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Volvelle

A volvelle is a calculation device consisting of concentric moveable circles. The earliest types were typically made of parchment or paper, with one or more moveable circles attached to a backboard, often the inside cover of a book. The range of information on them was large. Some were like early slide rules, used to calculate the results of mathematical equations. Others worked out the phases of the moon or times of high and low tide. The volvelles that solved astronomical problems could have as many as six rotatable dials.

Strictly, the term is applied only to such historical calculation devices. In more recent times, related ones (usually now called wheel charts or wheel calculators since volvelle is obsolete) have been used to display or calculate the details of everything from the date when a baby was due, through aircraft recognition and dieting data, to geography facts for school children. These were often given away as advertisements at trade shows or supplied with products. Americans of a certain age might recall the BAC (Blood Alcohol Content) calculators that were distributed in school so you could work out the safe limits for drinking. Even in the age of the computer, they’re by no means obsolete, being handy pocket-sized compendia of useful data for some specialist purposes.

The word is from the medieval Latin verb volvere, to turn.

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Copyright © Michael Quinion, 1996–. All rights reserved.
Page created 22 Nov. 2003

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The English language is forever changing. New words appear; old ones fall out of use or alter their meanings. World Wide Words tries to record at least a part of this shifting wordscape by featuring new words, word histories, words in the news, and the curiosities of native English speech.

World Wide Words is copyright © Michael Quinion, 1996–. All rights reserved.
This page URL: http://www.worldwidewords.org/weirdwords/ww-vol2.htm
Last modified: 22 November 2003.