View of the earths magnetic state. 



As the electrical currents in the earth and in the at- 

 mosphere are in close relation to the earths magnetism, 

 it will be convenient to remind briefly of the magnetic state, 

 which prevails on the earth at present. 



The way in which a magnetic needle, moveable in the 

 horizontal plan, behaves, shows that a force exercises al- 

 ways an effect on it. This force is called earth-magnetism 

 or magnetic force of the earth or to use the language of 

 the modern physic, the magnetic energy of the earth. The 

 force is fully dertermined on a place if we know the three 

 quantities: declination, horizontal intensity and dip, whose 

 scientific definition we suppose to be well known. These 

 three quantities have been measured on a great many 

 points on the earths surface. If we imagine all points, in 

 which the dip is = 0, united, we shall have a line round 

 the earth, named the magnetic equator. This line does not 

 agree with the astronomical equator but cuts it in two 

 points. The magnetic equator is represented on the figure 

 i by a broader line followed by two fine lines. If all points 

 with the same dip are united we shall have a system of 

 lines called magnetic parallels. They are alike the pa- 

 rallel-circles but with different directions. 



Furthermore if we, going out from a point on the 

 magnetic equator, draw lines parallel to the axis of the 

 declination needle and remove the needle from point to 



