IX 



PART III. 

 EARTH CURRENTS AND EARTH MAGNETISM. 



CHAPTER I. 

 EARTH CURRENTS AND THEIR RELATION TO CERTAIN TERRESTRIAL 



MAGNETIC PHENOMENA. Page 



Art. 140. Introduction . 725 



141. Strength and Distribution of Earth-Currents 728 



142. Diurnal Variation of Earth-Currents 729 



,, 143. Earth-Currents and Magnetic Disturbances 730 



144. Earth-Current Registerings at Kaafjord and Bossekop, 1902 1903 731 



,, 145. Constants for the Experimental Arrangements 734 



146. The Magnetic Effect of Earth-Currents 736 



,, 147. On the Connection between Polar Storms and Earth-Currents 741 



148. Earth-Currents and Positive Equatorial Perturbations 746 



,, 149. On the Simultaneity of Earth-Currents and Magnetic Disturbances 746 



150. Earth-Currents at Bossekop 748 



151. The Influence of the Earth- Current upon the Vertical Intensity 749 



,, 152. Observations of Earth-Currents at Kaafjord, May, 1910 751 



J 53- Theoretical Investigation of the Currents that are Induced in a Sphere by Variation of 



External Current-Systems 757 



154. Numerical Calculation of the Currents 768 



,, 155. Currents that are Induced by Rotation or Removal of the Systems 779 



156. Earth-currents in Lower Latitudes 784 



,, 157. Earth-currents in Germany 784 



,, 158. Earth-currents in France . 788 



159. Earth-currents in England 791 



,, 1 60. Earth-currents at Pawlowsk 792 



,, 161. Comparison of Simultaneous Earth-Current Observations 793 



162. Consideration of the Conditions during Positive Equatorial Storms 794 



163. The Diurnal Variation of the Earth-Currents 796 



