Dabchick. Diving bird. Particularly applied to the Little Grebe, which is frequently seen near coast. Dagger. Piece of timber used to support poppets of bilgeways during launching of a vessel. Dagger Keel. Deep and narrow drop-keel. Dagger Knees

D - English Maritime terminology

Dabchick. Diving bird. Particularly applied to the Little Grebe, which is frequently seen near coast.

Dagger. Piece of timber used to support poppets of bilgeways during launching of a vessel.

Dagger Keel. Deep and narrow drop-keel.

Dagger Knees. Knees placed obliquely, instead of vertically, to give as much-uninterrupted stowage space as possible.

Dagger Piece. Name applied to any oblique member in a vessel's framing.

Dagger Plank. Plank uniting poppets and stepping up pieces of a launching cradle.

Daltonism. Inability of eye to distinguish between red and green colours. A form of colour blindness.

Dalton's Law. In a mixture of gases each gas exerts its own pressure independently of the others, the pressure of the mixture being the sum total of the constituent pressures.

Damp. To damp fires is to reduce the air supply so that combustion goes on very slowly. 2. To damp a gyro is to constrain its move­ments to a limited amount.

Damp Aw. Atmospheric air when its water content is about 85% of maximum.

Dan Buoy. Pole or spar with ballasting weight at one end and buoyant unit at middle. Mooring rope, with weighted mooring, is attached to middle. Used by trawlers, surveying vessels, mine­sweepers and others as a temporary sea mark.

Dandy. Sloop or cutter with a jiggermast right aft, on which a small lugsail is set.

Dandyfunk. Kind of pudding made from crushed ship's biscuits.

Dandy Note. 'Pricking Note.'

Danger Angle. Vertical or horizontal sextant angle which, when used in conjunction with charted objects, will indicate when a vessel is approaching a position of danger.

Dangerous Goods. Commodities that seriously endanger the safety of a vessel in which they are carried. M.S.A. specifically mentions aquafortis, vitriol, naphtha, benzine, gunpowder, lucifer matches, nitroglycerine, petroleum and explosives.

Dangerous Quadrant. That half of front of a cyclonic storm that is on the side towards which recurvature is to be expected.

Danube Tonnage Rules. Special tonnage rules applied to vessels when navigating river Danube.

Dash. The longer flash or sign in Morse signaling. Is three times the length of the 'dot'.

Date Line. Line on which time zones —12 hours and +12 hours meet. The time is the same on either side, but the dates are one day different; 180°E being a day in advance of 180°W. This line is mainly, but not entirely, on the 180th meridian; varying between 170°E and 172 ½ °W, to avoid having different dates in a group of islands, or same area of land.

Datum. Given level, or other value, to which varying values are referred.

Davis Current. Alternative name for Labrador Current.

Davis Quadrant.* The 'Backstaff’ of Captain Davis, which was the usual navigating instrument from 1590 to latter half of 18th century.

Davit. Iron or steel (formerly wood) fitting projecting over ship's side for attachment of tackle for hoisting and lowering boat, accommodation ladder, anchor, stores, etc. Sometimes fitted at hatch.

Davy Jones. Evil spirit of the sea, who lies in wait for seamen. Said to be a corruption of 'Duffy Jones'; 'duffy' being a Negro word for 'ghost', and 'Jones' being a corruption of 'Jonah'.

Davy Jones Locker. The bottom of the sea, where Davy Jones holds drowned seamen and foundered ships.

Day. Period of time based on Earth's revolution on its axis. Its duration is based on successive transits of a point of definition at a given place. This point is, in most civilized countries, based on the mean Sun for civil time, and First Point of Aries for sidereal time.

Day Mark. Shape hoisted, in daytime, by vessels in specified cir­cumstances, and in accordance with international rules. 2. Distinguishing characteristic of a light vessel. 3. Navigational beacon that is not observable at night.

Days of Grace. Time allowed, beyond a time and date specified. during which no action will be taken for non-fulfilment of a contract. In the case of money bills the usual period is three days.

Day's Work. At one time called 'Day's works'. Practical methods of deducing ship's noon position, usually by dead reckoning, and computing course and distance made good and course to be steered.

Dead Beat Compass. Magnetic compass in which swing due to quick alterations of course, or liveliness of vessel, is greatly reduced both in time and amplitude. Has short but very strong needles, and comparatively large bowl.

Dead Calm. Perfectly smooth sea and no wind whatever.

Dead Door. Sliding wooden shutter for blanking square window of a cabin.

Deadeyc. Hard wooden block, pierced with holes, fitted in lower end of shroud to take lanyard for setting up.

Dead Flat. Midship frame of a vessel where breadth is greatest.

Dead Freight. Money paid to ship for failure to provide a full cargo promised.

Dead Head. Solid piece of wood used as anchor buoy.

Dead Horse. Performance of work that has already been paid for.

Dead Lights. Plates fitted over portholes to protect them or to prevent lights inside the ship from showing outboard.

Dead Man. Rope's end, or small piece of yarn or line, when left hanging untidily. 2. Counterbalancing weight that assists guy of derrick.

Dead Men's Eyes.* Early name for 'Deadeye'.

Dead Neap. Lowest possible high water of a tide.

