The Bell Rock—The good Abbot of Arberbrothok—Ralph the Rover—Rennie’s grand Lighthouse—Perils of the Work—Thirty-two Men apparently doomed to Destruction—A New Form of Outward Construction—Its successful Completion—The Skerryvore Lighthouse and Alan Stevenson—Novel Barracks on the Rock—Swept Away in a Storm—The Unshapely Seal and Unfortunate Cod—Half-starved Workmen—Out of Tobacco—Difficulties of Landing the Stones—Visit of M. de Quatrefages to Héhaux—Description of the Lighthouse Exterior—How it Rocks—Practice versus Theory—The Interior—A Parisian Apartment at Sea.
Some eleven miles eastward from the mainland of Scotland, near the entrances to the Firths of Forth and Tay, lies an extensive ledge of very dangerous rocks, nearly two miles in length. This sunken reef was a source of much peril to the unfortunate sailors [pg 173]driven too near its nearly hidden dangers, and early in the fourteenth century the Abbot of Arbroath, or Arberbrothok, caused a bell to be placed upon the principal rock, so that—
Southey has, in his ballad of “The Inchcape Rock,” immortalised the tradition56 that a notorious pirate cut the bell from the rock—
And so the rover sailed away, and grew rich with plundered store, till at length he thought of Scotland once again, and turned his vessel’s head for home. He approached her coasts in haze and fog, and knew he could not be far from the rocky shore.
Nothing was done to replace the bell or set a beacon on the reef until the beginning of the present century, when, after many plans had been discussed, John Rennie was ordered by the Board of Commissioners to examine the site and report on the subject generally. He recommended a substantial stone lighthouse, similar to that on the Eddystone. Although the Inchcape Rock was not so long uncovered by the tide as the former, after a few courses had been laid, there would be no greater delay in completing the building. The Commissioners obtained from Parliament the requisite powers in 1806; Rennie was appointed engineer, with Robert Stevenson as assistant engineer.
The whole of the year 1807 was occupied in constructing the necessary vessels for conveying the stones, and in erecting suitable machinery and building shops at Arbroath, which was fixed upon as the most convenient point on the coast for carrying on the land operations. Some progress was made on the rock itself, where a smith’s forge was erected and a temporary beacon raised, while a floating light, fitted up on an old fishing-boat, was anchored near the reef until the lighthouse could be completed. During the short [pg 174]period in which the rocks were uncovered or unexposed to the fury of the waves, some progress was made with the excavations for the foundations. The dangerous nature of the employment may be illustrated by the following brief account of an accident which happened to the workmen on the 2nd of September, before the excavation for the first course of stones had been completed. An additional number of masons had that morning come off from Arbroath in the tender named the Smeaton, in honour of the engineer of the Eddystone, and had landed them safely on the rock. The vessel rode off at some distance. The wind rising, the men began to be uneasy as to the security of the Smeaton’s cables, and a party went off in a boat to examine whether she was secure, but before they could reach the vessel’s side they found she had already gone adrift, leaving the greater part of the men upon the reef in the face of a rising tide.
By the time the Smeaton’s crew had got her mainsail set, and made a tack towards their companions, she had drifted about three miles to leeward, with both wind and tide against her, and it was clear that she could not possibly make the rock until long after it had been completely covered. There were thirty-two men in all on the rock, provided with but two boats, capable of carrying only twenty-four persons in fine weather. Mr. Stevenson seems to have behaved with great coolness and presence of mind; though he afterwards confessed that of the two feelings of hope and despair the latter largely predominated. Fully persuaded of the perils of the situation, he kept his fears to himself, and allowed the men to continue their occupations of boring and excavating.
“After working for about three hours, the water began to rise along the lower parts of the foundations, and the men were compelled to desist. The forge-fire became extinguished; the smith ceased from hammering at the anvil, and the masons from hewing and boring; and when they took up their tools to depart, and looked around, their vessel was not to be seen, and the third of their boats had gone after the Smeaton, which was drifting away in the distance! Not a word was uttered, but the danger of their position was comprehended by all. They looked towards their master in silence; but the anxiety which had been growing in his mind for some time had now become so intense that he was speechless. When he attempted to speak, he was so parched that his tongue refused utterance. Turning to one of the pools on the rock, he lapped a little water, which gave him relief, though it was salt; but what was his happiness when, on raising his head, some one called out, ‘A boat! a boat!’ and sure enough a large boat was seen through the surge making for them. She proved to be the Bell Rock pilot-boat, which had come off from Arbroath with letters, and her timely arrival doubtless saved the lives of the greater part of the workmen. They were all taken off and landed in safety, though completely drenched and exhausted.”
