106 ON MAGNETISM. 



At the magnetic equator, = 90, and total force 



At the magnetic pole, 6 = 0, and total force 



or double that at the equator. 



These three results, for horizontal force, for dip, and 

 for total force, are not materially disturbed if we 

 conceive the magnet to be excentric, provided that 

 magnetic latitude is always referred to its center. 



It was soon found that this elegant theory, though 

 well representing the broad facts of terrestrial mag- 

 netism, failed in accuracy when applied to many special 

 cases. Such curves, for instance, as those of equal dip, 

 Figures 20 and 21, could not possibly be explained by 

 it. It was modified by supposing the axis of the mag- 

 net to be distant from the earth's center by one-seventh 

 part of the earth's radius; but it could not then be 

 sufficiently reconciled with observations. 



46. Attempt to explain Terrestrial Magnetism by 

 the action of two magnets within the Earth. 



A celebrated Norwegian magnetical observer, Han- 

 steen, remarking the tendency to the exhibition of 

 two poles in the north and two poles in the south 

 which we have indicated as appearing in some of the 

 diagrams, Figures 20, 21, 28, 29, 35, 36, undertook the 

 task of investigating the effects of two large magnets 

 within the earth, both magnets being excentric, and 

 inclined to the Earth's equator in different planes. 



