Lightships and Lighthouses

by Frederick Arthur Ambrose Talbot

In a previous chapter I have mentioned that, although oil is the most popular form of illuminant in lighthouse engineering, electricity is maintained to be preferable, but labours under one heavy disadvantage which militates against its more general adoption. It is expensive to install and to maintain. Under these circumstances the system has been restricted to lights of the most important character, preferably landfalls or beacons indicating the entrance to a harbour. Thus, we have the Lizard at the entrance to the English Channel; St. Catherine’s on the Isle of Wight; the Rothersand at the entrance to the Weser; the Heligoland flaring over the island of that name; the Isle of May at the entrance to the Firth of Forth; Cape Héve near Havre; and the Navesink light on the highlands of the New Jersey coast, to guide the mariner into New York harbour.

The first attempt to apply electricity to lighthouse illumination was made in the year 1859, by the Trinity Brethren, on the strong recommendations of Professor Faraday, who was then scientific adviser to the British lighthouse authorities. The South Foreland light was selected for the experiments, and the magneto-electric machine invented by Professor Holmes, who subsequently perfected the siren, was used.

The installation was built with extreme care, as the imperative necessity of reliability, owing to the peculiar nature of the application, was recognized very fully. The large wheels made eighty-five revolutions per minute, and at this speed produced a very steady light. On a clear night, owing to the elevation of the cliff the light was visible for over twenty-seven miles, and could be descried readily from the upper galleries of the lighthouses on the opposite French shore. In order to determine the relative value of electric lighting in comparison with the other methods of illumination then in vogue, another light emitted by an oil-lamp, with reflectors characteristic of the period, was burned simultaneously from a point below the top light, so that passing mariners were able to compare the two systems of illumination under identical conditions.

The French lighthouse authorities were not dilatory in adopting the new idea, and electricity was installed in the Cape Héve lighthouse in 1863. The light was brilliant for those times, being approximately of 60,000 candle-power. The French investigators then embarked upon an elaborate series of experiments, and in 1881 an electric light of about 1,270,000 candle-power was established at the Planier lighthouse, near Marseilles. The investigations culminated in the great achievement of M. Bourdelles, who, while engineer-in-chief of the Service des Phares, designed a new electric installation for the Cape Héve light, of 25,000,000 candle-power.

Meantime British engineers had not been idle. In 1871 Messrs. Stevenson, the engineers-in-chief to the Commissioners of Northern Lighthouses, advocated strongly the establishment of an electric light upon the Scottish coast; but it was not until 1883 that the Board of Trade sanctioned the sum necessary to complete such an enterprise, and suggested that the innovation should be made at the Isle of May lighthouse, as being the most important on the East Scottish coast.

This is one of the historic light-stations of Scotland. Lying in the Firth of Forth, five miles off the Fifeshire shore, the islet obstructs a busy marine thoroughfare. For 276 years a light has gleamed from its summit, the change from the coal fire to Argand lamps with reflectors having been made by Thomas Smith, the first engineer to the Commissioners of Northern Lighthouses, when this body assumed its control in 1816. Twenty years later it was converted to the dioptric system, with a first-order fixed light apparatus having a four-wick burner. This arrangement was in service for half a century, when it was converted to electricity in conjunction with a dioptric condensing apparatus.

The electric installation was designed throughout by Messrs. Stevenson, and it possesses many ingenious and novel features to this day, while it was the pioneer of modern electric lighting systems as applied to lighthouse engineering. Although marked improvements have been effected in electrical engineering and science since its completion, it still ranks as one of, if not the, most powerful electric lighthouses in the world. The beacon is a prominent edifice on the summit of the island. The building is somewhat pretentious, rather resembling a battlemented castle than a warning for the mariner, the optical apparatus being housed in a square turret rising above the main part of the building. When electric illumination was adopted, the existing accommodation for three keepers was found insufficient, while a generating-station was necessary. Instead of extending the old building to accommodate the additional facilities, a second station was built at a low-lying point near the sea-level. This contains the engine and generating house, together with quarters for three more keepers and their families. This decision was made because at this point, 810 feet away and 175 feet below the lighthouse, there is a small fresh-water loch whence water is available for the boilers and condensers, while a marked saving in the cost of handling fuel as well as of the haulage of the building materials and machinery was feasible. The current is led from the power-house to the lighthouse by means of overhead copper conductors.

Some difficulty was experienced in securing electrical apparatus suited to the searching exigencies of lighthouse engineering, and the designers made one stipulation, which at first appeared to baffle fulfilment. This was the placing of the positive carbon below, instead of above, so as to enable the strongest light to be thrown upwards, to be dealt with by the upper part of the dioptric apparatus, whereby it could be used more effectively. One firm struggled with this problem for many months, and then was compelled to admit defeat, as time for further experimenting was unavailable, since the lighthouse was almost completed. Accordingly, the designing engineers had to revise their plans, and had to acquire alternate-current De Meriten machines, which, although more expensive and less powerful than those originally intended, yet were, and are still, wonderfully steady in working, while they had previously proved highly efficient for lighthouse service. Two generators of this description were secured, and they constituted the largest that had been made up to this period, each plant weighing about 4½ tons. Each machine has sixty permanent magnets, disposed in five sets of twelve each, while each magnet is made up of eight steel plates. The armature makes 600 revolutions per minute, and develops an average current of 220 ampères.

The installation is so designed that one-, two-, three-, or four-fifths, or the whole, of the current can be sent from each unit to the distributor for transmission to the lantern, or the two machines may be coupled and the full current from both utilized. The current is conveyed to the lantern through copper rods 1 inch in diameter, and this was the first occasion on which such conductors were utilized for lighthouse work. There are three lamps of a modified Serrin-Berjot type, one being in service, and the other two held in reserve. By means of a by-pass, or shunt, a large percentage of the current is sent direct to the lower carbon, only a sufficient amount to regulate the carbons being sent through the lamp. The carbons used are about 1½ inches in diameter, though two-inch carbons can be employed when both machines are running, and the rate of consumption is 1¼ inches, or, including waste, 2 inches, per hour. The power of the arc thus obtained with the current fed from one generator is between 12,000 and 16,000 candles. In the event of the electric installation breaking down, a three-wick paraffin oil lamp is kept in reserve, ready for instant service, and it can be brought into use within three minutes.