Dead on End. Said of wind when exactly ahead; and of another vessel when her fore and aft line coincides with observer's line of sight.

Dead Reckoning. Calculation of a ship's position by consideration of distance logged, courses steered and estimated leeway. Some­times said to be corruption of 'deduced reckoning'; but this is very debatable.

Dead Rising. Those parts of a vessel's floor, throughout her length, where floor timbers meet lower futtocks.

Dead Ropes. All ropes, or running rigging, that are not led through a block or sheave.

Dead Slow. Minimum speed that will give steerage way.

Dead Water. Eddy water immediately astern of a sailing vessel or boat.

Deadweight. Total weight, in tons, of cargo, stores and fuel carried by a vessel at her maximum permitted draught.

Deadweight Cargo. Cargo whose specific gravity is such that a vessel loading it will go down to her marks.

Deadweight Scale. Table, or graph, showing total weight of fuel, stores and cargo, and corresponding mean draught of vessel.

Deadweight Tonnage. Deadweight expressed in tons avoirdupois.

Dead Wind. Wind directly contrary to ship's course.

Deadwood. Flat, vertical surfaces at junction of stem or stern post with keel. Has no buoyant effect.

Dead Work.* Old name for 'Freeboard'.

Deals. Planks, particularly of fir, 7 to 11 in. in width and 2 to 4 in. thick.

Decca Navigator. A radio aid for fixing positions up to at least 300 miles from the transmitter. A master transmitter ashore controls a chain of other transmitters, designated Slaves. All transmit signals continuously. A ship provided with a special receiver can receive these signals, the phase-difference between them being measured by Decometers. The numbers indicated on the Decometers refer to coloured lattice lines printed on

special charts. The ship's position is where the numbered lines cross each other.

Deck. Horizontal flooring, or plating, above bottom of vessel. May be continuous or partial.

Deck Beam. Thwartship member that supports a deck and preserves form of a vessel.

Deck Bridge.* Former name for a navigating bridge.

Deck Cargo. Cargo that must be carried on deck. 2. Cargo that is customarily carried on deck. 3. Cargo actually carried on deck.

Deck Hand. Seaman, other than officer, who serves on deck. Man of 17 years of age, or over, with at least one year's sea service.

Deck Head. Underside of a deck.

Deck Hook. Thwartship frame across apron, to strengthen bow

and support fore end of deck.

Deck Light. Strong glass bull's eye fitted in a deck to light a com­partment below. 2. A permanent light fitted on a deck.

Deck Line. Horizontal mark, cut in plating of side and painted in a distinct colour, that indicates position of freeboard deck.

Deck Load. Deck cargo.

Deck Log. Log book kept by officer of watch and entered with events, changes of course, weather, log readings, work done and other items occurring during the watch. In harbour, is kept by duty officer.

Deck Nail. Large nail, of diamond section, used for securing deck plank to beam of a wooden ship.

Deck Officer. In general, an officer whose duties are connected with the deck department. Sometimes applied to the duty officer of 1 he deck or watch.

Deck Passage. Voyage of a passenger for whom no accommodation is available. Confined to short voyages and trades, such as the carrying of pilgrims.

Deck Pipe. Navel pipe, through which chain cable passes to chain locker.

Deck Sheet. Studdingsail sheet that leads directly from sail to deck.

Deck Stopper. Formerly, length of very strong rope to which cable could be lashed; one end of a stopper being secured to deck. Name is sometimes given to any fitting on deck for holding cable for a short time.

Deck Transom.* Formerly, a horizontal timber under counter of a ship.

Deck Watch. Watch that is used for timing sights taken on deck. Is compared with chronometer before and after sights are taken, so avoiding disturbance of chronometer.

Declaration of London, 1909. Rules and regulations framed by an International Naval Conference, but not formally ratified.

Declaration of Paris, 1856. Abolished privateering; declared that neutral flag covers enemy goods, but not contraband of war; neutral goods, other than contraband, not liable to capture;

blockade must be effective to be legal.

Declination. Angular distance, of a heavenly body, north or south of Equinoctial. 2. Former name for variation of compass.

Declination Circle. Great circle, of celestial concave, that is per­pendicular to Equinoctial. Also called hour circle, of circle of Right Ascension.

Declination Inequalities. Variations in heights or intervals of high and low waters of tides when due to variations in declination of Sun and Moon.

Deep. Navigable channel bounded by shoal water. 2. Applied to frames and stringers that have been widened, by extending plate between angle bars, to give additional strength. 'Deep.' Leadsman's call before naming a sounding in fathoms that is not marked in lead line.

Deep Sea Lead. 28-lb. lead used for taking soundings by hand in deep water.

Deep Sea Leadline. One-inch cable laid rope, 100 fathoms long, used with deep sea lead. Marked as hand leadline to 20 fathoms, then every 5 fathoms.

Deep Sea Sounding. Ascertaining sea depths beyond reach of hand lead. Also applied to a sounding exceeding 100 fathoms.

Deep Tank. Ballast tank extending from 'tween deck to bottom of ship, and from shipside to shipside. Has centre fore and aft bulkhead, with valve between compartments. May be utilized for cargo.

Deep Waist. Upper deck in a ship with high forecastle and poop.

Deep Waisted. Said of a ship having a deep waist.

