DATUM. The base level. DAVID'S-STAFF. A kind of quadrant formerly used in navigation. DAVIE. An old term for davit. DAVIT. A piece of timber or iron, with sheaves or blocks at its end, projecting over a vessel's quarter or stern, to hoist up and suspend one end of a boat.--_Fish-davit_, is a beam of timber, with a roller or sheave at its end, used as a crane, whereby to hoist the flukes of the anchor to the top of the bow, without injuring the planks of the ship's side as it ascends, and called fishing the anchor; the lower end of this davit rests on the fore-chains, the upper end being properly secured by a tackle from the mast-head; to which end is hung a large block, and through it a strong rope is rove, called the fish-pendant, to the outer end of which is fitted a large hook, and to its inner end a tackle; the former is called the fish-hook, the latter the fish-tackle. There is also a davit of a smaller kind, occasionally fixed in the long-boat, and with the assistance of a small windlass, used to weigh the anchor by the buoy-rope, &c. DAVIT-GUYS. Ropes used to steady boats' davits. DAVIT-ROPE. The lashing which secures the davit to the shrouds when out of use. DAVIT-TOPPING-LIFT. A rope made fast to the outer end of a davit, and rove through a block made fast to a vessel's mast aloft, with a tackle attached. Usually employed for bringing the anchor in-board. DAVY JONES. The spirit of the sea; a nikker; a sea-devil. DAVY JONES'S LOCKER. The ocean; the common receptacle for all things thrown overboard; it is a phrase for death or the other world, when speaking of a person who has been buried at sea. DAW-FISH. The _Scyllium catulus_, a small dog-fish. DAWK-BOAT. A boat for the conveyance of letters in India; _dawk_ being the Hindostanee for _mail_. DAY. The astronomical day is reckoned from noon to noon, continuously through the twenty-four hours, like the other days. It commences at noon, twelve hours after the civil day, which itself begins twelve hours after the nautical day, so that the _noon_ of the civil day, the _beginning_ of the astronomical day, and the _end_ of the nautical day, occur at the same moment. (_See the words_ SOLAR and SIDEREAL.) DAY-BOOK. An old and better name for the log-book; a journal [Fr.] DAY-MATES. Formerly the mates of the several decks--now abolished. (_See_ SUB-LIEUTENANT.) DAY-SKY. The aspect of the sky at day-break, or at twilight. DAY'S WORK. In navigation, the reckoning or reduction of the ship's courses and distances made good during twenty-four hours, or from noon to noon, according to the rules of trigonometry, and thence ascertaining her latitude and longitude by _dead-reckoning_ (which see). D-BLOCK. A lump of oak in the shape of a D, bolted to the ship's side in the channels to reeve the lifts through. DEAD-ANGLE. In fortification, is an angle receiving no defence, either by its own fire or that of any other works. DEAD-CALM. A total cessation of wind; the same as _flat-calm_.