The Collaborative International Dictionary of English v.0.48:
Log \Log\, n. [Icel. l[=a]g a felled tree, log; akin to E. lie.
See Lie to lie prostrate.]
1. A bulky piece of wood which has not been shaped by hewing
2. [Prob. the same word as in sense 1; cf. LG. log, lock,
Dan. log, Sw. logg.] (Naut.) An apparatus for measuring
the rate of a ship's motion through the water.
Note: The common log consists of the log-chip, or logship,
often exclusively called the log, and the log line, the
former being commonly a thin wooden quadrant of five or
six inches radius, loaded with lead on the arc to make
it float with the point up. It is attached to the log
line by cords from each corner. This line is divided
into equal spaces, called knots, each bearing the same
proportion to a mile that half a minute does to an
hour. The line is wound on a reel which is so held as
to let it run off freely. When the log is thrown, the
log-chip is kept by the water from being drawn forward,
and the speed of the ship is shown by the number of
knots run out in half a minute. There are improved
logs, consisting of a piece of mechanism which, being
towed astern, shows the distance actually gone through
by the ship, by means of the revolutions of a fly,
which are registered on a dial plate.
3. Hence: The record of the rate of speed of a ship or
airplane, and of the course of its progress for the
duration of a voyage; also, the full nautical record of a
ship's cruise or voyage; a log slate; a log book.
[1913 Webster +PJC]
4. Hence, generally: A record and tabulated statement of the
person(s) operating, operations performed, resources
consumed, and the work done by any machine, device, or
[1913 Webster +PJC]
5. (Mining) A weight or block near the free end of a hoisting
rope to prevent it from being drawn through the sheave.
6. (computers) A record of activities performed within a
program, or changes in a database or file on a computer,
and typically kept as a file in the computer.
Log board (Naut.), a board consisting of two parts shutting
together like a book, with columns in which are entered
the direction of the wind, course of the ship, etc.,
during each hour of the day and night. These entries are
transferred to the log book. A folding slate is now used
Log book, or Logbook (Naut.),
(a) a book in which is entered the daily progress of a
ship at sea, as indicated by the log, with notes on
the weather and incidents of the voyage; the contents
of the log board.
(b) a book in which a log is recorded.
Log cabin, Log house, a cabin or house made of logs.
Log canoe, a canoe made by shaping and hollowing out a
single log; a dugout canoe.
Log glass (Naut.), a small sandglass used to time the
running out of the log line.
Log line (Naut.), a line or cord about a hundred and fifty
fathoms long, fastened to the log-chip. See Note under 2d
Log, n., 2.
Log perch (Zool.), an ethiostomoid fish, or darter
(Percina caprodes); -- called also hogfish and
Log reel (Naut.), the reel on which the log line is wound.
Log slate. (Naut.) See Log board (above).
Rough log (Naut.), a first draught of a record of the
cruise or voyage.
Smooth log (Naut.), a clean copy of the rough log. In the
case of naval vessels this copy is forwarded to the proper
officer of the government.
To heave the log (Naut.), to cast the log-chip into the
water; also, the whole process of ascertaining a vessel's
speed by the log.
Bouvier's Law Dictionary, Revised 6th Ed (1856):
LOG BOOK. A ship's journal. It contains a minute account of the ship's
course, with a short history of every occurrence during the voyage. 1 Marsh.
Ins. 408. When a log books required by law to be kept, it is an official
register so far as regards the transactions required by law to be entered in
it, but no further. Ab. Sh. by Story, 468, n. 1; 1 Sumn. R. 373 2
Summ. 19, 78; 4 Mason, R. 544; 1 Esp. R. 427.