41 6 MAGNETIC CONDITION OF THE GLOBE. 



The formulas calculated by Gauss assign to the two poles the 

 following positions for the year 1838 : 



North Pole latitude 73 35' longitude 95 39' W, 

 South Pole 72 35' 152 30' E ; 



they are, as will be seen, far from corresponding to the ends of the 

 same diameter. 



The true magnetic axis, determined by the condition that the 

 sum of the projections of the moments is a maximum, is parallel to 

 the terrestrial diameter which corresponds to that point in the 

 northern hemisphere the latitude of which is 77 50', and the longi- 

 tude 63 31' W. Its direction does not coincide exactly with the 

 line of the poles. 



This direction is that for which the coefficient A 1 has its maxi- 

 mum value (370). The magnetic moment of the Earth is equal 

 to # 3 K. Comparing this moment with that of a magnetised steel 

 bar, which weighed about 500 grammes, and had been used in the 

 absolute determination of the Earth's magnetism, Gauss found that it 

 was about 8.io 21 times as great. If we suppose the Earth to be 

 uniformly magnetised, it follows from this number that the magnetic 

 moment of each cube metre of the terrestrial globe is the same as 

 that of eight of the magnets used by Gauss. Assuming that the 

 magnetisation of the bar was also uniform, the intensity of its 

 magnetisation would be about 2200 times that of the terrestrial 

 globe. 



440. Is THE MAGNETISM OF THE EARTH IN THE INTERIOR 

 ONLY ? It may be observed that if the acting masses were in part in 

 the interior and part outside, the potential might be expressed by the 

 sum of two series 



/a\ +i 



1 +A t 



the former relative to the internal masses, and the second to the 

 external masses. Denoting by V n the general term of the develop- 

 ment, we should have then 



V = 



