. The Ontario high school physics. Fig. 458. -Isogonic Lines for Canada and the United States (Janviary 1,1910).The data for regions north of latitude ° are very meagre and discordant; the regions west ofHudson Bay where recent determinations have been made show considerable local disturbance;the lines north of latitude 70° are drawn largely from positions calculated theoretically, butmodified where recent obser^ ations have been made. The above map was kindly drawn for thiswork by the Department of Research in Terrestial Magnetism of the Carnejrie Institution ofyVashington. 378 MAGNETISM.
. The Ontario high school physics. Fig. 458. -Isogonic Lines for Canada and the United States (Janviary 1,1910).The data for regions north of latitude ° are very meagre and discordant; the regions west ofHudson Bay where recent determinations have been made show considerable local disturbance;the lines north of latitude 70° are drawn largely from positions calculated theoretically, butmodified where recent obser^ ations have been made. The above map was kindly drawn for thiswork by the Department of Research in Terrestial Magnetism of the Carnejrie Institution ofyVashington. 378 MAGNETISM. Fig. 459.—a simple dip-ping needle. 439. Magnetic Inclination or Dip. Fig. 459 shows aninstruineut in which the magnetized needle can move in avertical plane. The needle before beingmagnetized is so adjusted that it will restin any position in which it is placed, butwhen magnetized the iV^-pole (in thenorthern hemisphere) dijos down, makinga considerable angle witli the horizon. Ifthe magnetization of the needle is reversed,the other end dips down. Such an instru-ment is called a dipping needle. Whenusing it the axis of rotation should pointeast and west {, at right angles to themagnetic meridian), and the needle should move with the leastpossible friction. The angle which the needle makes with the horizon is calledthe inclination or dip. At the magnetic equator the dip iszero (or the needle is horizontal), but north or south of thatline the dip increases, until at the magnetic poles it is 90°.Indeed the location of the poles was determined by the dippingneedle. At Toronto the
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