Rennie, accompanied by one of his sons, visited the rock on the 5th of October, 1807, the day before the works were suspended for the winter. They came off from Arbroath, and stayed on board the lighthouse-yacht all night, where Stevenson met him, and has recorded the delightful conversations held on general and professional matters. On the following morning Rennie landed, amidst great éclat and a display of all the available colours, to inspect the progress made. The whole party, workmen and all, returned to shore for the season that day.
[pg 175]The preparation of the stone blocks occupied next winter, and by the spring large numbers were ready and were floated off. In May, 1808, the excavations on the rock were continued, and on the 10th of July the first stone was laid with considerable ceremony. By the last week of November three courses of masonry had been laid. By the end of 1809 the tower had been built to a height of thirty feet, and was almost secure from the fury of the waves. “In his report to the commissioners he stated that he found that the form of slope which he had adopted for the base of the tower, as well as the curve of the building, fully answered his expectations—that they presented comparatively small obstructions to the roll of the waves, which played round the column with ease.” The curve of this tower at the base is much greater than that of the Eddystone. The Bell Rock Lighthouse was completed by the end of 1810, and the light was regularly exhibited after the 1st of February, 1811. Counting to the top of the lantern, it is 127 feet high. It may here be remarked that in many works the credit of designing and building this lighthouse has been given to Robert Stevenson, the resident engineer. Rennie, however, has the only rightful claim to be so considered; he acted throughout as chief engineer, furnished the design down to the pettiest details, settled the kind of stone and other materials to be used, down even to the mortar and mode of mixing it.
Another work of great labour and difficulty was the erection of a lighthouse on the Skerryvore Rocks, which lie twelve miles W.S.W. of the Isle of Tyree in Argyllshire, and were formerly the scene of numerous wrecks. The operations were commenced in 1838, the architect being Alan Stevenson, son of the Robert Stevenson who was employed on the Bell Rock Lighthouse. The engineer gave the world a succinct account57 of the difficulties, dangers, and successful issue of the undertaking.
The actual construction of the lighthouse had no very remarkable points of difference with the works of Smeaton or Rennie. Stevenson built a rather novel structure on the rock as a temporary barrack for the workmen. It consisted of a wooden tower perched upon a triangular framework, under which was an open gallery, the floor of which was removed at the end of each season, so as to allow free space for the passage of the sea during the storms of winter, but on which, during summer, they kept the stock of coals, the tool-chest, the beef and beer casks, and other smaller material, which they could not, even at that season of the year, leave on the rock itself. Next came the kitchen and provision-store, a six-sided apartment about twelve feet in diameter, and somewhat more than seven feet high, in which small space—curtailed as it was by the seven beams which passed through it—stood a caboose, capable of cooking for forty men, and various cupboards and lockers lined with tin, for holding biscuits, meal and flour, &c. The next storey held two apartments: one for Mr. Stevenson, in which he had his hammock, desk, chair and table, books and instruments. The top storey was surmounted by a pyramidal roof, and was lined with four tiers of berths, capable of accommodating thirty people. The framework was erected on a part of the rock as far removed as possible from the proposed foundation of the lighthouse tower; but in a great gale which occurred on the 3rd of November it was entirely destroyed and swept from the rock, nothing remaining to point out its site but a [pg 176]few broken and twisted iron stanchions, and attached to one of them a piece of a beam, so shaken and rent by dashing against the rock as literally to resemble a bunch of laths. Thus did one night obliterate the traces of a season’s toil, and blast the hopes which the workmen fondly cherished of a stable dwelling on the rock, and of refuge from the miseries of sea-sickness, which the experience of the season had taught many of them to dread more than death itself. A more successful attempt was subsequently made, and the second erection braved the storm for several years after the works were finished. “Perched forty feet above the wave-beaten rock,” says Stevenson, “in this singular abode, the writer of this little volume58 has spent many a weary day and night at those times when the sea prevented any one going down to the rock, anxiously looking for supplies from the shore, and earnestly longing for a change of weather favourable to the re-commencement of the works. For miles around nothing could be seen but white foaming breakers, and nothing heard but howling winds and lashing seas. At such seasons most of our time was spent in bed; for there alone we had effectual shelter from the winds and the spray, which searched every cranny in the walls of the barrack. Our slumbers, too, were at times fearfully interrupted by the sudden pouring of the sea over the roof, the rocking of the house on its pillars, and the spirting of water through the seams of the doors and windows: symptoms which, to one suddenly aroused from sound sleep, recalled the appalling fate of the former barrack, which had been engulfed in the foam not twenty yards from our dwelling, and for a moment seemed to summon us to a similar fate. On two occasions, in particular, [pg 177]those sensations were so vivid as to cause almost every one to spring out of bed; and some of the men flew from the barrack by a temporary gangway to the more stable but less comfortable shelter afforded by the bare wall of the lighthouse tower, then unfinished, where they spent the remainder of the night in the darkness and the cold.”
