Lightships and Lighthouses

by Frederick Arthur Ambrose Talbot

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.