Deface.* To strip a wooden ship of her planking and leave the ribs bare.

Deflector. Instrument invented by Lord Kelvin for measuring directive force of a compass mounted in a steel or iron ship. Measurements are made with ship's head on four cardinal points.

Degaussing. Neutralising magnetic effect of steel or iron vessel by encircling her with wires carrying electric current. Used as protection against magnetic mines.

Degree. Originally, arc of Ecliptic travelled by Sun in one day. Now, angle subtended by 1/360th of circumference of a circle.

Degree of Dependence. Measure of probable error in an observa­tion or assessment.

Dekad. Meteorological name for a period of ten days.

Delambre's Analogies. Formulae for solving spherical triangles in terms of those used for solving plane triangles.

De Laval Turbine. Uncompounded turbine that is used for driving pumps and dynamos.

Delta. Triangular area of sediment in mouth of a river, so giving river more than one discharging channel.

Delta Metal. Alloy of copper, zinc and iron. Much used for engineering purposes.

Demi-Culverin. Naval gun of Tudor times. Threw ball of 9-10 Ib.

Demise. Temporary transfer of a vessel to another party under such terms and conditions that the owner ceases to have any control over her for the period of the charter.

Demurrage. Money paid to shipowner, by charterer, when his ship is detained beyond the lay days mentioned in charter party.

Deneb Adige. Star aCygni. Usually called 'Deneb'. S.H.A. 50°; Dec. 45°N.

Deneb Aleet. Old name for star Denebola.

Denebola. Star b Leonis. S.H.A. 183°; Dec. 15°; Mag. 2-2.

Density. Weight per unit volume, e.g. weight in oz. per cub. ft. Relative Density = Specific Gravity == Ratio of unit volume of water compared with weight of same volume of fresh water. 2. Density of sea water is about 1026, but varies between 1000 and 1038 (Port Sudan) in ports. 3. Density of boiler water is expressed in 1/32nds of increase in weight, 3/32nds being upper limit tolerated. Due, principally, to sulphate of lime in suspension.

Departure. The distance made good due East or West when sailing on any course.

Departure Course. Course made good from a point of reference at which a voyage, or stage of voyage, commenced.

Departure Distance. Distance of a ship from a point of reference at which a voyage, or stage of a voyage, commenced.

Deposition. Statement made on oath or affirmation.

Deposit Receipt. Acknowledgement of receipt of a sum of money, from a receiver of cargo, when a general average contribution is likely to be claimed.

Depression. Of horizon, is angular distance of visible horizon, or shore horizon, below sensible horizon. Usually termed 'Dip'. 2. Atmospheric mass in which barometric pressure is lower than that of surrounding atmosphere.

Depression of Wet Bulb. Amount, in degrees, that registration of wet bulb thermometer is less than that of dry bulb. Occasionally there may be a negative depression when temperature is falling quickly. Depression is usually zero in fog or wet mist.

Depth. Of boat, is vertical distance from level of gunwale to keel. 2. Of flag, measure of its vertical length. More usually termed its 'breadth'. 3. Of hold, is vertical distance from underside of beam to top of keelson. 4. Of sea, is distance, in fathoms or feet, from level of low water spring tide to sea bed. 5. Of sail, is vertical distance from head to foot of square sail; length of leech of a fore and aft sail.

Depth Charge. Canister of explosive detonated at a required depth by a hydrostatic valve. Used against submerged submarines.

Depth Finder. Lead having a vane attachment that measures depth on the same principle that a towed log measures horizontal distance. See 'Harpoon Depth Finder'.

Deratisation. Extermination of all rats aboard a vessel.

Derelict. Floating vessel that has been totally abandoned.

Derrick. Boom or spar used for hoisting or lowering weights. Made of wood or steel, controlled by guys, supported by topping lift, and pivoted at lower end.

Derrick Post. Stump mast used for taking topping lift of a swing­ing derrick.

Descending Latitude. Decreasing celestial latitude of Moon or planet.

Descending Node. That point in Ecliptic at which Moon passes to South (minus) celestial latitude.

Deserter. One who leaves, or remains away from, his ship without permission and shows no intention of eventual return.

Desertion. Leaving, or remaining away from, a ship without permission and showing no intention of eventually returning.

Despatch. Quickness in performance. 2. To send away.

Despatch Money. Agreed amount paid by shipowner to receiver of cargo when cargo is discharged in less time than that contracted.

Destination. Port to which a vessel is bound, or at which cargo is to be delivered.

Destitute Foreign Seamen. In M.S.A. is applied to certain Asiatics, Africans, South Sea Islanders and foreign seamen of countries who have no Consul in the United Kingdom.

Destroyer. 'Torpedo Boat Destroyer.' Fast, unarmoured, warship armed with torpedoes and guns, capable of attacking large war­ships with her torpedoes and submarines with depth-charges.

De-Superheater. Appliance for removing excess heat from super­heated steam that is to be used for auxiliary machinery. Gener­ally effected by an automatically controlled system of water spraying.

Detention. The holding of a vessel in a port—without resorting to seizure, arrest or capture by a sovereign power or competent authority.

Determination. Exact ascertainment of position, amount, or other required information.

