When the caisson was completed on shore and sent into the water, it was an impressive-looking monster. The shell itself weighed 245½ tons, and with the various accessories aboard the weight was brought up to some 335 tons. It then had to be loaded down to the required depth for towing, for which purpose ballast in the form of pig-iron, concrete, and bricks, to the extent of another 245 tons, was stowed aboard, while delicate precautions were taken to maintain stability. The combined efforts of 120 men, working day and night for 127 days, were required to erect this caisson, and on April 1, 1883, it was ready for its transportation to the site.
The towing operation was extremely difficult, and the voyage out was full of exciting incident. It was possible to advance only on the ebb-tide, and the towing cables, 5 inches in diameter, were specially manufactured for the operation. Two of the most powerful tugs owned by the North German Lloyd Steamship Company were requisitioned, three other steamers engaged in the conveyance of requirements between tower and shore accompanying the procession. Although the engineers were ready, the weather, with aggravating persistence, refused to clear sufficiently to produce the smooth sea and calm demanded for the safe journey of the ungainly craft. Day after day slipped by, with eighty men on the alert, and with fires banked and steam raised on the vessels, ready to weigh anchor at the first favourable moment. Fifty-five days passed before the weather bureau recommended that the conditions were suitable. Under the foregoing circumstances the expense of this delay may be realized.
[Illustration: THE FOURTEEN-FOOT BANK LIGHTHOUSE, BUILT ON SAND.
The erection of this structure constitutes a brilliant achievement in United States lighthouse engineering.]
Directly the intimation was conveyed that the tow could be attempted, there was a scene of indescribable activity and bustle in the Bremerhaven dock, where the caisson was moored. Full steam was raised on the tugs, and at half-past three in the morning of May 26 the mighty steel barrel moved out of the dock. The towing ropes were hitched on, and very slowly the “Colossus,” as the caisson was named, moved down the harbour, accompanied by the whole fleet of nine vessels engaged in construction work, so that the procession was imposing. It dropped down the river without incident, when, the tide turning, anchor was cast, and all was made fast until another advance could be made at four o’clock in the afternoon. But the rising tide was stronger than had been anticipated, and trouble was soon encountered. The caisson, pressed by the current, dragged and strained at the two tugs by which she was being towed, causing them to slip their anchors. It was an anxious moment. The two vessels could not hold the “Colossus”; in fact, they were being towed backwards by it. Hurriedly another tug was called up, and helped in the effort; but although the three steamers put on full steam ahead, they failed to keep the mass in check. Another tug was signalled, and then, under the combined effort of 350 horse-power, driving for all it was worth against the current, the four vessels mastered the swing of the scurrying water, and had the “Colossus” under control.