harpoon log
Definition
Noun: A harpoon log is a cylindrical nautical instrument used to measure the distance a ship travels through water. It consists of a rotator (often with fins or blades) towed behind the vessel on a line. The rotation of the device, caused by water flow, is transmitted via the line to a mechanical register on the ship, which records the distance traveled.
Usage
The term is used in the context of traditional maritime navigation and ship instrumentation. * The captain checked the harpoon log to calculate the day's run. * Before modern electronic systems, sailors relied on devices like the harpoon log for speed and distance measurement.
Advanced Usage
- Historical Context: The harpoon log, specifically the "Cherub" or "Harpoon" patent log invented by Thomas Walker in the 19th century, was a significant improvement over earlier methods like the chip log or Dutchman's log. It provided a more continuous and convenient means of measuring a ship's progress.
Variants and Related Words
- Patent Log: A general term for mechanical towed logs, of which the harpoon log is a specific patented type.
- Taffrail Log: A later type of patent log mounted on the ship's stern (taffrail) rather than being towed.
- Chip Log: An older, simpler device consisting of a weighted wood panel and a knotted line, used to measure speed.
- Log (Nautical): The general term for any device used to measure a ship's speed or distance traveled.
Synonyms
- Distance Log
- Ship's Log (in the specific sense of the measuring device, not the record book)
- Nautical Log
Related Phrases/Idioms
- To heave the log: The traditional phrase for the operation of using a chip log to measure speed. While not specific to the harpoon log, it is part of the same conceptual family of nautical measurement.
Noun
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a cylindrical log with a device that registers distance
