Hand in hand with the development of the unattended light for service on land positions has proceeded the adaptation of the floating light. This may be described briefly as an enlarged edition of the lighted buoy, which is such a conspicuous feature of our harbours and estuaries. Yet it is more than a buoy. It can fulfil all the purposes of a light-vessel, both as regards the emission of a ray of light or a distinctive sound, so that both audible and visual warning are given simultaneously. These lights likewise are automatic in their action, and, when set going, require no further attention for some time. Nine months or more are often permitted to pass without human hands touching them, and they have solved some very abstruse problems in connection with coast lighting.

For instance, there is probably no such lonely stretch of coastline as that of British Columbia and Alaska. There is only one large port north of Vancouver—Prince Rupert—and this rising hive of maritime activity is 550 miles distant. The coast is as wild as that of Norway, which, indeed, it resembles very closely, bristling as it does with fjords and islands, with rugged cliffs rising abruptly from the water to a height of several hundred feet. Navigation at night is extremely hazardous, as the path leads by devious ways through deep channels intersecting the outer barriers of islands, where fogs hang low and thickly. The captain has to pick his way carefully, determining his course by timing the period between the blast of his siren and its echo, as it is thrown from headland to headland. As the passenger traffic developed, the masters of the vessels entrusted with so many human lives felt the increased responsibility keenly, and agitated for more adequate protection. The erection of lighthouses, even of the most economical type, would have entailed huge expenditure by both the United States and Canadian Governments, while the question of maintenance would have bristled with searching problems.

Accordingly, it was decided to adopt the floating automatic system, which had proved eminently satisfactory in other parts of the world. In this manner a highly successful and inexpensive solution of the difficulty was found. These buoys have been installed at all the most treacherous points leading to sounds and canals, as the lochs are called, and have been found in every way equal to the simplest type of attended lighthouse. The southern coast of Nova Scotia has been protected in a similar manner, a chain of automatic lights, spaced ten miles apart, having been completed, so that this wild, rugged shore is patrolled very efficiently at the present moment. Other countries have not been dilatory in adopting the same methods. Consequently, to-day the automatic floating lighthouse is one of the handiest, most efficient and reliable devices for assisting navigation that the lighthouse engineer has at his command.

The lights assume different forms, this factor being influenced by position, specific duty, and local conditions. Similarly, the character of the illuminant employed also varies, acetylene, compressed oil-gas, petroleum, and electricity, being utilized, according to circumstances. On the whole, however, acetylene gas appears to be the most favoured illuminating medium, inasmuch as the preparation of the carbide of calcium has undergone such marked improvement.

When Mr. Thomas L. Willson discovered the cheap process for the manufacture of carbide of calcium upon a commercial scale, and the new industry became placed upon a firm footing, it was only natural that the inventor should realize the possibilities of applying the new illuminant to the assistance of navigation. Acetylene gas gives a brilliant clear light of intense whiteness, which is capable of penetrating a great distance. Accordingly, he set to work to devise a buoy lighted by this gas, and able to carry sufficient storage of calcium carbide to burn for weeks or months without attention. When he had completed the first apparatus of this character, he handed it over to the Marine Department of the Canadian Government for submission to any test that they might consider expedient, in order to ascertain the limits of its application. The buoy was set in position and watched carefully. Periodically it was examined to ascertain whether overhauling and cleaning were necessary, as well as the behaviour of the light under all conditions of weather. Captains of vessels passing the beacon were requested to pronounce their opinions upon the quality of the light, and their remarks concerning its range, facility with which it might be picked up, reliability, and so forth, were carefully marshalled and digested by the authorities. Precisely what the officials thought of the invention is reflected most convincingly by the fact that to-day over 300 lights working upon this principle are stationed in Canadian waters, both upon the storm-bound ocean coasts and upon the wind-swept shores of the Great Lakes and waterways.

