Naval Reserve

From Encyclopediak

Naval Reserve, naval forces not in active commission in the navy which may be drawn upon in case of need. Ships of the naval reserve consist of those that are undergoing repairs, older and less efficient boats that may be of service, and such vessels as may be drawn from the merchant marine. The Spanish-American War called these naval-militia organizations out and proved them to be valuable. Since then there has been an effort to bring them into close contact with the regular naval service. Many officers and men wlio have served in the navy and passed into civil life may be depended upon to re-enlist in time of war. Navigation is the science of determining the position of a ship at sea, and of conducting a ship from one position on the earth to another. Though always responsible for the safe navigation of his ship, captain of a naval ship has one of the senior officers of the ship designated as navigator who is charged with this duty under his supervision on merchant ships each of the watch standing officers does part of the navigating. Recent progress has brought many aids to the navigator but those most essential are acompass with azinuth circle for taking hearings gyroscopic or magnetic, a set of mariners charts of the locality to be visited, Nautical Almanac, a sextant, one or more chronometers, leads for sounding the depth of water and some instrument for measuring the speed or distance traveled usually a log. Along the coast and in and out of harbor, the position of a ship is determined by piloting, that is, the position of the ship is frequently obtained by bearings of charted objects such as Light Houses, Light Ships, buoys, beacons, etc., courses being steered to pass these objects at safe distances. The compass is used to keep the ship on its proper course, and log or revolution counter give the distance traveled on the determined course. At sea the position of a ship is determined by two methods, by dead reckoning and by observations of heavenly bodies, as sun, stars, moon and planets. Dead reckoning is laying down the courses and distances the ship has traveled on these courses, on the chart and picking off its position, but this reckoning is not as accurate a method of navigation as that by observations, as bad steering, strong currents, storms and inaccuracies of log cause the ship to frequently be a considerable distance from her dead reckoned position. By observations with a sextant the navigator measures the altitude above the horizon of a heavenly body. The Nautical Almanac gives the position of the heavenly bodies on the celestial sphere for each day and hour of the day for the entire year, tabulated for the Greenwich Mean Time as a standard reference time. The chronometer which the ship carries, keeps Greenwich Mean Time. The navigator at the time of measuring the altitude of a body records the Greenwich Mean Time, then picks out of almanac several elements of the body which with the altitude he has measured permit him to solve the astronomical triangle. The solution of this triangle gives the navigator a position point through which he can draw a line of position at right angles to the true bearing of the body at time sight was taken. The ship is somewhere on this line. The intersection of two such lines is the ship's position and may be determined either by simultaneous observations of two heavenly bodies or by two successive "sights" of the same body, moving up first line for the distance the ship has steamed. The ship's course is frequently marked by buoys. See BUOY COMPASS, MAGNETIC LIGHTHOUSE SEXTANT.