Lightships and Lighthouses

by Frederick Arthur Ambrose Talbot

The external appearance of this interesting lighthouse is somewhat different from the general conception of such a building. Instead of being merely a circular top and lantern, there are three semicircular turret-like projections on the dwelling-room and lantern levels, which serve for directing and warning lights as well as for a lookout station.

The fickle character of the North Sea where it rolls over the Rothersand is reflected by an experience which befell the Harkort engineer and the superintendent of erection for the authorities, who wished to complete his duty of inspection. The finishing touches were being applied, a squad of twelve workmen being in the tower to continue the work during the winter. The early December day was fair and the sea smooth, as well as giving every indication of remaining quiescent for some hours. The superintendent had arranged to spend his Christmas holidays with some friends, and desired to complete his duty in good time, so that his sojourn might be free from care. The two started off in the steamer, and landed without effort. But while they were engaged in their work of inspection the wind and sea freshened, so that a boat could not be sent from the steamer to take them off. It was an amusing situation which was keenly enjoyed at Bremerhaven; but all would be right on the morrow, said everyone. But the next day the weather was worse, and continued so for day after day. When a fortnight had passed without it being possible to succour the weather-bound engineers, amusement gave way to anxiety, more especially as a signal was flying from the tower which conveyed the unwelcome intelligence that one of the workmen had fallen ill. The feelings of the superintendent may be imagined. He had visions of spending his Yuletide in a draughty, half-finished lighthouse tower, where comfort was conspicuous by its absence, and where seasonal fare such as he had been anticipating keenly was unknown. But on December 21 the constructional engineers, having grown impatient with the weather, sent out one of their boats, with instructions to bring everyone ashore at all hazards. The waves were running high and the wind was gusty, but the steamer anchored as near the lighthouse as she dared, and by means of her boats, which were in momentary danger of being swamped, brought off the two engineers as well as all the workmen except two. The latter remained behind as a guard, and, being given a good stock of seasonal provisions and other necessities, were left in their splendid isolation. The superintendent, after all, was able to enjoy his Christmas holidays.

The succeeding spring brought a resumption of toil, and by September the tower was completed except for the illuminating apparatus. One feature was observed during construction and had to receive attention. The free swing of the currents and tides, being obstructed by the tower, had commenced heavy erosion, big hollows being scooped out of the soft sea-bed around the caisson. As it was quite possible that in the course of time this scouring might imperil the safety of the building, protective works had to be undertaken. These were of an elaborate character, and comprised the sinking of mattresses, fashioned from brushwood, around the foundations, upon which were dumped boatloads of broken stone. This mattress had to be nearly 50 feet in width, and in some places about 15 feet in thickness. For this protective work alone some 176,550 cubic feet of brushwood, and 600 tons of block-stone to hold it down, were used. These measures, however, effectually overcame the danger of erosion.

On November 1, 1885, the light was shown for the first time, and the greatest peril at the entrance to the Weser was indicated far and wide by night and day. It was a magnificent achievement, carried through in the face of enormous difficulties, sensational incidents innumerable, and upon a foundation of disaster. The lighthouse is as firm as if it were anchored upon a solid granite rock, instead of having its roots thrust deep into treacherous shifting sand, and constitutes an imperishable monument to German engineering ability; while, all things considered, the cost was low, being only £43,400, or $217,000, in all. The light is electric, the power being supplied from a station on shore, and fed to the lighthouse through a submarine cable; the keepers are also in submarine telegraphic communication with the mainland.

When the United States set out to build a similar structure in the spacious Delaware Bay, they were confronted with a prospect just as forbidding, and a task in every way as difficult, as that offered in connection with the Rothersand. There is a dangerous shoal about twenty miles off the land, where the Atlantic beats with furious rage, and where vessels were apt to stick hard and fast. It was described as “Fourteen Foot Bank” by mariners, from the depth of the water flowing over the shoal, and this colloquialism has provided the name for the present guardian light. The open situation did not augur favourably for the completion of a lighthouse at this spot, but the American engineers were resolved to make the attempt. Accordingly, plans were prepared for a construction upon the caisson principle, which was the only method promising success.

The preliminary step was the fabrication of a caisson. The first part was more like a raft with sides. It was about 40 feet square, 5 feet thick, and with walls 7 feet deep. It was built of timber, the staves being 12 inches square, and upside down—that is, with the floor uppermost—on a building-slip, as if it were a ship, and was launched into the water upon similar lines. The sides and top were lined, so as to secure water-tightness. In the centre there was a circular space 5 feet in diameter to form the air-shaft.

As the structure was built upside down, the rim was brought to the lowermost position, and this formed the cutting edge, which was to be sunk into the sand. On this floating platform a circular iron cylinder was erected. This tube was 35 feet in diameter, and was built up in plates, 6 feet in width by 1½ inches thick. When three rings of iron were set up the cylinder was 18 feet in height. In order to sink it to a depth of 15½ feet into the water for towing purposes, it was charged with a layer of concrete, 9 inches in thickness, to serve as ballast, and in this condition the caisson weighed 400 tons.

This huge barrel was built at Lewes, Delaware, and when it was launched two powerful steam-tugs set out to drag it to the shoal, twenty miles away. As the tide rises and falls a matter of 6 feet in these waters, and the currents are somewhat wicked, the engineers displayed no undue haste. They waited for the first favourable opportunity, and seized it. But it took the two tugs some six hours to reach the site; an average speed of about three and a half miles per hour cannot be construed into fast travelling.

When the mighty caisson had been warped and nudged dead into position over the desired spot, water was admitted. With a gurgling and hissing the hulk sank slowly into the sea. At last a slight jolt, which quivered through the mass, signified that the structure was resting on the bottom. The engineers gave a sigh of relief, but the next instant changed it to a cry of dismay. The caisson began to heel over to one side. Was it going to capsize? That was the absorbing fear. It canted more and more, until at last it had a list of 12 degrees. It had not sunk vertically! There was less than 16 inches of water between the sea-level and the rim when the caisson first jarred against the sand, and if it careened over too far the water certainly would rush in, roll the whole tub over, and tumble it hither and thither over the sea-bed. The engineers watched that caisson as closely as a cat watches a mouse-hole. Presently it eased up, and then, as the tide rose some six hours later, it began to right itself. The engineers were relieved once more. The danger was over. But their self-satisfaction was soon upset as the tide began to ebb, because again the cylinder gradually fell over on its side. The cause of this strange behaviour flashed upon them. The surface of the sandbank was not level! The mass in sinking had touched bottom on the highest point of the shoal, and was trying to find its own level.

Without any further delay, the engineers decided upon an ingenious means of correcting this erratic and dangerous action. The tugs were despatched hurriedly to Lewes to bring out cargoes of broken stone, which had been delivered for the preparation of the concrete. While the steamers pursued their errand, the engineers fashioned large pockets on the elevated section of the structure, into which the stone upon its arrival was placed. Gradually but surely the caisson not only was corrected, but the weighted end was induced to settle into the sand, until the opposite free edge in its turn was resting upon the shoal.