98 ON MAGNETISM. 



But the forms of the southern curves only seem to 

 indicate the existence of two poles of magnetic force. 

 This indication differs remarkably from that which is 

 founded upon the system of curves to be mentioned 

 next. 



The curves of equal Total Magnetic Force present 

 us with the singular phenomenon of two poles of 

 maximum force in the north, and only one in the south. 

 The numerical values of the forces at the former are, 

 6*160 west of Hudson's Bay, and 5 '911 in Siberia: that 

 of the latter 7'898 in South Victoria. Proceeding from 

 these towards the equatoreal belt, the equatoreal max- 

 ima 3'6S6 and 3'649 are reached in longitude 252, 

 south latitude 7, and in longitude 110, north latitude 

 6, and the equatoreal minima 2'828 and 3'248, near 

 St. Helena in longitude 355, latitude 16 south, and 

 in longitude 179, latitude 6 north. There is a rude 

 approach to the law, that the Total Force at the 

 Magnetic Poles is double that at the Magnetic Equator. 



The theoretical connexion of these facts will be 

 treated in the next Section. 



At the end of Article 41 it was remarked that, 

 at Greenwich, the Dip and Total Force are diminishing. 

 Interpreting these by the remarks above, it would 

 seem that the Magnetic Equator is approaching to 

 Greenwich, or the North Magnetic Pole is receding 

 from Greenwich. And remarking also the westerly 

 change in direction of north magnetic meridian, from 

 the sixteenth century to the year 1824, and its subse- 

 quent easterly motion (Article 24), it would seem that 



