Mackerel Sky. Cloud form in which cirrocumulus and alto-cumulus are arranged in bands in a blue sky. Mac Ships. Merchant vessels converted into aircraft carriers during 1939-45 war. Name derived from initials of 'Merchant Aircraft Carrier'

M - English Maritime terminology

Mackerel Sky. Cloud form in which cirrocumulus and alto-cumulus are arranged in bands in a blue sky.

Mac Ships. Merchant vessels converted into aircraft carriers during 1939-45 war. Name derived from initials of 'Merchant Aircraft Carrier'.

Made Bill. Bill of exchange drawn and endorsed in United Kingdom and payable abroad. Specifies name of person entitled to payment.

Made Block. Built block. Shell is made up of parts.

Made Eye. 'Flemish Eye.'

Made Mast. Built mast, as differentiated from mast made from a

single tree.

Madrepore. A genus of coral.

Maestro. NW wind in Adriatic and Ionian seas and off coasts of Sardinia and Corsica.

Magazine. Compartment or structure in which explosives are kept. Name is given also to a warehouse.

Magellanic Clouds. Three masses of whitish nebulae near south pole of celestial concave.

Magnet. Body or substance having the property of attracting iron and steel. Usually iron or steel, but may be cobalt or nickel. Can have natural magnetism or electrically-induced magnetism.

Magnetic Amplitude. Angle of bearing measured from east or west point of a compass whose needle lies in magnetic meridian.

Magnetic Azimuth. Angle east or west of magnetic meridian and expressed in degrees.

Magnetic Bearing. Bearing of an object when referred to a compass whose needle lies in magnetic meridian.

Magnetic Compass. Compass whose directional property is due to its needles seeking the magnetic meridian.

Magnetic Compensation. Introduction of soft iron or magnets in the vicinity of a compass so that magnetic effects of iron or steel in ship or cargo can be neutralised or reduced. Magnetic Dip. Vertical angle that a freely-balanced magnetic needle would make with the horizontal plane at a given place.

Magnetic Equator. Line, on surface of Earth, passing through all positions at which there is no dip of a freely-suspended magnetic needle. It forms a dividing line between Earth's red and blue magnetisms.

Magnetic Field. Area, around a magnet, in which its magnetism is manifest.

Magnetic Meridian. Line of magnetic force, between North and South magnetic poles, in which a freely-pivoted magnetic needle would lie if all disturbing forces were removed. Magnetic Needle. Thin strip, needle, ring or cylinder of magnetised steel, so pivoted that it is free to respond to Earth's magnetic field and seek and lie in the magnetic meridian.

Magnetic Poles. Of Earth: areas in high latitudes North and South at which a freely-suspended magnetic needle would remain vertical. One area is near Hudson Bay, the other in South Victoria Land. Each area is about 50 square miles in extent. 2. Of magnet: are those points, near its ends, at which its magnetic force is at a maximum.

Magnetic Storm. Disturbance of Earth's magnetic field lasting for a period that may be measured in hours or days. Is world wide in effect and possibly due to sunspots.

Magnetic Variation. Horizontal angle, at a given place, between the magnetic and geographic meridians. Is the angle that a freely suspended and undisturbed magnetic needle would make with the geographic meridian at the place.

Magnetic Zenith. That point in the heavens indicated by a line passing upwards through a freely-suspended magnetic needle.

Magnetism. Property which can be imparted to certain substances, so causing them to attract or repel other magnetised substances and to exert a force on conductors of electrical current in their vicinity. Ferrous metals, cobalt and nickel can receive mag­netism. 2. The attractive or repulsive property of a magnet.

Magnetometer. Instrument for measuring intensity of Earth's magnetic force at any place.

Magneto - Striction. Contraction of a magnetic metal when subjected to magnetism. Particularly noticeable in nickel; this property being utilised in supersonic sounding apparatus.

Magnet Steels. Steels capable of being permanently magnetised. Usually alloyed with cobalt or tungsten.

Magnetron. The transmitter of a radar set.

Magnitude of Star. Its comparative brightness, as compared with other stars. May be 'relative Magnitude' or 'Absolute Mag­nitude'.

Mohammedan Calendar. Dates from flight of Mohammed from Mecca to Medina, July 16, 622 A.D. Has 12 lunar months of 29 or 30 days alternately. In every 30-year period there are 11 years of 354 days and 19 years of 355 days.

Maiden Voyage. First voyage made by a new ship after all trials have been carried out and she has been taken into service.

Maierform, Maier Form. Hull design that allows displaced water to flow aft by shortest route, reduces wave making to a minimum and keeps wetted area to small proportions. Forward and after deadwoods are largely removed. Pitching is reduced and direc­tional stability is good.

Mail. Letters, posted papers and parcels shipped for conveyance. 2. Interwoven metal rings fastened to a stout backing material and used for smoothing the surface of newly-made ropes.

Mail Boat. Vessel carrying mails.

Mail Pendant. 'Royal Mail Pendant.'

Mail Room. Compartment in which mail is carried in a ship.

Mail Steamer. Steamer carrying mail.

Main. Ocean, or open sea. 2. Principal. 3. Main mast. 4. Mainsail.

Main and Foresail Rig. Has a fore staysail and a fore and aft mainsail that is loose-footed or stretched along a boom.

Main and Mizen Rig. Small boat rig having two masts, each carrying a four-sided fore and aft sail, main being larger than mizen.

Main Boom. Spar to which foot of a fore and aft mainsail is extended.

Main Breadth. Greatest distance between any two opposite frames.

Main Course. Sail attached to main yard of a square-rigged vessel.

Main Deck. Principal deck. Next below upper deck in five-deck ships.

Main Halyard. Rope by which a mainsail is hoisted.

Main Hatch. Principal hatch, usually the largest.

Main Hold. Space entered through main hatch. Principal hold.

