THE HEART OF THE ANTARCTIC 



MAGNETIC OBSERVATIONS 

 THE MAGNETIC POLE AND THE AURORA 



Notes by DOUGLAS MAWSON, B.Sc, B.E. 



There are two* localities where the lines of magnetic 

 force stand perpendicular to the earth's surface. One of 

 these is situated in the Northern Hemisphere to the north- 

 west of Hudson Bay and is called the North Magnetic 

 Pole; the other, in the Southern Hemisphere, in the north- 

 ern part of South Victoria Land, is known as the South 

 Magnetic Pole. 



The lines of magnetic force are imaginary lines passing 

 through any place in the direction along which a freely 

 suspended magnet will ahgn itself. In the vicinity of the 

 magnetic poles such a magnet stands vertically and at 

 intermediate positions assumes an angle intermediate be- 

 tween a vertical and a horizontal position. The south- 

 seeking end of the magnet dips downwards and is attracted 

 towards the South Magnetic Pole in the Southern Hemi- 

 sphere, whilst in the Northern Hemisphere it is the north- 

 seeking end of the magnet which dips. 



Magnets mounted as compasses are balanced on a 

 vertical pivot and consequently they are free to swing 

 in a horizontal circle only. They are controlled by the 

 horizontal components of the earth's magnetic force at the 

 spot where any observations is made and consequently, 

 if used at the magnetic poles, where the whole of the 

 magnetic force is vertical, they are unaffected and useless. 



* Observations of dip in the Northern Hemisphere indicate the 

 existence of two magnetic poles of unequal strength. The stronger of 

 these is regarded as the North Magnetic Pole, the other is situated 

 in Siberia and is generally referred to as the Asiatic focus. 



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