The Willson buoys are absolutely automatic in their operation. All the impurities in the gas are removed by passing it through a special purifier, so that the burner cannot become clogged or the light impoverished. A charge of 1,300 to 1,500 pounds of carbide is carried within the apparatus, and the gas is generated under low pressure. The lantern is fitted with a Fresnel lens, so that the light is condensed into an intensely powerful and penetrating horizontal beam. One prominent feature is that the candle-power of acetylene gas is seven times as high as that of compressed oil-gas, while the reservoir of a given size will contain this equivalent of more light. The candle-power of these floating lights obviously varies, the largest size being capable of emitting a beam of 1,000 candle-power, this flame being the maximum that the lens will stand without breaking. The construction and the principle of operation are exceedingly simple, as may be gathered from reference to Fig.16. The beacon comprises a gas generator tube of steel (1), which is supported by the steel float chamber (2), on the upper side of which is placed the support (3) carrying the lantern (4). Stability is insured by means of the counterweight (6) attached to the lower end of the generator tube. A few feet from the bottom of the latter is a diaphragm (7), fitted centrally with a conically-seated valve (8) which is mounted on a stem (9). This extends through the centre of the generator and its head (10). The upper end of the valve stem carries a hexagonal nut (11), while the stem itself at this point has a keyway cut into it. A spline is fitted into the generator head to engage the keyway, and when the nut (11) is turned to close or to open the valve, the stem itself cannot move with it, except in two directions only—up or down. The nut itself cannot be turned too far, in which event it might drop the stem and valve, as there is a stop-collar (12). Leakage of gas is prevented by a cap (14), which is screwed into the generator head and sealed with a rubber washer. This cap is sufficiently long to permit the valve stem to be raised or lowered so as to adjust the movement of the valve. The stem of the valve is protected from the carbide by enclosure within a tube (13), which works through a guide bar (24) bolted to the side of the generator tube. A grid (23) is fitted in the centre of the diaphragm (7) and surrounding the valve (8), so as to prevent small pieces of carbide, which may pass through the grate (16), from falling into the water, and thereby being wasted. The steel grate upon which the carbide rests is attached to the inside of the generator, a short distance above the diaphragm. The grid (23) also acts as a valve seat, and is provided with a rubber packing (15), which is held in a groove in the seat, and projects a sufficient distance to make a good joint with the valve (8) when it is closed, even if the valve happen to be foul.

The carbide of calcium, in the form of large crystals measuring about 8 by 4 inches, is placed in the generator tube when the beacon is immersed in the water, the valve (8) being opened and the valve-cap (14) screwed down. In the centre of the counterweight (6) is an orifice through which the water enters from the outside, and passes through the open valve, to come into contact with the carbide resting upon the grate. Gas is generated instantly, to ascend through the carbide into the purifying chamber (5), where all deleterious matter is removed, the gas escaping thence through the small aperture (17) and pipe (18) to the lantern, to which the supply-pipe is connected by the aid of the coupling (19).

Of course, at times gas is liable to be generated more rapidly than it can be consumed. What happens? The apparatus is not provided with facilities to receive the surplus gas. Being unable to escape upwards through the generator tube, it collects at the bottom, and as the pressure increases it gradually forces the water away from the carbide, so that generation ceases, and is not resumed until the surplus gas has been absorbed, when the water once more is able to come into contact with the carbide. Thus it will be seen that the gas generation is controlled automatically, and that it is almost impossible for the gas pressure within the plant to reach a disruptive degree, owing to the fact that when it exceeds a certain limit it has a free vent from the bottom of the device, where the water normally is permitted to enter to carry out its designed purpose.

This invention has been utilized for a wide variety of purposes, from the lighting of harbours, navigable channels, rivers, bays, and so forth, to that of exposed coasts. The automatic beacon, properly so called, has a tower, which brings the focal plane to an elevation varying between 50 and 100 feet, this tower being built of lattice steelwork attached to the top half of the buoy, with a day mark surrounding the lantern gallery, access to which is secured by an iron ladder. This type of light carries a sufficient storage of carbide in a single charge to keep the light burning continuously for about forty weeks. In this instance the only modification from that already described is that the water for the production of the gas is admitted into the top instead of to the bottom of the generator. When an excess of gas occurs, the pressure thereof drives the water away from the carbide until the surplus has been consumed. Another type, somewhat smaller, carrying a charge sufficient for nearly six months, has proved highly successful as a coastal light, some thirty beacons of this class being stationed along the shore of British Columbia. The only trouble experienced therewith in these waters has been due to frost, which, solidifying the water around the buoy, has interrupted the designed functions.

