Fortin’s barometer and balance

On a wall at the back of our teaching lab stores hangs a case, dusty and forgotten, containing an old black and silver barometer almost a metre in length. It is a relic of a former age when precise measurement of atmospheric pressure was not available in two clicks of a mobile phone. Built by the British scientific equipment house Griffin and George, a close look shows it to be a Fortin barometer – the screw at the base gives it away – the first truly portable mercury barometer. Today few will have heard the name Fortin, and fewer realise the critical role that he played in establishing chemistry as a quantitative science and in defining the metric system of units.

Jean-Nicolas Fortin was born in 1750 in the village Heilles, some 20km south of the town of Beauvais in France. He had two brothers, neither of whom survived to adulthood, and one sister. His father was a labourer, while his mother died when he was 12. He must have been apprenticed in some way but there is no known record of his education and training. Although it is sometimes suggested that he started by making globes, this is almost certainly the result of confusion with his contemporary Jean-Baptiste Fortin (no relation), a map- and globe-maker who published a French edition of the British astronomer John Flamsteed’s star atlas.