Fortin, Jean Nicolas (1750-1831)

French physicist and instrumentmaker who invented a portable mercury barometer in 1800. Any barometer in which the mercury level can be adjusted to zero is now known as a Fortin barometer.

The barometer Fortin designed incorporated a mercury-filled leather bag, a glass cylinder, and an ivory pointer for marking the mercury level. Fortin did not invent these features but he was the first to use them together in a sensitive portable barometer.

Fortin was born in Ile de France and worked in Paris at the Bureau de Longitudes, and later for the Paris Observatory, constructing instruments for astronomical studies and surveying. He also made clocks, and precision equipment for many scientists, including a balance for French chemist Antoine Lavoisier which could measure masses as little as 70 mg/0.0025 oz. In 1799 he adjusted the weight standard, the platinum kilogram, which was stored in the French National Archives.