Correspondence and papers regarding the determination of longitudes by means of telegraph. There are papers on the difference in longitude between Paris and Greenwich, with observations and transits for clock errors; U.J.J. Le Verrier's determination of the longitude of Le Havre; A. Loussedat's determination of the difference in longitude between Toulouse and Montpellier; the longitude of Glasgow; and the difference in longitude between Altona and Schwerin. There are also papers relating to the project to establish the longitude of Newfoundland relative to Valentia (Valencia). This idea, which was suggested by J.D. Graham and carried out by B.A. Gould, involved the laying of a cable across the Atlantic to the United States. The material relating to the project includes tracings of Ordnance Survey maps; samples of signals from Greenwich to Valentia; transit observations and reduction of observations at Valentia; corrections and computations of factors of local collimation; clock errors; a record of Greenwich signals; and the final figure for longitude. The papers include correspondence with U.J.J. Le Verrier, L.A. Quetelet, P.A.E. Fayé, R. Grant, C.F. Varley, C.A.F. Peters, A.R. Clarke, M.F. Maury, S. Alexander, C.T. Bright, B.A. Gould, H. James, G.H. Richards and J. Graves.