. The Ontario high school physics. e through places having the samedeclination are called isogonic lines; that one along which thedeclination is zero is called the agonicf line. Along this linethe needle points exactly north and south. On January 1, 1910, the declination at Toionto was 5° 55W. of true north, at Montreal, 15° 4 W., at Winnipeg, 14° 4 E.,at Victoria, , 24° 25 E., at Halifax, 21° 14 W. These values * The cost of the arctic expedition, which was made by John Ross and his nephew James,was defrayed by a wealthy Englishman named Felix Booth,tGreek, igos = equal, gonia = angle; a
. The Ontario high school physics. e through places having the samedeclination are called isogonic lines; that one along which thedeclination is zero is called the agonicf line. Along this linethe needle points exactly north and south. On January 1, 1910, the declination at Toionto was 5° 55W. of true north, at Montreal, 15° 4 W., at Winnipeg, 14° 4 E.,at Victoria, , 24° 25 E., at Halifax, 21° 14 W. These values * The cost of the arctic expedition, which was made by John Ross and his nephew James,was defrayed by a wealthy Englishman named Felix Booth,tGreek, igos = equal, gonia = angle; a = not, gonia = angle. LINES OF EQUAL DECLINATION OR ISOGONIC LINES 877 are subject to slow changes. At London, in 1580, the decHna-tion was 11° 17 E. This slowly decreased, until in 1G57 itwas 0° 0. After tliis it became west and increased until in1816 it was 24° 30; since then it has steadily decreased and isnow 15° 8 W. In Fig. 458 is a map showing the isogonic lines for theUnited States and Caiiada for January 1, 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
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
