MAGNETISM

The ancients acre the; varies f namo to certain hard black stones, | 16¢0 th fariculariy sbundaat in Magnesia, in| the be; Minor, which po e ed tho gba posed north-« of attracting to them small pieces of iron | 24° 17’ and steel. Somewhere about the 11th | declina century it was discovered that, ah Me. is calcu en re rely suspended | needle iy a fine thread, it po e ed the remarkable | gouth, | property of pointing north and south.| to the discovery was made use of in naviga-| turban tion, and, from that time, the name/| which: Lodestone, i.e., leading stone, was applied | a cons i to the natural magnet. Dr. Gilbert | occurre further investigated its properties, and, in} A mag 1600, he published the result a of his} occurre oer He discovered that tho] greatly a ve force was ore at two pos i- | telegra; tions on the stone. a long pieco these | area. tivo positions are generally at or near the |¢ Ther ends, and the force gradually diminishes | Electrix m3 the "ihe pou ae - comyrgp Vee easily ace, ions grea a - | pa age tion he named the Poles, and tho neutral | a silk line he called the Equator of the magnet. | spiral o The stone is an oxide of iron, and is/ iron, o sbundant in Sweden, Spain, Elba, and magnet “orkid the United inset though a does | S = not always po e magnetic properties. | magn It has been found that the ichaatcoe strenct! hes the power of communicating its| the nu: 25 alge to small bars of stecl, and} A powe without aay Dom of magnetism to itself.| the she Thus, if a knitting-needle, or a piece | support of awatch-spring, be rubbed with oneend of | of ares a lodestone about twenty times, from end | Electro to end, in one direction only, it will acquire poten all the of a magnet: it wil) attract | for the adi places of iron or eked!: or, if balanced | by mes eon Will s06 iteelt in a motors, ar from north to =e and, if | electric: eflected from that position, will oscillate | makers from side to side, and at length come to | operati: rest pointing in the original direction, | the bar the end that pointed north at first | the elec always return ins to that position. If two | the opp puch needles are brought close to each | An elec other, the north-secking end (pole) of | of every the one will repel the north-seeking pole| MAG of the other, and will exert an attractive | song of force on the south-seeking pole. Every | It form magnet, whether natural or artificial, has| of the two poles. If it is broken into two parte, Charch each wil) still have two poles of | fact tha te kinds. A magnotisod bar of | is magn retains its magnetism almost in-| MAG 4 but its powers may be destroyed | of birds by maege, cr by heating the bar to | stand in redne . In tion to iron and steel, | dark p ost heen chromium, and manganese| can be are by a magnet; and, a short | phrases, time ago, Profe or Dewar showed that, | always if a powerful magnet were brought near | with st & ve el containing liquid oxygen, the | it to b liquid would spring upwards, and adhere | and th: magnet gla nearest to the poles of the | of ae compaas needle is a magnet properly | a branc mounted and balanced. ‘The tian allied | which hag takes is duc to the Laat hat the oe earth is a great an javes ag | remark: though a hige mageeti bar lay within its} MAH ma , with not quite coinciding | York, 1 oe Serer a phi cel poles. Bir James | critics a: discovered, in 1830, that the Rasenstio best kné North pole was situated in Boothia Felix, | Sea Po oe at Dey of North America, | officer ir Within the Arctic circle. The fixing | to the 7 of the position of the South Magnetic Pole | Govern Was one ci the scientific problems which} MAH the four expeditions to the Antarctic, in | who dis the period 1900-04, set themselves to | is believ solve, It is believed to be situated some- | reappea: where about 168° east longitude and 76° ana south latitude. In England the compa | seve f parenet point due north and south, | known in a which at present is | caused t geceephioal ieridan. The from Hp yee meridian, amoun exico, Variation or declination, as it ix called, | Indies, rom time to time. About the year, capab ecompa pointed true north, At/ much joking pole pointed ina divot i on | a po na oD west of trne north. Since then the! inhab tion has slowly et and it} Deccs lated that about the year 1076 the; Sir A will again point due north and} and ¢ after which the declination will be| Britis east of north. Occasionally dis- MA 3 occur in the earth’s oe fee & peas sffect all the compa needles over} the } Jerable region of the globe. Such} Englis nces are known as magnetic storms. | Jeann netic storm of unusual intensity} MA d on October 3lst, 1903, and/ persor interfered with tho working of the | be alw oh lines and cables over a wide) cight, » is a close cotreicey between | “ Hon ity and Magnetism. © one is| MA converted into tho other, The/| is on } of a current of clectricity through | ester. sorverod, copper wire, wound in a/| town € many turns round a core of soft/ and o mnverts the latter into a powerful | po es 28 long as the current is pa ing. | eries; aes SSS S| ee. epen on e 12 2 of the maznetising current, and | philos mber of turns of wire in its coils.|} MA rful magnet of this kind, bent into} Maing pe = Pasi yan is copes fs MA ing or évery square in prison » in the ends of “the on core, | the se ‘magnets are employed for the} She jon of the magnetic field nece ary | gover: indacing of a current of ragpineres A marri: eS SE and in el but b as explained in tho article on/ matte yf They are also used by magnet; MA ‘or magnetising bars of steel, an | town 9n which is accomplished by moving | Rhine from end to end, acro one pole of | surrov tro-magnet, and then moving it in | Mainz site direction acro the other pole. | distric tro-magnet is also an e ential part | princi; r electric bell. bathe NIF ‘ [s. 204]