194 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[JUMS, 



fence of the city : at this time the circuit was much extended, and many 

 towers added ; and subsequent extensions and reparations where efiected 

 under the Emperors Honorius and Justinian, and under Belisarius and Nar- 

 ses. A description was then given of the various modes of construction 

 adopted during the long intervening period which elapsed to the time of Pope 

 Leo IV. when tlie ci(y became papal, and on that of Pope Nicholas V., by 

 whom the ancient walls, which had been greatly injured during the repeated 

 convulsions of the empire, and by the devastations of succeeding ages, were 

 to a great degree restored. Mr. Burgess then explained the various additions 

 laade to the papal walls, by Pope Pius IV. and Urban VIII., and exhibited 

 some fragments of the constructions, showing that the materials employed 

 were different in the several portions. 



SIR JOHN RENNIE'S FIRST CONVERSAZIONE. 

 The first conversazione given by Sir John Rennie, the President of the 

 Institution of Civil Engineers, took place on Saturday evening, 24th ult., arid 

 although we were well assured that there would not be any diminution in 

 the hospitable reception, and the interesting collection of works of art, to 

 which we have been accustomed in former years, we were not prepared for 

 the tasteful preparations and brilliant display on this occasion. 



Ill addition to the ordinary suite of rooms, a large apartment had been 

 constructed specially for the occasion at the rear of the house, adjoining the 

 second saloon. The walls and ceiling were tastefully decorated in encaustic 

 painting, by Sang. The effect of the light upon the vivid colours of the en- 

 caustic decorations was particularly striking. In the centre of this room was 

 suspended a magnificent chandelier, made by Mr. Apsley Pellatt, from the 

 prize drawing at the School of Design. II was entirely composed of glass, 

 combining the effect of the prismatic colours, of cut white drops, with the 

 Bohemian stained glass. 



We can scarcely attempt to particularize all the numerous works of art, 

 and interesting models, which were profusely spread throughout the rooms ; 

 but we must notice the bronzes from Mr. DeviUe's collection, an exquisite 

 carving in Caen stone of St. George and the Dragon, by Mr. Thomas ; Mr. 

 Goadbv's highly interesting anatomical preparations ; the paintings and port- 

 folios of sketches ; beautiful specimens of Claudet's new process of Talbotype, 

 by which the accuracy of Daguerreotype, and the artistic efl'ect of oil pamt- 

 ing appear combined. There were some excellent wood carvings by Rogers, 

 almost equalling a case of ivory carvings by Flamingo, from the collection of 

 Mr. Vulliamy ; these appeared to excite much attention. 



The models were, perhaps, somewhat less numerous than usual, but they 

 were select and well displaved. We must mention from among them, Mit- 

 chell's screw-pile battery ; 'the Air Point Lighthouse, by Messrs. Walker and 

 Burgess ; Captain Boswall's plan for harbours built with arched piers ; the 

 original design, by Mr. Stephenson, for an iron bridge of two arches, each 

 of 3G0 feet span, to carry the Chester and Holyhead Railway across the 

 menai Straits, but which "is now to be superseded by the suspended tunnel- 

 bridge, formed of wrought iron ; the Folkstone Viaduct, by Mr. W. Cubitt; 

 an ingenious cast iron trussed girder bridge, by Mr. Bortbwick ; and a good 

 model of a stone bridge, with flat eUiptical arches, designed some years since 

 by Mr. Rennie, to replace Westminster Bridge. There was a fine model of 

 the " Great Britain ;" a steam-frigate, with direct-acting engines and screw- 

 propeller, by Mr. Rennie ; a beautifid pair of marine engines, by the late Mr. 

 Henry Maudslay ; Mr. Bodmcr's patent horizontal engines and screw-propel- 

 ler; Mr. Hicks's improved locomotive engine; Messrs. Grissell and James's 

 combinations of a weighing-machine and crane, to ascertain the weight of an 

 object while raising it. Our limits will not permit a more extended notice, 

 but next month we hope to be able to give a full account of the conversa- 

 zione on Saturday the 31st ult. 



la this cise, then, the force which A would have to bear will actually be ' greater than' vf, 

 for it will equal w + the thrust at B, or to express the same thing otherwise 



Pressure on A = w 



AB 



We hope that this brief consideration will assist the reader in eiamining Mr. Walker's 

 admirable evidence. 