But probably the most complete and useful type of Willson acetylene gas beacon is that in which the Courtenay whistling device is incorporated, so that in thick weather audible warning of the danger may be extended. In this instance the floating chamber which supports the superstructure carrying the light and also the generator tube, is fitted with two further tubes which project from the base like huge legs. These tubes are open at the bottom, but are closed at the top except for a connection with a valve-casing, which is fitted with a ball-valve, and upon which a powerful whistle is bolted. Now, if the buoy is lowered and anchored in absolutely still water, the water will rise to the same level within the tubes as it is outside; but when the buoy is lifted upon the crest of a wave, the level of the water falls, so that the air space within the tubes is increased. Air enters this augmented space through the ball-check inlet valve in the valve-casing. When the beacon falls, naturally the water endeavours to maintain its level within the tubes, and therefore the air which was admitted into the space becomes compressed, to be expelled through the only possible vent—the whistle—thereby producing a very powerful blast. Thirty of these combined light and whistling buoys have been strung along the rugged Nova Scotia coast, and have proved highly popular, that outside Halifax harbour being known colloquially among seafarers as the “Outer Automatic.” Another acetylene system, but working upon a better principle, has been perfected in Sweden, and, indeed, now has been adopted universally, owing to its many excellent features. This is the “Aga” light, which is the invention of Mr. Gustaf DalÉn,C and which has been brought to a high stage of commercial success by the Gas Accumulator Company of Stockholm. I have pointed out the one objection to the Willson acetylene automatic light—namely, its uselessness when the surrounding water becomes frozen. While this drawback does not affect its sphere of utility to a noticeable degree in Canadian waters, it acts somewhat adversely in other seas where similar conditions prevail, but where the navigable channels are kept open by ice-breakers, such as, for instance, in the Baltic Sea. Mr. DalÉn recognized this weak point in any system wherein contact with water is responsible for the generation of the gas, and accordingly sought for a superior method. Fortunately, the perfection of a new means of handling acetylene, by French inventors, offered the complete solution of the problem in a practical way. The principle of this lies in the use of dissolved acetylene, which is perfectly safe from explosion, and can be handled with the greatest facility. The gas can be stored in cylinders similar to those used for containing oxygen and hydrogen under pressure, gases which are easier to transport than carbide of calcium, and, what is far more important, climatic conditions do not exercise the slightest influence upon it.

Dissolved acetylene may be stored within the cylinder, or accumulator, as it is called, to a pressure of at least ten atmospheres, and at this pressure it contains 100 times its own volume of acetylene gas. The accumulators may be made of any desired size, this factor being governed by considerations of transport and application, as well as of the consumption of the burner.

The perfection of the dissolved acetylene process came as a great boon to the Swedish lighting authorities, inasmuch as they have probably the most difficult stretch of coastline in the world to protect. At the same time, owing to the wild, exposed character of many of the points which demanded lighting, a perfect, economical, and reliable automatic system was in urgent demand. Acetylene was an obvious illuminant, since, while the country is deficient in the essential resources for the preparation of other fuels, carbide of calcium is very cheap, Sweden, in fact, being the largest producer of this commodity. The Swedish Board of Pilotage experimented with acetylene lighting for six or seven years, submitting every known acetylene lighting system to searching practical trials, but failed to be sufficiently convinced on the vital question of reliability. Freezing-up was the most pronounced shortcoming, but when dissolved acetylene appeared as a commercial product this disadvantage was removed completely, and acetylene was adopted.

Yet dissolved acetylene, though completely successful, possessed one drawback. It was expensive as compared with oil-gas. Accordingly, there was great scope for a means of economizing the consumption of the fuel without interfering with its lighting value and efficiency. At the same time a superior flashing system was desired. The methods which were in vogue to this end were satisfactory so far as they went, but they involved a considerable useless consumption of gas.

This is where Mr. Gustaf DalÉn completed one of his greatest achievements. He perfected a flashing apparatus wherein the gas passes to the burner in intermittent puffs, to be ignited by a small invisible pilot light. The device was tested and proved so successful that it was adopted throughout the service. In Swedish waters to-day there are 127 aids to navigation operating upon this system, of which five are lightships. The success of the invention in the land of its origin attracted other nations to its possibilities. At the present moment over 700 lights, scattered throughout the world, are working upon this principle. If a beacon throws a fixed light, unless it is of extreme power, it is liable to be confused with a ship’s mast-light, a fact which was found to be one of the greatest objections to the fixed white light of the acetylene aid to navigation. On the other hand, a flashing warning must be of such a character that it cannot be mistaken for the twinkling of a brilliant star, or of a light which has nothing to do with navigation. This is where the “Aga” flasher emphasizes its value. It throws a short, powerful gleam at brief intervals. The mariner cannot possibly confuse or misconstrue it; the regularity of the flash arrests his immediate attention, and its purport may be divined instantly. The apparatus is simple and highly effective, while it has the advantage that the periods of light and darkness can be altered in relation to one another, or grouped, as desired.