Deviation. Applied to a voyage, is an unjustified and unnecessary departure from normal course or customary route; delay in sailing, tardiness on voyage, arrival at port other than that intended, or any divergence that makes the voyage other than that intended.

Deviation (or Compass). Angle that compass needle makes with the magnetic meridian at a place when due to attracting forces in ship or cargo.

Devil. Deck seam between ship's side and outboard line of planking.

Devil Fish. Large fish of ray family. Has enormous head, and is 3 to 5 ft. in length.

Devil's Claw. Two-pronged hook, or claw, that drops over side of link of cable. Attached to deck and used for holding cable temporarily.

Devil to pay and no pitch hot.' Refers to 'devil' deck seam. Means a difficult job to be done and no preparation made.

De Vries-Smitt Tide Gauge. Submerged tide gauge used by Netherlands Hydrographic Office. Records variations of water pressure due to change in height of water level; gauge being at constant distance from bottom.

Dew. Particles of water deposited by atmosphere when in contact with a surface whose temperature is below that of dew point.

Dew Point. Lowest temperature to which air can be cooled without condensation of its water vapour. Should temperature fall below this point fog or mist may form.

D.F. Bearing. Position line obtained from a directional radio beam.

Dghaisa. Open boat with greatly extended stem and stern posts. Peculiar to Malta. Two oars are pushed.

Dhow. Arab sailing vessel of about 150-200 tons. Has one mast and very large lateen sail.

Diacoustics. Science of direct sound.

Diagonal. Any knee, plank, brace, etc., that is placed diagonally. 2. Line cutting a body plan in an oblique direction.

Diagonal Built. Said of wooden boats and vessels in which side planking is made up of two layers at an angle of 45° with keel, upper layer crossing lower layer in opposite directions.

Diamagnetic. Name given to substance whose magnetic perme­ability is less than unity. 2. A substance which, when magnetised, lies across lines of magnetic force.

Diametral Plane. Great circle of a sphere.

Diamond Knot. Fancy bend in two ropes' ends made by inter­lacing them. Similar to 'Carrick Bend'. 2. Knot formed in a rope, somewhat similar to single 'Turk's Head'.

Diaphone. Sonic fog-signalling apparatus that gives a high note that descends to a low note of great carrying power. Fitted in light vessels.

Diatomic Ooze. Yellowish-brown ooze containing the algae 'bacillareophyta'. Found at depths from 600 to 2000 fathoms.

Dicrotum.* Boat propelled by two oars.

Dielectric. Insulating material that prevents conduction of elec­tricity but allows induction. Used in electrical condensers.

Diesel Engine. Oil engine in which ignition of fuel is caused by compression. Cycle comprises air compression, fuel injection, ignition, and scavenging. Cycle may be completed in two or four strokes.

Difference of Latitude. Angular value of arc of meridian intercepted between parallels of latitude passing through two different positions.

Difference of Longitude. Angle at pole, or intercepted arc of Equator, between two meridians.

Differences (Tidal). Amounts that heights or times of high and low water at a given place differ from the corresponding heights and times at a port of reference.

Differential Block. Wheel with two sets of sprockets around its circumference, one set being on a smaller diameter than the other, and so having less sprockets. Endless chain is laid in each wheel, each having hanging bight. Weight is lifted in bight of larger wheel, power is applied to bight of lower. Difference in number of sprockets is measure of lift.

Dikrotos.* Ancient Greek vessel similar to bireme.

Dingbat. Slang term for a small swab made of rope and used for drying decks.

Dinghy. Small boat, about 10-14 ft. long, pulling two oars and fitted with mast and one or two sails.

Dioptric. Applied to lenses and lights when concentration of light rays is obtained by refraction.

Dip. Angular amount that visible horizon is below horizontal plane due to height of observer's eye. 2. Angle that a freely-suspended magnet makes with horizontal plane when aligned with lines of magnetic force. 3. To lower a flag a small distance, either as salute or signal. 4. To commence to descend in altitude. 5. To pass a rope, end of spar or other article down and under an obstruction. 6. Amount of submergence of a paddle wheel.

Diphda. Star b Ceti. S.H.A. 350°; Dec. S18°; Mag. 2-2.

Dipper. Ladle used for baling a boat. 2. Name is common in U.S.A., and in Britain, for constellation Ursa Major.

Dipping a Light. Sailing away from a navigational beacon light and so causing it to dip below horizon.

Dipping Colours—Ensign. Lowering national colours as a salute.

Dipping Lug. Lugsail that has to be lowered a little, when going about, so that throat of sail and end of yard can be dipped round mast.

Dipping Needle. Magnetic needle on horizontal axis; used when measuring inclination of Earth's magnetic force.

Dipsy. Name sometimes given to deep sea lead. 2. Float on fishing line.

Direct Current. Electrical current flowing in one direction.

Directing Force. That component, of magnetism of a compass needle, that directs the needle into the magnetic meridian.

Direction. Of wind, is compass point from which it blows. Of current, is direction towards which it sets.

Direction Finder. Instrument for finding the bearing of a transmitt­ing radio station or radio beacon.

Directive Force. 'Directing Force.'

Direct Motion. Movement in space that is in direction of Earth's rotation and Sun's apparent motion in heavens. All planets have direct motion. Applied to movement of planet when its right ascension increases.

