Next in order of time is the far-famed Suspension Bridge erected by Telford over the Menai straits, for the purpose of carrying the Holyhead road, and thus connecting the Island of Anglesea with the mainland. This splendid work of art was completed in the year 1825, having been about six years in course of construction. It consists of one opening of' 570 feet span. The roadway being 100 feet above the level of high-water. The chains are formed of flat bars of iron 10 feet long, 31 inches deep, and nearly an inch thick. There are four rows of chains, each consisting of four tiers of bars ranged one above the other, so that, in all, there are 16 chains; to these, which are passed over the tops of two litfty towers placed at either side of the straits, and fastened at either shore into the solid rock, bars an inch square are attached, 5 feet apart, for the purpose of supporting the roadway, which has two carriage-ways, each 12 feet wide, and a central foot way 4 feet in width. The entire weight of this suspended platform, including the 16 chains, is about 2,186 tons. The Conway bridge, over the river Dee, is also a Suspension Bridge, and was built by Telford about the same time; it has a span of 327 feet, and likewise carries the great 1 lulvhead road. Sir Samuel Brown then erected, in the year 18.19, the Montrose Suspension Bridge over the Esk in Scotland, with a span of 412 feet, and a roadway 12 feet wide. This bridge
was all but destroyed during a great storm which took place in 1838; the platform not during sufficient rigidity to with stand the unequal force of the wind. The engineer, Bendel, however, has restored the bridge, and it is thought that such a disaster cannot again take place.
In the year 18297 Navier, an able French engineer, to whom we are indebted for a valuable work on Suspension Bridges, constructed the Pont des Invalides, on the suspen sion principle, over the Seine at Paris, with a span of 236 feet, and a deflection in the catenary formed by its chains, of about 26 feet. The Fribourg Bridge, which spans the valley of the Sarine in Switzerland, is one of the most splendid wire bridges ever built. It was constructed by Mr. Challey between the years 1832 and 34. It has a span of 870 feet, and the platform is 167 feet above the surface of the water, which runs at the bottom of the valley. This platform is suspended from four iron-wire ropes, two on each side of the bridge. The ropes are composed of SO wires, each A of an inch dia meter, tied up by coils of wire at regular intervals ; these chain-ropes arc made fast to the rock on either side, after passing over the tops the towers. Suspension rods are then hung upon the chain-ropes, to which the joists forming the roadway are fixed ; the cost of this magnificent and truly wonderful structure did not amount to more than .£2-1,000.