any of various devices for determining the speed of a ship by means of a vaned rotor streamed at the end of a log line upon which it exerts a torsion transmitted to a registering device on board.
Also called screw log.
Origin
1875-80
British Dictionary definitions for patent log
patent log
noun
1.
(nautical) any of several mechanical devices for measuring the speed of a vessel and the distance travelled, consisting typically of a trailing rotor that registers its rotations on a meter Compare chip log