Mainmast. Principal mast. Second mast in vessels having two or more masts, except when second mast is smaller—in which case forward mast is mainmast, after mast is mizen.

Main Pendants. Two short pieces of strong rope having thimbles in lower ends. Secured under upper ends of shrouds of main­mast to take hooks or shackles of main tackles.

Main Piece. Of rudder, is the vertical piece to which the steering-gear is attached. Of a wooden ship, is a piece stepped into stem head and notched for heel of bobstay piece.

Main Post. 'Stern Post.'

Main Rigging. Shrouds and ratlines on main lower mast.

Mainsail, Main Sail. Principal sail. In fore- and aft-rigged ships is sail on after side of mainmast; in square-rigged vessel is sail bent to main yard.

'Mainsail Haul.' Order given when tacking a square-rigged vessel. As ship's head comes to wind the main yard and all after yards are braced for new tack—yards on foremast are then aback to assist ship's head to pay off.

Main Tack. Rope or purchase by which weather clew of mainsail is hauled out and down.

Main Tackle. Purchase attached to main pendant when setting up main stays.

Main Top. Platform at head of mainmast. 2. Division of the watch in R.N.

Main Yard. Lower yard of a mainmast.

Make and Mend. Afternoon watch allotted to R.N. seaman for making and mending clothes. Afternoon watch in which no work is done.

Make Sail. To set sail, or to increase the sail already set.

Make the Land. Steer towards land so as to bring it into sight.

Make Water. To take in water through a leak.

Making. Said of tide when it is increasing from neap to spring tide.

Making Her Number. Said of a vessel when indicating her name by signal.

Making Iron. Rather large caulking iron used for final hardening

up of oakum when caulking a seam.

Making Way. Moving ahead or astern through the water. See

Under Way.

Malinger. To feign illness to avoid work.

Mallet. Small maul.

Mallock's Rolling Indicator. Instrument for indicating amplitude of roll of a vessel. Consists of a circular box in which a paddle-wheel is mounted in jewelled bearings and immersed in liquid, on a vertical bulkhead. As ship rolls, paddle-wheel maintains an attached and graduated scale in true horizontal. A vertical line on glass face of box indicates amount of roll.

Malone CO2 Indicator. Instrument that measures CO2 content of air, as a percentage, by automatically weighing unit volume of air against unit volume of air mixed with CO2.

Mammatocumulus. Cumulus cloud with udder-shaped projections downward from lower edge.

Mammatus. Udder-shaped cloud form.

Man. To provide with men, or manpower.

Managing Owner. Shipowner who actively controls, the com­mercial affairs of his ship or ships.

Manavalins. Seaman's word for 'odds and ends'.

Manganese. Black oxide of manganese sometimes found on sea­bed when sounding.

Manger. Space, on cable deck, between hawse pipes and thwart-ship breakwater in vessel where cable deck is below forecastle deck.

Mangrove. Tropical tree, or shrub, that covers large areas of coast in tropics. Seed germinates on trees and send roots down to the water. Wood is straight-grained, elastic and hard; often used for boat and shipbuilding.

Manhelper. Paint brush fastened to a long wooden pole.

Man-Harness Hitch. Put in a rope when dragging or towing by manpower. Large 'half crown' is made in rope and laid across it; bight on one side of rope is taken under the rope and through the other bight.

Manhole. Perforation in a boiler shell, tank top or other enclosed space, to allow a man to enter. As this usually demands the smallest possible removal of metal, the opening is approximately the shape of a man's transverse section, this shape allowing the covering piece to be inserted from outside.

Manifest. Document given to Master when cargo is shipped. Con­tains particulars of cargo, shipper's name, marks and numbers, quantities, where loaded. Master's name, ship's name, tonnage and port of registry.

Manifold. Group of valves for pump suctions and deliveries. Small compartment in which such valves are placed.

Manilla Hemp. Product of a species of banana, principally from Philippine Islands.

Manilla Rope. Made from manilla hemp. Contains natural oil, so does not need tarring. Is about three-quarter weight of hemp rope of same size, and has a higher breaking point.

Manning Scale. Statutory scale (1936) specifying minimum number of efficient deck hands to be carried in steamships of stated tonnages.

Manoeuvre. Regulated change of direction, position or speed to attain a desired end. 2. To change direction, position or speed for a specific purpose.

Man-of-War. A warship.

Manometer. Instrument that measures pressure and elastic pro­perties of gases. Barometer and steam gauges are examples.

Man Overboard.9 Call and report given when a person has been seen to fall into the sea from a vessel.

Manropes. Protective ropes at side of a ladder or inclined wooden steps. Short ropes, used when embarking or disembarking from, or into, boats from lower platform of accommodation ladder; ropes being attached to stanchions on the platform.

Manrope Knot. Made in end of manrope to form standing part at eye of stanchion on platform of accommodation ladder, or at a hatchway. Is a wall knot with crown above and all parts followed round once.

Man Ship. Naval ceremony indicating compliment and, formerly, peaceful intentions. Crew are spaced at regular intervals along sides of upper decks. 2. To provide a crew for a vessel.

Man Yards. Ceremonial disposition of crew of sailing ship. Men are placed at intervals on all yards, standing on the yards and being steadied by jackstays stretched from mast to lift of yard. Discontinued by R.N. in 1902, by order of King Edward VII.

Marconi Rig. Nickname for 'Bermuda Rig'.

Marcq St. Hilaire Method. Procedure for finding ship's position line from an observation of a heavenly body and the calculation of the altitude and azimuth it would have if ship were at esti­mated position. The difference between the calculated altitude (or zenith distance) and observed altitude (or zenith distance) is the error in locus of assumed position line. The position line is moved towards or away from the geographical position of the observed body according to the amount the two altitudes (or zenith distances) differ.

Mareel. Shetland name for phosphorescence of the sea.

Maregraph Plongeur. Instrument for measuring changes in sea level by automatically recording changes in pressure at sea bottom. Two Bourdon tubes are open to pressure and mech­anism records the resultant movements of their free ends.

