Southern France was the source of several other astronomical instruments as well.
Robertus Anglicus, writing at Montpellier ca. 1276, described a form of quadrant
(quadrans vetus) whose ultimate origins lie in India. Shortly thereafter, a member of the
scholarly Provençal family of translators Yacob ben Machir ibn Tibbon (Prophatius
Judaeus; d. ca. 1304), developed the “quadrant of Israel” incorporating features from
astrolabes. It later was known as the “new quadrant” (quadrans novus). Another Jewish
scholar born in Languedoc, Levi ben Gershom, invented ca. 1342 a simplified form of
measuring device, the cross-staff or Jacob’s staff, later favored by mariners. Sightings
from the cross-staff or the mariner’s astrolabe were referred to tables like that mentioned
above to determine latitude while at sea. These instruments remained in common use into
the 17th century.
A novel navigational instrument appeared in the 12th century, the magnetic compass.
Although there is still controversy over how the compass reached Europe, its Chinese
origin is indisputable. The earliest European description comes from an English scholar
resident in Paris, Alexander Neckham, writing in 1187. The earliest complete treatise on
the compass was composed by the French soldier Pierre de Maricourt (Petrus Peregrin-
us) in 1269.
Medieval adaptations of earlier instruments include the addition of a sighting tube to
the armillary sphere. Resembling a modern telescope but lacking lenses, the tube was
apparently used to better orient the sphere to the north celestial pole by sighting Polaris in
isolation from its surrounding stars. The earliest representation of such a device is in a
manuscript by Gerbert of Aurillac (930–1003), later Pope Sylvester II. Perhaps related to
the sighting tube was the nocturlabe, or nocturnal, a device with a dial and a sighting
hole. One aligned pointers on the device with stars in the circumpolar constellations and
read the time from a dial.
Bert S.Hall
Gunther, Robert T. Early Science in Oxford. 15 vols. Oxford: Clarendon, 1920–40, Vol. 2:
Astronomy (1927).
North, J.D. “The Astrolabe.” Scientific American 230(1974): 96–106.
Poulle, Emmanuel. “Le quadrant nouveau médiéval.” Journal des savants (1964): 148–67, 182–
214.
——. Les instruments astronomiques du moyen âge. Paris: Brieux, 1983.
ASTRONOMY
. See LIBERAL ARTS
Medieval france: an encyclopedia 148