At this juncture an unexpected competitor appeared on the scene. One of the engineers engaged in the preparation of the Harkort designs severed his connection with that firm, and, securing the collaboration of two engineering colleagues, established a rival concern, which tendered for the contract. They would follow the same lines, but would complete it for £22,750, or $113,750, instead of £24,025, or $120,125, asked by the Duisburg firm. The lower price was accepted, the more readily since it included the foundations, whereas the Society Harkort set these down as an extra. Naturally, the society was somewhat chagrined at this turn of events, after all the trouble and care it had taken to discover the most satisfactory solution of the problem, but subsequently it had good reason not to regret its loss.
The new engineers set to work and during the winter of 1880–81 constructed a huge caisson, which was launched and on May 22 of the latter year started down the Weser in charge of tugs. Then came a whole string of accidents. One night the unwieldy fabric got adrift and drove its nose into a sandbank, where it settled down with the tide. The towing cables were attached once more, and after a great struggle the structure was extricated on the next high-tide, and resumed its journey. Reaching the site without further incident, it was lowered by admitting the water within the barrel. But this task being accomplished somewhat crudely, the water rushed in with such force that the caisson commenced to spin round like a top, as well as bobbing up and down like an angler’s float. It threatened to topple over and founder every moment, but, luckily keeping upright, finally touched bottom. Lowering was completed. Night having approached, workmen made themselves comfortable on the caisson, while the constructional steamer stood off and cast its anchor.
The men on the caisson, however, experienced one of the most sensational nights in their lives. As the tide rose, they found their novel home to be behaving somewhat curiously. It moved, and then heeled over. This was an alarming state of affairs, especially as the list gradually became worse and worse. They shouted frantically for help, but, a heavy fog having descended upon the shoal, their cries were absorbed by the white pall. At last the caisson careened over to such a degree that the men could not keep their feet, while the depressed edge was in danger of being submerged. The men crawled to the opposite or elevated side, and held on for their lives, expecting every moment that the structure would give a heave and roll over. It was a terribly anxious time for them, and at last, when the constructional steamer came alongside in the morning, they scuttled down the ropes from their perilous perch to the deck below, thankful for having escaped, as they thought, a certain watery grave.
The engineers spared no effort to save their work. They were harassed at every tide because the water rose above the depressed edge and flooded the interior. With all speed the wall at this point was increased in height, so as to prevent inundation. Then, stormy weather having cut away the sand under the elevated side, the structure gradually righted itself. When it had regained its vertical position, it was found that no serious damage had been done, but rather that the engineers had profited, inasmuch as the caisson had buried itself some 16 feet into the sand.
Winter was approaching, and so the engineers crowded on every man and effort possible, in order to get the structure sunk to the requisite level before work would have to be abandoned for the season. They departed from the engineer’s axiom, “Make haste slowly,” and paid the penalty. When the bad weather broke, compelling the return of all the workmen to shore, the fabric was left insecure. The lower part had been given its filling of concrete, but above a certain level the fabric depended only upon the iron shell of the cylinder. It was stiffened as much as possible with cross-timbers and bracing, but the elements soon made short work of this puny defence. The North Sea, in common with the other large stretches of water throughout the world, was swept by terrible storms that winter, and one morning, when the sea was scanned from shore through glasses, strange to say the caisson was nowhere to be seen. All sorts of rumours were circulated to account for its disappearance, among others being a sensational theory that the caisson, having reached swampy ground while being sunk, had simply dropped suddenly into the submarine quagmire, and had been swallowed up completely. But the divers, when they could get out to the site and could venture into the ocean depths, returned to the surface with a very different story. The waves had snapped off the top of the caisson at the upper level of the concrete within, and had carried it away. Thus ended summarily the first attempt to build a lighthouse upon the red sand at the entrance to the River Weser.
Photo by permission of the North German Lloyd S.S. Co.
THE ROTHERSAND LIGHTHOUSE.
This magnificent light marks a dangerous shoal in the estuary of the Weser. The masonry tower is built upon a massive concrete caisson driven deeply into the sand.
The project, however, was not abandoned. The Society Harkort was approached once more, and requested to undertake the work upon its own terms. The invitation was accepted, but the firm, realizing the abnormal risks incidental to the enterprise, revised their price, so as to provide for contingencies. It demanded a sum of £42,650, or $213,250, in return for which it undertook to supply a fully-equipped lighthouse less the illuminating apparatus. The terms were accepted, but the responsible authorities, having suffered a heavy loss from the first failure, decided to protect themselves against a similar disaster, so exacted a bond for £12,000, or $60,000, to be returned when the work should be completed and accepted by the Government. The Society Harkort, on its part, reserved the right to withdraw from the undertaking in the event of the caisson sharing the fate which overtook the first structure.