| TERMS | MEANING: |
|---|---|
| M.G.B. | The abbreviation for motor gunboat in the British Navy in the Second World War. |
| M.T.B. | The abbreviation for motor torpedo boat in the British Navy in the Second World War. |
| M.V. | The prefix placed before the name of a ship to indicate that she is a motor (diesel) vessel. |
| M.Y. | A prefix used before the name of a yacht to designate a motor yacht. |
| MACARONI LUG | An obsolete name for the standing lug rig. |
| MACARONI MATE | A man signed on as mate in a merchant vessel though without the required qualifications and without pay. The origin of the term, and the practice, is believed to have arisen at the time of the Napoleonic occupation of Genoa and Leghorn in 1 796 when many of the sons and favourite employees of the English merchants there were thus signed on in American merchant ships with the object of escaping both capture and imprisonment by French troops and possible impressment at sea if the ship were stopped by British cruisers. |
| MACSHIP | A merchant vessel, usually a tanker or grain ship, fitted during the Second World War with a temporary flying deck above her superstructure from which, initially, land-based fighter aircraft could be flown off and landed on. The requirement for such ships arose from the attacks on convoys in the Atlantic made during the first three years of the war by German long-range Focke-Wulf aircraft which could operate up to 700 miles out to sea. With fighter protection provided within the convoy, these aircraft could be shot down or driven off before making their attacks or reporting the convoy’s position to waiting U-boats. |
| MAELSTROM | A term commonly accepted as meaning a whirlpool, but in fact referring to a strong current which rips past the southern end of the island of Moskenaes in the Lofoten group off the west coast of Norway. It is also known as the Maskenstrom. It is marked on the map of the area which appears in Mercator’s Atlas of 1595. The word would appear to come from the Dutch maleiu to grind, and strom, stream or current. |
| MAGELLANIC CLOUDS | A popular name for the two nebiculae. Or cloudy-looking areas in the southern sky. Which consist of a great number of small stars much resembling the Milky Way. They were named after Ferdinand Magellan. |
| MAGNETIC POLE | The point on the earth’s surface to which the needle of a magnetic compass points. It is not at the North Pole but some distance away in the Canadian Arctic, nor is it in a fixed position, but wanders according to the vagaries of terrestrial magnetism. Although its approximate location had been known for many years, it was not until 1 83 1 that Sir James Clark Ross discovered that it was on the west side of the Boothia Peninsula. The angular difference between the magnetic pole and the North pole at the point of a magnetic compass is known as variation, and must be applied to a magnetic course or bearing to obtain the true course or bearing. |
| MAGNITUDE | As it applies to nautical astronomy, refers to the apparent brightness or luminosity of any of the navigational stars or planets. First to classify stars according to their apparent brightness was Hipparchus, the prince of ancient astronomers. His system comprised six magnitude classes, the small group of some fourteen of the brighter stars forming those described as being of the first magnitude, and the relatively large number of faint stars just visible to the unaided eye forming the group of sixth magnitude stars. This rough and ready classification was improved during the 19th century with the introduction of a decimal scale of magnitudes and the extension of the magnitude scale to include telescopic stars, whose magnitude numbers are more than six, and fractional and negative magnitudes. Sir John Herschel, son of the astronomer Sir William Herschel, is credited with having suggested that a star of magnitude 10 should be regarded as being 100 times as bright as a star of magnitude 6-0. |
| MANGER | A small space in the bows of a ship immediately abaft the hawse pipes and bounded on the after side by a low coaming called a manger-board. Its purpose was to prevent any water from running aft along the deck should it enter through the hawse pipes. It applied principally to sailing ships and the early steamships when the hawse pipes were on the main deck level. In modern ships, where the hawse pipes are on the forecastle deck level, the same purpose is achieved by an athwartships breakwater abaft the cable-holders. |
| MARITIME LAW | That branch of international law which concerns maritime matters and causes. It was originally derived chiefly from the ancient codes of laws of the sea, particularly those of 01eron, but it is, of course, continually amended and expanded as modern experience brings in new examples and conditions requiring international legislation. It covers such subjects as Rule of the Road at sea, territorial and international waters, ocean fishery, contraband, blockade, belligerent rights, etc. The usual means of change and modernization are international conferences and conventions, at present held under the auspices of the United Nations. Judgement, on the international scale, is exercised by the International Court at The Hague. |
