Volvelle
（重定向自Volvelles）
![A volvella of the moon. A volvella is a moveable device for working out the position of the sun and moon in the zodiac, 15th century](/Images/godic/202502/20/P.9_a_volvella_of_the_moon._A_volvella_is_a_moveable_device_for_working_out_the_position_of_the_sun_and_moon_in_the_zodiac0911.jpg")
![A sixteenth-century wheel chart, a page of Astronomicum Caesareum by Petrus Apianus, 1540, apparently relating to the Moon. The red dragons mark out one odd-sized and 26 equal-sized central divisions; the orbital period of the moon is 27.3 days.](/Images/godic/202502/20/Astronomicum_Caesareum0911.jpg")
![A volvelle from the sixteenth century edition of the De sphaera mundi by Johannes de Sacrobosco.](/Images/godic/202502/20/Sacrobosco_Lunar_eclipse0911.jpg")
A volvelle or wheel chart is a type of slide chart, a paper construction 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 treatises on humoral medicine" and to the Persian astronomer, Abu Rayhan Biruni (c. 1000), who made important contributions to the development of the volvelle.