Mare's Tails. Tufted cirrus clouds.

Margin of Safety Line. Line drawn parallel to bulkhead deck at side line, and three inches below the upper surface of that deck at sides.

Margin Plate. Plating forming side of double-bottom ballast tank.

Marina. A yacht harbour which usually provides fuel, fresh water and other facilities besides moorings, for yachts.

Marine. Pertaining to the sea. 2. A Royal Marine.

Marine Barometer. Mercurial, Kew-pattern barometer mounted in gimbals.

Marine Engine. In general, is any engine designed for propulsion of ships. More especially applied to compound, triple-expansion and a quadruple-expansion engines that are fitted with a con­denser.

Marine Glue. Usually a compound of crude rubber oil and shellac. Used for paying deck seams, closing small leaks, and other purposes.

Marine Growth. Marine vegetation and fauna that attach to the underwater body of floating craft.

Marine Insurance. Insurance against losses occurring at sea, or in sea-going ships, or in relation to a marine adventure.

Marine Insurance Act, 1906. First codification of rules governing marine insurance. Before this date marine insurance was governed, largely by precedent.

Marine Insurance Corporations. Companies who insure against marine risks and are corporately liable for payment. Insurance made by Lloyd's is paid individually by all underwriters who subscribe to the contract.

Mariner. In general, a person employed in a sea-going vessel. In some cases, applied to a seaman who works on deck.

Mariner's Compass. Compass used for directing course of a ship. The card, or 'fly', is mounted in a ballasted bowl fitted with a lubber line or pointer that coincides with ship's fore and aft line;

the compass graduation coinciding with this indicates direction of ship's head. Usually mounted in a binnacle containing lighting arrangements, corrector magnets and soft-iron compensations.

Mariner's Splice. Long splice put in cable-laid rope. Made in same manner as long splice with the addition that the three small ropes forming the strand are unlaid into 'readies', and are also spliced.

Marine Society. Instituted 1756; incorporated 1772. Principal objects are to train and fit out poor boys of good character for the sea services, and to ensure a steady stream of lads of good character and physique into the Royal and Merchant Navies.

Marine Store. Warehouse or shop in which rope, canvas and other ships' stores are bought and sold.

Marine Store Dealer. Person who buys and sells marine stores. His business is controlled, in part, by Merchant Shipping Act, 1894, Sections 538-542.

Marine Surveyor. One who surveys ships to ascertain if all statutory and appropriate measures have been taken for the good order and safety of ships, cargoes and personnel. 2. One who surveys seas, and waters connected with them.

'Marine Surveyor.' Early 19th-century spiral-towed log. Invented by Henry de Saumarez, of Guernsey.

Maritime. Pertaining to the sea, to navigation, to shipping and to shipping commerce. 2. Bordering on the sea.

Maritime Air. Air-mass that has travelled over the sea for a considerable distance.

Maritime Conventions Act, 1911. Modifies Merchant Shipping Acts of 1897 and 1906 relative to collisions due to infringement of Collision Regulations. Failure to go to assistance of a vessel in distress is made a misdemeanour.

Maritime Courts. Those courts of law that deal with shipping matters: Court of Admiralty, Court of Appeal, Judicial Commit­tee of Privy Council, are the British Maritime Courts.

Maritime Interest. Interest chargeable on a bottomry bond.

Maritime Law. Law as relating to shipping, seamen, navigation and harbours.

Maritime Lien. Legal right of Master and seamen to have a ship held as security for wages unpaid. Takes precedence over any other lien on ship.

Maritime Polar Air. Air stream, from high latitudes, that has passed over an appreciable expanse of sea before reaching observer.

Mark. One of the marked fathoms in a lead line. 2. Beacon or erection, marking a navigational danger or a position of navi­gational interest.

Mari(ing). To bind or frap with small line in such a manner that each turn is an overhand knot.

Marline. Superior kind of spunyard laid up left-handed.

Marline Hitch. Half hitch made by passing end over and under, so that an overhand knot is formed.

Marline Spike. Tapered and pointed iron pin used for opening up a rope when splicing. Has a perforation at larger end to take a lanyard.

Maroon. To put a man ashore, forcibly, on desolate land. Form­erly done as a punishment, or as a criminal act. 2. Pyrotechnic signal exploding with a loud report.

Marry. To interlace the strands of two ropes preparatory to splicing. 2. To put two ropes together, side by side, so that they can be hauled upon simultaneously.

Marryat's Code. 'Code of signals for the Merchant Service', com­piled by Captain Frederick Marryat, R.N., 1817.

Marry the Gunner's Daughter. Old Navy nickname for a flogging, particularly when across a gun.

Mars. Fourth planet from Sun and, therefore, next outside Earth. Diameter is about half that of Earth. Has two satellites, Deimos and Phobos. Named after Roman god of war, on account of its ruddy colour.

Marsden Square. Area of Earth's surface bounded by meridians 10° apart and parallels of latitude 10° apart, so forming 100 squares. Used for identifying position of a meteorological report, first figure denoting latitude, second figure denoting longitude.

Mart. To traffic. 'Mart' is often corrupted to 'Marque'.

Martelli's Tables. 'Short, Easy and Improved Method of Finding Apparent Time at Ship.' G. F. Martelli has not been identified. The tables give quite trustworthy results, but the tabulated quantities have been so disguised that the underlying principle

has been obscured. Basic formula is:

Martinet. 'Martnet.'

Martingale. Stay leading downward to prevent upward movement of a jib boom or flying jib boom.

Martnet. Leechline for tricing up a square sail when furling.

