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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



53 



has succeeded so well that it is worthy of adoption elsewhere. The span- 

 drils are composed of cast iron (iiagonal pieces, connected together in a 

 similar manner, and the roadway is formed by solid plates of cast iron 

 resting upon the spandrils, and joined together by iron cement. The piers 

 and abutments are of stone, founded upon timber plutfoinis, resting upon 

 bearing piles, and surrounded by sheathing piles, driven sutHcienlty deep 

 below the bed of the river. The masonry is tied througliout by vertical 

 and horizontal bond stones, so that the nhole acts as one mass in the best 

 position to resist the horizontal thrust. The ribs forming the arches were 

 commenced in the centre, and were continued regularly on each side to- 

 wards the piers and abutments, upon which a cast iron bed and connect- 

 ing plate were laid, nicely let into the masonry to receive the ribs forming 

 the arches; when the last segment of each rib was fixed in its place, three 

 cast iron wedges, each 9 feet long and 9 inches wide, were placed behind 

 each rib, and nicely adjusted and filled to them; these having a very slight 

 taper, were driven simultaneously by heavy hammers, and thus the arches 

 were nearly lifted from the centres, so that the wooden wedges upon which 

 the segment pieces rested were easily removed by a few blows of a ham- 

 mer; the arches were thus relieved from the centres in a very simple and 

 efficient manner. The whole of the iron-work had been so well put 

 together by Messrs. Walker, of liotherham, the founders, and the masonry 

 by the contractors, Messrs Jollille and Banks, that when the work was 

 finished, scarcely any sinking was discernible iu the arches. During lbs 

 progress of the work, some experiments were made, in order to ascertain 

 the extent of the expansion and contraction between the extreme range of 

 winter and summer temperature, and upon taking the aveiage of numerous 

 trials by different gauges, it was found that the crown of the arch rose in 

 the summer about an inch to an inch and a half. I'he work was commen- 

 ced in 1813, and the bridge was opened in 1819. 



Whilst upon the subject of cast iron bridges, we must not omit the 

 Swivel or Turning Bridge. The invention, if it may be so termed, is, it is 

 believed, due to England, and one was firot made of iron about the year 

 ISIO. They are now almost universally adopted over locks, to the extent 

 of 60 feet span, iu preference to the old lifting bridge. Since the introduc- 

 tion of the railway system, cast iron bridges have become very general, 

 and have been particularly serviceable, being formed of girders, where the 

 height was too limited to admit of the arch principle being adopied. Ex- 

 perience of the value of wrought iron in roofs and for otlier building pur- 

 poses has induced If, Stephenson to propose that material for constructing 

 the bridge lo carry the Chester and Holyhead Kaihray across the Menai 

 Straits. His design consists of a close wrought iron tunnel or tube, 14 

 feet wide, 30 feet deep, and 1500 feet long, supported in the middle by a 

 &tone pier built upon a rock in the middle of the Straits, with two other 

 piers at the low-water mark on either side, leaving four openings, two of 

 them 4()0 feet, and two of 230 feet each, and 100 feet above high water, so 

 a» to admit of masted vessels sailing under it. Cubitt has also proposed 

 to adopt wrought iron on a great scale, for construciing lauding platforms 

 at Liverpool, where the difficulty of building docks or quays, which large 

 steam vessels can approach at all times of tide, render works of this kind 

 necessary to accommodate the immense traffic frequenting Liverpool. The 

 landing platform designed by Cubitt, and now iu course of construction, 

 consists of a wooden frame, 500 feet long, by 80 feet wide, floated upon a 

 number of wrought iron ptintoons, each 80 feet long, 10 feet wide, and 

 C feet deep ; it is connected with the shore by two bridges, eac!i formed of 

 two hollow wrought iron beams, 150 feet long, carrying the platform of the 

 bridge; the attachment with the shore and the stage is so made as to 

 pdmu of motion, both vertically and horizontally, to accommodate itself to 

 the rising, falling, ebbing, and flowing of the tide, which there rises about 

 30 feet. 



