Protractor
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Revision as of 08:16, 26 July 2010
Name currently in use, deriving from the Greek gonia (angle) and metron (measure).
Description
Generic name for instruments used to divide circles and measure plane angles. They can be circular, semicircular or rectangular. To increase its accuracy, the protractor was often inserted in a nonius, a device for enhancing the precision of the measurements made by a direct readout on a graduated scale. The instrument often came with other accessories, such as folding metal arms and plumb bobs. A singular variant for the layouts of fortresses is described by Giacomo Contarini as one of Fabrizio Mordente's inventions.
Bibliographical Resources
Contarini, Giacomo. Figure d'Istromenti Matematici e loro uso, ms, ca. 1590, Oxford, Bodleian Library, Ms. Canon. Ital. 145, c. 23.
Existing Instruments
Florence, Museo Galileo. Institute and Museum of the History of Science, inv. 613.
Florence, Museo Galileo. Institute and Museum of the History of Science, inv. 1126, 612.
Author of the entry: Filippo Camerota