Mr. JAMES WALKER.— I am a civil engineer, residing in London, and have for 10 

 years past, until the present session, filled the situation of President of the Civil Engi- 

 neers' Institution. I came to Yarmouth, at the request of Sir James Graham, for the 

 purpose of examining into the cause of the falling of the suspension bridge ovtr the river 

 Bure, situate at tlie north end of Yarmouth. I will, at the risk of respecting some things 

 which may have already been given in evidence before, proceed to give a very short 

 historyof the biidge. It belonged to the late Mr. C017, father of the present owners, and 

 was constructed from a design of j\lr. Scoles, an architect in London. At first it was only 

 a substitute for a ferry orer the river Bure to the marshes, and to certain pleasure grounds 

 called Vauxhall-gardens, belonging to Mr. Cory. Mr. Scoles. who h.is attended from 

 London on this occasion, and who has assisted me very liberally with his drawings and 

 calculations, states, that he made desijns for a bridge of sulficieut width for a carriage 

 and two footways. The design was made from memory of the particulars given to him by 

 Mr. Cory, but I understand that he never was at Y'armouth until the day before the bndge 

 was opened ; that these drawings were given to Mr. Green, a surveyor, at Yarmouth, who 

 was at that time employed here, and who was well known in this district. Mr. Scoles 

 thinks Mr. Cory had at that time in view the mailing of a new turnpike-road from Yar. 

 mouth to Aclewhich-road, which was to pass over the bridge, although Mr. Cory at that 

 time did not so inform him. It appears that the work was offered for competition, and 

 that Mr. Goddard ivaa the contractor (who is since dead) for the bridge work, according 

 to specifications prepared by Mr. Green, the surveyor I before referred to. These speci- 

 fications were embodied in the contract, which contract I have seen, but which does not 

 give tlie size of the principal parts, although it refers to drawings which it states are at- 

 tached to the contract, but which are not, nor have I beeu able to see them. It appears 

 that they are either mislaid or lost. The specifications describe that the iron shall be of 

 the best quality. The specification describes it as the best charcoal iron. Now, this is a 

 description of which very little is made in this country ; the meaning of the term is, that 

 it was to be British iron of the very best quality. The specifications make no mention as 

 to the quality of the iron being tested, as far as I have observed. From a drawing which 

 is now in Mr. Scolcs's possession there appears no reason to doubt that the main or sus- 

 pending chains and other parts of the bridge are of the size which were intended. The 

 drawing which I have in my hand is e.iecuted in a very excellent and workmanlike man- 

 ner. There- are altogther four suspending bars, two on each side, to form a chain. The 

 connected together by bolts passing through openings or eyes at each end of 

 These bars are 24 inches wide by seven-eights thick ; from them rods of 1 inch 

 SQuare were suspended to carry the roadway, which was 14 feet 6 inches in width and di- 

 vided by an iron kerb or carriage-way from a footpath on each side 4 feet in width. The 

 length between the centre of the towers is 92 feet; the deflection of the chains is 7 feet 

 4 inches. An act of Parliament, constituting the bridge a turnpike road, was passed m 

 May, 1830, and th« road was opened in 1832 ; in 1842 the Yarmouth and Norwich Kailway 

 Act was passed, which contains a clause, obtained, as I understand, after much litigation 

 and opposition, by which this bridge was constituted the only communication between the 

 railway station and the terminus, Mr. Cory agreeing '" ' 



widen it, and afterwards to suspend it. It appears 

 respecting the enlargement of the carriage-way 

 pass abreast — the footway being formed 

 attached 





„ the tolls, stipulating 



that Mr. Scoles was again consulted 

 vidth su/ficieut for two carriages to 

 each side by planks separated by iron straps 

 the framing of the bridge. This footway was therefore outside the suspending 

 hains. That was in 1844. Mr. Cory says, that after the above alteradons weie made, 

 he consulted an eminent engineer as to the suificiency of the bridge, who said that it was 

 fit tor any traffic. I cannot help observing on this that any opinion taken from an engi- 

 neer, however eminent, in an off-hand manner, is what the engineer would not ■<" 



himself bound by, and which I should think it very unfair to implicate li: 

 sometimes a gentleman is asked a question 

 ing of politeness 



off-hand 

 id of it altogether, b 

 than he would if he had an opportunity of 

 dations appear to have been piled well, aud to have stood well 

 drawing of the piling, and, if the work 

 doubt of the soundness of the foundation. 



FALL OF THE SUSPENSION BRIDGE AT YARMOUTH. 



On the 2nd of May a frightful loss of life was occasioned at Yarmouth by the fall of the 

 suspension bridge over the river Bure. The government ha\ 

 eminent engineer, to examine into tlie causes of the catastroph 

 Inquest the following evidence, which we have extracted from tl 

 similar to this at Yarmouth are, unhappily, by no means singuli 

 Montrose suspension bridges, one of those in the Regent's Pa 

 those over the Seine at Paris, have given way to a greater 



. Walker, the 

 , he gave at the coroner's 

 the ' Times.' Accidents 

 r. The Menai and the 

 k, London, and two of 

 less extent. The inevitable 

 effect on the public mind will be a distrust of suspension bridges generally, and a suspi- 

 cion that they are not usually constructed of sufficient strength. The case of the Y'ar- 

 mouth bridge, however, has features peculiarly its own. By the addition of footways, 

 • outside- Ihe chains and the collection of a large crowd on one footway only, one of the 

 chains became useless and contributed nothing to the support of the weight. 



