US NAVAL OBSERVATORY / SCIENCE PHOTO LIBRARY US NAVAL OBSERVATORY / SCIENCE PHOTO LIBRARY
Longitude determination. US astronomer George Andrews Hill (right, 1858-1927) listening to time signals from Paris, France, as part of longitude determination at the US Naval Observatory, Washington DC, USA, in August 1913. The Arlington (USA) and Eiffel (France) towers were used for transmitting such signals across the Atlantic, part of co-ordinating the official timing and co-ordinate systems. Photographed in the passageway to the south transit house at the US Naval Observatory.
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