Direct Tide. Undulation of tide that synchronises with Moon's transit at a place.

Dirk. Short sword forming part of R.N. midshipman's uniform. Also, colloquial name for a seaman's knife.

Disbursement. The paying of money. Sum of money paid out.

Disbursements. Sums of money paid out of a fund credited or allotted.

Disc. Circular face of a solar system body.

Discharge. To put cargo out of a ship and obtain freedom of responsibility for it. 2. To pay off a man, or crew, and relinquish all claims for service.

Discharge Book. Continuous record of a seaman's service at sea. Issued by D.T.I, and held by man except when actually serving in ship. Contains names and particulars of ships served in, rating, reports on character and ability. Held in custody of master while serving in ship.

Discipline. Due and honest rendering of service and obedience. Equitable co-ordination of duties and responsibilities for the common benefit. Maintenance of proper subordination.

Disembark. To come out of a ship. To put out of ship and put ashore.

Disengaging Gear. Applied to fittings, to boat and falls, that release a boat from her falls simultaneously and rapidly.

Dismast. Carry away, or remove, the mast or masts of a vessel.

Dispatch. 'Despatch.'

Dispatch Money. 'Despatch Money.'

Dispatch Note. 'Despatch Note.'

Displacement. Amount of water displaced by a floating vessel in a given condition. May be expressed in tons, or volume in cubic feet; tons being weight of vessel and contents, volume being that of immersed part of vessel.

Display. Visual presentation of received radar signals. Relative Display. The observer's position remains stationary and the movement of targets (coastline, ships, etc.) is thus relative to the observer. Stabilised Display in which the heading marker and bearings of targets are stabilised by a transmitting compass. True-motion Display. The observer's position moves across the display in accordance with his ship's course and speed. Move­ments of targets are thus in their proper direction and at their proper speed.

Disrating. Degrading from one rank or rating to a lower. With­drawal of a rating given to a man.

Distance. Length in a particular direction of course. Length of shortest track between two places. Length of customary track between two places. Time difference between two given meri­dians. Angular value, at a given point, between two other points.

Distance of Visible Horizon. Varies with height of observer's eye. Can be found, in miles, from product of square root of height of eye, in feet, and constant factor of 1-15.

Distance Recorder. In general, any log or log mechanism that records distance. In particular, see 'Forbes Distance Recorder'.

Distant Signals. System of shapes used between ships when far apart in daytime, and colours of flags were indistinguishable. With development of brilliant Morse lamps and radio the system became unnecessary.

Distiller. Combined condenser and aerator used when converting steam to drinking water.

Distortion of Charts. See 'Chart Distortion.'

Distraint. Legal seizure of ship or goods in satisfaction of a debt.

Distress. In a state of danger and in need of assistance. Also alternative name for 'Distraint'.

Distressed Seaman. Seaman, who, through no fault of his own but through some event in his employment, is in need of assist­ance, to maintain himself and to return home or to a proper return port.

Distress Signals. Customary and statutory indications that a vessel, or her personnel, are in danger and in need of assistance.

Ditch. Colloquial name for the sea. To ditch is to throw overboard.

Ditcher. Name given to a small light draught vessel that can navigate narrow, shallow channels.

Ditty Bag. Small canvas bag in which a seaman keeps his small stores and impedimenta.

Ditty Box. Small wooden box, with lock and key, in which seamen of R.N. keep sentimental valuables, stationery and sundry small stores.

Diurnal. Daily. Occurring once a day.

Diurnal Aberration. Apparent error in position of heavenly body due to light rays from the body being received )6y an observer who is being moved by Earth's diurnal rotation.

Diurnal Arc. Apparent arc made in the sky, by a heavenly body, when due to Earth's diurnal rotation.

Diurnal Circle. Circle in celestial concave in which a heavenly body, when viewed from Earth, seems to move.

Diurnal Components. Those tidal components whose maximum values are attained once a day approximately.

Diurnal Inequality of Tides. Difference, in time or height, between two successive semidiurnal tides when a diurnal factor has affected one tide differently from the other.

Diurnal Liberation. Parallactic effect due to Earth's rotational movement, in which we see a little around western side of Moon when she is rising, and a little around eastern side when she is setting.

Diurnal Motion. Measure of arc through which a solar system body moves in celestial concave during a day. Also applied to apparent movement of heavenly bodies when due to Earth's rotation on axis.

Diurnal Parallax. Difference between position of heavenly body, when viewed from a point on surface of Earth, and its position when viewed from centre of Earth. Difference varies throughout day.

Diurnal Tide. Tide that has one high water and one low water in a tidal day.

Diurnal Variation of Barometer. Small rise of barometric pressure between 4 a.m. and 10 a.m., then fall until 4 p.m., followed by rise till 10 p.m. and fall to 4 a.m.

Diver. One who goes under water. Particularly applied to man who goes under water in a special dress in which he can be supplied with air. 2. Long-necked bird that dives into ocean in search of fish.

Divert Palsy. 'Caisson Disease.'

Dividers. Instrument for measuring distance on a chart with two legs connected at one end by a movable joint.

Divisions. Daily morning muster of ship's company in R.N. Men muster by divisions and proceed to prayers. Introduced by Kempenfeldt, 1780.

