Chip log and sandglass
Corredera de barquilla y ampolleta (reloj de arena)
- Date
- c. 1570 · confidence medium
- Place
- England (described by William Bourne)
- Credited to
- English sailors; described by William Bourne (1574)
- Field
- Movement
What it is
A weighted board tied to a knotted line, paid out over the stern while a half-minute sandglass measured the time: the knots counted gave the speed. It quantified dead reckoning and gave rise to the unit 'knot'.
The knots were spaced according to the 28-second sandglass from the 17th century onwards.
What it led to
- Quantified dead-reckoning navigation and log books
- The unit of nautical speed (the knot)
- More accurate charts of oceanic routes
Built on
- Hourglass
- Speed estimation by floating object
Made possible
- Patent log (19th century)
- Standardised logbook