Volvelles...moveable paper charts

These are curious mechanical devices.

Wikipedia...

Volvelles, also called wheel charts, are a type of slide chart, paper constructions with rotating parts. It is considered an early example of a paper analog computer. Volvelles have been produced to accommodate organization and calculation in many diverse subjects. Early examples of volvelles are found in the pages of astronomy books. They can be traced back to "certain Arabic treateses on humoral medicine" and to the Persian astronomer, Abu Rayhan Biruni (c. 1000), who made important contributions to the development of the volvelle.

I was at a rare book website and discovered the following...an early 17th Century book with a volvelles intact.

Tractatus de Sphaera

by

Sacrobosco

1619

[A reprint of a 1230 edition]

Sacrobosco discusses the Earth and its place in the Universe.




Volvelles [wheel charts] are still used today for various functions in science, HVAC, mathematical conversions, and photography. And many are made from plastic and metal but still employ the same idea.

Reinventing the Wheel

by

Jessica Helfand

ISBN-10: 1568983387
ISBN-13: 978-1568983387