Mascaret. Local name for tidal bore in Seine and Garonne rivers

Mast. Vertical wooden pole—made of single tree or lengths of wood or a tube of steel or metal, erected more or less vertically on centre-line of a ship or boat. Its purpose may be to carry sail and necessary spars, to carry derricks, to give necessary height to a navigation light, look-out position, signal yard, control position, radio aerial or signal lamp. Tall masts are usually made up of three or four masts, one above the other. From the deck, they are named lower mast, topmast, topgallant mast, royal mast - the last two usually being one piece.

Mast Bands. Iron bands clamped round a mast to take upper eyes of rigging, belaying pins, etc.

Mast Carlings. Fore and aft timbers - or girders -on underside of deck and on either side of mast. Also called 'mast partners'.

Mast Clamp. Semi-circular band for securing lower part of a boat's mast to thwart of a boat.

Mast Coat. Conical-shaped canvas covering over wooden mast wedges. Painted to protect wedges from water; which would cause wedges to set up exceptional stresses, and to rot.

Master. Merchant Navy officer in command of ship. Name was given, formerly, to the navigating officer of H.M. ships.

Master-at-Arms. Senior chief petty officer of regulating staff in H.M. ships. Formerly, senior rating in merchant ship whose duty was to see that passengers maintained good order and, especially, committed no offence likely to cause fire.

Master Attendant. Officer of Royal Dockyard next in rank below Superintendent.

Master Compass. Principal gyro compass controlling the repeaters.

Master Gunner. Formerly, officer-in-charge of gunnery equipment of a vessel of R.N. Now, superseded by gunnery lieutenant, senior commissioned gunner or commissioned gunner.

Master Mariner. Officer of the Merchant Navy holding a certificate entitling him to command a vessel.

Master of Trinity House. Senior of the Elder Brethren of Trinity House - who are known as 'Trinity Masters'.

Master's Bond. Bond for £2000-£5000 if owner or charterer are resident abroad - required by Crown before granting outward clearance of an emigrant ship.

Master's Declaration. Short name for 'Master's Declaration and Stores Content for Vessels Outward in Ballast', which is signed by Master when clearing outwards in ballast.

Mast Head. That part of mast between truck and upper eyes of rigging.

Masthead Angle. Angle, at observer's eye, between truck of a vessel's mast and the waterline vertically beneath it. By means of tables—or by trigonometry - this can give ship's distance off when height of eye and height of masthead are known.

Masthead Battens. Vertical strips of wood or metal placed on lower masthead to protect mast from chafe of wire rigging, and to protect eyes of lower rigging from chafe by masthead hoops.

Masthead Light. White, screened light required to be carried on fore or mainmast of a vessel propelled by engines.

Mast Hole. Circular hole in deck through which a mast passes.

Mast Hoop. Circular ring, of metal or wood, that encircles a mast and is free to move up and down it. Often fitted in luffs of gaff sails.

Mast House. Long shed in which masts are built.

Masting. Erecting masts in a vessel.

Masting Sheers. Tall sheer legs used for stepping a mast, or for removing it from a vessel. Erected near edge of a fitting-out berth, with line of splay parallel to edge of berth. Heels are hinged so that sheers can be inclined until head is over centre­line of vessel.

Mast Knife. Clasp-knife with 9- to 12-inch blade, used for scraping wooden mast.

Mast Lining. Doubling piece of canvas on after side of a topsail. Takes the chafe against topmast and cap.

Mastless. Having no mast.

Mast Prop. Long spar formerly used to strut a mast when vessel was careened.

Mast Rope. Rope by which an upper mast is hoisted. A 'Heel Rope.'

Mast Scraper. Triangular scraper used on wooden masts. Edges are concave to fit round of mast. Bevel is away from handle.

Mast Step. Socket into which heel of a mast is stepped. Strength­ened fitting to which heel of mast is secured.

Mast Tackle. Purchase for hoisting or lowering a mast. 2. Heavy-lift tackle depending from a mast.

Mast Trunk. Casing into which mast of a small vessel may be stepped.

Mat. Woven strands of rope, or thrummed yarns on canvas, used as protection against chafing, or for controlling a small leak.

Mate. An officer assistant to Master. A 'Chief Officer'. From time immemorial he has been responsible for stowage and care of cargo and organisation of work of seamen, in addition to navigat­ing duties.

Matelot. French for 'Sailor*. In common use on lower deck of R.N.

Mate's Log. Book kept by Mate, and recording work done by crew and, with particular emphasis, all matters concerning stowage, carriage, ventilation and discharge of cargo.

Mate's Receipt. Document signed by Mate when goods for carriage are received into ship's charge.

Matthew Walker. Knot put in end of rope. Made by unlaying end of rope, making a bight of one strand, passing second strand over bight of first, passing third over bight of second and through bight of first.

Matting Sword. Length of thin wood used for beating in the wheft of a woven, or 'sword', mat.

Maul. Heavy hammer of iron or wood.

Mayday. (French 'm' aidez', 'Help me'.) The international spoken radiotelephony signal of distress.

Maximum Altitude. Greatest angular distance above horizon.

Maxwell's Rule. 'Corkscrew Rule.'

McIntyre System. Double-bottom construction involving the cut­ting of frames and reverse frames and the fitting of a continuous water-tight angle bar to take lower edge of tank margin plate.

McIntyre Tank. Water-ballast tank seated on top of ordinary floors. Preceded double-bottom tank.

Meade Great Circle Diagram. Graticule for solving great circle sailing problems from projection of course on a Mercator chart.

Mean Draught. Half sum of forward and after draughts of a vessel. It differs slightly from draught at half length.

Mean High Water. Mean of all high waters at a place when observed during a lunation of 29 days.

Mean High -Water Springs. Mean height of spring high waters at a place when deduced from an adequate number of observations.

Mean Latitude. That latitude whose numerical value is half the sum of a latitude left and a latitude reached.

Mean Low Water. Mean of all low waters at a place when observed during a lunation of 29 days.

Mean Low-Water Springs. Mean height of spring low waters at a place when deduced from an adequate number of observations.

Mean Noon. Instant in which Mean Sun is on meridian of a place.