Suspension Bridges. 

 The invention of chain or suspension bridges is said to have been im- 

 ported from China and India. The first of the kind in England was that 

 across the Tees, at Middleton, consisting of two common chains stretched 

 across the river, and secured to the adjoining rocky banks ; the span was 

 70 feet. To Capt. Sir Samuel Brown, however, wiio had previously 

 brouglit chain cables into use for ships, may be attributed tlie introduction 

 into England of the improved system of the bar link, whicii is now so 

 generally adopted. Brown, in 1818, first constructed a large model of 100 

 feet span, capable of supporting a carriage and horses, indeed adapted lor 

 general traffic. He afterwards constructed (1819), upon this principle. 

 Union bridge, for general traffic across the Tweed, near Berwick ; tbe span 

 was 450 feet betv\een the supporting towers, which were of masonry. He 

 eubsequen.ly built another, of smaller dimensions, across the Tweed, at 

 Dryburg. He also constructed that at Montrose, one oier the Hundred 

 Feet river in the Fens, and others, and applied the .same principle with 

 effect for landing-piers at Brighton and Leith. This s> stem was afterw ards 

 carried out to a far greater extent by Telferd, in ins great suspension 

 bridge acioss the Menai, at Bangor, in 1818-20, so well described by l-"ro- 

 vls. It consists of three openings, the centre is 580 feet span, the deflec- 

 tion of the chain being 42 feet, and the two side openings are 2(i0 feet span 

 each; the platform of the roadway is 100 feet above high-water mark ; 

 the sustaining towers of masonry are 50 feet above the roadway, and are 

 connected to the shore by three stone arches ou one side, and four on the 

 crther, 52 ft. G in. span each. There are sixteen main chains, each 1770 feet 

 long, in sets of four each, suspendi-d above each other, on each side of the 

 roadway, which is 30 feet wide from out to out, divided into tiiree parts, 

 two for carriages, oq the outside, 12 feet wide each, and one for foot-pas- 



sengers, in the middle, 6 feet wide. Each main chain consists of five bars 

 or links, 10 feet long each, by 3J inclies and 1^ inch, connected together 

 by plates and pins, on Brown's sv-ilem, the whuie being properly secured 

 to the solid rock ou each side, the total suspended weight of the main 

 opening is 044 tons. About the same time, he constructed another upon 

 tlje same principles, 300 feet span, across the river Conway, at Conway. 

 These are fine works, and will remain as lasting monuments to his fame. 

 The recent structures of Hammersmith, across the Thames, and Shoichani 

 across tbe Adour, by Tierney Clark, wlio is now erecting anotlier upon a 

 grander scale, 7oO feet span, across the Danube; and, lastlv, that of 

 Brunei across the Thames, at Hungerford Market (1845), show' the pro- 

 gress made in this class of structures, which are well adapted for crossing 

 large and deep rivers w here economy is an object ; great care, howeier, is 

 necessary in proportioning the strength of the chains, and their curve ; the 

 selection and manufacturing of the iron for them, and also in the connexion 

 and bracing of the roadway platform, in order to insure the greatest 

 strength and solidity of construction ; of this, the improvements to the 

 Monlrose Bridge, by Kendel, is a good example, and the system should be 

 generally followed, as several disastrous failures have occurred from ne- 

 glect of these important particulars. 



Amongst varialions of the system, that of Dredge may be mentioned. 



The wire suspension system, although in extensive use on the Continent, 

 the largest example of which is at Fribourg, in Swiizcrlaud, where a 

 bridge has been constructed of 800 feet span, for carriages as well as foot 

 passengers, has been rarely used in this couulry. Although economical ia 

 the first cost, it requires conntant attention, and it scarcely possesses suffi- 

 cient durability for permanent structures. 



Wooden Bridges. 

