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Marc SEGUIN

Description d'un pont en fil de fer, par Seguin aîné

Chez Bachelier, Libraire pour les Mathématiques, la Physique, les Arts mécaniques, etc., Paris s.d. [1824-1825], 15x22cm, relié.

First edition. Illustrated with a lithograph showing sections and views of the Tain-Tournon bridge project, then under construction.
3/4 marbled roan binding, spine framed and decorated in gilt, red morocco title-piece, marbled paper boards, marbled paper endpapers and flyleaves. Spine, spine-ends and corners rubbed, contemporary binding signed by Stroobants.

Extremely rare pamphlet by Seguin on a prototype suspension bridge built over the Galore river at Saint-Vallier in Isère. It served as an experimental construction for the Tain-Tournon bridge, the world's first large suspension bridge invented by Seguin using metal wires.

This was the first published volume of Seguin's work on wire suspension bridges. His publication the previous year, Des ponts en fil de fer, preceded his first constructions and remained purely theoretical. Seguin advocated the use of intertwined wire cables instead of metal chains popular among his predecessors. The experimental bridge, described in great detail and calculation in the present study, was designed for pedestrians, horse riders and pack animals. It rose 5 meters above water level for a total length of 30 meters. The results of this first construction, described here, were published again in a chapter of the second edition of Seguin's treaty Des ponts en fil de fer in 1826.

After this successful experiment, “M. Seguin considered that the possibility of providing a passage of this kind over the largest rivers, not only for pedestrians, but also for the heaviest carriages, had been perfectly demonstrated. On January 22, 1824, the government granted the Seguin brothers authorization to build, at their own risk, a wire bridge over the Rhône between Tain and Tournon, and they immediately set to work, all the more vigorously executing a project they had promised to complete in eighteen months, since all the experts in the field had their eyes fixed on them wondering if these new builders, hitherto strangers to public construction, were deserving of attention. The promise was scrupulously kept, and the Tournon bridge, the first wire bridge to be built over a major river, was solemnly inaugurated on August 25, 1825. This bridge, which consists of two equal spans, each 85 metres wide, and two abutments and one pier, fully satisfies all expectations” (Abbé Filhoi).

Following the success of the Tournon bridge, Seguin and his brothers built no less than a hundred suspension bridges within twenty years. This exceedingly rare booklet was published several months before the construction of the famed Tournon bridge detailed by Seguin:

“This great construction was begun on May 12, 1824. Constantly high water during the summer forced us to make all our foundations about one meter below the water level, by means of a very simple diving bell of our own invention, whose description I intend to publish, and which I hope will not be without interest for the art [of building]. No sooner had we started pouring our concretes than an extraordinary flood removed our service bridges, as well as part of the cribbing and concrete. But a few weeks of good weather were enough to repair everything, and give us hope that in July 1825 the bridge can be opened to the public.

This clarification sheds light on the circumstances and reasons for the publication of this pamphlet, of which only a few rare copies in European libraries remain. This one bound by Stroobants is the author's own copy, preserved in the family to this day. The problems caused by the summer flood of 1824 undoubtedly raised doubts about the viability of the revolutionary structure. This publication in the prestigious scientific publishing house Bachelier was probably intended to prove the reliability of the invention to public authorities:

“Very solid parapets give it such rigidity that 15 to 20 people can walk on it simultaneously without causing noticeable vibrations. I've been told that several people have crossed it without dismounting, despite the fact that the bridge was loaded with three other riders, who, being more cautious, had dismounted. I'm even assured that I've seen a man gallop across it without the bridge vibrating in any noticeable way.”

It seems even more designed to attract the attention of investors, as these bridges are built entirely at the expense and risk of the Segin brothers, who benefited for the occasion from the very first concession for a public utility granted by the government to a private company. All costs are detailed, as noted in the June 1925 issue of Revue Encyclopédique: "This brochure by M. Séguin teaches more than its title suggests. It contains not only the description but also the cost estimate for the wire bridge (...) The abutments of this bridge were already built, but in a deteriorated state. The repairs cost 1,493 francs, and the rest of the construction, 1,825 francs and 40 centimes. Thus, this construction, remarkable for its elegance and solidity, only required a total expenditure of 3,318 francs and 40 centimes, compared with the initial estimate of 4,000 francs."

After Seguin's purely theoretical study in the first edition of Des Ponts en fil de fer, published the previous year, this extremely rare pamphlet is the first account of the success of a major innovation that became a cornerstone of modern engineering: the wire suspension bridge.

Author's copy. No copy in American libraries (OCLC mixed the records with his treaty "Des ponts en fil de fer").
Quérard, IX, 22.
History of the modern suspension bridge, p. 48-52.

Revue Encyclopédique

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