Compasses

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Revision as of 11:09, 12 November 2009

Since Renaissance times synonymous of seste (compasses), the name derives from the Latin "cum" and "passus", literally "with step", that is, at a measured or constant rhythm.

Description

Instrument for drawing circles, ellipses and other curved lines. Also instrument of measurement and for transferring measurements. The term "compass" or "compasses" denotes a wide range of instruments for drawing, measurement, and proportional calculation. Besides the more common compasses for drawing circumferences, widespread since antiquity, the Renaissance has left us a great number of special compasses, whose names reflect their specific functions: oval compasses to draw ellipses, hyperbolas and parabolas; two-point compasses—also called dividers—to divide lines and transfer measurements; single-handed dividers, to track routes on sea-charts; compasses with curved points, called Caliper compasses, to measure mouths of cannons, cannon balls, and columns; three-point compasses to reproduce maps; four-point compasses, or reduction compasses, to enlarge or reduce drawings, divide lines and circumferences proportionally, and draw polygons; eight-point compasses to measure fractions of degrees and carry out proportional calculations; proportional compasses to perform arithmetic, geometric, and trigonometric calculations and to measure weights, gradients, and distances for military use; and sophisticated surveying compasses that combined a magnetic compass, a windrose, and optical sights for surveying and for drawing topographic maps.

Bibliographical Resources

Scamozzi, Vincenzo. L’idea della architettura universale, Venezia 1615, Parte I, Lib. I, Cap. XV, p. 49: "…I compassi siano piuttosto d’ottone, che d’altra materia che s’irrugginisca; ben leggieri e sottili di gambe, purchè non tremino, all’uso di Francia…".

Images

Ara di Lucius Alfius Statius (dettaglio), vi sono riprodotti un regolo di due piedi romani, un archipenzolo, un compasso, una squadra e un martello. Aquileia, Museo Archeologico Nazionale.	Nicolas Bion. Traité de la construction et des principaux usages des instruments de mathematique : avec les figures necessaires pour l'intelligence de ce Traité, Paris, 1725, tav. VIII p.70	Jacob Leupold. Theatrum machinarum, oder Schau-Platz des grundes mecanischer Wissenschaften / deutlich vor Augen gestellet von Jacob Leupold. Leipzig, 1724-1739, tav. XX a.
George Adams. Geometrical and graphical essays, containing a general description of the mathematical instruments used in geometry, civil and military surveying, levelling and perspective : with many new practical problems. London, 1813., tav. I.

Author of the entry: Filippo Camerota