Yet life on the Skerryvore was by no means destitute of its peculiar pleasures. The grandeur of the ocean’s rage, the deep murmur of the waves, the hoarse cry of the sea-birds, were varied by peaceful hours, when the sea was glassy and the deep blue vault of heaven was studded with a thousand stars. “Among the many wonders of the ‘great deep,’ ” says Stevenson, “which we witnessed at the Skerryvore, not the least is the agility and power displayed by the unshapely seal. I have often seen half a dozen of these animals round the rock, playing on the surface or riding on the crests of curling waves, come so close as to permit us to see their eyes and head, and lead us to expect that they would be thrown high and dry at the foot of the tower; when suddenly they performed a somersault within a few feet of the rock, and diving into the flaky and wreathing foam, disappeared, and as suddenly re-appeared a hundred yards off, uttering a strange low cry.”
On one occasion the tender could not come off to the poor people on the rock for seven weeks. The seamen passed a most dreary time. Their provisions and fuel were short; their clothes were worn to rags; and, what was to them of more importance still, they were out of tobacco!
One of the great difficulties experienced was landing the stones on the rock from the lighters, which, towed out by a steamer, were cast off as near the landing-place as possible and then towed in by boats. The landing service throughout the whole progress of the works was one of danger and anxiety, and many narrow escapes were made. On many occasions the men who steered the lighters ran great risks, and it was often found necessary to lash them to the rails, to prevent them being thrown overboard by the sudden bounds of the vessels, or being carried away by the weight of water which swept their decks as they were towed through a heavy sea. Sometimes they were forced, owing to the heavy seas which threatened to throw the vessels on the top of the rock, to draw out the lighters from the wharf without landing a single stone, after they had been towed through a stormy passage of thirteen miles. One day, during the very best part of the season, so sudden were the jerks of the vessel before the sea, that eight large warps, or cables, were snapped like threads, and the lighter was carried violently before a crested wave which rolled unexpectedly upon her. Those who stood on deck were thrown flat on their faces, and imagined that the vessel had been laid high and dry on the top of the rock. Yet, in spite of the short season and great difficulties of the work, no less than 120 lighters were towed out and discharged in the summer and autumn of 1841. During the progress of building the lighthouse, cranes and other materials were swept away by the waves, and daily risks were run in blasting the splintery gneiss, or by the falling of heavy bodies from the tower on the narrow space below, to which so many persons were necessarily confined. Yet no loss of life or limb occurred; and “our remarkable preservation was viewed,” says Stevenson, “as in a peculiar manner the gracious work of Him by whom ‘the very hairs of our head are all numbered.’ ”
The light was first exhibited on the 1st of February, 1844. It is a revolving apparatus, [pg 178]and the light appears at its brightest state once in every minute. The lantern is no less than 150 feet above the sea, and its flashes may be seen from the deck of a vessel eighteen miles off. It is frequently seen from the high land of Barra, distant thirty-eight miles. The mass of stonework is double that of the Bell Rock Lighthouse, and five times that of the Eddystone; it measures 58,580 cubic feet. The Skerryvore Light-tower was erected at a cost of £86,977 17s. 7d.
