The experience at Conway was of great benefit to the gigantic undertaking at the Menai Strait. The floating of the first tube was to take place on the 19th of June, 1849, in the evening; but owing to some of the machinery having given way, the great event was put off to the next night. The shores were crowded with spectators. When the tube was finished it could be transferred to the pontoons; for the tubes had been built at high-water mark. When the pontoons were fairly afloat on this fateful evening, they were held and guided by leading strings of mighty strength. Stephenson himself directed in person, from a point of vantage at the roof of the tube. Thence he gave the signals which had been agreed upon, whilst a crew of sailors, directed by Captain Claxton, manned the strange barque. A pontoon is a light, buoyant boat, and the tube was supported on sets of these, their speed increasing terribly as they approached their place by the towers. The idea was, as related by Mr. Edwin Clark, Stephenson’s assistant, that they should strike a “butt” properly, underneath the Anglesey Tower, “on which, as upon a centre, the tube was to be veered round into its position across the opening. This position was determined by a twelve-inch line, which was to be paid out to a fixed mark from the Llanfair capstan. The coils of the rope unfortunately over-rode each other upon this capstan, so that it could not be paid out.” Destruction seemed imminent. The capstan was actually dragged from the platform, and the tube seemed likely to be swept away. Then Mr. Rolfe, the captain of the capstan, shouted to the spectators, and threw out a spare twelve-inch rope. Seizing this, the crowd, with right good-will, rushed it up the field, and clung tightly to it, checking the voyage of the mighty tube. It was brought to the “butt,” and duly turned round. A recess had been left in the masonry of the tower, and the end near the Britannia pier was drawn into it by means of a chain. The Anglesey end followed. Then the tide gradually sank, the pontoons sank with it, and the tube subsided also to a shelf which had been made at either end. The first stage was accomplished; the mighty tube was in position to be raised. Shouts of rejoicing burst from the sympathetic crowds, and the boom of cannon joined its congratulatory note at the grand success. But the further stages remained. At midnight the pontoons were all cleared away, and the huge, hollow beam hung silent over the surging water. It rested on the shelves or beds prepared for it at either end. The second great operation, of course, was to haul it up the towers to its permanent position. This was to be performed by hydraulic machinery of great power, and Mr. Stephenson’s instructions were to raise it a short distance at a time, and then build under it.