Object 15

Carpentier, Paris
Mascart’s bifilar
Observation of the Earth magnetic declination, ~1875
Royal Meteorological Institute
Inv. N/A


Mascart's bifilar was used to measure Earth's magnetic declination. It was invented by Eleuthère Mascart (1837-1908), the first director of the French central meteorological office (from 1878 to 1906) and author of the 1990 Traité du Magnétisme Terrestre. It is made from red copper and composed of a cylindrical box with two graduated horizontal circles featuring silver scales, attached to a hollow cylindrical central column that bears the suspension system for the compass needle at the top. The device is mounted on a three-legged stand. The graduated circles have a vernier allowing minute of angle readings.



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