| TERMS | MEANING: |
|---|---|
| ICEBERG | A floating island of ice. Icebergs in the northern hemisphere almost all originate in Disko Bay in Greenland. The mountains of northern Greenland are covered by a vast ice-cap which moves slowly down the valleys until it reaches the sea, where great sections break away in a process known as calving. They float out to sea and are then carried southward by the Labrador Current. Their usual life-span is about two years, the second summer finding them at their most southerly point in the region of the Grand Banks off Newfoundland. Small portions which break away from the main icebergs and are still large enough to constitute a danger to navigation are known as growlers. Only one ninth of the total mass of an iceberg is visible above water level. They are. of course, a considerable hazard to shipping, especially in the summer months in the North Atlantic when most transatlantic shipping lines route their ships farther to the northward to make a shorter passage (see, in this connection, great circle sailing). The best remembered disaster at sea caused by an iceberg was when the White Star liner Titanic sank on 14 April 1912 after striking an iceberg near the Grand Banks off Newfoundland with a loss of 1,589 lives. Today an ice patrol, directed from Halifax, is maintained in the North Atlantic to observe the position of all icebergs, the rate and direction of their drift, and to report them so that all shipping can be warned of their presence. In many cases the warning comes to a ship in the form of a chart transmitted by wireless, so that the navigator has a copy of the actual chart in front of him when plotting his course. |
| ICE-BREAKER | A vessel specially designed with a reinforced bow and forefoot and with extremely powerful engines to force a way through pack ice in extreme northern latitudes. The largest and best-known of modern icebreakers is probably the Russian Lenin, a nuclear-powered ship of 16,000 tons. Her engines develop 44,000 horse power and give her a maximum speed of 18 knots. She is said to be able to clear a channel 100 feet wide through pack ice eight feet thick at a speed of four knots. Larger nuclear-powered ice-breakers, able to clear a passage through even thicker ice, are reported to be under construction in Russia. The Lenin and other Russian ice-breakers are used to clear a shipping lane in the ‘Northern Sea Route’, which connects the Atlantic with the Pacific Ocean north of Russia and Siberia (see also north-east passage). Similar attempts have been made to open the North-West passage, which runs north of Canada, especially in connection with the discovery of immense oil deposits in Alaska and the surrounding area. Many other ports which are frozen up in winter employ ice-breakers to clear a passage for ships. |
| IDLERS | The name which used to be given to those members of a ship’s crew who, by reason of their employment, do not stand the normal watches. The carpenter, cook, sailmaker, boatswain, painter were the usual members of the round house mess where idlers were accommodated. The name has now largely fallen into disuse, but was widespread in navies and merchant navies during the days of sail. |
| IN SOUNDINGS | A vessel is said to be in soundings when she is being navigated in water sufficiently shallow for soundings (see sound, to) to be made and used as a means for ascertaining the approximate position of the ship. Traditionally a ship is reckoned to be in soundings when she is within the 100 fathom line, this isobath being taken as marking the edge of the continental shelf. |
| IN STAYS | A sailing vessel is said to be in stays when she is head to wind and temporarily unable to pay off on either tack, though in its original meaning the term was used to indicate the act of tacking. |
| INTERCEPT | The difference, measured in nautical miles, which the navigator obtains when he works a sight of an astronomical object. It is the difference between his estimate of the ship’s position by dead reckoning and the position obtained from his altitude observations. He transfers this to the chart by measuring the length of his intercept along the azimuth of the observed object and drawing his position line at that point at right angles to the azimuth. |
| INTERNATIONAL CODE OF SIGNALS | A series of signal flags and pendants, one flag for each letter of the alphabet and one pendant for each number between and 9, with three additional pendants for substitutes and four for special meanings, which has been agreed and adopted by all maritime countries for communication between ship and ship, and ship and shore. It was founded in 1817 on Captain F. Marryat’s code of signals and consisted originally of only fifteen flags and pendants. By 1855 it was being widely challenged by codes developed in France by Captain Reynold de Chauvaucy. In Great Britain by Rohde (1836) and Watson (1842), and in the U.S.A. by Rogers, but an international committee was set up in 1856 to try to reach agreement on a single code for universal use. Its final recommendation was based almost entirely on Marryat’s original flags and it published a Commercial Code of Signals which received universal recognition. In 1887 the existing code ran into difficulties because of the adoption of the four-letter group for ship identification. Additional coloured flags and pendants were incorporated into the code, making a total of forty in all. The revised code, universally agreed in 1900, was brought into use in 1902. |
