Material regarding preparations for the project to ascertain the longitude of Valentia (Valencia), Ireland, by means of an arc of parallel. The papers begin with correspondence with the Admiralty and Ordnance Survey, including S. Herbert, T.F. Colby, Captain Larcom and C.M. Pasley, and letters concerning arrangements for the transportation of chronometers. The correspondents on the project include Sir J. Barrow, Sir F. Beaufort, W. Cubitt, E. Dunkin, W.H. Smyth and S.H. Christie. The papers also include computations of longitude; requests for chronometers directed to E.J. Dent, R. Molyneux and Parkinson and C. Frodsham; instructions for the use of the chronometers; accounts for the venture; work on the publication of the report; three plans of Valentia Island; two timetables for the London and Birmingham Railway and Grand Junction Railway; and a geodetic map of the British Isles.