| MARITIME TERRITORY | A term in international maritime law to denote coastal waters which, although not within the strict territorial waters limit, are in direct contact with the open sea. There is no limitation over the dominion of maritime territory. A bay or gulf, no matter how large, that cannot be held to be part of an open ocean highway is considered to be the maritime territory of the nation which occupies its shores, as, for example, the Gulf of St. Lawrence would be the maritime territory of Canada. A strait, of which both shores are within a national boundary, is also considered to be maritime territory, and the passage of foreign ships through it can be forbidden. But where the two shores of a strait are held by different countries, as for example Britain and France in the case of the Straits of Dover, the water between the shores cannot be claimed as maritime territory by either nation but is an international ocean highway. |
| MARLINE | A small light line used for a variety of purposes on board ship. It is two-stranded, loosely twisted, and was originally used for bending light sails to their yards or stays. It is usually supplied both tarred and untarred. |
| MARLINE SPIKE | A steel spike pointed at one end and used for lifting the strands of a rope to make room for another to be tucked in when splicing. |
| MARLING HITCH | A series of round turns in which the end is passed over the standing part and under the bight and pulled taut on each turn. Unless there is an eye in the end of the rope a marling hitch is usually started with a timber hitch and is used for lashing up sails, awnings, hammocks, etc. |
| MAROON | Deliberately to put ashore a sailor and leave him there when the ship sails away. The action usually implies being left, or marooned, in some relatively inaccessible place. Perhaps the best-known case of a marooned seaman was that of Alexander Selkirk. |
| MARTINGALE | (1) The stay which holds the jib-boom down against the pull exerted by the fore topgallant-mast stays in a square-rigged ship. It runs from the outer end of the jib-boom to the dolphin-striker. Martingale guys hold the dolphin-striker firm, being run from its end and secured on either bow of the ship.
(2) A rope or strap which runs from a point on the boom of a dinghy’s mainsail to the foot of the mast, designed to prevent the boom from rising when it swings outwards and thus to present a flatter sail surface to the wind. It is normally fitted only in racing dinghies, and is usually known as a kicking-strap. |
| MARTNETS | A term no longer employed but one which was used in older days in square rigged ships to describe the leech-lines of a square sail. When these martnets were used to haul the leeches of the sail up to the yard, for furling or shortening sail, they were said to be topped. |
| MAST | A vertical spar set in a ship. Its prime use was, of course, to carry sails, but in modern mechanically propelled ships the mast usually serves to carry such essentials as wireless aerials, radar arrays, etc., and is not necessarily a vertical spar, particularly in warships in which the masts are more usually of steel lattice. Flag signals at sea are hoisted on halyards led to the mast, or to a yard across it, in order to obtain the maximum visibility through the height of the hoist, and a mast also carries on it the compulsory steaming lights which a vessel has to display when under way at night. |
| MAST COAT | A covering either of painted canvas or of rubber, secured round the foot of a mast and to the deck around it, which prevents water running below through the opening in the deck where the mast of a vessel goes down to its step in the keelson. It is mainly used in sailing vessels where the masts have to be allowed a certain amount of play as they go through the openings in the deck in order to absorb the pressures of wind upon sails. |
| MASTER | (1) Originally an officer in a warship responsible solely for the navigation of the ship. In the British Navy, he was appointed by the commissioners of the Navy Board, and his duties, in addition to a responsibility for all navigational problems, included working the ship into her proper station in the line of battle. He ranked with the lieutenants but was subordinate to them in command although he was usually accommodated in a better cabin in the coach. After 1814 masters in the navy ranked with commanders and the rank was known as master and commander, but this term lapsed towards the end of the 19th century when the study of navigation became a specialization within the executive hierarchy.
