n the 10th April, 1846; and on the 12th May following that of the Conway
Bridge was laid. Suitable platforms and workshops were also erected for
proceeding with the punching, fitting, and riveting of the tubes; and
when these operations were in full progress, the neighbourhood of the
Conway and Britannia Bridges presented scenes of extraordinary bustle and
industry. About 1500 men were employed on the Britannia Bridge alone,
and they mostly lived upon the ground in wooden cottages erected for the
occasion. The iron plates were brought in ship-loads from Liverpool,
Anglesey marble from Penmon, and red sandstone from Runcorn, in Cheshire,
as wind and tide, and shipping and convenience, might determine. There
was an unremitting clank of hammers, grinding of machinery, and blasting
of rock, going on from morning till night. In fitting the Britannia
tubes together, not less than 2,000,000 of bolts were riveted, weighing
some 900 tons.

The Britannia Bridge consists of two independent continuous tubular
beams, each 1511 feet in length, and each weighing 4680 tons, independent
of the cast-iron frames inserted at their bearings on the masonry of the
towers. These immense beams are supported at five places, namely, on the
abutments and on three towers, the central of which is known as the Great
Britannia Tower, 230 feet high, built on a rock in the middle of the
Strait. The side towers are 18 feet less in height than the central one,
and the abutment 35 feet lower than the side towers. The design of the
masonry is such as to accord with the form of the tubes, being somewhat
of an Egyptian character, massive and gigantic rather than beautiful, but
bearing the unmistakable impress of power.

The bridge has four spans,--two of 460 feet over the water, and two of
230 feet over the land. The weight of the larger spans, at the points
where the tubes repose on the masonry, is not less than 1587 tons. On
the centre tower the tubes rest solid; but on the land towers and
abutments they lie on roller-beds, so as to allow of expansion and
contraction. The road within each tube is 15 feet wide, and the height
varies from 23 feet at the ends to 30 feet at the centre. To give an
idea of the vast size of the tubes by comparison with other structures,
it may be mentioned that each length constituting the main spans is twice
as long as London Monument is high; and if it could be set on end in St.
Paul's Churchyard, it would reach near