102 COSMOB. 



Inclination. 



The knowledge of the isoclinal curves, or lines of equal 

 inclination, as well as the more rapid or slower increase of 

 the inclination by which they are determined, (reckoning 

 from the magnetic equator where the inclination = to 

 the northern and southern magnetic pole where the horizontal 

 force vanishes,) has acquired additional importance in modern 

 times, since the element of the total magnetic force cannot 

 be deduced from the horizontal intensity, which requires to 

 be measured with excessive accuracy, unless we are previously 

 well acquainted with the inclination. The knowledge of the 

 geographical position of both magnetic poles is due to the 

 observations and scientific energy of the adventurous navi- 

 gator, Sir James Ross. His observations of the northern 

 magnetic pole were made during the second expedition of 

 his uncle, Sir John Boss (1829 1833), 23 and of the southern 

 during the Antarctic expedition under his own command 

 (1839 1843). The northern magnetic pole in 70 5' lat., 

 96 43' W. long., is 5 of latitude farther from the ordinary 

 pole of the earth than the southern magnetic pole, 75 35' lat., 

 15410'E. long., which is also situated farther west from 

 Greenwich than the northern magnetic pole. The latter be- 

 longs to the great island of Boothia Felix, which is situated very 

 near the American continent, and is a portion of the district 

 which Captain Parry had previously named North Somerset. 

 It is not far distant from the western coast of Boothia Felix, 

 near the promontory of Adelaide, which extends into King 

 William's Sound and Victoria Strait. 24 The southern mag- 

 netic pole has not been directly reached in the same manner 

 as the northern pole. On the 17th of February, 1841, the 

 Erebus penetrated as far as 76 12' S. lat., and 164 E. long, 

 As the inclination was here only 88 40', it was assumed that 

 the southern magnetic pole was about ] 60 nautical miles 

 distant. ** Many accurate observations of declination, deter- 



23 Sir John Barrow, Arctic Voyages of Discovery, 1846, pp. 521 

 529. 



24 The strongest inclination which has as yet been observed in 

 the Siberian continent, is 82 16', which was found by Middendorf, on 

 the river Taimyr, in 74 17' N. lat, and 95 40' E. long. (Middend. 

 Siber. Reise, th. i, s. 194). 



25 Qir James Eoss, Voyage to the Antarctic Regions, vol. i, p. 246. "I 



