Lightships and Lighthouses

by Frederick Arthur Ambrose Talbot

The details he had secured, though hastily prepared, were sufficient for the purpose. His report was considered and the character of the beacon decided. There was some discussion as to the most favourable situation for the light upon the rock, so a more detailed survey was demanded to settle this problem. This task was entrusted to an Englishman, Mr. John R. Trewavas, who was familiar with work under such conditions. He was a master-mason of Portland and had been engaged upon the construction of the Wolf Rock, one of the most notable and difficult works of its kind in the history of lighthouse engineering.

He pushed off to the rock on September 18, 1879, in a surf-boat, only to find the usual state of things prevailing. The boat was run in, and, emulating the first engineer’s feat, he cleared the water and landed on the steep, rocky slope; but it was wet and slippery, and his feet played him false. He stumbled, and stooped to regain his balance, but just then a roller curled in, snatched him up and threw him into the whirlpool of currents. Life-lines were thrown, and the surf-boat struggled desperately to get near him, but he was dragged down by the undertow and never seen again. This fatality scared his companions, who returned hastily to the mainland. The recital of their dramatic story stirred the public to such a pitch that the authorities were frantically urged to abandon the project of lighting the Tillamook.

Mr. David Stevenson related to me an exciting twenty minutes which befell him and his brother while surveying a rock off the west coast of Scotland. They had been waiting patiently for a favourable moment to effect a landing, and when at last it appeared they drew in and clambered ashore. But they could not advance another inch. The rock was jagged and broken, while its surface was as slippery as ice owing to a thick covering of slimy seaweed whereon boots could not possibly secure a hold. Having gained the rock with so much difficulty, they were not going away empty-handed. As they could not stand in their boots, they promptly removed them, and, taking their line and levels, picked their way gingerly over the jagged, slippery surface in their stockinged feet. Movement certainly was exceedingly uncomfortable, because their toes displayed an uncanny readiness to find every needle-point on the islet; but the wool of their footwear enabled them to obtain a firm grip upon the treacherous surface, without the risk of being upset and having a limb battered or broken in the process. Twenty minutes were spent in making investigations under these disconcerting conditions, but the time was adequate to provide all the details required. When they had completed the survey and had regained their boat—a matter of no little difficulty in the circumstances—their feet bore sad traces of the ordeal through which they had passed. However, their one concern was the completion of the survey; that had been made successfully and was well worth the toll exacted in the form of physical discomfort.

THE ALCATRAZ LIGHTHOUSE UNDER CONSTRUCTION.

THE ALCATRAZ LIGHTHOUSE COMPLETED.

This tower off the Californian coast is one of the latest works of the American Lighthouse Department. It has a range of 21 miles.

As a rule, on a wave-swept rock which only shows itself at short intervals during the day, the preparation of the foundations is not an exacting task. A little paring with chisels and dynamite may be requisite here and there, but invariably the engineer takes the exposed surface as the basis for his work. The sea has eaten away all the soft, friable material in its ceaseless erosion, leaving an excellent foundation to which the superstructure can be keyed to become as solid as the rock itself.

When the beacon is to be erected upon a sandy bottom, the engineer’s work becomes more baffling, as he is compelled to carry his underwater work down to a point where a stable foundation may be secured. When the Leasowe lighthouse was built on the sandy Wirral shore, the builders were puzzled by the lack of a suitable foundation for the masonry tower. An ingenious way out of the difficulty was effected. In the vicinity an incoming ship, laden with a cargo of cotton, had gone ashore and had become a total wreck. The cotton was useless for its intended purpose, so the bales were salvaged and dumped into the sand at the point where the lighthouse was to be erected. The fleecy mass settled into the sand, and under compression became as solid as a rock, while its permanency was assured by its complete submersion. The stability of this strange foundation may be gathered from the fact that the tower erected thereon stood, and shed its welcome light regularly every night, for about a century and a half, only being extinguished two or three years ago as it was no longer required.

In the Old World, and, indeed, in the great majority of instances, the lighthouse is what is described as a “monolithic structure,” being built of courses of masonry, the blocks of which are dovetailed together not only laterally, but also perpendicularly, so that, when completed, the tower comprises a solid mass with each stone jointed to its fellow on four or five of its six sides. This method was first tried in connection with the Hanois lighthouse, off the Guernsey coast, and was found so successful that it has been adopted universally in all lighthouses which are exposed to the action of the waves.

The upper face and one end of each block are provided with projections, while the lower face and the other end are given indentations. Thus, when the block is set in position, the projections fit into corresponding indentations in the adjacent blocks, while the indentations receive the projections from two other neighbouring pieces. The whole is locked together by the aid of hydraulic cement. Consequently the waves, or any other agency, cannot possibly dislodge a stone without breaking the dovetails or smashing the stone itself. For the bottom layer, of course, the surface of the rock is pared away sufficiently to receive the stone, which is bedded in cement adhering to both the rock and the superimposed block. A hole is then drilled through the latter deep into the rock beneath, into which a steel rod or bolt is driven well home, and the hole is sealed up with cement forced in under such pressure as to penetrate every interstice and crevice.