Seguin, Marc (1786-1875)

French engineer who, in 1825, built the first successful suspension bridge in Europe using cables of iron wire. He also invented the multitubular boiler.

Seguin was born in Annonay, Ardèche, and was self-taught in engineering science. Seguin's first suspension bridge was built in Geneva in association with Swiss engineer Henri Dufour (1786-1875). Over the next 20 years, Seguin and his brothers erected cable suspension bridges in France, beginning with one over the River Rhône at Tournon in 1827. Seguin established France's first modern railway between Lyon and St Etienne, completed 1832.

In physics, Seguin argued that matter consisted of small, dense molecules constantly on the move in miniature solar systems and that magnetic, electrical, and thermal phenomena were the result of their particular velocities and orbits. He identified heat as molecular velocity and explained that its conversion to a mechanical effect occurs when the molecules transmit their velocities to external objects. In De l'Influence des chemins de fer 1839 he tried unsuccessfully to determine the numerical relationship between heat and mechanical power.