BRI 



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breadth of the bridge. The spandrels, 

 or the spaces between the arch and the 

 road- way, are filled up by cast iron cir- 

 cles, which touch the outer circumfer- 

 ence of the arch, and at the same time 

 support the road-way, thus gradually di- 

 minishing from the abutments towards 

 the centre of the bridge. There are al- 

 so diagonal iron bars, which are laid on 

 the tops of the ribs, and extended 10 the 

 abutments, to keep the rib* from twisting. 

 The superstructure is a strong frame of 

 timber, planked over, to support the car- 

 riage-road, which is composed of marl, 

 lime-stone, and gravel, with a cement of 

 tar and chalk immediately upon the 

 planks, to preserve them. The whole 

 width of the bridge is 32 feet. The abut- 

 ments are masses of almost solid masonry, 

 24 feet in thickness, 42 in breadth at bot- 

 tom, and 37 at top. The south pier is 

 founded on the solid rock, and rises from 

 about 22 feet above the bed ot the river. 

 On the north side the ground was not so 

 favourable, so that it was necessary to carry 

 the foundation 10 feet below the bed. 

 The weight of the iron in this extraordi- 

 nary fabric amounts to 260 tons ; 46 of 

 these are malleable, and 214 cast. The 

 entire expense was 27,000/. 



The splendid example of the bridge at 

 Wearmouth gave an impulse to public 

 taste, and caused an emulation among ar- 

 tists, which lias produced many examples, 

 and more projects of iron bridges. The 

 Coalbrook Dale Company have construct- 

 ed several, among which is a very neat 

 one over the river Parrot, at Bridge water. 

 Mr. Wilson, the engineer employed by 

 Mr. Burdon, has also built several, and 

 some years since finished a very elegant 

 one over the river Thames, at Slaines, 

 which is by far the most complete in de- 

 sign, as well as the best executed, of any 

 that has hitherto been erected. This 

 bridge consists of a single arch, 181 feet 

 in span, and 16 feet 6 inches in rise, being 

 a segment of a circle of 480 feet. The 

 blocks of which the ribs are composed 

 are similar to those in the Wearmouth 

 bridge, except that these have only two 

 concentric arcs instead of three, as at the 

 latter. The arcs are cast hollow, and the 

 block connected by means of dowels and 

 keys ; thus obviating the great defect ob- 

 served at Wearmouth, of having so much 

 hammered iron exposed to the action of 

 the air. Four ribs form the width of the 

 arch, which are connected together by 

 cross frames. The spandrels are filled in 

 with circles, which support a covering of 

 iron plates an inch thick: on this is laid 



the road- way, 27 feet wide. Two hundred 

 and seventy tons is the weight of the iron 

 employed in the bridge, and three hun- 

 dred and thirty of the road-way. 



Public bridges, which are of general 

 conveniency, are of common right to be 

 repaired by the inhabitants of that county 

 in which they lie. Where a man makes 

 a bridge for the common good of the 

 King's subjects, he is not bound to repair 

 it. No one can be compelled to build, or 

 contribute to the charges of building any 

 new bridge, without act of parliament: 

 and if none are bounden to repair by 

 tenure of prescription at common law, 

 then the whole county or franchise shall 

 repair it. 



BRIDGES, pendent or hanging, called also 

 philosophical bridges, are those not sup- 

 ported by posts or pillars, but hung at 

 large in the air, sustained only at the two 

 ends or abutments. 



BRIDGE, draw, one that is fastened with 

 hinges at the one end only, so that the 

 other may be drawn up ; in which case the 

 bridge stands upright, to hinder the pass- 

 age of a ditch or moat. 



BRIDGE, flying or floating, is generally 

 made of two small bridges, laid one over 

 the other in such a manner, that the up- 

 permost stretches and runs out, by help 

 of certain cords, running through pullies 

 placed along the sides of the under 

 bridge, which push it forwards, till the 

 end of it joins the place it is intended to 

 be fixed on. 



BRIDGE of boats, boats made of cop- 

 per, and joined side by side, till they 

 reach across a river, which being covered 

 with planks, are fastened with stakes or 

 anchors. 



BRIDGE of communication, is that made 

 over a river, by which two armies, or forts, 

 which are separated by that river, have a 

 free communication with one another. 



BRIDGE, floating, a bridge made use 

 of, in form of a work, in fortification, call- 

 ed a redoubt, consisting of two boats, 

 covered with planks, which are solidly 

 framed, so as to bear either horse or can- 

 non. 



BRIDGE, in gunnery, the two pieces of 

 timber which go between the two tran- 

 soms of a gun carriage, on which the bed 

 rests. 



BRIDGE, in music, a term for that part of 

 a stringed instrument over which the 

 strings are stretched. The bridge of a 

 violin is about one inch and a quarter 

 high, and near an inch and a half long. 



BRIEF, in common law, a writ, where- 

 by a man is summoned or attached to 



