Dryburgh Abbey Bridge

Mr. Robert Stevenson writes in his 1821 "Description of Suspension Bridges":

"Dryburgh Chain-Bridge - The wire-bridges of Galashiels, Kingsmeadows, and Thirlstane, above described, are suspended by diagonal braces, as shewn in Fig. 2. The same plan was also followed in the first erected bridge at Dryburgh Abbey, where the suspending rods were also made to radiate from their points of suspension on either side, towards the centre of the roadway for as yet the catenarian principle had not been introduced upon the Tweed. The bridge at Dryburgh in 260 feet in extent between the points of suspension, and is 4 feet in breadth. It was executed by Messrs John and William Smith, builders and architects near Melrose, at the expence of the Earl of Buchan, as proprietor of the ferry, and has altogether cost his Lordship about L. 720. This bridge is constructed for foot passengers and led horses. It was originally begun on the 13th of April 1817, and was opened to the public on the 1st day of August following, having required little more than four months for its erection.

It is observed by Mr. John Smith, one of the gentlemen above alluded to, that when the original bridge of Dryburgh was finished, upon the diagonal principle like Fig. 2., it had a gentle vibratory motion, which was sensibly felt in passing along it; the most material defect in its construction arising from the loose state of the radiating or diagonal chains, which, in proportion to their lengths, formed segments of catenarian curves of different radii. The motions of these chains were found so subject to acceleration, that three or four persons, who were very improperly amusing themselves, by trying the extent of this motion, produced such an agitation in all its parts, that one of the longest of the radiating chains broke near the point of its suspension. On another occasion, in a very high wind, one of the horizontal chains, stretched under the beams of the roadway, gave way. But, on the 15th of January 1818, after this bridge had been finished about six months, a most violent gale of wind took place, when the vibrating motion of the bridge was so great, that the longest radiating chains were again broken, the platform blown down, and the bridge completely destroyed. Messrs Smith happened unluckily to be from home at the time of the accident, but on examining a number of persons who saw it, these all concurred in stating, that the vertical motion of the roadway of the bridge before its fall, was as nearly as may be equal to its lateral motion, ad was altogether concluded to be such as would have pitched or thrown a person waling along it into the river.

The eyes, formed on one end of the rods or links of the chains of the bridge, were welded, but the other end was simply turned round, and fixed with a collar, as shewn in the connecting diagrams, marked b, Fig. 3. It further deserves particular notice, that after the bridge fell, and on a careful examination of the rods or links, not more than one or two instances appeared of the iron having failed at the welded end, but had uniformly broken at the open eye of the link, as shewn n the diagrams b, b above alluded to, -- a mode of construction which had been recommended to Messrs Smith, by an experienced blacksmith.

The sudden destruction of this bridge, created a great sensation of regret throughout all parts of the country, and was considered an occurrence of so much importance in the erection of chain-bridges, that several of the gentlemen of Liverpool, interested in the proposed bridge at Runcorn, made a journey to Scotland, for the express purpose of inquiring into the circumstances of the misfortune. Messrs Smith, the contractors, had engaged with the Earl of Buchan, to erect this chain-bridge for somewhat less than L. 500, and were bound to uphold it against all accidents only during the period of its erection, so that the loss fell wholly upon Lord Buchan."