(2) The usual name given to the captain of a merchant vessel, qualified to take command by passing a professional examination for a master’s ticket. |
| MASTER-AT-ARMS | The officer, appointed by warrant, who is responsible for police duties on board a naval ship. In the early days he was also responsible for exercising the crew in the use of small arms, but this duty was later taken by the junior lieutenant on board who was known as the lieutenant-at-arms. |
| MASTER’S MATE | An old naval rate in all navies during the days when the master of a warship was the officer responsible for her navigation. His mates were petty officers entered in the ship’s muster list to assist him in his duties. |
| MATE | The rank in the merchant marine next below that of master. They are divided into first, second, third, etc., to indicate their seniority on board, and in Britain and most other countries with a merchant navy have to pass an examination (in Britain known as a certificate or ticket) to qualify for the rank, such examination being held under the control of the government department normally responsible for overseas trade. In fighting navies, mates originally held the rank of petty officer, being allocated to certain duties under the charge of a warrant officer, e.g., boatswain’s mate, carpenter’s mate, etc. Later, in the British Navy, a mate was an officer commissioned from the lower deck and ranking with a sub-lieutenant. The tendency in the British merchant marine today, particularly in the larger steamship companies, is to substitute the word officer for mate, seniority being denoted by the prefixes first, second, third, etc. |
| MATTHEW WALKER KNOT | A stopper knot near the end of a manrope or the end of a lanyard to prevent it running through an eye. It is made by forming a half hitch with each strand of the rope in the direction of the lay and then tucking the strands over and under until the knot is formed. A finished Matthew Walker knot looks similar to other stopper knots. |
| MAYDAY | An international distress signal made by voice radio on a wavelength of 2,182 kHz, a wave which is permanently watched ashore. It is said that the origin of the signal is the French m’aidez, help me. |
| MERCHANT NAVY | A collective name to describe the merchant ships on the official registers of any one nation. It embraces merchant ships of all varieties, from passenger liners and very large tankers and bulk carriers to small coasters, but does not normally include vessels used in fishing. |
| MERIDIAN | From Latin medius meaning middle, and dies meaning day, is a semi- great circle joining the earth’s poles. Meridians, better known perhaps as lines of longitude, cross the equator and all parallels of latitude at right angles. Owing to the uniform rotation of the earth, all celestial bodies appear to revolve around the earth towards the west, making one revolution in a day. When the sun crosses an observer’s meridian, the time is reckoned to be midday, that is to say the local time is 12 noon at the instant the sun is at meridian passage. |
| MESSENGER | (1) An endless rope which was used in weighing the anchor in the days before the introduction of steam power in ships and when the capstan was worked by hand. As the hemp anchor cables of those days were generally too thick and heavy to be brought themselves round the capstan direct, a messenger was used instead. It was led through two single blocks from the vicinity of the hawseholes, along the main deck so that it ran close alongside and parallel with the cable, round the capstan, where three or four turns were taken round the barrel, and back along the main deck on the other side of the ship. As the capstan was turned, so the messenger moved with it, and the cable was bound fast to the messenger with nippers so that it was hove in at the same rate as the messenger.
(2) A snpall rope attached to the eye of a hawser and used to haul it out to the ring of a mooring buoy is also called a messenger. |
| METACENTRE | The point of intersection of a vertical line, in relation to the ship’s structure, drawn through the centre of gravity of a ship when she is lying upright and a vertical line drawn through the centre of buoyancy when the ship is heeled. To make certain that a ship is stable so that a righting moment comes into play when she is heeled, the metacentre must be above the centre of gravity. The theory of the metacentre in shipbuilding was first evolved by the Frenchman Pierre Bouguer in the mid- 18th century. |
| METACENTRIC HEIGHT | The vertical distance between the centre of gravity of a ship and her transverse metacentre. It is an important element of the righting moment exerted to bring a ship back to the vertical when she rolls under the influence of the sea or wind; the greater the metacentric height, the more the righting moment. At angles of roll of more than about 10°, the position of a ship’s metacentre, and therefore her metacentric height, varies, and a designer must arrange the shape and dimensions of a ship’s hull to provide not only reasonable initial stability at normal conditions of loading but also reasonable stability at the probable angles of heel to which a ship may roll in heavy weather. This becomes particularly important in the case of container ships where the stowage of containers on the upper deck, in addition to in the holds, obviously raises the position of the vessel’s centre of gravity and thus reduces her metacentric height. |
