“ Their sustaining power has been calculated at 2016 tons, while the whole weight of the suspended part of the bridge is only 489 tons. During a gale a slight oscillation is noticeable on the bridge itself and from the shore. The tubular bridge carries the London & North Western railway. Here the channel is about 1100 ft. wide, and divided in the middle by the Britannia Rock, bare at low water. The tide generally rises 20 ft., with great velocity. ”