LOG-BOARD and LOG-BOOK. These contain the account of the ship's progress, as deduced from observations of the log. The log-board is either a large piece of plank, blackened, ruled, and prepared for writing on with chalk, or else a elate with divisions scratched upon its surface. As soon as the seaman has hove the log, and the rate of motion is ascertained, the number of knots, with the odd tenths, or odd fathoms, eight of which equal one knot, are written on the board, each in its proper ruled column ; also the course of the vessel, the direction of the wind, and any remarks made at the moment. This is repeated every time the is hove, and once in twenty-four hours the whole is copied into a book called the logbook, which is ruled fur the purpose in the same way as the log-board, and in which alio all the transactions relative to navigation are inserted, such as bearings and distance of lands, rocks, and shoals, the direction and velocity of currents, the state of the weather, and also whatever principal operations are performed in the ship, such as reefing topsails, tacking, wearing, kc. It is also usual to set down every day the whole course and distance run, calculated from the results of all the several trials made by the log, with the distance and bearing of some port to which the ship is approaching. The account thus obtained is technically termed dead.reekoning, and is never quite correct, being subject to ell the errors caused by changing the direction and velocity in the intervals of observing, by the sort of guess usually made at the course and rapidity of currents, and at the amount of the falling off of the vessel from its apparent course, technically called lee-way. The dead reckoning is believer necessarily used until an opportunity Is afforded of taking observations for latitude end longitude, or until some place whose position is known comes in sight; the true place of the ship is then aubstituud in the log-book for that obtained by dead reckoning, and frum that place subsequent reckonings are made until another observation.
by 17 & 18 Viet. c. 104, the Board of Trade sanction certain forms of log-Looks (called official lop) as adapted to certain kinds of voyages, and it is rendered impel-nth° on every commander to see that all entries therein be made as soon as possible after the occurrences happen which are therein noted.
The official log-book is supposed to contain, in addition to the nautical memoranda above named, a faithful register of every crime and offence, with their punishment, on board the ship ; every calm of accident or illness, with particulars of treatment ; the cause of every death ; register of births ; every marriage ; the sale of deceased seamen's effects; the character of each of the crew, or sufficient reasons for withholding the opinion thereupon ; it full account of all accidents to the :ship and storm ; details of collisions, &e.: indeed the ship's lug, book terms not only a complete history of the voyage, but adds to our knowledge of marine statistic., and thus furthers materially the Interests of commerce, while Its records promote the ends of justice, f r entries In the vial log are received as evidence in any court of law.
sur is commerce alone the gainer by attention to the logbook. Remarks on temperature, winds, weather. and indeed all notable diurnal phem–mena, have, by indefatigable comparison. end well digested de. ductions, eulightened the meteorologist; while the hydrographer has enriched with no leas zeal the treasures of nautical science from the mere notes of the observant sailor. These would seem to be the only legitimate subjects which claim a navigator's attention in keeping his logbook, but the progress of education among sea-officers is shown year by year in a manner as pleasing as it is important. The zoologist, the natural historian, and indeed the philosopher himself, perceive and acknowledge the vast benefit., which a judicious naval observer may yet confer on science. The field for research is a wide one : the heavens, the atmosphere, the ocean, each yields its quota of absorbing interest and improving pastime to the intelligent sailor, and impressions as indelible as they are ennobling lead him insensibly towards social elevation. Little indeed should we know of currents, trade winds, the gulf stream, dust showers, kc., but for the mamas' " log-book," official or private.