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Nanosecond: Thousand-millionth of a second. Used mainly for measuring electronic time intervals.
National Association of Watch and Clock Collectors: Organization of collectors in the U.S.A. formed in 1943 to stimulate interest in studying and collecting timepieces. Publishes a bulletin and a 'mart', arranges meetings, has a library and a museum at the Franklyn Institute in Philadelphia, and 33 local chapters. Address: P.O. Box 33, Columbia, Pa., U.S.A.
National Maritime Museum Collection: Fine examples of navigational timekeepers including HARRISON'S, the world's second largest collection of ASTROLABES, and many other timekeeping instruments from SAND-GLASSES to TRANSIT INSTRUMENTS, including the first French watch known. At Greenwich.
National Physical Laboratory: Tests of timekeepers carried out at the Laboratory in Teddington, Middlesex, include the CRAFTSMAN TEST for watches, equivalent to Observatory tests in other countries; sporting tests for time of day CHRONOGRAPHS used for international sporting events; stop-watch and chronograph test; testing of stop-watches used for checking electricity meters; and chronometer test for survey and MARINE CHRONOMETERS. The ATOMIC CLOCK was developed by the N.P.L.
Nautical Almanac: Astronomical tables giving star positions at different latitudes for every hour throughout the year, for NAVIGATION. Compiled by the ROYAL OBSERVATORY and published by H.M. Stationery Office. The title was changed to Astronomical Ephemeris in 1959, but other publishers still use the original name.
Navigation: A navigator or surveyor can calculate his position north or south (latitude) by finding the height of the Sun or some other celestial body and referring to the NAUTICAL ALMANAC or AIR ALMANAC. Finding his position east or west (longitude) is complicated by the rotation of the Earth. LOCAL TIME becomes earlier west and later east of Greenwich. As the Earth revolves 360° in 24 hr., it moves 1 ° of longitude in 4 min. So if a sailor finds his local time is 5 hr. earlier than G.M.T. he is 75° west of Greenwich. To find local time he must know the date and take a 'fix' (find the position) of a star with a SEXTANT, in order to look up the local time in his almanac. G.M.T. 1S given by the ship's MARINE CHRONOMETER Or RADIO TIME SIGNALS and must be accurate because an error of only 4 seconds equals one nautical mile. Most air navigation is done by special radio signals which fix the position of the aircraft at once. At other times the sailor's method is used, but by the time the position has been found the aircraft may have moved about 100 miles away from it.
Negro Clock: Early German AUTOMATON clock with a ballshaped clock on a post intended to look like a palm tree. Beside it stand a negro and a dog. The negro has a pointer which indicates the hour against a MOVING BAND around the ball. At the hour, the negro moves his head and the dog tries to jump.
Newsam, Bartholomew (d. 1593): Clockmaker to Queen Elizabeth I after Nicolas Urseau. Worked in the Strand, having probably come from Yorkshire. Fine clock by him in the BRITISH MUSEUM.
Night Clock: The first known was by Johann Treffier and is in the KASSEL Museum Collection. As well as an ordinary dial for day, this has a glass dial with an oil lamp behind it. Another revolving glass dial carries a single hand. Clocks with illuminated hour numerals moving past a fixed point were common in Italy at the end of the seventeenth century. FROMANTEEL, EAST, and Joseph KNIBB made some in England. In these an oil lamp in the case shines through a perforated hour numeral, and marker hole above it, which moves during the hour round a large semi-circular slot in the dial. The slot is marked into four quarter hours and minutes for daytime use. At night, the time can be estimated to about five minutes by the position of the illuminated numeral. Night clocks had SILENT ESCAPEMENTS. Another type is the magic lantern clock. Current alarm clocks for night use have LUMINOUS dials, extra electric lamps, or are electro-luminescent, i.e. a glow of light is produced in the dial itself without bulbs by the tension of electricity.
Nivarox: A nickel-iron alloy with a little beryllium, invented by Carl Hass, Germany, as an improvement on ELINVAR for HAIRSPRINGS. By heat treatment during manufacture, its elasticity can be fixed at almost any value required. Thus it can be made t0 give any TEMPERATURE COMPENSATION desired, t0 eliminate temperature error in watches and clocks with balance wheels. It is non-magnetic, rustless, and tougher than steel. Other alloys with similar properties have been developed; they are Isoval, Durinval, and Nispan-C.
Nocturnal: Instrument invented about 1520 for measuring the time at night. It is held at arm's length to sight the Pole Star. A lever is turned to line up the Great Bear constellation which appears to rotate once in 24 hours; thus the lever can indicate the time on a scale.
Non-Magnetic: Fields of MAGNETISM have most effect on steel BALANCE WHEELS and HAIRSPRINGS. In the modern watch these are usually made of special alloys for TEMPERATURE COMPENSATION, which are also, fortunately, non-magnetic. Such watches are called 'non-magnetic' and are fairly resistant to magnetism, but not entirely as there are still steel parts that can be affected. Some special watches have a protective screen over the MOVEMENT inside the case. See Demagnetizer.
Numerals: Hour numbers on a DIAL, once almost universally Roman, now usually Arabic. Today BATONS are often used instead.
Nuremberg Hours: Early system of time reckoning in Nuremberg. The 24 hours in a day and night period were numbered afresh from 1 at each sunrise and sunset.
Nurnberg (Nuremberg): This town in the Bavarian district of Germany was one of the first centres of clockmaking, with Augsburg. In 1565 the Rat (mayor) issued a decree forming clockmakers, firearm makers, and locksmiths into a guild. Masterpieces had to be made by all men before they were allowed to practise their trade, those for clockmakers being an iron striking chiming and alarm clock six inches high in a brass case, or one of the big striking and alarm watches of the time worn on a ribbon round the neck.
Nurnberg Egg: Some of the earliest watches were made in NURNBERG in the early sixteenth century. Doppelmeyer, writing a history some 200 years later of the clockmakers there, called these watches 'eyerlein' or little eggs. He had mistranslated 'Ueurlein' meaning 'little clocks', but the false name still persists today, although these watches were ball shaped. A few egg-shaped watches were made in later years. See Watch and Musk Ball Watch.
Nutation: A nodding movement of the Earth during its rotation, which affects its time of rotation (i.e. SIDEREAL TIME) to the extent of about 20 MILLISECONDS every 15 days, as well as by about 1.2 seconds over 18 years. Discovered in the eighteenth century but not applied in TIME DETERMINATION until 1926 when the SHORTT CLOCK could measure it. Sidereal time has to be corrected by a nutation figure to give mean sidereal time, in the same way as SOLAR TIME has to be corrected by the EQUATION OF TIME to give mean solar time.