If the line below represents a section of the platform, and A, B he the two points of 

 w W 



iuipension, any weight at W, between A and B, will press o& those two points m the in- 

 verse ratio of its distance from either of them, that is — 



Pressure at A : Pressure at B : : B W : A W. 

 But If the weight were not between A and B, but placed at w, for instance, not only would 

 none of the downward pressure of w be boine at B, but w would actually produce an 'up- 

 ward' force at that point— so that the ' tension' at B would be changed into a ' thrust.' 



ther from a feel- 

 n a favourable man- 

 iiiing it. The foun- 

 Scoles showed me a 

 ecuted according to that, I have very little 

 probably aware that I am very well 

 acquainted with the foundations of this part of the country, having been consulting engi- 

 neer to the Haven and Pier Commissioners for many y«ars. I have also made drawings 

 for a fixed bridge over the Y'are, and I erected the temporary bridge which is now there. 

 It la stated that the crowd collected on the 2nd of Way was confined to the south side ; 

 that the crowd was composed chiefly of children in the front rank, with adults behind, to 

 see some exhibition which was then to be seen on the water. They were supposed to be 

 four or five deep, and it appears that they had collected on the bridge to the number ol 

 from 300 to 600. The coro'ner has stated to me that he has seen double the number on 

 the bridge (or even more than that), but that on those occasions they were spread over on 

 both sides of the bridge, so that all four bars or two chains were equally loaded. It has 

 been stated, I believe, by one of the witnesses who has been examined before, that some 

 sort of cracking noise was heard, which induced him to look up, when he saw that one of 

 the bars or rods of the suspeuding-chain was broken— that two points where the fracture 

 had taken place were entirely separated, and that in about five minutes afterwards came 

 the fatal catastrophe. This cracking was no doubt occasioned by the snapping in pieces 

 of the bar which first gave way. There was now only one bar left to support the whole 

 weight, and this bar consequently gave way in five minutes after the one on the opposite 

 side 1 the platform, being then entirely unsupported, fell into the river. I have seen and 

 examined the two bars which gave way— they form the link next but one to the saddle 

 or top of the chain on the east side of the bridge- The fracture in the bar which first gave 

 wav is about eight inches from the other end, and there is the same distance Irom the 

 lower end of the bar. It appears that in forming these bars the two circular ends and 

 about six inches of the straight bar were first made. Between these a straight bar of the 

 properlength was afterwards introduced, each of the pieces having been what is termed 

 kcarled-that is, terminating diagonally, and not in a straight line across. These three 

 nieces being heated and welded together made one bar or link. Then each bar had in it 

 two joint., six inches from one and six inches from the other. In work of this kind there 

 is great difficulty in getting iron so constructed as to make a perfect union or junction 

 with the two ends. It was at Ihese points that both bars in the present case broke. On 

 minutely examining the fracture of the bar, it is evident that for some length of time, or 

 from perhaps its original manufacture, the "weld" was i.Dperfect— not more than one- 

 third of the melting surface being united, and the other two-thirds presented a rusty sur- 

 face. This would have been doubtless seen, as it is evident on a very slight inspection. 

 The ioint or weld of the other link is good— the corresponding one forming the bar. but 

 I find that this bar (the second one) is one inch longer than the one which broke first; lu 

 the bar which broke second, putting the bolts through the eye at the lower end, I find 

 that it does not fit, but passes obliquely, and is or.e inch longer than the other. This ex- 

 tension or difference of length is caused without doubt by the stretching ot the unsup- 

 ported rod before it broke, during the five minutes that it had the whole weight to carry 

 I have no doubt but that this caused it to stretch quite an inch in length. Having nan 

 the quality of the iron tested in a variety of ways, by a very intelligent blacksmith (Mr. 

 Gooda), I find the straight pieces, or middle of the bar, to be much better than the other 

 end; the straight piece is better than the end pieces, which contain the eyes, which are 

 very coarse and inferior in quality. This, (holding a bar up to thejury)isone of the mid- 

 dle pieces i not the one which broke, but one taken indiscriminately. I desired Mr. Gooda 

 to lengthen it, and to apply a power to twist it. As far as I can judge this iron 13 good. 

 I also desired a screw to be formed in another bar, and I am of opinion that that bar is 



