The idea of using the telegraph to transmit a time signal for longitude determination was suggested by François Arago to Samuel Morse in 1837, and the first test of this idea was made by Capt. Wilkes of the U.S. Navy in 1844, over Morse's line between Washington and Baltimore. The method was soon in practical use for longitude determination, in particular by the U.S. Coast Survey, and over longer and longer distances as the telegraph network spread across North America and the world, and as technical developments improved accuracy and productivity