The bridge over the Pease, or Peaths, between and Berwiek-upon-Tweed, is rather an uncommon structure. It crosses a deep ravine, and consists of four semicircular arches. The arch on the east side of the ravine is 54 feet wide ; the second 55 feet ; the third 52 feet ; and the tburth, or western arch, 48 feet. From the bottom of the ravine to the surface of the road, the height is 124 feet. it was designed and built by the late N r. D. Henderson, of Edinburgh.
The bridges of Edinburgh are Ludt, not over water, but over dry land. They are distinguished by the name of iVorth :Bridge and South Bridge, and aflbrd an easy com munication between the New Town and the royalty and suburbs on either side of it. The North Bridge, which forms the main communication between the Old and New Towns, was projected in the year 1763 ; but the contract for build ing was not signed till the 21st of August, 1765. The arehiteet was Mr. William MyInc, who agreed with the town-council of Edinburgh to finish the work for X10,1-10, and to uphold it for ten years. It was also to be finished betilre Alartitimas, 1709 ; but on the Sth of August that year, when the work was nearly completed, the vaults and side walls on the south fell down. This misfortune was occasioned by the foundation having been laid upon the rubbish of the houses which had long before been built on the north side of the High-street ; and which had been thrown out into the hollow to the northward ; of this rub bish there was a depth of no less than eight feet between the of the bridge and the earth. Besides this deficiency in the inundation, an immense load of earth, which had been laid over the vaults and arches, in order to raise the bridge to a proper level, had, no doubt, contributed to produce the catastrophe above-mentioned. The bridge was repaired by pulling down some parts of the side walls, and afterwards rebuilding them ; strengthening them in others bars ; removing the quantity of earth laid upon the vaults, and supplying its place with hollow arches, &c. The whole was supported at the south end by very strong buttresses and irts on each side ; but on the north it has only a single support. The whole length of the bridge, from lligh-strect, in the Old Town, to Princes-street, in the New Town, is 1.125 feet ; the total length of the piers and
arches, is 310 feet. The width of the three great arches, is 7:2 feet each ; of the piers, 131 feet ; and of the small arches, each 20 feet. The of the great arches, from the base to the top of the parapet, is OS feet ; the breadth of the bridge, within the wall over the arches, is 40 feet ; and the breadth at each end, 50 feet. The South Bridge is in a line with the North Bridge, so as to make but one street, crossing the I ligh-street almost at right angles. It consists of twenty t•o arches of different sizes ; but only one of them is visible, viz. the large one over the Cow-gate; and even this is small in comparison with those of the North Bridge, being no more titan 30 feet wide, and 31 feet high. On the south, it ter minates at the University on one hand, and the Royal In firmary on the other.
The aqueduct bridge at Glasgow, over the river Kelvin, which conducts the great canal front the Forth to the Clyde, is the work of that great engineer, Mr. Smeaton. its length between the abutments, or land-piers, is 245 feet ; the arches, which are fai• in number, are each 50 feet in span, rising 15 feet 3 inches, from 151- feet above the footing of the piers; the three piers are each fifteen feet thick, and 54 feet high, ex clusive of the footing. The extrados is a straight surface for the canal. This bridge is constructed upon true mechanical principles, and the parapet is recessed opposite to the arches in order to resist the pressure of the water in the canal. The land-piers are also ingeniously contrived to be concave out wardly, so as to spread out at the base.
The bridge at Perth was erected between the years 1766 and 1771, according to a plan by Smeaton, under the patronage of the late Earl of Kinnoul. It consists of ten arches, one of which is a land arch. The clear water-way is 5S9 feet ; the extent of all the arches, 7301 feet ; and the wing-walls 176 feet : so that the total length of the bridge is 900-1 feet. The expense of building amounted to £26,446 1:2s. 3d., and was defrayed by public subscription. Blenheim bridge consists of three arches, the chief of which is 1011 feet in the span.