Description

THE MESSUM NAUTICAL PROTRACTOR, English, c.1910, signed “Cary, London, Regd. No. 475601.” Made of thermoplastic or heavy celluloid, 7″ overall, the protractor is engraved on both sides with numerous scales in black and red. Included are a “Masthead Angle Table” and a “Tide Scale For 6 Hr. Tide.” The inventor was apparently Cmdr. Stuart V.S.C. Messum, author of Hydrographic Surveying in 1910. Messum does discuss various scales and designs of protractors, as well as the practicality of surveying by measuring the angular height of the top of a ship’s mast above water line. He also devotes many pages to tidal calculations. A rare mathematical instrument, with complex calibrations, in fine condition.