Reference Work Entry

Biographical Encyclopedia of Astronomers

pp 769-769


Fusoris, Jean

Alternate Name

Fusoris, Johanne

BornGiraumont, (Meurthe-et-Moselle), France, circa1365

Died circa 1436

Jean Fusoris is best known for his astrolabes, of which at least 13 survive, and for a treatise on the astrolabe. His design innovations became standard in the construction of these instruments.

Fusoris was born the son of a pewterer. He studied arts and medicine, attaining the bachelor’s degree in 1379. After learning his father’s craft, he returned for his master’s degree, which he obtained in 1391. Fusoris then served as one of the master’s regents in Paris until 1400. He established a school and opened an instrument workshop in Paris making astrolabes, clocks, and other instruments. Fusoris continued to study theology and accumulated various canonries.

Fusoris was elected a member of the French embassy in England in 1415, where he met Richard of Courteny, Bishop of Norwich. Norwich bought an astrolabe from Fusoris but did not pay for it. When Fusoris returned to England in an attempt to collect the debt, war had broken out between France and England, and he was arrested as a suspected spy. He was exiled to Mézières-sur-Meuze and later to Reims, but continued to accept and fill commissions for instruments while in exile. In addition to his instruments, Fusoris wrote a treatise on the astrolabe, in which he detailed the improvements he incorporated into his instruments, and other tracts on mathematics and astronomy.

Fusoris was one of the first philosopher-churchmen to set up a commercial workshop to produce instruments. His workshop represented several turning points in the history of instrument manufacture in general and in the history of the astrolabe in particular. It was unique at the time for a person of his prestige and position to establish a commercial enterprise. Prior to this time, nameless guild craftsmen or others produced most astrolabes. It cannot be said that Fusoris started a revolution in the instrument industry, but his shop certainly anticipated later ateliers headed by prominent scholars. His influence on the astrolabe cannot be overstated. He was the first to integrate all of the astrolabe elements into a uniquely European instrument, and the design elements of Fusoris’ astrolabes became virtually universal. Among his innovations were dividing the limb by equal hours, the use of a rule (ostensor) on the front of the instrument, and improvements in the design of the alidade. His elegant and artistic design of astrolabe components was a milestone compared with the bulky and awkward instruments that preceded his.

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