Dock. Artifical excavation or construction in which ships can be placed for loading, unloading, fitting out, or repairing. Principal types are wet, dry and floating docks.

Dock Dues. Money paid for use of a dock and its equipment.

Docket. Label or document giving particulars of goods to which it refers.

Docking. Placing of a vessel in dock. 2. Overhaul of a vessel in dock.

Docking Bridge. Small thwartship bridge on poop, to give clear view to officer in charge aft when docking a ship.

Docking Keel. Name sometimes given to bilge keel.

Docking Stresses. Particular stresses set up in a ship in dry dock. Due to lack of water support. Most important are compressive stresses on bottom, shearing stresses in decks, tensile stresses at upper edges of floors.

Dockmaster. Official in charge of a dock.

Dock Pass. Receipt for dock dues paid, and authorisation for ship to leave dock and proceed to sea. Authorisation for a person to leave or enter a dock area.

Docks Regulations. Rules and regulations governing ships when in a dock.

Docks Regulations, 1934. S.R.O. 279. Those sections of the Factory Act that apply to the loading, unloading, handling and moving of goods in a ship or dock, or on wharf or quay.

Dock Rent. Charges made for storage of goods in a dock warehouse.

Dock Warrant. Receipt given by dock warehouseman for goods deposited with him.

Dockyard. Enclosed space containing docks, storehouses and workshops, and having facilities for the fitting, refitting and repair of ships.

Doctor. Usual nickname for a ship's cook.

Dodger. Small piece of canvas spread as wind screen for man on watch.

Dog. Short form of 'Dog Watch', or of 'Dog shore'. 2. Meteor when seen low in horizon at dawn or sunset. 3. Short iron bar fitted with teeth at one end and ring at other end. Used as a

lever, with tackle hooked in ring.

Dogger. Dutch fishing vessel, with two masts, employed on Dogger Bank.

Dogging. Passing twine or small rope rightly around another rope.

Dog's Lug. Projection of boltrope of sail, between earing cringle and reef cringle, when sail is reefed.

Dog Star. Sirius, a Canis Majoris.

Dog Vane. Small piece of bunting stopped to shroud, when under sail, to indicate wind direction to helmsman.

Dog Watch. One of the two-hour watches between 4 p.m. and 8 p.m., introduced to effect changes in watches kept on con­secutive days.

Doldrums. Comparatively windless zone, along Equator, that separates the prevailing winds of north and south latitudes.

Dolphin. Mammalian marine creature that frequently sports around ships' bows at sea. 2. Iron or wood structure, in harbours, for mooring of ships. 3. Moored spar to which a

ship can be moored. 4. Plaited cordage formerly put around mast, immediately below jaws, to support yard if lifts were shot away.

Dolphin Striker. Spar vertically below end of bowsprit to give downward lead to martingales of jib boom and flying jib boom.

Dominical Letter. Letter that Sundays will have in a given year when January 1 is A and days are successively lettered from A to G.

Donkey. Short form of 'Donkey Boiler', 'Donkey Engine' or 'Donkeyman'.

Donkey Boiler. Small boiler, often vertical, used for generating steam (or winches and other machinery used in harbour.

Donkey Engine. Small steam winch used in sailing ships to reduce number of men required when weighing anchor, pumping, or working cargo.

Donkeyman. Rating who tends a donkey boiler, or engine, and assists in engine-room.

Donkey's Breakfast. Merchant seaman's name for his bed or mattress.

Donkey Topsail. 'Jack Topsail.'

Dory. Flat-bottomed boat with sharp ends, and sides sloping upward and outward. 2. Edible fish sometimes found in British waters. Has spiny rays along back and on lower side.

Dot. Short flash in Morse signalling. One-third length of 'dash'.

Double. To alter course round a point of land.

Double Altitude. Two altitudes of one heavenly body, with an elapsed interval; or approximately simultaneous altitudes of two bodies. Taken to obtain position lines.

Double Bank. To put two men to pull one oar.

Double Banked. Said of a boat in which two oars are pulled on one thwart. Said of an oar pulled by two men.

Double Block. Pulley block having two sheaves on the same pin.

Double Bottom. Space between inner and outer bottom plating of hull.

Double Chronometer. Name given to the finding of a ship's position by Sumner's Method, and using two heavenly bodies sufficiently distant from the meridian.

Double Clewed Jib. Four-sided jib with two clews. Introduced by Sopwith in 'Endeavour', 1934, to take place of jib and jib top sail.

Double Compound Engine. Reciprocating engine consisting of two engines having h. p. and l. p. cylinders.

Double Luff. Purchase having two double blocks with standing part of rope made fast at head of one block.

Double Summer Time. See 'Summer Time.

Double Tide. Occurrence of two high waters in one semidiurnal period. Noticeable at Portland, Southampton and other places.

Double Topsail. Two topsails, without reefs, that take the place of a large topsail that can be reefed. Sail area is reduced by furling upper topsail.

Double Up. (Moorings.) To duplicate all mooring ropes.

Double Whip. See 'Whip'.

Doubling Angle on Bow. Method of finding distance from a fixed point, or object, by measuring distance run from a point where its angle on bow has certain value, to another point where the angle on bow of same object, is double the value of the first. Distance run between bearings will be equal to distance of observed object at second bearing if course steered and distance run through water are made good over the ground. Correction must be made for any leeway, or set and drift of tidal current.

