488 



BRIDGE. 



Wooden 

 bridge at 

 Schauff- 

 hausen. 



Bridge, other materials have been successfully employed. 

 * <r Bridges of great extent have been constructed of 

 wood 



With the exception of drawings made by Palladio 

 and others, from the descriptions given in Czsar's 

 Commentaries, of his bridge over the Rhine, we have 

 no satisfactory account of any ancient wooden bridge. 

 Of those of more modern times, there is one describ- 

 ed by Palladio, said to be situated upon the Cismone, 

 at the foot of the Alps, between Trente and Bassane 

 in Italy. It is of very simple construction ; the whole 

 being suspended by the framing, which forms the 

 sides ; the opening between the abutments is 109 feet. 

 Palladio also gives sundry designs for wooden bridges 

 formed in different ways, some of which are sup- 

 ported by the sides only ; and one is in the form of 



fxxXVt!I an arch ' Scc Plate LXXXVIII. Gautier gives 

 designs of his own, and one from Mathourin Jousse ; 

 the last mentioned consists of one passage over it 

 for cavalry, and another for infantry, and is pro- 

 tected by a roof But the boldest and most inge- 

 niously constructed wooden bridge on the European 

 continent, was that at Schauffhausen, in Switzer- 

 land. 



We are informed that there was formerly a stone 

 bridge at Schauffhausen, that the Rhine injured the 

 piers, and that in the year 1754 three arches fell ; 

 that the depth of water immediately on the upper 

 side of the old piers being, during summer, from 18 

 to 20 feet, and from 28 to 30 feet below them, the 

 idea of rebuilding a stone bridge was abandoned, and 

 that the old piers, excepting one near the middle, 

 were taken away ; that Ulric Grubenman, a com- 

 mon carpenter of Tueffen, produced a model for a 

 wooden bridge, supported only by the abutments on 

 the banks of the river ; that after some hesitation on 

 the part of the committee of Schauffhausen, his pro- 

 posal was adopted, and that he completed this truly 

 extraordinary work in the year 1758. The total 

 length of the bridge was 364 feet, and its breadth 

 18 feet. It was eight feet out of a straight line, and 

 the angle pointed down the river; the distance from 

 the abutment next the town to the angle was 171 

 feet, and from the angle to the opposite shore 193 

 feet. This magnificent and ingenious bridge was 



LXXXIX destroyed by the French in April 1799t See Plates 



and XC. LXXXIX. and XC. 



About the same time that Ulric Grubenman was 

 engaged at Schauffhausen, his brother John construct- 

 ed a bridge of the same kind at Ruichenau, 240 feet 

 in length ; and some years afterwards they jointly 



At Baden, erected one near Baden, 200 feet in length over the 

 river Limmat. 



We know of no wooden bridges in Europe of an 

 extent equal to those constructed by the beforemen- 

 tioned ingenious men. But one upon nearly the same 

 principles, and of 250 feet span, has been constructed 

 O ver the Portsmouth river in North America, by a 

 Mr Bludget. Yet, though of inferior magnitude, 

 several upon principles equally simple and effective, 

 e Deen erected upon rivers in Scotland by James 

 Burn, of Haddington, in East Lothian. The largest 

 is over the river Don, about seven miles from the city 

 of Aberdeen, upon the road which leads from that 

 place to Banff ; the extent between the abutments is 



Bridge 



PLATE 



At Ruiche- 

 nau. 



In North 

 America. 



In Scotland. 



109 feet 3 inches, and the breadth 18 feet. The 

 frames which support the roadway are composed of 

 short pieces of timber, but instead of being elevated 

 above t'ne level of the roadway in order that it may be 

 suspended from them, ihey here support it after the 

 manner of stone voiissoirs. This bridge was erected 

 in 1803. See Plate LXXXVI II. LXXXV 



There is an elegant wooden bridge in the park at AtWotu 

 Wotton, a seat of the Marquis of Buckingham, con- 

 structed precisely upon the principle of one given by 

 Palladio. The span of it is 87 feet, the versed sine 

 1 3, and the breadth across 20 feet. 



Small timber bridges, being, in all countries 

 abounding in wood, so obvious a means for crossing 

 streams, it is impossible to trace their origin and pro- 

 gress ; and those consisting of rows of piles driven 

 into the bed of a river, and supported by common 

 trussings and bracings, being found in most countries, 

 and being familiar to every body, it is only necessa- 

 ry, in what regards them, to refer to the Plates, and 

 to what is said under the head of Practice. 



IRON BRIDGES. 



IN Britain, of late years, the application of iron Iron 

 having been greatly extended, and practical mechanics bridges 

 having been also brought to much perfection, that 

 valuable metal has been used in the construction of 

 large arches over rivers. 



The first cast iron bridge was erected upon the 

 river Severn, about two miles below Coalbrook Dale, At Coa 

 and between the villages of Madely and Broseley, in broukD 

 the county of Salop. The form of the ribs or in- 

 trados is nearly semicircular, the span being 100 feet 

 6 niches, and the rise from the level of the springing 

 plates to the soffit at the middle is 45 feet, the height 

 from the ordinary low water to the springing plate 

 is about 10 feet, making the whole height from the 

 low water to the soffit 55 feet. This bridge was 

 constructed by Abraham Darby j it was cast at the 

 Coalbrook Dale foundenes, and erected in 1777. The 

 design was bold and well executed; it formed a new 

 aera in bridge building. The banks of the river ad- 

 jacent to the bridge are exceedingly high and steep, 

 and composed of alluvial matter which slips over the 

 points of the coal strata. The effect of this opera- 

 tion not having been sufficiently provided against, 

 some years ago, the top part of one of the stone 

 abutments was pressed in a few inches, and of course 

 raised up the iron work about the middle of the arch. 

 Steps have been since taken to secure the western 

 abutment ; but the other, by having valuable houses 

 built close up to it, is more entangled, and it may in 

 time suffer from that cause ; but the iron work has 

 not been the least affected by the weather, cr the in- 

 tercourse over or under the bridge during 34 years. P'.ATZ 

 See Plate XCI. 



The next cast iron bridge in point of time, was At Builc 

 likewise erected upon the river Severn, about three wa? - 

 miles above the former, at the expence of the county 

 of Salop. Here the banks being low, Mr Telford, 

 as county surveyor, under whose direction it was 

 built, introduced the principle of suspending the 

 roadway by two large ribs, one on each side of the 



