity and power of sound. It is the ordinary locomotive whistle, of a varying diameter, from six to eighteen inches, operated by steam from an ordinary and often an upright boiler, with a pressure of from fifty to one hundred pounds to the square inch. It can be made to produce any combination of shrieks, in a given time, so that it can be identified by its published characteristic. These are produced and regulated automatically by an engine taking its steam from the same boiler, which, at arranged intervals, opens and closes the valves, thus shutting off or letting on the steam. The machinery is simple and the piston-pressure quite light; and, while it is not liable to get out of order, it requires no more attention than an ordinary stationary engine.

A great number of experiments have been made with these three signals. From their average it appears that the power of the firstclass siren, the twelve-inch whistle, and the first-class Daboll trumpet may be thus expressed: siren, nine; whistle, seven; trumpet, four; and their relative expenditure of fuel is recorded as, siren, nine; whistle, three; trumpet, one.

The board had in operation on July 1, 1880, fifty-seven fog-signals operated by steam or hot air.

Bells are also largely used as fogsignals. When the board assumed charge of the establishment, they were rung by clock-work, rude in kind and wasteful of power, its weight constantly descending even during the silent intervals. This defect was remedied, under the suggestion of the board, by Mr. Stevens, of Boston, who introduced an escapement arrangement, somewhat like that of a clock, and moved by sinall weight, the larger one operating only to strike the bell itself.

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The large, unwieldy bell-boats of the early days of the establishment have mostly gone out of use.

The Brown bell-buoy, recently invented by the master of one of the lighthouse tenders, is a simple arrangement by which the bottom section of a first-class iron nun-buoy is decked over and fitted with a framework of three-inch angle iron, nine feet high, to which a bell is rigidly fixed. Under the bell, which, if of the first-class, weighs 300 pounds, a concentric grooved iron disk of chilled cast iron is fastened to the frame around the disk; opposite each groove a spring is fastened, and on the disk a heavy iron ball is allowed to roll. The swaying of the buoy, by the undulations of the sea, causes the ball to roll from side to side and to strike the bell with each roll. The

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springs throw the ball from the bell after each blow, permitting vibration, and causing the bell to give out the largest volume of sound possible under the circumstances. This signal is never silent, but the heavier the sea the louder is the sound.

The automatic signal- or whistling-buoy invented by Mr. J. M. Courtenay, of New York, consisted originally of an iron, pear-shaped bulb, say twelve feet in diameter, with a tube, twenty inches across and forty feet long, descending through its bottom. The water in this tube acts by its own inertia as a piston to draw in air through an orifice supplied with a retaining valve, and to expel it through a ten-inch whistle. The sound produced is only comparable to itself in kind, and it is of a quality which asserts itself over all others, and of a power audible several miles even against the wind. Its dimensions have been recently largely but proportionately reduced without detracting from its usefulness. As its action depends on the undulation of the surface, and, as from its great draught it must be moored in deep water, it is only used in roadsteads or in the open sea. But it has proved so successful that it is used at some points where a light station would otherwise be required, and, in one instance, las, satisfactorily to mariners, replaced a light-ship. At the date of its last report,

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COURTENAY AUTOMATIC WHISTLING BUOY.

July 1, 1880, the board had twenty-five of the whistling-buoys in position.

The purpose of a light-ship is to do the work of a lighthouse in a place where one is necessary, but where it has not been erected because of the great difficulty, not to say expense, of plac

ing such a structure. But the light-ship should have the permanency and efficiency of a lighthouse, and should give as good a light in clear weather and sound as far-reaching a fog-signal in thick. To insure permanency of position is a matter of great difficulty. When moorings have been made too heavy to drag, chains have broken; when they have held, mooring-bitts have been torn out; when they have held, the ship has foundered at her anchors, or the cable has been slipped, and the ship has sought a harbor or gone to sea for safety. But under the present rules of the board rigid inspection is frequently made of their riding-gear, and the absence of a light-ship from her moorings is now quite unusual.