From the maintenance point of view, however, the invention is of far greater significance. As the gas is consumed only during the light periods, which are very brief in comparison with the eclipse, the economy effected is very appreciable. When the apparatus was first brought within the range of practical application, many authorities, which had become wedded to the oil-gas lighting system, wherein the light flashes are of long duration in comparison with the dark periods, maintained that the DalÉn flash was too short to be of any value. They disregarded the fact that the power of the acetylene-gas flash is about seven times as intense as that of the oil-gas light. For instance, when the United States acquired the first Aga light in the autumn of 1908, the authorities demanded either a characteristic signal comprising ten seconds of light followed by five seconds of darkness, or flashes and eclipses of equal duration—five seconds.

There was a prejudice against short, powerful, and oft-repeating flashes, mainly because their advantages were misunderstood. Practical experience, however, demonstrated the fact that the period of light might be reduced very considerably, and, as a result of prolonged investigations, the Swedish Board of Pilotage adopted a characteristic comprising 0·3 second light followed by darkness for 2·7 seconds. This has become known since as the “one-tenth flash,” owing to the luminous interval occupying one-tenth of the combined period of light and darkness. It will be seen that, as a result of this arrangement, twenty flashes are thrown per minute.

As the flame is lighted for only one-tenth of the signal period, it will be seen that the saving of gas amounts to 90 per cent., as compared with the light which is burning constantly. Accordingly, the gas charge will last ten times as long with the flashing apparatus; consequently, the accumulator need have only one-tenth of the capacity of that for a similar beacon which burns constantly. The economy really is not quite 90 per cent., as a certain volume of gas is consumed by the pilot flame, which ignites the charge of gas issuing from the flasher burner. This, however, is an insignificant item, inasmuch as the quantity of gas burned by the pilot light does not exceed one-third of a cubic foot per twenty-four hours.

Not only has this highly ingenious system been adapted to varying types of buoys, similar in design and range of action to those described in connection with the Willson apparatus, wherein the light may be left unattended for as long as twelve months, according to the capacity of the accumulator, but it has also been applied to “light-boats” and light-vessels. The “light-boat” is a hybrid, being a combination of the buoy and the lightship, and was devised to meet special conditions. Thus, the “Gerholmen” light-boat stationed in the mouth of a Swedish river, where the current runs exceedingly strongly, resembles a small boat with a water-tight deck. From the centre of this rises a steel tripod, at the top of which the lantern is placed. The gas accumulators are stored within the hull, and are of sufficient capacity to maintain the light for a round twelvemonth without attention, as the flashing apparatus is incorporated.

The Aga light has come to be regarded as one of the greatest developments in lighthouse engineering, and has been adopted extensively throughout the world in connection with either floating or fixed aids to navigation. The United States have decided to adopt the system exclusively henceforth, until a further progressive step is achieved, and several floating lights of this type have been acquired already to guard wild and lonely stretches of the coastline.

Here and there attempts have been made to apply electricity to inaccessible lights. The most interesting endeavour in this direction was in connection with the lighting of the Gedney Channel from the open Atlantic to New York harbour. This formerly constituted the only available highway for the big liners, and it is exceedingly tortuous and treacherous—so much so that vessels arriving off Sandy Hook in waning daylight invariably anchored and awaited the dawn before resuming the journey. The great difficulty in connection with Gedney’s Channel was the distance of the main lights on shore, the direct range at one part being over thirteen miles. Consequently the land lights were of little utility to the pilot.