| INTERNATIONAL CONVENTION FOR THE SAFETY OF LIFE AT SEA | The official body, composed of government representatives of all maritime nations, which among other responsibilities draws up the International Regulations for Preventing Collisions at Sea. More widely known as the Rule of the Road. The Convention is called together from time to time by member governments to review the existing rules and to propose amendments when required. The existing regulations were last approved in full by the Convention in 1960; the most recent meeting was held in London in 1972 when two modifications to the existing regulations were proposed. The first suggests the introduction of one-way traffic for ships in congested waters; the second the adoption of special distinguishing marks for extra-large ships, such as very large crude carriers, to warn all other ships to keep clear of them in shallow waters where their ability to manoeuvre is limited. These amendments are intended to come into force in 1976, but in order to become part of the international regulations they need first to be ratified by a minimum of fifteen nations representing between them not less than 65 per cent of the world’s merchant tonnage. |
| INTERNATIONAL DATELINE | A line running mainly along the longitude of 180° but with adjustments to avoid the division of certain island groups which lie astride that longitude. |
| INTERNATIONAL REGULATIONS FOR PREVENTING COLLISIONS AT SEA | The official title of the internationally agreed rules by which ships at sea keep clear of each other, more generally known as the Rule of the Road. They are drawn up and approved by the International Convention for the Safety of Life at Sea, which meets from time to time to review the existing regulations and propose amendments when required. The regulations are binding on all ships using the sea and govern every case in which a danger of collision may arise when ships meet at sea or congregate in narrow waters. But the fact that a strict interpretation of the rules may give the right of way to one of two vessels where there is a risk of collision if they both continue on their present course, does not absolve the master of the vessel with the right of way from taking the necessary action if a collision appears imminent. For example, although the regulations lay down that in all cases of danger of collision a vessel under steam power gives way to a vessel under sail, it would be unreasonable to expect a giant tanker navigating in narrow waters to give way to a yacht under sail. It is for reasons such as these that the regulations lay down on all masters of vessels, whether they have the official right of way or not, a duty to avoid a collision by taking whatever action is necessary. The steering and sailing rules currently in force, with the rules governing sound signals in fog, are set out under rule of the road. |
| IRISH HORSE | The sailor’s name in the old days for salt beef which was tougher than usual, probably based on the belief in those days that the Irish, being so poor, worked their horses much harder and longer than the English. There was a sailor’s song of the 18th century in which he addressed his ration of salt beef: ‘Salt horsersalt horse, what brought you here? You’ve carried turf for many a year. From Dublin quay to Ballyack You’ve carried turf upon your back.’ |
| IRISH HURRICANE | A sailor’s name for a flat calm, when no wind blows. It was also sometimes referred to by seamen as a Paddy’s hurricane. |
| IRISH PENNANTS | The seaman’s name for loose ends of twine or ropes left hanging over a ship’s side or from the rigging, a sure sign of a slovenly crew. Similarly, the name given to the ends of gaskets and reef points left flapping on the yard when the sail is furled in a square rigged ship. See also dead men. |
| IRONS | (1) A sailing ship is in irons when, by carelessness or through a fickle wind, she has been allowed to come up into the wind and lose her way through the water so that she will not pay off again on either tack. It is in the process of tacking, which entails a vessel coming up head to wind and bringing the wind on the other side, that the most frequent cause of a ship being in irons occurs.
(2) Another word for the bilboes. IWO JIMA 421 a punishment on board ship in which men had their legs shackled to a long iron bar, somewhat in the nature of the punishment of the stocks ashore. A man was said to be put in irons. or ironed, when undergoing this punishment. It was a punishment fairly common in ships of all nations, both warships and merchant vessels, and is said to have been introduced into England from Spain, theArmada ships all having them on board. Some of the irons fitted in the Armada ships are still to be seen in the Tower of London. |
| ISOBATH | From the Greek iso, equal, and bathos, depth, a line on a chart linking points of equal depth, sometimes called a depth contour. |
| ISOBATHYTHERM | A line connecting points in vertical sections of the sea which have the same temperature. |
| ISOGONIC LINES | Lines drawn on a chart which connect points of equal variation of the compass. The first world chart to incorporate isogonic lines was published by EdmundHalley in 1701. a notable landmark in the history and development of cartography and navigation. |
| ISOHALSINE LINES | Lines on a chart joining parts of the sea which have an equal salinity. |