machine used to measure the ship's headway, or the rate of her velocity as she advances through the sea. It is composed of a reel and line, to which is fixed a small piece of wood, forming the quadrant of a circle. The term log however is more particularly applied to the latter. See Navigation.

It is usual to heave the log once every hour in ships of war and East-Indiamen; and in all other vessels, once in two hours; and if at any time of the watch, the wind has increased or abated in the intervals, so as to affect the ship's velocity, the officer generally makes a suitable allowance for it, at the close of the watch.

Log-Board, a sort of table, divided into several columns, containing the hours of the day and night, the direction of the winds, the course of the ship, and all the material occurrences that happen during the 24 hours, or from noon to noon; together with the latitude by observation. From this table the different officers of the ship are furnished with materials to compile their journals, wherein they likewise insert whatever may have been omitted, or reject what may appear superfluous in the log-board.

Log-Book, a book into which the contents of the log-board is daily copied at noon, together with every circumstance deserving notice, that may happen to the ship, or within her cognizance, either at sea or in a harbour, &c. The intermediate divisions or watches of the log-book, containing four hours each, are usually signed by the commanding officer thereof, in ships of war or East-Indiamen. See Navigation.

LOGWOOD. See HAMATOXYLON.