BRIDGES. 



are decayed. The bridge consists of nine 

 large, handsome, and nearly elliptical 

 arches ; the centre arch is 100 feet wide, 

 and the four arches on each side, reck- 

 oning towards the shores, decrease gra- 

 dually, being 98, 93, 83, and 70 feet re- 

 spectively, leaving a water-way of 788 

 feet. The whole length from wharf to 

 wharf is 995 feet, the breadth of the car- 

 riage-way 28 feet, and that of the raised 

 foot way on each side 7 feet. The upper 

 surface of the bridge is a portion of a ve- 

 ry large circle, which forms an elegant fi- 

 gure, and admits of convenient passage 

 over it. On each pier there is a recess 

 or balcony, with two Ionic columns and 

 pilastres, which stand on a circular pro- 

 jection of the pier above high-water 

 mark. The bridge is rounded on at each 

 extremity to the right and left, in the 

 form of a quadrant of a circle, rendering 

 the access commodious and agreeable. 

 This edifice must be regarded as a fine 

 specimen of Mr. Milne's ingenuity and 

 judgment, though the method of con- 

 struction has never been made public. 



Wooden bridges now demand our at- 

 tention. The simplest case of these edi- 

 fices is that in which the road-way is laid 

 over beams placed horizontally, and sup- 

 ported at each end by piers or posts. 

 This method, however, is deficient in 

 strength and width of opening; it is, 

 therefore, necessary, in all works of any 

 magnitude, to apply the principles of 

 trussing, as used in roofs and arches. 

 Wooden bridges of this kind are stiff 

 frames of carpentry, in which, by a pro- 

 per disposition, beams are put so as to 

 stand in place of solid bodies, as large as 

 the spaces which the beams inclose ; and 

 thus two or three, or more, of these are 

 set in a butment with each other, like 

 mighty arch stones. At Schaffhausen, in 

 Switzerland, where the Rhine flows with 

 great rapidity, several stone bridges had 

 been destroyed, when, in 1754, Gruben- 

 hamm offered to throw a wooden bridge 

 of a single arch across the river, which is 

 nearly 390 feet wide The magistrates, 

 however, required that it should consist 

 of two arches, and that he should, for that 

 purpose, employ the middle pier of the 

 last stone bridge, which would divide the 

 new one into two unequal arches of 172 

 and 193 feet span. The carpenter did so, 

 but contrived to leave it a matter of doubt, 

 whether the bridge is at all supported by 

 the middle pier. It was erected on a plan 

 nearly similar to the Wittengen bridge, at 

 the expense of about 8,000/. sterling. 

 Travellers inform us, that it shook if a 

 man passed over it ; yet waggons, heavi- 



ly laden, also went over it without danger 

 This curious bridge was burnt by the 

 French when they evacuated Schaffhau- 

 sen, in April, 1799. 



Iron bridges are the exclusive invention 

 of British artists. The first that has been 

 erectfd on a large scale is that over the 

 river Severn, at Coalbrook Dale, in 

 Shropshire. This bridge is composed of 

 five ribs, and each rib of three concen- 

 tric arcs, connected together by radiating 

 pieces. The interior arc forms a com- 

 plete semi-circle, but the others extend 

 only to the cills under the road-way. 

 These arcs pass through an upright frame 

 of iron at each end, which serves as a 

 guide ; and the small space in the haunch- 

 es between the frames and the outer arc 

 is filled in with a ring of about seven feet 

 diameter. Upon the top of the ribs are 

 laid cast iron plates, which sustain the 

 road-way. The arch of this bridge is 100 

 feet 6 inches in span ; the interior ring 

 is cast in two pieces, each piece being- 

 about 70 feet in length. It was construct- 

 ed in the year 1779, by Mr. Abraham 

 Darby, iron-master at Coalbrook Dale, 

 and must be considered as a very bold ef- 

 fort in the first instance of adopting a 

 new material. The total weight of the 

 metal is 378^ tons. 



The second iron bridge, of which the 

 particulars have come to our knowledge, 

 was that designed by Mr. Thomas Paine, 

 author of many political works. It was 

 constructed by Messrs Walkers, at Ro- 

 therham, and was brought to London, 

 and set up in a bowling green at Pad- 

 dington, where it was exhibited for some 

 time. After which it was intended to 

 have been sent to America ; but Mr. 

 Paine not being able to defray the ex- 

 pense, the manufacturers took it back, 

 and the malleable iron was afterwards 

 worked up in the construction of the 

 bridge at Wearmouth- 



The third iron bridge of importance 

 erected in Great Biitain was that over the 

 river Wear, at Bishop Wearmouth, near 

 Sunderland, the chief projector of which 

 was Rowland Burdon, Esq. M. P. This 

 bridge consists of a single arch, whose 

 span is 236 feet ; and as the springing 

 stones at each side project two feet, the 

 whole opening is 240 feet. The arch is 

 a segment of a circle, of about 444 feet 

 diameter, its versed sine is 34 feet, and 

 the whole height from low water about 

 100 feet, admitting vessels of from two to 

 three hundred tons burden to pass un- 

 der, without striking their masts. A se- 

 ries of one hundred and five blocks form 

 a rib, and six of these ribs compose the 