| METACENTRIC SHELF | A method of indicating the relative balance or imbalance between the forebody and afterbody of a vessel under varying angles of heel by plotting the metacentric positions of the sections of the vessel’s hull lines when heeled. The form of this plotted curve, which is termed the metacentric shelf, reveals any lack of balance or irregularities in the vessel’s submerged form which, it is claimed, can be corrected before the final design draught is reached. This metacentric shelf method of checking a vessel’s lines for balance when heeled was invented by Engineer Rear Admiral Alfred Turner, of the British Navy, in about 1935. |
| METEOROLOGY | The study of weather patterns with the object of predicting change in the weather. It is a complex and still inexact science, based on current weather reports over a large area, but it is of great importance to navigators, particularly to those of small vessels and yachts, in enabling them to avoid areas in which stormy weather is predicted. |
| MILLIBAR | A unit of measurement of atmospheric pressure, 1,000 milli-bars equaling the atmospheric pressure required to raise a column of mercury in a vacuum tube to a height of 29-53 in. (750 mm). Lines drawn on a synoptic chart connecting points of equal atmospheric pressure in milli-bars are known as isobars. |
| MITRE | The seam in a sail where cloths which run in two directions are joined. Triangular sails, such as staysails and jibs (and occasionally yachts’ Bermudian mainsails), are normally made with the lines of the cloths running in two directions; for example, the upper cloths of a jib might run at right angles to the leech, and the lower cloths at right angles to the foot. The mitre seam usually forms a strengthened narrow cloth running diagonally from the clew to some point on the luff. Different sailmakers have their own ideas of the best method of setting the cloths and the mitre seam, but the latter is usually arranged to run more or less in line of the sheet so as to distribute the strain of the sheet evenly throughout the sail cloths. |
| MIZEN or MIZZEN | The name of the third. after most, mast of a square-rigged sailing ship or of a three-masted schooner, or the small after mast of a ketch or a yawl .The word probably came into the English language either from the Italian mezzana or the French misaine, which in fact are the names in those languages for the foremast, but for some reason its position in the ship was changed round when the word was adopted in Britain. The French word for mizen is artimon, and artemon was the name given in England to an additional mast in the forward end of a vessel, probably the forerunner of the bowsprit. |
| MOLE | A long pier or breakwater forming part of the sea defences of a port. It can be built either in the form of a detached mole constructed entirely in the sea or with one end of it connected to the shore. The ports of Dover and Gibraltar, for example, are protected by three moles, two of them attached to the shore on the eastern and western boundaries of the harbour, with a detached mole to seaward, providing an entrance to the harbour at each end of it. In old days the word, sometimes written as mole-head, was also used, wrongly, to describe a harbour protected by a mole. |
| MONKEY BLOCK | The name given to a small single block stropped with a swivel, and used on board in places where it is awkward to get a straight haul. The name was also used in square rigged ships to describe the blocks fastened to the yards through which the bunt-lines are rove. |
| MONKEY JACKET | Originally a thick, closefitting, serge jacket worn by seamen while keeping watch in ships at night or in stormy weather; now the usual jacket worn by officers and petty officers of ships for everyday wear. |
| MONKEY-PUMP | The seaman’s name for a straw or quill inserted through a gimlet hole in a cask of wine or spirits, combined with the necessary mouth suction to draw off some of the contents. |
| MONK’S SEAM | The seam made by a sailmaker after sewing the overlapping edges of cloths together to make a sail. It is a line of stitches through the centre between the two rows of edging stitches. |
| MONSOON | A seasonal wind caused by the summer heating and winter cooling of a large land mass. The most important monsoons occur in the Indian and western Pacific Oceans where the huge land mass of Asia is the dominant factor. Only in the western part of the Arabian Sea and the northern part of the China Sea does a monsoon wind reach gale force; for the most part the winds are no more than fresh, about force 5 on the Beaufort scale. There are three recognized monsoons, the South-West monsoon which blows from about May to September over the northern Indian Ocean and western North Pacific, the North-East monsoon which blows over the same areas from about October to April, and the North-West monsoon which blows from about November to March over parts of the Indian Ocean and western Pacific Ocean south of the equator. This last is in effect the North-East monsoon after it crosses the equator where the reversed effect of the earth’s rotation changes it into a north-westerly wind. |