The authorities decided to convert the channel into an electric-lighted waterway. Buoys were laid down on either side of the thoroughfare. They were of the spar type, resembling decapitated masts projecting from the water, and were held in position by mushroom anchors, weighing 4,000 pounds, or nearly 2 tons, apiece. Each buoy was crowned with a 100 candle-power incandescent electric lamp, encased within a special globe having a diameter of 5 inches. An electric cable was laid on either side of this street and connected with each buoy. The first section was completed in 1888, the electric gleams being shed for the first time on November 7 of that year. The system appeared to give such complete satisfaction that it was extended. Altogether six and a quarter miles of cable were laid down, which in itself was no easy feat, while prodigious difficulties were experienced in its maintenance, owing to the severity of the currents and the treacherous character of the sea-bed. The lights were controlled from a central point ashore, and the idea of being able to switch on and off a chain of aids to navigation by a simple movement presented many attractive features. Although navigation appreciated this improvement, the Great White Waterway did not prove a complete success. It did not possess that vital element of complete reliability which is so essential to navigation.

Compressed oil-gas has been employed extensively for unattended floating lights, but it possesses so many shortcomings that it is being superseded on all sides by acetylene, with the exception of one or two countries which appear to be inseparably wedded to this principle. It is expensive both to install and to maintain, while the “radius of action”—otherwise, the period during which it may be left without human attention—is unavoidably brief. For temporary purposes, such as the indication of a submerged wreck, it is efficient, while it is also serviceable for accessible positions, but it is not regarded as being a satisfactory system for places which human hands cannot reach for months at a time.

Crude petroleum in conjunction with the Wigham long-burning petroleum lamp, wherein the flame is produced from a moving wick, has been adopted widely. Lights installed upon this principle may be left for ninety-three days at a time without anxiety. In many instances the Wigham light is mounted upon steel boats; in other cases it is attached to floating wooden structures. The British Admiralty in particular is partial to this type of light, and it must be confessed that it has proved highly serviceable and reliable.

I have described already the general principles and features of this system. When it is applied to a floating beacon, and it is desired to save the oil dropping from the drip valve, a tank is fixed to the deck of the floating structure, and connected by a flexible pipe to the coupling at the bottom of the float cylinder. A universal joint is attached to the connection on the top of the tank to prevent the pipe being twisted by the swinging and swaying motion of the lamp on the gimbals. When the lamp is inspected, the oil may be pumped out of the tank, strained, and used time after time in the float cylinder. One of the most interesting of this type of floating boat-lights is to be seen in Queenstown harbour. The hull is 30 feet in length, and has a beam of 11 feet. On this, within a conical structure measuring 7½ feet high and 6½ feet in diameter at the deck, is mounted the lantern. Although the lamp is exposed to drenching seas and heavy storms, it has never yet failed, a fact which conclusively points to its efficiency. It rides well, and the lamp is kept much drier than the lights on ordinary buoys, according to the observations of the engineer responsible for its maintenance. In this case the focus of the light is brought 12 feet above the level of the sea.

Probably the most compelling illustration of the utility of the automatic beacon is offered by the unattended lightship. The Otter Rock vessel is one of the most interesting examples of this development. It was designed by Messrs. D. and C. Stevenson, and comprises a substantial steel hull, the deck of which is covered so that the interior is absolutely water-tight. The craft is provided with a central and heavy bilge keels, so as to reduce rolling to the minimum. Two heavy steel bulkheads divide the craft into three water-tight compartments, in the centre of which two large welded-steel gas tanks are stowed. These are of sufficient capacity to feed the light for several months without replenishment. The light is mounted upon a steel tower placed amidships, which brings the focal plane 25 feet above the water. The gas is fed from the tanks to the lantern through the tower, a valve reducing the pressure, while a ladder enables the attendants to climb to the lantern gallery to adjust the burner and flame, and to clean the lenses, upon the occasion of their periodical visits.

The gas cylinders are charged from the supply-ship through flexible hoses, the gas being compressed to about 180 pounds per square inch. The light is of sufficient power and elevation to be seen from a distance of some twelve miles. The beacon gives not only a visual, but also an audible warning. On the deck of the boat a bell is mounted, this being rung not only by the motion of the ship, in the manner of a bell-buoy, but also by the gas on its passage from the tanks to the lantern, the bell being fitted with two clappers for this purpose. The gas in passing from the tank enters a receptacle having a flexible diaphragm, which, as it becomes filled with gas, is naturally pressed outwards. On this is mounted a central metal piece, which is connected to a rod and lever. As the diaphragm is forced outwards, it moves the rod and actuates the lever, which, when the diaphragm falls, return to their normal positions. Attached to this mechanical arrangement is the bell-clapper, which alternately is lifted and dropped upon the dome of the bell, thereby causing it to ring. After the gas has performed its duty in raising the clapper lever and rod, it passes to the lantern to be consumed. Thus, while the light gleams brightly and steadily, the bell rings with unerring regularity—about three times per minute—day and night for months on a single charge; both must continue in operation until the supply of gas is expended. The success of this interesting and novel lightship has been responsible for similar installations in other similarly wild and exposed positions where approach is uncertain and often impossible for weeks at a time.

