Maritime Hourglass

Timeline

1. c. 1100–1250Eastern Mediterranean routes · Eastern MediterraneanVenetian and Genoese merchant ships recorded voyage intervals with hourglasses on Levant routes, combining astrolabes and lead lines to estimate speed; the hourglass was adapted from a land timer into a hangable, capsize-resistant shipboard form.
2. c. 1341–1350Venice Arsenal shipbuilding district · VeniceIn the 1340s, Mediterranean and North Sea merchant ships commonly carried half-hour or four-hour hourglasses for watch changes; glass workshops calibrated them to standard sand measures, ship articles and sailing regulations incorporated hourglass timing into crew duty rules, and the revival of shipping after the Black Death further entrenched the practice.
3. c. 1400–1600Iberian and North Sea ports · North SeaOn ocean voyages of the 15th–16th centuries, the maritime hourglass worked with the compass and chip log to record course and elapsed time; Portuguese and Dutch sailing regulations both required standard hourglasses, until mechanical marine chronometers gradually displaced them in the 17th century.