Doubling. Sailing round a point of land. 2. Extra strip of canvas stitched to sail for strengthening. 3. Turned in edge of sail that takes boltrope. 4. Piece of timber on after side of wooden bitts. 5. Additional timber fastened to outer skin of vessel when working amongst floating ice. 6. Generally applied to any lap of plate, planking or canvas.

Doublings. Those parts of a built mast where the upper end of one mast lies abaft the lower part of a mast extending above it.

Douglas Protractor. Square, transparent, protractor with a graticule of squares, and degrees marked on the edges.

Douglas Sea and Swell Scale. International scale for recording state of sea by a figure between 0 and 9; and swell by figures between 00 and 99, upper and lower figures inclusive.

Douse. To lower quickly and suddenly. To extinguish a light by dousing an extinguisher. To take in a sail. 'Douse the glin': Put out the light.

Dousing Chocks. Pieces of wood laid across apron of wooden ship, and extended to knight heads.

Dow. 'Dhow.'

Dowel. Small circular piece of wood let into deck plank to cover countersunk head of fastening bolt.

Dowelling. Joining wood spars by making shaped projections, on one of the parts, fit into corresponding cut-out portions in the other part.

Down. Said of a tiller when it is put to leeward while sailing.

Downhaul. Rope rove for hauling down purposes. Especially applied to rope by which jib, staysail, jaw of gaff, or flag are hauled down.

Downton Pump. Double-acting pump in which piston is solid, and valves are so placed as to be easily accessible for clearing. Used for pumping bilges, or for sea suction.

Dowse. 'Douse.'

Drabler. Strip of canvas laced to bonnet of square sail to increase its area.

Draco. Winding constellation between Lyra and Ursa Minor.

Draft. Old name for a chart. 2. Document authorising one party to draw on the funds of another. 3. Draught.

Drag. To draw an anchor along the bottom. 2. Difference between propeller speed and ship's speed through water when ship is going faster than propeller's speed. 3. Alternative name for 'Drogue'.

Drag Anchor. Old name for 'Drogue' or 'Sea Anchor'.

Drag Net. Net dragged along the bottom by fishing vessel.

Dragon. 1. Norse Longship of about 900 A.D. of largest size. The biggest had a keel 148 ft. long and rowed 68 oars. Named from its figurehead. 2. Northern constellation 'Draco'.

Drag Sheet. Sail laced to a spar that is weighed at, foot, and used as a drogue.

Draught. Depth in water at which a ship floats.

Draught Indicator. Instrument fitted inside a ship to indicate draught at which she is floating.

Draught Gauge. Instrument that indicates a ship's draught.

Draught Marks. Figures cut into stem and sternpost and painted. Used for ascertaining draught at any moment and for finding trim.

Draughts.* Old name for charts or plans.

Draw. To submerge hull a specified distance. To require a stated depth of water to be afloat. 2. Sail is said to draw when filled with wind and straining at sheets and attachments to ship. 3. To draw a jib is to shift it to leeward when aback. 4. To draw a splice is to withdraw the spliced strands.

Drawback. Money paid back. More especially applied to refund of import duties when goods are re-exported; and to remission of excise duties on goods of home manufacture, when consigned to a port abroad.

Drawee. Firm or persons responsible for redeeming a bill of exchange or money order.

Dredge. Drag net drawn along sea bed when fishing. 2. Apparatus for bringing up a sample of the sea bed when surveying. 3. Bucket of a dredger.

Dredger. Vessel fitted with an endless chain of bucket dredges that bring up the bottom ground when deepening a channel or area.

Dredging. Manoeuvring a vessel in a tideway by dragging an anchor on bottom and using difference in speed, between rate of current and speed over ground, for steerage purposes.

Dressing Line. Line to which flags are stopped when preparing to dress ship.

Dress Ship. To pay compliment or respect by hoisting flags at mastheads, bow and stern. To dress ship overall is to hoist ensigns at mastheads and a continuous line of flags from stem to fore masthead, between mastheads and from after masthead to stern.

Driers. Pastes or liquids mixed with oil paints to accelerate the solidifying of the oil.

Drift. Name given to ocean current that is generated and main­tained by a more or less constant wind. 2. To be carried along by a current. 3. Distance a current flows in a given time. 4. Tapered steel tool of circular section. Used for fairing rivet holes.

Drift Anchor. Sea anchor. Drogue.

Drift Angle. Difference between course steered and course made good when due to action of current.

Drifter. Fishing boat that streams very long buoyed nets, and rides to the leeward end of them.

Drift Ice. Ice in an area containing several small pieces of floating ice, but with total water area exceeding total area of ice.

Drift Lead. Hand lead dropped on bottom, and with end of line made fast inboard, to indicate if an anchored vessel commences to drag anchor.

Drift Net. Fishing net about 120 ft. long by 20 ft. deep. Buoyed with cork along head. Several of these are joined to form a very long net; so that nets may extend a considerable distance to windward of the drifter to which they are attached.

Drift Piece. Upright or curved timber connecting plank sheer with gunwale of wooden ship.

Drifts. In sheer draught, are where rails are cut, and ended with scroll iron.