Mean Place of Star. That position on the celestial concave at which a star would appear to be if viewed from Sun. It is expressed in declination north or south of Equinoctial and sidereal time angle from First Point of Aries on January 1 of current year.

Mean Sea Level. Level that sea would maintain if no tidal effect were manifested and average meteorological conditions pre­vailed. For hydrographic and surveying purposes the level is derived from very prolonged and careful observations at an appropriate position - Newlyn, Cornwall, being selected for British standard level.

Mean Solar Day. Interval between successive transits of Mean Sun across a given meridian. Its length is the mean length of all apparent solar days in a year.

Mean Solar Year. Average time taken by Sun to go round Ecliptic or, to be precise, for Earth to go round Sun. Due to slight irregularities in the movement of First Point of Aries the time varies slightly and irregularly. Mean value, when taken over about 100 years, gives 365 days. 5 hrs. 48 mins. 48 sees. (approx.).

Mean Sun. Fictitious body that travels along Equinoctial at a constant speed, and in the same time that true Sun takes to travel round Ecliptic at a variable speed.

Mean Tide Level. Average tidal height above chart datum. Found by evaluating half sum of Mean High Water and Mean Low Water at a given place. Name is sometimes applied to mean level of a tide.

Mean Time. Time regulated by Mean Sun.

Measured Distance. Accurately measured distance used for determ­ining speeds of ships. Most of the so-called 'measured miles' are measured distances, and require adjustment when calculating speeds in knots.

Measured Mile. Measured distance of 6080 ft. See 'Measured Distance'.

Measurement Goods. Cargo in which freight is based on the amount of space goods occupy in the ship carrying them.

Measurement of Ships. Determination of a ship's displacement. Gross, Net and Under-Deck Tonnages, Draught, Freeboard, Length and Breadth.

Mechanical Advantage. Ratio between force applied and weight lifted when using a purchase or other machine.

Mechanical Integrator. Instrument used for finding a vessel's displacement and moments of displacement by moving a pointer along line of sections of body plan; this movement actuating registering mechanism.

Mechanical Navigation.* Former name for ship handling and manoeuvring.

Mechanical Stoker. Machine that feeds furnaces of a coal-fired vessel.

Median. Middle quantity of a series of values; not necessarily the mean value. 2. Line, from angle of a triangle, bisecting opposite side.

Medusa. Umbrella-shaped jelly-fish with several long and hairlike tentacles.

'Meet Her.' Order to helmsman when helm is righted during a turn

and he is required to check swing of ship's head. Mega. Prefix meaning 'Great' or 'Million'. Megadyne. Million dynes. Pressure of one megadyne per square centimetre is equivalent to 1000 millibars.

Mend. To put additional service on a rope. 2. To loose a sail and refurl it.

Meniscus. Curved upper surface of liquid in a tube, particularly mercury in a barometer. Curve can be concave or convex. 2. Concave-convex lens.

Menkalin. Star b Aurigae, S.H.A. 271°; Dec. N45°; Mag. 2-1.

Menkar. Star a Ceti. S.H.A. 315°; Dec. N4°; Mag. 2-8.

Menkent. Star q Centauri. S.H.A. 149°; Dec. S36°; Mag. 2-3.

Merak. Star b Ursae Majoris. S.H.A. 195°; Dec. N57°, Mag. 2-4.

Mercantile Marine. Merchant shipping, including personnel.

Merchant Navy. Merchant Service.

Mercantile Marine Fund. Fund into which various fees and charges were paid, and from which salaries and expenses were recovered. Abolished 1898.

Mercantile Marine Office. Established and controlled by Merchant Shipping Acts for giving effect to the Acts as regards employment and discharge of personnel, keeping registers of men and their characters, facilitating apprenticeship to the sea service and other matters of like nature.

Mercantile Marine Superintendent. Officer in charge of a Mercantile Marine Office.

Mercantile Marine Uniform. Standard uniform for officers of British Merchant Navy in accordance with Orders in Council of 1918 and 1921. Penalty for unauthorised wearing is up to £5; for wearing it in such a manner as to bring it into contempt, £10 or up to one month's imprisonment with or without hard labour.

Mercator Chart. Projection of Earth's surface in which all meri­dians are made parallel and the latitude scale is increased in the same ratio as the expansion of the longitude scale in the area. All straight lines are rhumb lines. Distances are measured by minutes of latitude in area considered. Distortion in high latitudes is very great.

Mercatorial Bearing. Bearing of a given position as deduced from a rhumb line passing through the position and position of observer. Differs from great circle bearing by half the convergency between meridian of observer and meridian passing through the given point.

Mercator Sailing. Method by which problems of sailing on spher­ical surface of Earth can be solved by plane trigonometry. Its fundamental equation is: Difference of Longitude = Meridional Difference of Latitude X Tangent of Course. It requires that difference of latitude shall be converted into the invariable units of the longitude scale; this being done by tables of 'Meridional Parts'. Disadvantages of this sailing are that: (1) Course is a Loxodrome, and not a great circle; (2) Method cannot be used in high latitudes except for very short distances.

Mercator's Projection. Delineation of Earth's surface on a chart or map in accordance with the principles used in making a Mercator chart.

Merchant Captain. Captain of a merchant vessel. Captain in the Merchant Navy.

Merchant Navy. Ships and personnel of the British Mercantile Marine.

Merchant Seaman. Seaman employed in a merchant vessel.

Merchant Service. 'Merchant Navy.'

Merchant Shipping Acts. Acts of Parliament governing the building? manning, employment, fitting-out, seaworthiness, registration? management, governance, etc., of British ships. Embrace num­erous Acts, from 1882 onwards, the principal being those of 1894, 1906, and 1932.

Mercurial Barometer. Barometer that indicates atmospheric pressure by height of a balancing column of mercury—as distinguished from an aneroid barometer.