The eminent French naturalist, M. de Quatrefages, has given us an admirable description59 of a visit paid by him to the lighthouse of Héhaux, on a rock near the Isles of Bréhat, [pg 179]off the coast of Brittany. He says, after some very beautiful remarks on the contemplation of nature, and its alleviation of the worst heart-sorrows: “Twilight often surprised me in the midst of my reveries, and often, too, the shades of night fell around me while I lay stretched beneath the star-bespangled deep azure canopy of heaven. I could then see another star shining in the far distance, which had been lighted by the hand of man. From the position I had chosen I could recognise the beacon-towers of Héhaux, of which the seamen of the islands had spoken to me with the liveliest expressions of enthusiasm, and which I had frequently watched by day as it stood out like a black line drawn along the whitish background of the sky. I would not leave Bréhat without visiting it. A few slight services had secured me the good-will of the officers of customs, who willingly consented to take me to Héhaux. Accordingly, one splendid day in October we left the harbour of La Corderie in a pinnace, manned by six sturdy seamen. The weather was splendid; not a cloud obscured the sky, which was reflected on the mirror-like surface of the ocean, whose depths it seemed to double. Impelled by the combined action of a light wind, which swelled out two small square sails, and of the rapid current imparted to the waters of Kerpont by the force of the tide, our pinnace shot across the waves as a sledge glides over the snow. Sometimes, indeed, we passed through a whirling eddy, which shook every part of our frail craft, and betrayed the vicinity of some submarine rock; but we soon regained the unruffled sea, and without having taken cognisance of the rapid rate at which we were moving, we saw Bréhat sink below the distant horizon behind us, whilst rock after rock and islet after islet seemed at every moment to emerge from the waves towards which we were advancing.... The nearer we drew to Héhaux the taller seemed the beacon-tower, which stood forth from the tower, with its lofty granite column and glass lantern, protected by that magical rod which is able to attract and safely conduct to earth the destructive force of the thunderbolt. We landed, and at once began our inspection of this colossal block, which has been upreared by the hand of man on the Epées de Tréguier, which, once the dread of the seaman, have become his protecting guides through the storms and darkness of night.
“The Héhaux Lighthouse would be regarded as a most remarkable monument even in our principal towns, but standing, as it does, alone in the midst of the ocean, it acquires by its very isolation a character of severe grandeur, which impresses the mind most powerfully. Figure to yourself a wall of granite, where the current and the storm do not even permit the hardiest ferns to take root, with here and there a twisted and deeply wave-worn mass projecting beyond the rest of the rocky ledge. It is here that the architect has laid the foundation of the tower. The base, which is of a conical form, is surmounted by a circular gallery. The lower portion curves gracefully outwards, spreading over the ground like the root of some colossal marine plant springing up from the foundation stones, which have been inserted far within the rock. On this base, which measures about twenty yards across, rises a column twenty-six feet in diameter, surmounted by a second gallery, whose supports and stone balustrades call to mind the portcullis and battlements of some feudal donjon. From the summit to the base this part of the edifice is composed of large blocks of whitish granite, arranged in regular strata, and carefully dove-tailed into one another. As far as a third of the height of the building the rows of stones [pg 180]are bound together by granite joggles, which at the same time penetrate into the two superposed stones. The stones have been cut and arranged with such precision that there has been hardly any reason for using cement, which has only been employed in filling up a few imperceptible voids: and hence the lighthouse, from the base to the summit, seems to form one solid block, which is more homogeneous and probably more compact than the rocks which support it. The platform which crowns this magnificent column, at an elevation of more than 140 feet above high tide watermark, is surmounted by a stone cupola, at once solid and graceful, supported by pillars which are separated by large panes of glass. It is within this frame of glass that the beacon is lighted, which may be distinctly seen from every direction at a distance of twenty-seven miles.
“At low tide the sea leaves a space of several hundred square yards uncovered round the base of the edifice; at high tide it entirely surrounds it. It is then that the tower of Héhaux rises in its solemn isolation from the midst of the waves, as if it were a standard of defiance upraised by the genius of man against the demon of the tempest. At times one might almost fancy that the heavens and the sea, conscious of the outrage offered to them, were leagued together against the enemy, which seems to brave them by its imperturbability. The north-west wind roars round the tower, darkening its thick glass windows with torrents of rain and drifts of snow and hail. These impetuous blasts bear along with them from the far-spread ocean colossal waves, whose crests not unfrequently reach the first gallery, but these fluid masses slide away from the round and polished surfaces of the granite, which leave them no points of adhesion, and darting their long lines of foam above the cupola, they break with thundering roar against the rocks of Stallio-Bras or the boulders of Sillon. The tower supports these terrific assaults without injury, although it bends, as if in homage, before the might of its foes. I was assured by the keepers that during a violent storm the oil in the lamps of the highest rooms presents a variation of level exceeding an inch, which would lead us to assume that the summit of the tower describes an arc of about a yard in extent. This very flexibility seems, however, in itself a proof of durability. At all events, we meet with similar conditions in several monuments, which for ages have braved the inclemency of recurring seasons. The spire of Strasburg Cathedral, in particular, bends its long ogives and slender pinnacles beneath the force of the winds, while the cross on its summit oscillates at an elevation of more than 450 feet above the ground.
