At Mantes is a bridge of three arches, likewise over the Seine. It was begun in 1757, by M. Hupeau, and finished by N. Perroet. The centre arch is 120 feet French (128 feet English) in the span ; the side arches arc each 12 feet less. The piers are 25i feet wide, and the abutments 29 feet thick.
In the year 1771, M. Regemortes constructed a flat bridge over the river Allier, at Noulins, consisting of 13 semi-ellip tical arches, of 64 feet span each, and 24 feet high.
Over the river Oise, on the great road from Paris into Flanders, is the bridge of St. Maxence, 41 feet wide, built by N. Perronet. The arches, three in number, each describe the segment of a circle, whose radius is 118 feet, leaving a water-way of 77 feet. The piers are singularly constructed ; each being composed of four cylindrical pillars, nine feet in diameter, leaving between them three spaces or intercolum niations, which are arched over ; those on the outsides are closed with a thin walling, and the middle one is left open.
The last foreign bridge we shall notice, is that of Orleans, over the Loire, built by N. Hupean, bet ween the. years 1750 and 1760. It comprises nine oval arches, described from three centres, Nyhielt spring at 12 inches above low water. The middle arch is 106 feet in span, with a rise of 30 feet ; the extreme arches at either end, are each 98 feet wide, and 26 feet high; the intermediate arches increase gradually in dimensions as they approach the centre. 'Ile four middle piers are 19 feet wide ; the others, 18 feet each; and the abutments 23., feet thick ; making the whole length of the bridge 1,100 feet.
We conic now to speak of bridges in our own country, beginning with those of the greatest antiquity. The Gothic triangular bridge at Croyland, Lincolnshire, is supposed to Le the most ancient structure remaining entire in the king dom. It was erected about the year 860, but for what pur pose, it is difficult, if not altogether impossible to determine; it is, however, obvious that utility was not the motive of the builder ; though it may be allowed to claim the qualities of boldness of design and singularity of construction, as pow cr. fully as any bridge in Europe. It is formed by three semi :11.6es, whose bases stand in the circumference of a circle, equidistant from each other, and uniting at the top. This curious triune formation has led many persons to imagine, that the architect intended thereby to suggest an idea of the Holy Trinity : nor is this improbable, considering the age in which it was built. The ascent on either side of the
semi-arches is by steps paved with small stones, and so steep that foot-passengers only can go over the bridge. horsemen and carriages frequently go under it, as the river is in that place but shallow. Although this structure has been built for so many centuries, the arches are still sound and free from fissures, and the building in general exhibits very trifling marks of decay.
The bridge of Burton-upon-Trent is 1,545 feet in length. It consists of 34 arches, all of free-stone, and is strong and lofty. It was erected in the 12th century, by Bernard, abbot of Burton.
Near Old Aberdeen is a celebrated Gothic bridge, over the river Don.
The centre arch of the bridge at York is 82:1 feet wide, and 27 feet high.
At Winston, Yorkshire, is a bridge of a single arch, 108 feet nine inches in width, built of rubble stone, for the small cost of £500. It was designed by Sir Thomas Robinson, and built by John Johnson, a common mason, of Walsingham, in the year 1762.
At Kelso, is an elegant stone bridge over the Tweed, built by Mr. Rennie. It is quite level at the top, having five elliptical arches, each of 72 feet span ; every pier bas a circular projection, on which stand two Doric pilasters, supporting a simple block cornice. This bridge cost about £13,000 exclusive of the new roads at each end, which cost. about £3,000 more.
Mr. Rennie also constructed the aqueduct bridge over the river Lune, at Lancaster, which is considered as one of the most magnificent works of the kind extant. At the place where it is built, the water is deep and the bottom had : the foundations are therefore laid 20 feet below the surtitce of the water, on a flooring of timber resting on piles. The arches are five in number, of 70 feet span each, and rise about 39 feet above the surface of the water. It has a hand some cornice, and every part is finished in the best manner. The total height from the surface of the river, to that of the canal, is 57 feet ; and the canal admits barges of 60 tons burden to navigate upon it. The foundation alone of this building cost £15,000, and the superstructure more than double that sum, although the stone was obtained from a quarry less than a mile and a half from the spot.