| MOORING | A permanent position in harbours and estuaries to which ships can secure without using their own anchors. For large ships, a mooring consists of two or three large anchors laid out on the bottom and connected with a chain bridle, from the centre of which a length of chain cable leads upward to a large mooring buoy, to the ring of which a ship can lie in safety by shackling on her own cable. The vertical cable is short enough to ensure that the ship swings with the tide within her own length. Smaller moorings for smaller ships may require only one anchor or a block of concrete, with a chain rising to a small buoy. For yachts, a very small buoy, light enough to be lifted easily on board with a boathook, is attached by a length of rope to a light chain, itself attached to a concrete block, and the mooring is hauled up until the chain reaches the surface and the yacht secured with it. |
| MOORSOM’S RULE | A mathematical formula for determining the cubic capacity of ships. It came into force in 1849 on the recommendation of a committee under the chairmanship of Admiral Moorsom set up by the British Admiralty at the request of the Board of Trade to recommend rules for assessing the tonnage of ships. By dividing the calculated cubic capacity of the entire British merchant fleet by the total of its registered tonnage, the figure of 98-22 was arrived at. Moorsom suggested that the figure of 100 cubic feet of capacity per gross ton should be adopted, and it is on this basis that the gross tonnage of ships is calculated. |
| MORSE CODE | A method of signaling much used at sea. It was invented by Samuel Finley Breese Morse (1791-1872), who got the first ideas for his invention during a voyage on board the packet ship Sully. He nearly starved to death while perfecting his invention, only to discover that most of the nations to whom he offered it refused to give him a patent for it. Eventually, however, the U.S. government gave him an appropriation to cover his costs, and the first Morse signals were passed between Washington and Baltimore on 24 May 1844. In 1858 most nations in Europe contributed 400,000 francs as payment to him for the use they had made of his invention. The Morse code was one of the best methods of signaling at sea until the introduction of the radio-telephone, its system of alphabetical and numerical symbols made up of dots and dashes making it as easy to transmit in sound, as by wireless; in light, as by searchlight or Aldis lamp; or by motion, with hand signal flags. It was a quick and easy code to master, and has proved invaluable for communication at sea. |
| MOULDING | The shipbuilder’s term to describe the depth of any member of a ship’s construction, such as her frames, keelson, keel, stern, sternpost, beams, etc. The width measurement is known as the siding. |
| MOULD-LOFT | A long building with a considerable floor area on which a naval architect’s draught, or lines, of various parts of the hull of a newly designed vessel can be laid off in their full dimensions. These full-dimensional drawings can then be moulded, with the aid of moulds, to provide the patterns to which the steel angle frames, in the case of ships built of steel, or the timbers, in the case of a wooden-hulled vessel, are bent or shaped. |
| MOULDS | The name given to the thin, flexible lengths of wood used on the floor of a mould loft to form a pattern of the various frames used in the construction of the hull of a vessel. Being flexible, the moulds can be easily bent to take up the required shape, and they form the pattern from which in the actual construction of the ship, the steel frames are shaped to the design of the naval architect. In a wooden-hulled vessel, they form the pattern to which the timbers are to be shaped. See also shipbuilding, modern developments. |
| MOUSE | A stop made of spunyarn fixed to the collar of the stays in a square-rigged ship to hold the running eye of the rigging from slipping down the stay. It is also a mark fixed on the braces and other rigging of the yards to indicate when they are square. In general, any small collar made with spunyarn round a wire or rope with the object of holding something in place, such as an eye threaded on the rope, would be called a mouse. |
| MOUSE A HOOK | The operation of passing two or three Turns of spunyarn across the jaw of a hook to prevent it jumping out of a ringbolt or eye into which it has been hooked, or to prevent a rope running across the hook from jumping clear. |
| MULTI-HULL | A type of vessel formed of two or more hulls or floats which is propelled by paddles, sails, or mechanical power. Sailing catamarans (two identical hulls) and trimarans (a central hull with twin floats) have been built during the 20th century in large numbers and increasing sizes for ocean voyaging and racing. Craft having more than one hull have been known in the Indian and Pacific Oceans for many hundreds of years but their use in the western 1874 the London, Chatham, and Dover Railway built a twin-hulled ferry of 1,533 gross tons, named the Castalia, for their cross-Channel service, and followed her a few years later with the Calais-Douvres of 1,820 gross tons. Both these vessels were propelled by paddle-wheels working between the two identical hulls. |