TERRESTRIAL MAGNETIC MERIDIANS. 



51 



The directions of the Local Magnetic Meridian 

 being found at numerous points of the Earth, it is not 

 difficult to trace through them a curve starting from 

 any assumed point, and so drawn that in every part of 

 its course its direction represents the direction of the 

 Local Magnetic Meridian at that point. Such a curve 

 may properly be called a Terrestrial Magnetic Meridian : 

 and a number of these, at convenient intervals of 



(A is the North Magnetic Pole. See Article 42.) 



geographical longitude, may be advantageously used 

 as a system of Terrestrial Magnetic Meridians. Such 



42 



