misc: volvelle

A volvelle is an movable illustration, with rotating discs or other slips of paper that can be moved to calculate formulas, determine astronomical positions, or perform other mechanics.

Apian, Cosmographicus, 1524 (C4v)

With this 4-part movable diagram from Apian’s Cosmographicus, the user can practice a series of complicated calculations, including latitude, the times of sunrise and sunset, the duration of dawn and dusk, and the height of the sun.

Apian, Cosmographicus, 1524 (H4r)

In the center of this complicated volvelle, you can see the thread used to attach the moving parts to the page; in this picture you can see the other side of this leaf and thread.

Apian, Cosmographicus, 1524 (H4v)

In this middle of this page, and obscuring some text, is the string and paper securing the discs of the volvelle on the other side of this leaf.