One misadventure befell the Otter Rock light-vessel, which is moored in an open position over the rock of that name near Islay, although it was not the fault of either the system or the designing engineers. There was a flaw in one of the shackles, and while the ship was sawing and tugging at her anchors during a heavy gale the flaw asserted itself, the shackle broke, and the lightship got away. She was recovered with some difficulty, after having drifted about twenty miles. She was found stove in, having embraced the rocks during her wayward journey, but otherwise was unharmed. She was towed into port, repaired, and then taken back to her station, where she was secured more firmly than ever, while her chains were closely inspected to make assurance doubly sure. No repetition of the accident has occurred since, and the Otter Rock lightship, tethered firmly to the rock, rides gales and calms, throwing her welcome rays and droning her musical warning the whole year round as steadily and efficiently as if she had a crew aboard.

A similar lightship was built for the Trinity House authorities from the designs of their engineer, Sir Thomas Matthews, for service on the English coast. This boat, built of steel, measures 65 feet in length, by 18½ feet beam and 10½ feet depth, with the lantern carried at the point of an open steel pyramidal structure, rising sufficiently high above the boat’s deck amidships to bring the focal plane 26 feet above the level of the water, thereby giving it a visible range of some ten miles. The boat is provided with two holds, in which the gas reservoirs are placed, the total gas capacity being about 1,500 cubic feet—enough to keep the light burning for one hundred days.

This light is of the revolving type, and the rotation of the apparatus is accomplished very ingeniously. Before the gas passes to the burner, it drives a tiny three-cylinder engine, the crank-shaft of which is connected to the revolving apparatus through gearing. The speed of the turntable is kept constant by the aid of a governor, and the apparatus works so smoothly and perfectly that there is not the slightest divergence from the rate at which the apparatus is set. As the gas emerges from the engine, it passes to the burner to be consumed. By means of a novel apparatus, should anything befall the little motor or the rotating mechanism, the light does not drop out of service. In that event the gas flows directly to the burner, the only difference being that a fixed instead of a revolving light is emitted.

When the Scandinavian liner Norge, while on her way to the United States in July, 1904, fouled the terrible Rockall and lost 750 of her passengers, the outcry about the absence of all means of indicating this spot to the navigator vibrated round the world. Yet it was a useless agitation. Rockall is a no-man’s land; no nation has planted its flag upon its cone of granite; no Power cares whether it continues its harvest of human lives or otherwise. The various countries appear to think that it is too much off the map to be worthy of a moment’s thought; its existence is brought home only by a holocaust.

After this heartrending disaster, Messrs. D. and C. Stevenson adumbrated a promising means of indicating this awful graveyard to the seafarer. They suggested that two automatic unattended lightships should be constructed, and that one should relieve the other every six months. The project was eminently practicable, but every country seemed to shirk responsibility in the expense of its adoption. But Rockall is a unique danger spot; in no other part of the known world does such a formidable isolated peak of granite rise from the ocean depths, for it is in mid-Atlantic, 160 miles west of St. Kilda, and 290 miles off the Scottish mainland. It may be away from the great steamship lanes of the Atlantic, yet a vast volume of shipping passes within sight of its curious formation. Seeing that the foremost maritime Powers defray between them the cost of maintaining the light off Cape Spartel, surely the dictates of humanity are sufficiently pressing to secure the indication of this islet. The maintenance of an unattended automatic beacon, such as Messrs. Stevenson advocated, would not impose a severe strain upon the treasuries of the leading Powers of the world, whose interests are associated intimately with the North Atlantic.

The perfection of the unattended lightship, working automatically, has provided the lighthouse engineer with a powerful weapon for marking the most exposed and out-of-the-way danger spots. When the new development is carried to its uttermost lengths, no graveyard of the ocean, no matter how remote and inaccessible, need be without means of warning shipping of its whereabouts.