Mural circle transit instrument, Paris Observatory, France, 1884.
© Science Museum / Science & Society Picture Library
Photograph of one the meridian instruments at the Paris Observatory in France taken around 1884. This view shows the shows the 240 cm (diameter) mural transit circle made by the French maker, Henri Prudence Gambey (1787-1847) for the observatory in 1827. Used in conjunction with an accurate timepiece, the instrument was used to measure the position of stars as they cross the north-south meridian.