. . of the Magnetic Poles of the Earth. 69 



Hence, in 35 years, the pole n has moved 14° 35' 30 ", or 

 25/128 per annum. 



Hence it appears, that the magnetic pole n has a motion 

 from west to east, and that its period of complete revolution 

 is 860 years. 



4. On the Position of s, the weakest Magnetic Pole in the 

 Southern Hemisphere south of Terra del Fuego. 



By combining the observations made by Captain Cook 

 and Fourneaux in 177^ Professor Hansteen has obtained the 

 following results : 



But, in 1676, from observations mentioned by Halley in the 

 Phil. Trans., No. 148, Professor Hansteen found the position 

 of this pole to be, 



Distance from the Pole in 1670, - - 15° 53' 



Long. West from Greenwich, - - 94 33J 



Hence, in 104 years, the pole s has moved westward 28°43^', 

 or 16 ; .57 annually ; and we have its period of complete revo- 

 lution, 1303 years. 



From these determinations, it appears that the two magnetic 

 poles in the northern hemisphere, N and n, move eastward, while 

 the txoo S, s, in the southern hemisphere move westward. 



As the poles N and S are nearly about the same distance 

 from the terrestrial poles, and, therefore, almost diametrically 

 opposite, and as they are also much stronger than n and s, 

 Professor Hansteen properly assumes, that N and S are the 

 terminating points of one magnetic axis, and n and s those of 

 the other axis. Therefore, says he, these two magnetic axes 

 cross without intersecting one another, or passing through the 

 centre of the earth. The centre of both lie much nearer the 

 surface in the South Sea than in our hemisphere. 



