Fortin, Jean Nicolas

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Fortin, Jean Nicolas

(b. Mouchy-la-Ville, Îlede-France, France, 9 August 1750; d. Paris, France, 1831)

scientific instruments.

Fortin was one of the most skilled precision mechanics and scientific instrument makers of his time. Lavoisier realized his potential and asked him, at the beginning of his career, to make several new laboratory instruments for him. Of special note is a precision balance made in 1788, which had an arm one meter long and was sensitive to weights as slight as 1/400 ounce. For the Commission of Weights and Measures he made a similar precision balance with the necessary weights, and another instrument to compare the dimensions of the cylinders that constituted the standards for weights. In 1799 Fortin adjusted the platinum kilogram standard that was deposited in the National Archives of France. He also made instruments for the Paris observatory.

Around 1800 Fortin made a barometer whose distinctive feature was the combination of a leather bag containing mercury, an ivory pointer indicating the zero point of the barometric scale, and a glass cylinder. By this simple combination Fortin made it possible to adjust the level of the mercury surface in the cylinder to coincide with zero on the scale. The device made transportation of barometers easier, and later any barometer in which the mercury could be adjusted to touch a point was known as a Fortin barometer.

Fortin devised many instruments that were used by scientists and engineers in famous experiments: the study of the expansion of gases by Gay-Lussac; the verification of the Boyle-Mariotte law at high pressures by Arago and Dulong; the triangulations between Barcelona and Formentera by Biot and Arago; and so on. He was a member of the Bureau des Longitudes, and in 1776 he reduced Flamsteed’s Atlas céleste to about a third of its former length.


Fortin’s only publication was his edition of J. Flamsteed’s Atlas céleste (Paris, 1776).

On his work, see M. Daumas, Les instruments scientifiques aux XVIIe et XVIIIe siècles (Paris, 1953), passim.

Asit K. Biswas

Margaret R. Biswas