Maritime hourglass

Timeline

1. c. 1300–1400Mediterranean merchant ships · MediterraneanHourglasses were fixed on the bridge, turned on the half-hour or hour and rung with a bell; officers used them to record dead reckoning and watch changes, making them part of ocean-going operating procedures.
2. 1500–1700Atlantic and Indian Ocean routes · ocean routesPortuguese, Spanish, Dutch, and English ocean fleets commonly carried multiple hourglasses; logs recorded wind direction, sail trim, and estimated latitude by hourglass intervals, supporting transoceanic colonial and spice-trade networks.
3. 1700–1800Royal Navy and merchant fleets · EnglandPrecise marine chronometers developed by Harrison and others made longitude determination and continuous timing possible, relegating hourglasses to auxiliary or ceremonial use; naval regulations gradually replaced hourglasses with mechanical clocks as the official timekeeping standard.