Drift Sail. Sail used as a drogue.

Drive. To carry too much sail. To run before a gale.

Driver. Alternative name for a spanker. 2. Foremost spur in bilgeways of a vessel on the stocks. Heel is fayed to foreside of foremost shore.

Driver Boom. Spanker boom.

Driver Spanker. Sail that is also called 'Driver' and 'Spanker'.

Drizzle. Precipitation of very small rain drops.

Drogner. Sailing boat that both caught and cured herrings. Also, West Indian boat used for cargo carrying. Has light mast and lateen sails.

Drogue. Drag anchor. Sea anchor. 2. Square piece of wood attached to harpoon line of whaler, to check speed of whale.

Dromon. A light, swift sailing vessel. At one time the name was given to any sailing vessel.

Dromoscopic Card. Compass card having two graduations, the outer giving true bearings, the inner one giving magnetic bearings. Could be used only in one locality, and for a limited time.

Drop. The depth of a sail measured on its middle line. 2. Machine for lowering a coal waggon from a staith to a position just above hatch of a ship. Used to avoid breakage of coal while loading.

Drop Anchor. To let go anchor.

Drop Astern. To fall astern.

Drop Keel. Metal plate keel that can be withdrawn into a water­tight box over a slot in bottom of boat. When boat is heeled and trimmed by the stern a capsizing moment is generated. Has obvious merits when working in shoal water, or beaching.

Drum Head. Head of a capstan.

Drummer's Plait. Simple plait made by passing bight of rope through each preceding loop.

Dry Card Compass. Mariner's compass having no liquid in bowl.

Dry Compass. Dry card compass.

Dry Dock. Excavated dock, fitted with watertight entrance, from which water can be pumped to allow work to be done on under­water portion of a docked ship. Floating dry docks are usually called 'floating docks'.

Drying Features. Underwater obstructions that appear as tide recedes, but are covered as tide rises.

Drying Height. Height that a drying feature is above level of chart datum.

D shacke. Shackle having its sides parallel to one another.

Dub. To shape a smooth and even surface on a spar or timber.

Dubhe. Star a Ursa Majoris. S.H.A. 195°; Dec. N62°; Mag. 2-0.

Du Boulay Roller Jib. Works on principle of roller blind. Luff of sail is attached to hollow spar through which passes fore stay. Bottom of spar carries a grooved wheel to which furling-reefing line is attached. Hauling on this line furls, or reduces area of, sail. Invented by Captain E. du Boulay.

Duck. Flax fabric that is lighter and finer than canvas. 2. To dip into the sea.

Ducking (a Sail). Tricing, or clearing it, so that helmsman's view is not obstructed.

Duck Lamp. Small oil container with an inclined spout that holds wick. Burns colza oil.

Duct Keel. Twin centre girders with space between them. In­creases longitudinal strength and allows bilge and ballast piping to lie in the space and be easily accessible.

Dumb Barge. Barge with no sail, engine or rudder and unable to move except by towing or, to a limited degree, by sweeps.

Dumb Compass. Compass card that has no needle, but is adjust­able by hand. A pelorus.

Dummy Gantline. Rope rove through a block to act as a reeving line for a gantline.

Dumb Lighter. Lighter with neither means of propulsion nor rudder.

Dummy Piston. Disc on shaft of a reaction turbine. Steam impinges on this disc, so reducing end thrust.

Dumb Fastening. Short screw fastening that holds a strake until a through fastening is passed.

Dune. A low sand hill.

Dungiyan. One-masted Arabian sailing vessel.

Dunnage. Any material, permanent or temporary, that is used to ensure good stowage, and protect cargo during carriage.

Dunstos Rudder Brake. Fitting for preventing sudden snatches on rudder chains during heavy weather. Thwartship wire, with ends secured on either side of ship, passes around a sheave on tiller. At normal speed of rudder, the sheave 'rolls' along wire;

with sudden stresses, wire temporarily grips sheave, so absorbing stress that would, otherwise, come on engine and steering chains.

Duration of Tide. Time interval between occurrence of low water and the following high water, or between high water and follow­ing low water.

Dutchman's Log. Piece of wood thrown overboard, well forward and used for ascertaining speed of ship by timing its passage between two marks, of known distance apart, on ship.

Duty. Service or work that should rightly be rendered. 2. Tax or custom charge imposed by a government on goods imported, exported or consumed.

Duty Free. Exempted from customs duty.

Dwarf Star. One of small mass and low candle power, but of enormously high density. Dwarf star companion of Procyon weighs about 250 tons per cubic inch.

Dygogram. Geometrical construction representing the direction and amount of each force acting on a magnetic compass.

Dynamical Mean Sun. Imaginary body moving along Ecliptic and travelling from perigee to perigee at a constant speed and in the same time as that taken by true Sun. Not considered

in navigation.

Dynamical Stability. Of a ship, is amount of work necessary to heel the vessel through a given angle.

Dynamo. Machine that converts mechanical energy into direct electric current. Effected by revolution of an armature in a magnetic field.

Dyne. C.G.S. unit of force, representing amount necessary to produce or accelerate, velocity of one gramme mass by one centimetre per second.

Dysa, Dyso, Diso. 'Dghaisa.'

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