What term refers to the method for measuring a ship's speed through the water?

• A. Chronometer
• B. The log and line
• C. Latitude and longitude
• D. Magnetoreception

Answer: (B)

Measuring a ship’s speed through the water is done with the log and line. A log is cast overboard and attached to a line that has knots or marks along its length. The line is paid out for a fixed interval, usually timed with a sandglass, and then the number of knots that passed over the line is counted. That count translates into speed in nautical miles per hour, which sailors call knots. This method gave a practical way to gauge speed at sea before more modern instruments were developed. The other options relate to timekeeping for determining longitude, identifying a position by coordinates, or sensing the Earth’s magnetic field, none of which measure how fast the ship is moving through the water.