Chap. VIII.

BRITAIN.

509

one above the other. They pass over rollers on the English side of the river, and cast-ironbedded in the masonry on the other ; the rollers have axles resting on iron embedded inthe masonry, and the chains, instead of being formed of bars 15 feet long, are composed ofvery short links, so that they may work freely over the rollers. After the chains havetraversed the masonry of the piers, they are further strengthened by long links passing24 feet underground, and are attached to masses of cast-iron 6 feet long, 5 feet wide, 5inches thick in the middle, and 2^ inches at the edges; to these they are secured by strongoval bolts, and the masses of iron are loaded with stone to the level of the road ; the corre-sponding masses on the English side of the river are not buried as on the other, but are abovethe level of the foundation of the piers. They are placed nearly vertical, corresponding withthe strain of the chains. A horizontal arch, the stones of which are embedded in the rocks,keeps the iron plates in their right position.

Menai Bridge , over the strait which separates the Isle of Anglesea from the county ofCaernarvon ; erected by Mr. Telford.

The work was commenced in May, 1819, and the rock called Ynys-y-moch, which wasaccessible at low water, was, by blasting, brought to an even surface ; on this was laid thefoundation for the west main pier on the Anglesea side. A temporary causeway, on which

TRANSVERSE SECTION AND ELEVATION ON THE CAERNARVON SIDE.

was a railroad for sledges, drawn by horses, was made, at a considerable elevation abovethe level of high water, over the space between the Anglesea shore and the rock.

The tide through the strait runs with great velocity, and being now shut out, thecurrent in the centre of the channel is greatly increased in velocity. The rise at ordinaryspring tides is about 22 feet; it sometimes exceeds 30, and winds from the range ofmountains in the vicinity of Snowdon are frequently strong and violent; the breadth of theestuary at high water is 918, and at low' water 480 feet.

The first stone was laid upon the Ynys-y-moch rock on the 10th of August, 1819, andin the autumn of the same year the main pier on the Caernarvon side of the strait was com-menced ; the beach, being first excavated to the depth of 7 feet where the solid rock sustainsthe east main pier, a greater mass of masonry is given to the foundations of this pier than tothe other on the Ynys-y-moch rock.

The height of the main piers, from the level of high water springtides to the roadw’ay, is100 feet; from that of low water spring tide 121 feet; from thence to the top 53 feet.