Mercury. White metal with melting point of –38.5°C. Specific gravity about 13-55. Used in thermometers and barometers for registration purposes, and in some gyro compasses as a ballistic pendulum.

Mercury. Innermost of the planets. Greatest angular distance from Sun is about 29°. Very rarely observable, and then only near sunrise or sunset. Nautical almanac then gives a warning that its appearance may cause it to be mistaken for a star or another planet.

Mercury Ballistic. Pots of mercury, one on either side of a Sperry Gyro Compass. These have a connecting tube through which mercury flows when compass tilts and tends to wander out of meridian. Extra weight on one side causes gyro to precess into meridian and regain horizontal position.

Mercury Trough. Receptacle in which mercury is placed to form an artificial horizon when taking celestial observations ashore. Has a glass roof to ensure unruffled surface of mercury.

Meridian. Semi-circle of terrestrial sphere passing between the poles. All positions on this line have noon at the same instant, and the same longitude.

Meridian Altitude. Value of intercepted arc of observer's meridian, between horizon and a celestial body on the meridian of observer - thus having its greatest altitude.

Meridian Distance. Distance between any two meridians expressed as the difference in their respective local times.

Meridian Line. Line connecting North and South points of observer's sensible horizon.

Meridian Passage. Transit of heavenly body across a given meridian.

Meridian Transit. 'Meridian Passage.'

Meridian Zenith Distance. Arc of meridian intercepted between the zenith and a heavenly body in the meridian.

Meridional. Pertaining to the meridian. Sometimes has the mean­ing 'facing the direction of the noon Sun'.

Meridional Difference of Latitude. Difference of Latitude expressed in meridional parts of Mercator projection.

Meridional Distance. Old name for 'departure' between two places on different meridians.

Meridional Parts. Length of any part of an extended meridian of a Mercator chart when expressed in units that are the length of a minute of longitude.

Meridional Projection. Projection of a sphere to a plane that is parallel to the meridian, or coincident with it.

Mermaid. Fabulous creature having upper part of a woman and lower part of a fish. Dugong is an animal somewhat of this type.

Merman. Masculine counterpart of a 'Mermaid'.

Mesh Stick. Flat, wooden slat used when net making. Width of slat forms mesh and regulates its size.

Mess. Group of persons who feed at the same table. The space table, and utensils allocated to a group of persons.

Mess Deck. Deck on which the feeding places and tables of a ship's company are situated.

Messenger. Endless chain, or rope, passing round barrel of capstan and through block, or blocks, some distance away—thus moving as capstan is turned. Formerly used when cable was stowed some distance away from capstan. Slack cable was attached to messenger by short rope 'nippers', which were cast off as cable came to locker. 2. Endless chain, passing over sprocket-wheels, , used for increasing power of a windlass by connecting it with a winch. 3. A light rope used to haul in a heavier one.

Mess Kit. Utensils supplied to a mess for eating, drinking and cooking.

Mess Traps. R.N. name for 'Mess Kit'.

Metacentre. Theoretical point considered in questions of ship stability. When a floating vessel is upright and afloat in water the upward force of buoyancy is equal to the downward force of gravity, and a vertical line through centre of buoyancy will pass through centre of gravity. When vessel is heeled by extraneous forces, centre of buoyancy will shift to low side. Where the vertical line, passing through the new centre of buoyancy, cuts the former vertical line is termed the 'metacentre'. This point is more or less static for angles of heel up to about 15°. Similarly, we can consider a metacentre in a fore and aft plane. We thus have a longitudinal and a transverse metacentre, their positions changing with draught and inclination of vessel.

Metacentric Height. Distance that metacentre is above centre of gravity in a ship.

Metallic Barometer. Name formerly given to an aneroid baro­meter.

Metalling Clause. Inserted in policy of insurance to exclude loss of metal sheathing due to action of water.

Metal Mike. Seaman's name for 'Automatic Helmsman'.

Meteorological Wind Scale. Development of Beaufort Wind Scale, and relating wind-force to wind-speed. Introduced 1926.

Meteorology. Science concerned with study of Earth's atmosphere, its phenomena and variations.

Meteors. Fragments of solid matter in space that meet Earth's atmosphere. Friction with atmosphere heats them to incan­descent point. Altitude of incandescence is probably less than 120 miles. Size of fragments is usually between that of a pea and that of a grain of sand. Occasionally, fragments of considerable size reach Earth's surface.

Meteor Shower. Succession of meteors observable when Earth's atmosphere passes through a ring of meteors.

Mete Stick. Horizontal batten extending from a vertical timber. Formerly used for levelling ballast, or for measuring height in a hold.

Metonic Cycle. Period of 19 years in which 12 years consisted of 12 lunar months, and 7 years of 13 lunar months. Dates of new Moon were practically invariable, the error being one day in 237 years.

Mexican/Mexico Current. Cold current that sets SE'ly down west coast of Mexico and eventually merging in the NE Trade Drift.

Miaplacidus. Star b Carinae. S.H.A. 222°; Dec. S70°; Mag. 1-8.

Michell Thrust. Thrust block in which the thrust is taken, primarily, on segments that can cant slightly away from collars on shaft. In the space thus formed is oil, so that frictional resistance and wear are reduced to a minimum.

Micrometer Screw. Screw for making very small adjustments with a large movement. In measuring instruments it permits very accurate measurements to be recorded.

Microsecond. One millionth (0-000,001) of second of time.

Middle Deck. Second deck below upper deck in a three-decker (which had five decks).

Middle Ground. Shoal area between two navigational channels.

Middle Latitude. That latitude in which the length of a parallel intercepted between two meridians is equal to the departure made when sailing between the two meridians on a rhumb. Owing to spheroidal shape of Earth, middle latitude differs from mean latitude, but can be derived from mean latitude by Workman's Table.