The board has thirty light-ships of various sizes on duty in the service. The smaller, slighter built, and older vessels are moored in sounds and bays. The larger, stronger, and later built are anchored in the open ocean. Among the latter is that on New South Shoals, some twenty-seven miles at sea, the nearest land being Nantucket; Pollock Rip lightship, moored at the eastern entrance to Nantucket Sound; another is moored at the western entrance to Vineyard Sound; two off Sandy Hook entrance to New York Bay; another off the mouth of Delaware Bay; another on Winter Quarter Shoal, off the coast of Virginia; another on Frying Pan Shoal,

off the mouth of Cape Fear River, North Carolina; another on Rattlesnake Shoal, off the entrance to Charleston, South Carolina; another off Martin's Industry Shoal at the entrance to Port Royal, South Carolina; and the last light-ship built (1880) is on Trinity Shoal, off the coast of Louisiana. This last is fitted with a twelve-inch steam-whistle fogsignal, and is perhaps the strongest and bestequipped light-ship afloat. The light-ships on Pollock Rip and at the mouth of Vineyard Sound have fog-signal sirens operated by hotair engines, which are to be replaced by steamengines, as it is found that hot air endangers the health of the crew and shortens the life of the ship.

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Each light-ship shows either one or two lights. Each light has eight reflectors, each twelve inches in diameter, set upon a ring which encircles the mast, and can be lighted and hoisted to the masthead by night and lowered and housed by day. These reflectors are illumined by a kind of Argand lamp, in which the sperm-oil formerly burned was succeeded by lard-oil, and that is now superseded by mineral-oil, burned in a lamp specially adapted to the purpose. The lighting apparatus is inclosed in a lantern, with large panes of glass which protect the light from the wind. The light-ship shown in the accompanying

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tern required to tell their allotted story, fitted at the larger end with an iron sleeve, to which the stone or iron anchor can be attached by a mooring chain, when they are packed in classes or sizes on skids to season, and finally to take their tour of duty in the water to replace others which are to rest a while on shore, be freed from acquired barnacles, take on a fresh suit of paint, and, by drying, recover their buoyancy. Spar-buoys are classified first by length and thickness, and then by acquired color; but they are interchangeable within these conditions. The cuts represent sparbuoys and their appendages, much as they appear in the water.

this vessel from dragging her anchors that she is now fitted with moorings as heavy as those of a frigate. In spite of her brilliant lights and her powerful fog-signal, she has been repeatedly run into by passing vessels and more or less damaged, as have most of the other light-ships in the service. She has a master, a mate, two engineers, and a force of six men. Her cost was $50,000, and it requires about $5,000 a year to maintain her exclusive of repairs-a larger sum than is needed for smaller ships, or for those without fog-signals. It is estimated, however, that it costs $10,000 per year to maintain and keep in repair each of the first class light-ships in the service, and this is urged as a reason for replacing them as fast as possible with lighthouses.

The buoy is to the seaman by day what the light is at night, and what the fog-signal is in thick weather. It tells him by its size, form, color, and number how to avoid the rocks and shoals, and shows the way in and out of harbor.

The growth of the buoy service may be measured by its cost, which was for the five years preceding the organization of the board, in 1852, about $75,000 per year, and for the five years after about $82,000 per year.

In 1842 there were nearly 1,000 buoys in position: in 1855 the board had 1,034; in 1860 it had 1,738; during the war it lost those on the southern coasts, but in 1867 it had so far replaced and added to them that it had 2,044; in 1875 it had 3,002; and on June 30, 1880, it had 3,140 buoys in the waters of the several districts. An appropriation of $325,000 was made for maintaining the buoyage of the United States coasts during the year ending June 30, 1882.

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The buoy service has its own code of laws, state and national, a fleet of small tenders for its maintenance, besides a corps of contractors to attend to the buoyage of coves and inlets impracticable to the lighthouse tenders. It has its depots for the storage of iron buoys, where they are painted and numbered, or repaired, and also where wooden buoys are made ready for service. It has its own directory printed yearly, in twelve volumes, distributed gratuitously for the benefit of commerce, in which each one of the more than 3,000 buoys is mentioned by name, located by station, and is described by size, shape, color, number, and vicinity. The problems connected with its improvement, as well as its maintenance, are considered as of grave importance, and are made the subject of deep consideration by the best scientific aid at the disposition of the board.

IRON CAN-BUOY.

Buoys are of wood or iron. The wooden buoys now in use are sticks from twelve to sixty feet long, of pine or spruce, but preferably of cedar. The board frequently contracts for the delivery at one of its depots of a cargo of logs, in the rough, at from $10 to $15 each, where they are freed of their bark, smoothed most conical in form; the can-buoy is in shape of their protruding knots, painted to the pat- the frustum of a cone nearly approaching a

IRON NUN-BUOY.

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