“To construct a monument on these rocks, which seemed the very focus of all the storms which raged on that part of our coasts, was like building an edifice in the open sea. Such a project must, indeed, have appeared at first sight almost impracticable. After their third season of labour, the workmen completed the foundations of the tower and fixed the key-stone of the cupola. In vain did difficulties of every kind combine with the winds and waves to oppose the work; human industry has come forth victorious from the struggle, and although a thousand difficulties and dangers beset the labourers, no serious accident to them or their work troubled the joy of their triumph. Only on one occasion was science at fault. In order to facilitate the arrival of the stones, which had to be brought from a distance of several leagues, and cut at Bréhat, the skilful engineer who had furnished all the plans and superintended their execution wished to construct [pg 181]a wooden pier for the disembarkation of the stones at the spot where they were required. Several of the older seamen objected to the plan as impracticable, but M. Reynaud, who was not familiar with the sea, and who, moreover, was proud of having stemmed the current of rapid rivers, trusted to the stability of his massive piles, clamped together with iron and bronze. But he was soon compelled to admit his mistake. The first storm sufficed to scatter over the waters the whole of these ponderous and solid materials like so many pieces of straw. So a crane was attached to the summit of a rock, to which boats could be moored, and the materials for building were then drawn up to a railway which had been thrown over the precipice that separated this natural landing-place from the site of the tower.
“Now that we have admired the exterior of the lighthouse, follow me into the interior by the help of these steps, which have been formed by the insertion of bars of copper into the stone. Let us pause for a moment to admire the ponderous bronze doors which hermetically seal the entrance, before we plunge into those vaults which look as if they had been cut out of the solid rock. We are in the first storey, surrounded by stores of wood and ropes and workmen’s tools. Above, we perceive cases of zinc, which, we are told, contain oil to feed the lamps and water for the use of the men employed in the building. In the third storey is the kitchen, with its pantry and larder, on a level with the first gallery. We need not enter the three apartments appropriated to the use of the men, for, beyond being very simple and clean, there is nothing to record concerning them. But we have now reached the seventh storey, and we must rest for a few moments in the little octagonal saloon, set apart for the engineers, when they come to inspect the condition of the lighthouse. Here, in the midst of the ocean, more than a hundred feet above the level of the sea, you will find the comfort and almost the elegance of a Parisian apartment.
“Let us now return to the spiral staircase which has brought us thus far, and which will carry us at once to the portion of the edifice which is more particularly destined to fulfil the special purpose for which the tower is designed. The eighth storey contains vessels of oil, glasses, revolving lamps, some admirable instruments intended for meteorological observations, a thermometer, barometer, and chronometer. Here the spiral staircase terminates in a flattened arch, which supports a slender pillar, cut into steps, which are the only means of communication with the watch-tower above, in which the men take it by turns to keep guard every night. You will be surprised on looking round to perceive that this apartment is coated with different coloured marbles, which line the walls and vaulted roof, and even cover the floor. But this luxury, which may appear to you so much out of place, has been introduced from necessity. The apparatus for lighting the building enters the room through a circular aperture in the ceiling, and hence the most extreme cleanliness becomes necessary, which could alone be obtained by the aid of perfectly polished surfaces.”
The tenth and last flight of steps brings one beneath the cupola, and to the machinery by which a light of the first order is maintained.
Lighthouses on Sand—Literally screwed down—The Light on Maplin Sands—That of Port Fleetwood—Iron Lighthouses—The Lanterns themselves—Eddystone long Illuminated with Tallow Candles—Coal Fires—Revolution caused by the invention of the Argand Burner—Improvements in Reflectors—The Electric Light at Sea—Flashing and Revolving Lights—Coloured Lights—Their Advantages and Disadvantages—Lanterns obscured by Moths, Bees, and Birds.
The difficulties involved in constructing a lighthouse on solid rock have been shown, and it was at one time thought absolutely impossible to erect—with any prospect of permanent duration—one upon storm-exposed sands. Nous avons changé tout cela. It is no longer necessary to place floating lights in places of great danger, although for other reasons they are constantly used. One of the greatest modern triumphs of engineering is Mitchell’s screw-mooring apparatus. To describe it fully would necessitate several pages of technical matter. Suffice it to say that enormous cast-iron screws, having hollow cylindrical centres, through which wrought-iron spindles pass, are literally screwed down into the sand, or its substratum of other soil. One of the earliest experiments was made on the verge of the Maplin Sand, at the mouth of the Thames. Nine of the mooring-screws were inserted into the sand 21½ feet, one in the centre, the rest forming an octagon 42 feet in circumference, having standards or posts which stood 5 feet above the surface of the sand. A raft of timber was floated over the spot, and a capstan in its centre drove the screws to the required depth. This raft was afterwards sunk, by covering it with 200 tons of rough stone. Two years were allowed to elapse, at the termination of which time the whole mass was found firmly embedded, and then a lighthouse, raised on a strong open framework, was erected over this sub-structure. During these long preparations a very similar structure was commenced and finished at Port Fleetwood, on the River Wyre, near Lancaster.
