John Smith Gallery

Apian’s Cosmographia [D.20.13]

Like many cosmography books of the period Apian’s Cosmographia contains a number of volvelles. Rather like a circular slide chart, a volvelle was typically included in a cosmographical work to enable the reader to calculate the current time at different locations across the globe, or establish one's latitude, given the height of the Sun above the horizon. The volvelle on display here enables the reader to calculate and visualise the hours of daylight across the northern hemisphere, as determined by its relationship to the position of the sun.