Compasses
From Inventions
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
 Funerary monument of Lucius Alfius Statius (detail), on which are carved a Roman two-foot rule, an archipenzolo (plumb level), a compasses, a square and a hammer. 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
