26S 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



SUSPENSION BRIDGES. 



Oil the Thtiinj 0/ Suspension Bridges, loitli some account of their carhj 



histon/. By Mr. G. F. Fokdham, read at the Scientijic Society, March 



12, 1810. 



Suspension bridges appear to be of very ancient origin; travellers 

 li.ivc discovered tlieir existence in South America, in Cbin 1, in Tliibet, 

 and in tlie Indian Peninsula. They are most frequently met with in 

 mountainous regions, and being suspended across a deep ravine, or an 

 impetuous torrent, permit the ))assage of the traveller wlie.re the con- 

 struction of any utlier kind of bridge would be entirely impracticable. 

 Hiunbdlilt informs us, that in Soutli .\merica there are numerous bridges 

 of tins kind formed of ropes made from tlic fibrous parts of the roots 

 of the American agavey (^4garc amcricana). These ropes, which are 

 three or four inches in diameter, arc attached on each bank to a clumsy 

 frame work composed of the trunk of the Schijiiis mollc ; where, how- 

 ever, tlic banks are flat and low, this framework raises the bridge so 

 much above tlie ground as to prevent it from being accessible. To 

 remedy this inconvenience steps or ladders are, in these cases, placed 

 at cacli extremity of the l)ridge, by ascending which all who wish to 

 pass over, readily reach the roadway. The roadway is formed by 

 covering the ropes transversely, with small cylindrical pieces of bam- 

 boo. The bridge of Fenipe, erected over the Chambo, is described as 

 being 12U feet long, and 8 feet l>roail, but there are others winch have 

 much larger dimensions. A bridge of tliis kind will generally remain 

 in good condition 20 or 25 years, though some of the ropes require 

 renewing every s or 10 years. It is worthy of remark, as evincing 

 the high anti(pMty of these structures, tliat they are known to have 

 existed in South America long prior to the arrival of Europeans. The 

 utility of these bridges in mountaino\is countries, is placed in a strik- 

 ing point of view by the fact mentioned by Ilinnboldt, of a permanent 

 communication having been establislied between t^uito and Lima, by 

 means of a rope bridge of extraordinary length, al'ter 40,000^ had been 

 expended in a fruitless attempt to build a stone bridge over a torrent 

 which rushes from the Cordilleras or the Andes. Over this liridge of 

 ropes, which is erected near Santa, travellers with loaded mules can 

 ])ass in safety. 



But suspension bridges, composed of stronger and more durable 

 materials than the twisted fibres and tendrils of plants, are found to 

 •«xist in these remote and semi-barbarous regions ; in Thibet as well 

 as in China many iron suspension bridges have been discovered, and it 

 is no improbable conjectiM'e, that in countries so little known and visited 

 by Europeans, otiiers may exist of which we have as yet received no 

 accounts. The most remarkable bridge of this kind, of which we have 

 any knowleilgc in Thihet, is the bridge of Chuka-cha-zum, stretched 

 over the Tehintchieu river, and situated about Is miles from Muri- 

 clioin. "(.)nly one horse is admitted (o go over it at a time : it swings 

 as you tread upon it, re-acting at the same time with a force that im- 

 pels you every stej) you take to (inicken your pace. It may be ne- 

 cessary to say, ill explanation id' its construction, tliat on the five chains 

 ■which support th'' platform, are placed several layers of strong coarse 

 mats of bamboo, loosely put down, so as to play with the swing of the 

 bridge; and that a fence on eacliside contributes to the security of tlie 

 jiassenger."* The date of the erection of this bridge is unknown to 

 the inhabitants of the country, and they even ascribe to it a fabulous 

 origin. The length of this bridge appears to be about l.'iO feet. 



Turner describes in the following terms a bridge for foot passengers 

 of an extraordinary construction. " It was composed of two eliains 

 stretched parallel to each other across the river, distant four feet from 

 eacli other, and on either side resting upon a ])ile of stones, raised upon 

 each bank about S feet high; they were carried down with an easy 

 slope and buried in the rock, where being fastened round a large stone, 

 they were ccnifincd by a quantity of broken rock hea])ed on them. A 

 plank about H inches broad, hung, longitudinally suspended, across tlie 

 river with roots and creepers, wound over the chains with a slackness 

 sutlicient to allow the centre to sink to the depth of four feet below 

 the chains. This bridge, called Selo-cha-zum, measured, from one 

 side of the water to the other, seventy feet. The creepers are changed 

 annually, and the jilanks are all loose ; so that if the creepers give way 

 in any part, (hey can be removed, an^l the particular part repaired 

 without disturbing the whole." 



Numerous suspension bridges formed of iron chains exist also in 

 China; and though the accounts wliidi travellers have transmitted 

 respecting them are less detailed and explicit than would have been 

 desirable, descriptions of two of them have been furnished, which are 

 sufliciently minute and intelligible to excite considerable interest. The 

 first to which 1 refer is contained in Kiicher's China lllustrata. Tlie 

 following is a translation of the author's words. "In the province of 



to* Turner's linilajsv to ihi; Court oflhibet. 



