51‘2 HISTORY OF ENGINEERING. Book 1.

111 sleepers; the number of trussed rods and king-posts which support the suspended roadis altogether 444.

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Fig. 517. PLAN OP CHAINS.

Iron frames to which the suspension chains are made fast. — Three oblique circular cavitieswere blasted in the solid rock on the Anglesea side, 6 feet in diameter, care being taken toleave a considerable portion of rock between the openings; through these the suspensionchains pass down an inclined plane of not less than 60 feet in length.

Fig. 518. SECTION THROUGH MAIN CHAINS AND ROADWAY.

At the lower ends of these inclined tunnels is another at right angles, which connects themtogether, through which the workmen passed to fix the iron plates into the natural rock,and a passage is left on the south-west side of the bridge, which communicates with thesesubterraneous chambers.

On the Caernarvonshire side there is the same arrangement, but the depth of earthwas considerable before the native rock could be arrived at, which occasions a differentlength to be given to the catenary on this side to that on the other.

The fiat cast-iron plates were let into the natural rock, and so firmly secured that they