Middle-Latitude Sailing. Method of solving certain navigational problems when sailing between two points in different latitudes and longitudes. The length of intercepted arc of parallel midway between the two latitudes is taken to be equal to the departure made, and is found by formula Dep. = D. Long. x Cos Mid. Lat. The method is said to have been introduced by Ralph Handson, a mathematician, in 1614.

Middle Passage. Area of Atlantic Ocean between West Indies and U.S.A. Is an old 'Slave Trade' name.

Middle Topsail. Deeply-reached topsail formerly set at heel of topmast in some schooners and sloops.

Middy. Colloquial name for a 'Midshipman'.

Midland Sea. Mediterranean Sea.

Mid Main. Said of a position far out at sea. Sometimes used to denote a position halfway between an observer and his horizon.

Midship. Situated in or near the middle line - transversely or longitudinally of a vessel.

Midship Beam. Longest beam in midship body of a vessel.

Midship Bend. Largest of the transverse sections of a vessel.

Midship Body. That part of hull of a ship in which there is little change in transverse shape.

Midship Frame. Largest transverse frame of a ship.

Midshipman. Young subordinate officer in R.N. Intermediate between cadet and sub-lieutenant.

Midshipman's Hitch. Alternative but little-used name for a 'Marlinespike Hitch'. Midshipmen's Nuts. Broken ship biscuit.

Midships. Commonly used form of "Amidships*.

Mid Stream. Middle line of a stream or current.

Mile. Unit of geographical distance. Has various values and names, those that concern seamen being Statute, Nautical, Standard Nautical, International Nautical and Geographical miles. Each of these will be found under its prefix.

Milky Way. Unsymmetrical and irregular belt of luminosity extend­ing round the heavens. Is an immense congregation of stars in shape of a lens—roughly. Diameter is about 150,000 light years, Earth being about 40,000 light years from centre.

Millibar. Unit of barometrical pressure. 1/l000th of a 'Bar'.

Minelayer. Vessel specially fitted for carrying mines and laying them at sea.

Minesweeper. Vessel specially fitted for sweeping up enemy-laid mines and for destroying them.

Minimum Altitude. Altitude of an observed object at the instant its altitude ceases to decrease.

Minion. Small gun that threw a ball less than 4 Ib.

Ministry of Agriculture and Fisheries. Government department that regulates the sea fishing fleets and the carriage of live stock from British ports.

Minor Planet. One of the asteroids.

Minute. Interval of time equivalent to 1/60 of an hour. 2. 1/60 of a degree of arc.

Minute Gun. Firing of a gun, at intervals of about one minute, as a signal of distress.

Mirage. Optical effect, caused by unusual atmospheric refraction, by which distant objects appear to be nearer, or in remarkable positions.

Mirfax. An apparatus for transmitting and receiving weather-charts by radio.

Missing. Said of a vessel when no news has been heard of her and it is feared, but not proved, that she has been lost.

Missing Stays. Failing to go from one tack to the other when attempting to go about close-hauled.

Mist. Thin fog that reduces visibility to less than two miles. Meteorologists have a visibility limit of one mile, but the usual practice of seamen is to assume mist to be present when ships

and ships' lights are not visible at two miles.

Mistral. Strong NW to North wind that is met with in Gulf of Lions and Gulf of Genoa.

Mitchboard. Wooden stanchion, with curved socket, for taking weight of a boom when not in use.

Mixed Policy. Marine insurance policy covering two or more different kinds of risk, such as 'sea' and 'land' risks; or a 'Voyage' risk with a 'time' element incorporated. A 'mixed*

policy, covering a voyage and a period of time exceeding 30 days, is not uncommon.

Mixed Tide. Tidal undulation in which both semi-diurnal and diurnal constituents are definitely manifested.

Mizen, Mizzen. Fore and aft sail, with gaff and boom, set on after side of mizen mast. Small sail, set on small mast, right aft in a boat having a mainmast.

Mizen, Mizzen Mast. Third mast from forward in a vessel having three or more masts.

Mizzle. Combination of drizzle and thick mist. 'Scotch mist'.

Moderate Speed. In fog, is such a speed that all way can be taken off the vessel before she has travelled a distance equal to half the range of visibility.

Modulator. A device for generating a succession of short pulses of energy which cause a radar transmitter valve to oscillate during each pulse.

Molgogger. A folding or removable fairlead fitted to the bulwarks of a tug.

Moment of Change Trim. Weight and leverage necessary to change trim of a vessel by one inch.

Monitor. War vessel in which speed and other considerations have been sacrificed to obtain maximum gun power and armour protection.

Monkey Block. Large iron-bound block bolted to a wooden chock on deck of a sailing vessel. 2. Block fastened on topsail yard as a fairleader for buntlines.

Monkey Boat. Long, narrow canal boat. 2. Small boat used in a dock.

Monkey Chains. Small rigging chains abaft main chains. Royal and topgallant backstays are set up in them.

Monkey Face. Shamrock-shaped connecting piece of a mooring swivel.

Monkey Fist Knot sometimes put in end of heaving line to increase its carrying power. Three round bights are made in end, leaving enough end to cross first turns with three round turns, and then a further three turns going over second turns and under first turns.

Monkey Gaff. Gaff hoisted above a spanker gaff.

Monkey Island. Screened navigating and compass position on top of a wheel house or chart house.

Monkey Jacket. Uniform jacket as distinguished from frock coat.

Monkey Lever. Iron lever operating tumblers that release securing chains of an anchor stowed on an anchor bed.

Monkey Poop. Low poop. Sometimes applied to a deck above an after cabin.

Monkey Rail. Light rail on and above a quarter rail.

Monkey Seam. Flat seam put in centre of sail when making it. Made by overlapping selvages of two cloths, and then tabling them.

Monkey Tail. Rope attached to end of a lever so that extra hands can heave on it.

Monkey Topsail. Sail that was used in instructional ships for teaching young seamen to hand, reef, furl and loose a topsail; to lay out on a yard; to bend and unbend a sail; to pass an earring. The yard was crossed a small distance above the deck; the names of the various parts of the sail were tainted on it.

