Astronomical rotula by Thomas Jones, 1818.
© Science Museum / Science & Society Picture Library
Thomas Jones, a London instrument maker, produced this paper and card astronomical instrument in 1817. Consisting of circular rotating dials (vovelles) the device was used to determine the position of the Sun and Moon in the heavens. It is based on an instrument called an astronomical rotula, which was designed by the astronomy lecturer, James Ferguson (1710-1776) in 1739. It could also be used to find the dates of solar and lunar eclipses along with times of sunset and sunrise.