The preparatory steps were similar to those already described. The foundation of the lighthouse was formed of seven screw-piles, six of them occupying the angles of a hexagon 46 feet in diameter, the seventh being in the centre. From each screw proceeds a pile 15 feet in length, having at the upper end another screw for securing a wooden column. These columns are of Baltic timber, the one in the centre being 56 feet, the others 46 feet in length, firmly secured with iron hoops and coated with pitch. The platform, upon which the house stands, is 27 feet in diameter, the house itself being 20 feet in diameter and 9 feet high. From the summit of the house rises a twelve-sided lantern, 10 feet in diameter and 8 feet high. Altogether the light is elevated about 46 feet above low-water level, and ranges over an horizon of eight miles. The light is of the dioptric kind—bright, steady, and uniform, and when the weather is too foggy to allow it to be seen, a bell is tolled by machinery, to give the needful warning.
At the period when screw-pile lighthouses were being thus successfully erected, other and most valuable suggestions were being made for the building of bronze and cast-iron lighthouses. The great advantage of iron over stone and other materials in those portions of the building not actually in contact with sea-water soon became apparent. Upon a [pg 183]given base a much larger internal capacity could be obtained; plates could be cast in large surfaces and with few joints, and a system of binding adopted which should ensure the perfect combination of every part. The comparatively small bulk and weight also of the component parts gave great facilities for the transport and rapid construction of such structures. The initial cast-iron lighthouse was designed by Mr. Gordon in 1840, and was cast and put together within three months from the date of the contract. It was then taken to pieces and shipped for Jamaica, on which island it now lights up Morant Point, a point of great danger. The Commissioners of the House of Assembly had applied to Mr. Gordon to supply a suitable lighthouse at the smallest possible cost, and in furnishing them with the structure of cast-iron he fulfilled their wishes admirably, the expense not exceeding one-third of the cost of a similar building in stone. This elegant lighthouse, the outline of which resembles that of the Celtic towers of Ireland, was exhibited to visitors while it stood complete in the contractor’s premises. The diameter of the tower is 18 feet 6 inches at the base, diminishing to 11 feet under the cap. The tower is formed of nine tiers of iron plates, each tier being 10 feet high and about three-quarters of an inch thick. At the base of the structure eleven plates are required to form the circumference, at the top nine plates; they are cast with a flange around their inner edges, and when put together these flanges form the joints, which are fastened together with nut-and-screw bolts and caulked with iron cement. The interior of the tower, to the height of 27 feet, was to be filled up with masonry and concrete of the weight of 300 tons; the remainder is divided into store-rooms and berths for the attendants. The tower is finished by an iron railing, within which rises the light-room, also of cast-iron, with windows of plate-glass. A copper roof and a short lightning-rod complete the whole. The Admiralty notice announced the exhibition of this light on Morant Point November 1st, 1842, and stated that the elevation of the light is 97 feet above the level of the sea, and that in clear weather it is visible at a distance of twenty-one miles. The light is of the revolving kind, consisting of fifteen Argand lamps and reflectors, five in each side of an equilateral triangle, and so placed as to produce a continuous light, but with periodical flashes. The tower is painted white, and the lower portion is coated with coal-tar to preserve it from rust. It rests on a granite base, and is also cased with granite near the foundation, the more certainly to prevent the action of the sea-water on the metal.
