Four-Point Compasses

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-	Unavailable image | 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, particolare.<br />	+
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-	Unavailable image | 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, particolare.<br />	+
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	|autore_scheda= Filippo Camerota		|autore_scheda= Filippo Camerota

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Revision as of 09:48, 26 July 2010

Name currently used for the reduction compasses.

Description

Also called double compasses or "compass with double points" (Muzio Oddi, Fabbrica et uso del compasso polimetro [Construction and operation of the polymeter compass] Milan 1633, introduction), the instrument was used as a proportional compasses, for measuring simple proportional ratios, or as a reduction compasses to enlarge or reduce drawings. The compass was composed of two intersecting legs with points on all ends and a fixed or variable pivot depending on the proportional ratios desired. Ancient examples of this instrument have been found in the excavations of Pompeii.

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Author of the entry: Filippo Camerota