Land and Sea

The “rule of marteloio” is a procedure of calculation widely used in Mediterranean navigation during the Middle Ages to determine, during tacking operations, the progress a ship was making toward its destination. Due to changing winds, a ship is often compelled to tack, that is to deviate from its direct route and instead advance by zig-zagging toward its destination.

During tacking operations, the ship goes off its straight route at an angle that varies according to the winds. To calculate how far the ship has deviated from the route and redirect it toward its destination, sailors developed two instruments: a numeric table, the “toleta de marteloio” (in Venetian dialect, “toleta” means “tablet”) that indicates the distance traveled for each quarter-wind; and the “tondo e quadro” (“circle and square”), a geometric diagram based on the wind rose.