While the engineer had attained some of his greatest triumphs in the construction of lighthouses, the optician had not once directed his attention to the invention of a brilliant light, worthy to be placed upon the structure which proudly rose high above the fierce waves with the strength and solidity of a rock. During a period of forty years after the completion of the Eddystone tower by Smeaton, the lantern was illuminated by tallow candles stuck in hoops, just as a stand or booth is lighted at a country fair, and so lately as the year 1811 it was lighted with twenty-four wax candles. In 1812 the Lizard Light was maintained with coal fires; and in 1816, when the Isle of May Light, in the Firth of Forth, was taken possession of by the Commissioners of the Northern Lighthouses, a coal fire was exhibited in a chauffer—a description of light which had been exhibited for 181 years. In 1801 the light at Harwich, in addition to the coal fire, had a flat plate of [pg 184]rough brass on the landward side, to serve as a reflector. Such methods of lighting were of course very deficient in power, and did not enable the mariner to distinguish one light from another—a point which is often of as much importance as the brilliancy of the light itself. Prior to the invention of the Argand lamp (about 1784) the production of a strong and brilliant light from a single source was scarcely possible, and even such a lamp, by its unassisted powers, would not be of very great value in giving early notice to the mariner of his approach to the coast, which ought to be the primary object of a lighthouse. As the rays of a luminous body proceed in all directions in straight lines, it is obvious that in the case of a single lamp the mariner would derive benefit only from that small portion of light which proceeded from the centre of the flame to his eye. The other rays would proceed to other parts of the horizon, or escape upwards to the sky, or downwards to the earth, and thus be of no value to him. By increasing the number of burners a small portion of light from each burner would slightly increase the effective action, but by far the greater portion of the light produced would escape uselessly above and below the horizon and also at the back of each flame. Next, these defects were remedied, and the efficiency of the light greatly increased, by placing behind each lamp a reflector of such a form as to collect the rays that would otherwise be lost, and throw them forward to the horizon. The adoption of such a method has led to what is called the catoptric system of lights.
Alan Stevenson states that the earliest notice he has been able to find of the application of paraboloidal mirrors to lighthouses is in a work on “Practical Seamanship” (Liverpool, 1791), by Mr. William Hutchinson, who notices the erection of the four lights at Bidstone and Hoylake for the entrance of the Mersey, in 1763, and describes large paraboloidal moulds of wood lined with mirror glass and smaller ones of polished tin-plate, as in use in those lighthouses. In France M. Téulère, a Member of the Royal Corps of Engineers of Bridges and Roads, is regarded as the inventor of the catoptric system of lights. In a memoir dated 26th June, 1783, he is said to have proposed for the Cordouan Lighthouse a combination of paraboloidal reflectors with Argand lamps, arranged on a revolving frame, a plan which was actually carried into execution, under the direction of the Chevalier Borda.60 The plan was so successful that it was soon adopted in England by the Trinity House of London; and in Scotland the first work of the Northern Lights Board, in 1787, was to light a lantern on the Old Castle of Kinnaird Head, in Aberdeenshire, by means of parabolic reflectors and lamps. These reflectors were formed of facets of mirror-glass placed in hollow paraboloidal moulds of plaster. The more complicated arrangement of lenses placed round a centre in concentric circles is due to the great Fresnel, a practical man of science, whose abilities are acknowledged as fully in England as in France.
The oil used in the lighthouses of the United Kingdom has generally been sperm. Colza, the expressed oil of the wild cabbage (Brassica oleracea), was very generally used in France, and occasionally in Great Britain. Gas is used in a few places, where its application is easy. There can hardly be any doubt now, however, that the coming light will be the electric, since its steady production is becoming a matter of scientific certainty. As early as 1857 Professor Holmes submitted to the Trinity House a method of employing this light, which was submitted to Faraday, and approved. The Board then allowed a trial at the South Foreland Lighthouse. The light was first displayed on the 8th of December, 1858. In June, 1862, it was permanently fixed at Dungeness. In Faraday’s Report to the Trinity House, published in 1862, he says: “Arrangements were made on shore by which observations could be made at sea, about five miles off, on the relative light of the electric lamp and the metallic reflectors with their Argand oil-lamps, for either could be shown alone, or both together. At the given distance the eye could not separate the two lights, but by the telescope they were distinguishable. The combined effect was a glorious light up to five miles; then, if the electric light was extinguished, there was a great falling off in the effect, though, after a few moments’ rest to the eye, it was seen that the oil-lamps and reflectors were in their good and proper state. On the other hand, when the electric light was restored, the glory rose to its first high condition.... During the day-time I compared the intensity of the light with that of the sun, and both looked at through dark glasses. Its light was as bright as that of the sun, but the sun was not at its brightest.”
