Dutchman's log: Meaning and Definition of

Dutch'man's log"

Pronunciation: [key]
— Naut. Naut.
  1. a method of gauging a ship's speed, in which the distance between two shipboard observation stations is divided by the time elapsing between the throwing overboard of an object by the first station and the sighting of it by the second.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.