 In wooden bridges, little was formerly done in Britain beyond the com- 

 mon pile bridge. These were formed by rows of piles for piers, driven at 

 short distances from each other, and connected together by straight girders 

 planked across to form the roadway, with a wooden railing on each side. 

 Of this kind of construction, the bridges of Londonderry, across the Foyle, 

 Waterford, across the Suir, Battersea, Fulhani, and others, across the 

 Thames, are examples. In some cases, this system was extended, by 

 adopting larger openings, having diagonal struts, or butting pieces, be- 

 tween the underside of the girders and tlie piles forming the piers, iu order 

 to reduce the bearing of the girders, and thus give them greater stability. 

 The straight trussed frame or girder, so much used in America, was em- 

 ployed by Reiinie, to a considerable extent, as service bridges, during the 

 construction of tlie Waterloo and Southwark bridges, in 1800-19, and at 

 New Loudon Bridge, in 182.) 31, with openings of above 100 feet, capable 

 of supporting the heaviest weights. The late Colonel By, of the Kojal 

 Engineers, gave an account of a bridge of this description, said to have 

 been built acioss the Terrebonne, a large river near Montreal, iu Canada, 

 COO feet span between the piers. It is said that this was carried into 

 efiect, and actually stood for a short time ; but, in consequence of its hav- 

 ing been badly constructed, it required heavy repairs, and whilst these 

 were being eliected, the \^hole structure came down, and was carried away 

 by the floods. The trnsed system has been applied with considerable 

 success iu some well-constructed bridges across the Tyne, for the New- 

 castle and Carlisle Railway, by Blackmore, and in several other places. 

 Tbe system of Wiebikiug, of combining small curved pieces of timber 

 connected together in the form of an arch, adapted for large spans, was 

 first introduced, I believe, on the Ancholme, in 1826, when a bridge of 100 

 feet span was constructed with complete success. This has been used by 

 Green, in the viaducts fur the Newcastle and North Shields liaihvay ; and 

 has been followed by others also. Price, long ago, proposed a similar 

 system ; but the scarcity and deaniess of timber, and the prevalent use of 

 iron, probably prevented its application before. The lattice bridge, of 

 American origin, has latterly been introduced on the Birmingham and 

 Gloucester liailnay, by Moorsoni, and on the Dublin and Drogheda Rail- 

 way by McNeil, and as they are economical and simple in their construc- 

 tion, Ihey are applicable iu some cases with advantage. 



In tbe designing and constructing of bridges of stone, wood, cast and 

 wrought iron, an accurate knowledge of the strength of malerials is pecu- 

 liarly important, nay absolutely indispensable ; and the profession is much 

 indebted to George Keunie, who commenced a series of investigations on 

 this subject in 1817, which were communicated to tiie Koyal Society, and 

 published in their Transaclions in 1818. These experiments were among 

 the first to determine with precision the absoluie and relati\e strengths of 

 materials, under the effects of tension and compression. He subsequently 

 made above six hundred experiments in 1827, ou the friction of plane and 

 round surfaces, with and witliout unguents, under the dilfereut circum- 

 stances of time, surface, and pressure, which were published in the Phi- 

 losophical Transactions, iu 1828. Iu 18X0 he also made experiments on 

 the friction and resistance of fluids, which were published in 1831. Mo- 

 rin's experiments did not appear until 1834 — Tredgold, Barlow, Fairbairn, 

 Hodgkiuson, U ood, and others, have since carried thesa experiments lo a 

 grea'er extent. 



Co7icrt(t', a mixture of gravel, sand, lime, and other cements, in certain 

 propurtions, was well known to the ancients, and iu conjunction with the 

 invaluable natural cement, Pozzolana, was aiipiicd with the greatest suc- 

 cess in the then numerous moles and other submarine works, and its use 

 has been still continued in Ita'y lo the present day. Wren is said to haie 

 used it for a portion of the fouudaliuu ot St. Paul's, where it was defec- 

 tive. Semple also alludes lo it in 17io. Its use appears to ha\e been 