The number of lights on a well-frequented coast being considerable, it is of the utmost importance to arrange them so as to enable the mariner easily to distinguish [pg 186]them from each other. Catoptric lights admit of nine separate distinctions:—1, fixed; 2, revolving white; 3, revolving red and white; 4, revolving red with two whites; 5, revolving white with two reds; 6, flashing; 7, intermittent; 8, double fixed lights; 9, double revolving white lights. Mr. Stevenson thus defines their distinctive features:—“The first exhibits a steady and uniform appearance which is not subject to any change, and the reflectors used for it are of smaller dimensions than those employed in revolving lights. This is necessary in order to permit them to be ranged round the circular frame, with their axes inclined at such an angle as shall enable them to illuminate every point of the horizon. The revolving light is produced by the revolution of a frame with three or four sides, having reflectors of a larger size grouped on each side with their axes parallel, and as the revolution exhibits once in two minutes or once in a minute, as may be required, a light gradually increasing to full strength and in the same gradual manner decreasing to total darkness, its appearance is extremely well marked. The succession of red and white lights is produced by the revolution of a frame whose different sides present red and white lights, and these afford three separate distinctions, namely, alternate red and white, the succession of two white lights after one red, and the succession of two red lights after one white light. The flashing light is produced in the same manner as the revolving light; but, owing to a different construction of the frame, the reflectors on each of eight sides are arranged with their rims or faces in one vertical plane, and their axes in a line inclined to the perpendicular. A disposition of the mirrors, which, together with the greater quickness of the revolutions, which shows a flash once in five seconds of time, produces a very striking effect, totally different from that of a revolving light, and presenting the appearance of the flash alternately rising and sinking, the brightest and darkest periods being but momentary; this light is further characterised by a rapid succession of bright flashes, from which it gets its name. The intermittent light is distinguished by bursting suddenly into view and continuing steady for a short time, after which it is suddenly eclipsed for half a minute. Its striking appearance is produced by the perpendicular motion of circular shades in front of the reflectors, by which the light is alternately hid and displayed. This distinction, as well as that called the flashing light, is peculiar to the Scotch coast. The double lights (which are seldom used except where there is a necessity for a leading line, as a guide for taking some channel or avoiding some danger) are generally exhibited from two towers, one of which is higher than the other. At the Gulf of Man a striking variety has been introduced into the character of leading lights, by substituting for two fixed lights two lights which revolve in the same periods and exhibit their flashes at the same instant; and these lights are of course susceptible of the other variety enumerated above, that of two revolving red and white lights, or flashing lights, coming into view at equal intervals of time. The utility of all these distinctions is to be valued with reference to their property of at once striking the eye of an observer and being instantaneously obvious to strangers. The introduction of colour as a source of distinction is necessary in order to obtain a sufficient number of distinctions; but it is in itself an evil of no small magnitude, as the effect is produced by interposing coloured media between the burner and the observer’s eye, and much light is thus lost by the absorption of those rays which are held back in order to cause [pg 187]the appearance which is desired. Trial has been made of various colours, but red, blue, and green alone have been found useful, and the two latter only at distances so short as to render them altogether unfit for sea-lights. Owing to the depth of tint which is required to produce a marked effect, the red shades generally used absorb from four-sevenths to five-sixths of the whole light—an enormous loss, and sufficient to discourage the adoption of that mode of distinction in every situation where it can possibly be avoided. The red glass used in France absorbs only four-sevenths of the light, but its colour produces, as might be expected, a much less marked distinction to the seaman’s eye. In the lighthouses of Scotland a simple and convenient arrangement exists for colouring the lights, which consists in using chimneys of red glass, instead of placing large discs in front of the reflectors.”
The construction of the lantern is a point of importance; and one of the first order will cost about £1,260. On the level of the top of the lower glass a narrow gangway is usually built for the keeper to stand upon in order to clean the panes, an operation which in snowy weather may have to be frequently repeated during the night. At some of the lighthouses on the Mediterranean the lantern is at certain seasons so completely covered with moths as to obscure the light and to require the attendance of men with brooms. Mr. Tomlinson was informed by the keepers at the Eddystone that bees and other insects were much attracted by the light, and collected round the lantern in great numbers. Larks and other birds flew against it, and, becoming stunned with the blow, were picked up on the balcony and were cooked by the men for breakfast. The lantern is very liable to injury in high winds, or the glass may be broken by large sea-birds coming against it on a stormy night, or by small stones violently driven against it by the wind. Extra plates of glass are always kept to take the place of broken panes. The number of light-keepers employed varies, ranging from two to four, and in the latter case one is usually allowed to remain on shore, the men taking the privilege in turns. When the situation admits, it is usual to have the keeper’s rooms in a building outside the lighthouse to avoid dust, which is most injurious to the delicate apparatus of the light-room. Great cleanliness is enforced in all that belongs to a lighthouse, the reflectors and lenses being constantly burnished, polished, and cleansed.
And so we have traced the history and progress of lighthouses, and it is hard to believe that any great change can be advantageously made in their construction, though their mode of illumination will doubtless be greatly improved. As we have seen, the electric light was used practically in a lighthouse long before it was in the streets of the great metropolis, and not in a merely experimental way, but with the most successful results.
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