Horizontal Staff

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Name in use since the Middle Ages (in Latin, virga).



Thales of Miletus (7th-6th cent. B.C.)
Euclid (3rd-2nd cent. B.C.)

Historic Period

7th-6th cent. B.C.


In Theorem XXI of Euclid's Optics, the verge is positioned horizontally to measure an unknown length. This is a problem amply discussed in gromatic codices (F. Blume and others, 1967, p. 193) up to and beyond the abacus treatises. From the gromatic tradition of the fluminis varatio (measuring the width of rivers), linked to bridge-building, derives the use of a horizontal verge attached to another vertical one to form a square. This variant is found in the Geometria incerti auctoris (G. d'Aurillac, 972-1003, III, 11 and 24) and in other treatises on practical geometry (D. da Chivasso, 1346, I, 1; C. di Gherardo Dini, 1442, p. 95; F. di Giorgio Martini, c. 1480, fol. 31r).

Bibliographical Resources

Gerbert d'Aurillac, Geometria incerti auctoris, in Gerberti postea Silvestri II papae Opera Mathematica (972-1003), ed. Nicolaus Bubnov, Hildesheim, Georg Olms Verlagsbuchhandlung, 1963.
Domenico da Chivasso, Practica geometriae, ms. Bibl. Laurenziana, San Marco 215, cc. 124v-144r, in The Practica Geometriae of Dominicus de Clavasio (Cod. lat. Monac. 410), ed. H.L.L. Busard, in «Archive for the history of exact sciences», 2, 1965, 6, pp. 520-575.
Arrighi, Gino, a cura di, La Pratica di Geometria, volgarizzata da Cristofano di Gherardo di Dino cittadino Pisano, dal cod. 2186 della Bibl. Riccardiana, Domus Galileiana, Pisa 1966 (1442), p. 95.
Martini, Francesco di Giorgio, La pratica di gieometria dal codice Ashb. 361 della Biblioteca Medicea Laurenziana di Firenze, a cura di Gino Arrighi, Giunti-Barbèra, Firenze 1970, c. 31 r.

Author of the entry: Filippo Camerota

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