108 TERRESTRIAL MAGNETISM. 



the observations of very few years. The comparison of my 

 results with those of Rudberg, in the years 1806 and 1832, 

 would indicate for Berlin a small decrease. ( 122 ) 



Inclination. 



We are indebted for the knowledge we possess of the 

 geographical position of both the magnetic poles where the 

 Inclination is 90, to the observations and scientific activity 

 of one and the same adventurous navigator, Sir James Ross : 



O * 



in the north, in the second expedition ( 123 ) of his uncle Sir 

 John Ross, (1829 to 1833), arid in the south in the Antarctic 

 expedition commanded by himself (1 839 1843). According 

 to his observations, the northern magnetic pole (in 70 5' N. 

 lat., 96 43' W. long.) is five degrees of latitude further from 

 the pole of the earth than the southern (75 5' S. lat., 

 154 10' E. long.) ; and the difference of longitude between 

 the two magnetic poles is 109. The northern pole is situ- 

 ated on the large island of Boothia Felix (very near the 

 American continent), a part of which had been previously 

 called by Captain Parry, North Somerset. The observations 

 of Sir James Ross place the pole, at the date referred to, at a 

 short distance from the western coast of Boothia Felix, not 

 far from Cape Adelaide, which projects between King 

 William's Sea and Victoria Strait. ( 124 ) The south magnetic 

 pole has not been, like the northern one, directly reached. 

 On the 17th of February, 184i, Sir James Ross in the 

 'Erebus/ attained 76 12' S. lat. in the meridian of 

 163 02' E. long., but the magnetic inclination did not 

 exceed 88 40', so that the south magnetic pole was supposed 

 to be still 160 English nautical miles distant. ( 125 ) Numerous 

 and very exact observations of declination, (determining the 