Junnan, over a valley of great depth, and through which a torrent of 

 water runs with great force and rapidity, a bridge is to be seen said to 

 have been built by the Emjieror Mingus, of the family of the Haniae, 

 in the year of Christ 0.5, not constructed of brickwork, or of blocks of 

 stone cemented together, but of chains of beaten iron and hooks, so 

 secured to rings from both sides of the chasm, that it forms a bridge 

 by planks placed upon them. There are 20 chains, each of which is 

 20 perches or 300 palms in length. When many persons pass over 

 together, the bri<lge vibrates to and fro, afl'ecting them with horror and 

 giddiness, lest whilst passing it should be strucK with ruin. It is im- 

 possible to admire sufficiently the dexterity of the architect Sinensius, 

 who had the liardihood to atti^mpt a work so arduous, and so conducive 

 to the convenience of travelling." Another suspension bridge in this 

 country is described in the (ilh vol. of the " Ilisloire ghit'-rale dcs 

 /'oijagis." The following is a translation: "The famous Iron Bridge 

 (such is the name given to it) at C^uay-Cheu, on the road to Yun-Nan 

 (Junnan?) is the work of an ancient Chinese general. On the banks 

 of the Pan-Ho, a torrent of inconsiderable breadth, but of great depth, 

 a large gateway has been formed between two massive pillars, G or 7 

 feet broad, and from 17 to 18 feet in height. From the two pillars of 

 the east depend four cliains attached to large rings, which extend to 

 the two pillars of the west, and which being connected together by 

 smaller chains, assume, in some measure, the appearance of a net. On 

 this bridge of cliains a number of very thick jilanks have been placed, 

 some means of connecting which have been ado]ited in order to obtain 

 a continuous platform ; but as a vacant space still remains between 

 this plathnan and the gateways and pillars, on account of the curve 

 assumed by the chains, especially wdien loaded, this defect has been 

 remedied liy the aid of planking supported on trusses or consoles. On 

 each side of this planking small pilasters of wood have been erected, 

 which support a roof ot the same material, the two extremities of 

 which rest on the pillars that stand on the banks of the river."* The 

 writer proceeds to remark that, "the Chinese have made several other 

 bridges in imitation of this. One, on the river Kin-cha-Hyang, in the 

 ancient canton of I.o-Lo, which belongs to the province of Yun-Nan, is 

 particularly known. In the province of Se-Chuen there are one or 

 two others, wdiich arc sustained only by ropes, but though of an incon- 

 siderable size, they are so unsteady and so little to be trusted that they 

 cannot be crossed without sensations of fear." 



While our attention is directed to early accounts, and to the origin 

 of suspension bridges, it may be proper to remark, that altliongli, as we 

 liave seen, the inhaliitants of the moinitainous districts of South Ameri- 

 ca, or the wild and barbarous regions of Thibet, appear to have been 

 well ac(|uainled with the purposes for which these structures are best 

 adapted, and to have practised their construction from the most re- 

 mote ages, neither the (ireeks, the Romans, nor the Egyptians, ac- 

 cording to all we know of those nations had any knowledge of their 

 uses or properties, or ever employed them as a means for crossing a 

 river, or other natural impediment. It is not, therefore, from these 

 celebrated nations of antiquity that the engineer has derived his first 

 hints for the construction of suspension bridges, but from those rude 

 and unpolished people, the results of whose ingenuity have just been 

 described. 



Hut it will now be interesting to inquire how far we can trace back 

 the antiquity of suspension bridges in more civilized countries, — on 

 the Continent, in the British Isles, and in the Vnited States of America. 

 Scamozzi speaks of suspension bridges existing in Europe in the be- 

 ginning of the seventeenth century, but it is very questionable if he 

 employed that term to designate the same structure to which it is now 

 ap]ilied, and this is rendered the more improbable as no such bridges 

 are now in existence, an<l other writers are totally silent upon the 

 subject. It docs not appear then that suspension bridges of other than 

 recent erection have existed on the Continent, and in England the 

 oldest of which we have any account has not been constructed more 

 than a century. The first suspension bridge in the United States was 

 erected in the year l/'.Ki. In England the oldest bridge of the kind 

 is believeil to have been the Wincli Chain Bridge, suspended over tlie 

 Tees, and liius forming a communication between the counties of Dur- 

 ham and York. Mr. Stevenson (Edinburgh Philosophical Journal) 

 expresses his regret at not having been able to learn the precise date 

 of the erection of this bridge; from good authority, however, he con- 

 cludes it to be about the year 17-11. It may also be mentioned here, 

 that at Carric-a-rede, near Ballantoy, in Ireland, there is a rope bridge, 

 which in 1800 was reported to have been in use longer than the pre- 

 sent generation could remember. 



In the years 18 Ki and 1817 some wire suspension bridges were exe- 

 cuted in Scotland, and, though not of great extent, are the first example 

 of this species of bridge architecture in Great Britain. As, however, 



1 See Navier, Memoire sur les Fonts suspcndus. 



