Images Dated 2nd March 2004

Navigational sextant on a historical map

Sextant. Historical sextant on an old map witha book and a feather quill pen. Sextants are usedto measure the position of heavenly bodies to aidin navigation. This is because the exact positionin the sky of the Sun and stars depends upon thetime and location. If a navigator knows the time, the location can be calculated from the positionof these bodies. The sextant was invented in about1730 due to independent work by Englishmathematician John Hadley and American inventorThomas Godfrey. Photograph of a map of Falmouth, Britain. This town was a major port during the18th and 19th centuries

© Ed Young/Science Photo Library