101 



presented by the line n' s' fig. 11, it will describe a coni- 

 cal curface with a very acute angle in the centre of the 

 Earth and the endpoints of it will describe small cireles 



Fig .11. 



around the magnetic poles. Because the Earth possesses a 

 certain magnetic inerlia, viz because it needs a certain time 

 to produce its magnetisme or to change its direction, this 



