TERRESTRIAL CURVES OF EQUAL- TOTAL FORCE. 99 



the north magnetic pole has rotated round the ter- 

 restrial pole in a small circle from east to west, and 

 having passed the point where its westerly azimuth 

 as viewed from Greenwich is maximum, it is still 

 continuing its course in that circle. It seems probable 

 that in the fifteenth or sixteenth century it was situ- 

 ated between North Cape and Spitzbergen: it is now 

 north-west of Hudson's Bay. 



Valuable information on these changes, from the 

 earliest period to the years about 1830, will be found 

 in the work "Terrestrial and Cosmical Magnetism, 

 the Adams Prize Essay for 1865, by Edward Walker, 

 M.A." (Deightons, Cambridge). There is also some 

 accurate information applying to later years, but not 

 possessing all the completeness which might have been 

 obtained from published records. 



7-2 