Monsoon. Persistent wind that blows from one direction in summer, and from an approximately opposite direction in winter. Speaking generally, they come from seaward in summer, and from landward in winter. They are well developed in E and S Asia, and may be noticed in China Sea, Indian Ocean and off African coast. The West African monsoon prevails from S to SW throughout the year.

Month. Period of time based on Moon's revolution around Earth. It has various values, depending on the epoch used. The Anomalistic, Nodical, Periodic, Sidereal, Synodical and Tropical months are dealt with under their prefixes.

Moon. Secondary planet that is a satellite of Earth. Distance from Earth varies between 225,463 miles at perigee to 252,710 miles at apogee. Diameter 2160 miles. Plane of orbit is slightly more than 5° from plane of Ecliptic. Declination varies between 18 ½ ° and 28 ½ ° when maximum in a lunation. Moon's gravitational effect on Earth has important effects in tidal phenomena.

Moon Culminating Star. Star sufficiently near Moon, both in R.A. and Declination, that observations could be taken of it to determine difference of longitude.

Moon in Distance. Term denoting that angular distance of Moon from another heavenly body allowed measurement of lunar observations.

Moonraker. Sail that was sometimes carried above skysail in square-rigged ships during fine weather and light airs.

Moonsail. Alternative name for 'Moonraker'.

Moonsheered. Said of a vessel whose upper deck has exaggerated' sheer forward and aft.

Moor. To secure a ship in position by two or more anchors and cables. 2. To attach a vessel to a buoy, or buoys. 3. To secure a vessel by attaching ropes to positions ashore.

Mooring Buoy. Buoy, carrying a large ring or shackle, securely moored so that a vessel can be attached to it and ride in safety.

Mooring Swivel. Strong swivel piece for insertion in cables of a vessel riding by two anchors in a tideway. Each end of swivel is connected to a strong trefoil member that is pierced with three holes, one of which is for its connection to swivel, the other two being for inboard or outboard connections of ship's cables. Use of swivel necessitates disconnection of each of ship's cables, and a reconnection to the swivel.

Moral Hazard. Term used in marine insurance to denote possible risk of dishonesty in an assured person or his representatives.

Morning Watch. Division of nautical day from 4 a.m. to 8 a.m.

More Vinta. Vessel of China Seas. About 40 ft. long. Has tripod mast, lugsail and outrigger.

Morse Code. Alphabet and numbers used in signalling. Each letter or figure is represented by a long sign, a short sign or a combination of them. May be transmitted by light, sound or

graphically. Invented by Professor Morse of Massachusetts.

Mortar. Short ordnance used for firing projectiles at short ranges. Angle of elevation was constant, about 45°, range being increased or decreased by increase or decrease of propelling charge. Now used only for line-throwing purposes.

Mortar Vessel. Small, broad beam vessel in which a mortar was mounted for bombardment purposes. Bomb Ketch.

Mortgage. The granting of a ship as security for money advanced. Any mortgage of a ship must be registered with Registrar at ship's port of registry. Mortgage can be raised by the owner only.

Mortice Block. Clump block.

Moseley's Formula. Equation by which the dynamical stability of a vessel may be ascertained from inclining experiments.

Mother Gary's Chickens. Stormy petrels.

Motor Ship/Vessel. Vessel propelled by internal combustion engines.

Mould. Pattern or template from which a member of ship's structure is shaped.

Moulded Depth. Vertical depth, measured amidships, between the horizontal plane passing through ship's keel and a parallel plane passing through top of freeboard deck beams at sides.

Moulding. Correctly forming the depth and outline of a vessel's frames or timbers when building.

Mould Loft. Large covered space, in shipbuilding yard, where moulds, or templates, are made for the various members to be erected.

Mount Misery. Colloquial name for an unprotected or unsheltered upper bridge.

Mouse, Mousing. To pass turns of yarn, or small line, across open part of hook to prevent accidental unhooking. Formerly: a knot worked in eye of stay to take chafe against the mast.

Mousing Hook. 'Self-mousing hook.'

Mudhole. Small door, in lower part of boiler shell, through which sediment may be withdrawn when not under steam.

Mudian. Bermuda-rigged boat.

Muffle (Oars). To put soft material around loom of oar, where it rests in crutch or rowlock, to deaden sound when rowing.

Mulct. To fine, or impose a penalty.

Multihull. A vessel which has more than one hull, e.g. a catamaran or trimaran.

Mumbleby. Devonshire name for a fishing boat rather smaller than a trawler.

Mumford Boiler. Water-tube boiler somewhat similar to Thorny-croft type, but having tubes more curved. Practically obsolete.

Munnions. Decorative work separating windows in sterns of old ships.

Munro Wind-Speed Recorder. Instrument that points a pressure head into the wind and, by means of measuring elements and a clockwork attachment, gives an anemogram.

Mush Ice. Broken ice in pieces up to 6 ft. across.

Mushroom Anchor. Umbrella-shaped anchor. Invented 1809 by Hemman of Chatham.

Mushroom Head. Domed top of a ventilator.

Mussel Bow. Name given to yachts that were cut away at fore- , foot, thus having a broad shallow part forward.

Muster. To assemble at a specified place.

Mutatis Mutandis. Latin term used in Lloyd's Salvage Agreement, and other documents. Means, 'after making the needful changes.'

Mutiny. Revolt from, or forcible resistance to, duly constituted authority.

Mutual Indemnity Insurance Association. Group of shipowners, and others, who combine to carry those risks excluded from policies of marine insurance. They are conducted on a non-profit-making basis, and mutually subscribe to make good an uninsured loss sustained by a member. 'Small Damage Club.'

Muzzier. Very strong head-wind.

Mystery Tables. Name given to Martelli's “Tables for Finding Apparent Time at Ship” on account of the obscuration of their basic formulae.
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