Discoveries and Inventions of the Nineteenth Century

by Robert Routledge

Fig. 306.—Stevenson’s Holophotal Light.

It may be interesting to mention that the holophotal light at Baccalieu, in Newfoundland, is visible in clear weather from another point 40 miles distant. So long a range as this is seldom possible at sea, on account of the rounded form of the earth rendering it necessary to raise the light nearly 1,000 ft. above the water, if it is required to be visible at 40 miles’ distance. A shorter distance generally suffices for the requirements of the navigator; and therefore lighthouse towers rising from the water are seldom carried to a greater height than something between 100 ft. and 150 ft. A light elevated 100 ft. above the water would be seen from the deck of a vessel 14 miles distant, and from the masthead a much greater distance.

The optical apparatus of a lighthouse is protected by an outer metal framework glazed with thick plate glass. This framework is made of iron, or of gun-metal—the latter being preferred on account of the frequent painting which iron needs in order to preserve it from corrosion. The glass is carefully fitted into the framework, so as to avoid exposure to strains from the shocks and vibrations to which a lighthouse is exposed. The keepers are always provided with a store of panes of glass, ready for fitting into their places in case of accidents. Sometimes the glass is broken by large sea-birds dashing against it, and by pebbles which are thrown up by the waves, or driven by the wind against the panes. It is the interior of this lantern which forms the light-room already spoken of. Great pains have been bestowed on the proper ventilation of these light-rooms, as not only must the air have access to the lamp to supply the flame, but the carbonic acid which escapes from the chimney of the lamp must be promptly removed. Another serious inconvenience of an ill-ventilated light-room would be the condensation, in the inner surface of the plate glass, of the aqueous vapour, which is also a product of the combustion.

The lenses and circular prisms for lighthouses are usually made of crown glass, and are ground by fixing them on a large revolving iron table, on which they are bedded in plaster of Paris and cemented by pitch—great care being taken to place them in the exact position required, for only about one-eighth of an inch is allowed for grinding down to shape the glass as it comes from the moulds. Sand, emery, and finally rouge, are used with water for the grinding and polishing processes. The cost of the optical apparatus alone of a light of the first order, like that shown in Fig. [305], amounts to upwards of £1,500. The lenses and prisms are very carefully adjusted in their framework after this has been fixed, and no plan of testing the adjustment has been found more efficient than that of viewing the sea horizon through them from the position which the flame will occupy.

The men to whom the charge of a lighthouse is confided undertake a duty involving the gravest responsibilities, and demanding unremitting care. In those lighthouses where a number of reflectors are hung upon a revolving frame, the extinction of one lamp may not be a matter of much consequence; but where only one lamp is used, life and death depend upon its burning. To isolated lighthouses—such as those of Skerryvore and the Bell Rock—four keepers are appointed, and one of these is always on shore on leave, so that the men may be relieved at intervals; for it has been found that a residence in these lonely towers cannot be continued long together without bad effects. The duties of the lighthouse-keepers must be performed with the greatest regularity. The glasses of the light-room and the optical apparatus are carefully cleaned every morning; the lamps are supplied with oil, the wicks trimmed or renewed, the machinery oiled and adjusted, and everything prepared in readiness for the evening. At sunset the lamps are lighted, and one keeper takes his watch until midnight, when he is relieved by another, who maintains the vigil till sunrise, when the lamps are extinguished.

The expediency of the regulation appointing three men to be always at the lighthouse may be illustrated by an incident which occurred about the beginning of the present century at the lighthouse on the “Smalls,” a rock in the Bristol Channel. Two keepers held watch over the light on that rock, which for months together is sometimes cut off from all communication with the shore. At the time alluded to, after the weather had for two weeks prevented access to the lighthouse, it was rumoured among the seafaring men of the neighbouring ports that something was wrong at the “Smalls,” for a signal of distress had been observed; but the boats could not go within speaking distance, although many attempts were made to reach the rock. The relatives of the men became anxious, and night after night watched for the light. But the light never failed to appear at the proper hour. After four months came calmer weather, and then a boat brought to shore one lightkeeper alive, the other dead. What the former felt when he found his comrade to be dying in their dreadful isolation, or what his emotions were when he found himself there alone with the lifeless body, is not recorded. But the thought occurred to him that he must not commit the body to the waves, lest any suspicion of foul play might fall upon himself. He therefore contrived a sort of coffin for the dead man, and dragging it up to the gallery of the lighthouse, tied it there. Punctually and faithfully for four long months did he perform all the duties of his position, keeping watch from twilight till dawn in that lonely light-room, while his ghastly charge remained there within sight. But he came on shore strangely altered—a sad, silent, gloomy, worn man—so that even his intimate friends hardly knew him.

Here we close this brief account of the modern lighthouse, and of its beautiful appliances, by which Science “has given new securities to the mariner,” in addition to those with which she furnished him when she showed him the use of the compass, supplied him with the chronometer, and placed the sextant in his hands. How anxiously must the seaman who has been prevented by unfavourable skies from ascertaining his exact position, and has been trusting to the log and the compass to work his reckoning, scan the horizon for the first glimpse of the hospitable light beacon, which seems to say that the country he is approaching has been watching for his coming, and welcomes him to its shores.

Fig. 307.