( 780 ) 



It is seen that A H and L I) generally coi respond ; only for H 

 the introductory movement is «nore fre(iuent at (lireenvvich ; L Z \s 

 regularly opposite, for Greenwich positive and for Paris negative. 



It is remarkable to notice out of the reproduced registering fines 

 how the oscillations following upon the initial movement correspond 

 again for the two places; a single striking quick movement amid the 

 disturbance, as it were a new starling impulse, is then again opposite. 

 This repetition seems to be a real phenomenon. Thus the initial 

 shock on Oct. 30''> , 1903 was a clear initial movement amid a distur- 

 bance going on already for hours. At places with higher latitude it 

 lost itself in the oscillations of that older disturbance. The phenomenal 

 violence of the second part of the disturbance is perhaj)S owing to 

 two disturbances being placed one above the other. At the violent 

 disturbances of Febr. 13^'S March 6^'' and June 27, 1892, as well 

 as of Aug. 6'^' , 1893 two initial impulses appeared. 



The causes of the initial movement. 



The remarkable inequality of the movement in the vertical force, 

 so constant for places situated close to each other, offers us perhaps 

 a means to clear up what is puzzling in this phenomenon. 



If we attribute the appearance of those vectors of disturbance 

 to that of electric currents, as is more than probable, then it 

 is impossible to assume that the movement of electricity which 

 generates these vectors would have in the free atmosphere such a 

 distribution limited to the j)lace. The cause of this must be in the 

 appearance of the electric earth-cun-ent. We must assume that, when 

 suddenly a disturbance arises, the earth-current then generated selects 

 fixed paths through the earth-crust. 



That the earth-current for diiFerent places of the earth situated 

 close to each other may be different, is highly probable ; at least for 

 the surface-current 1 have found it lately ^) for North- and South- 

 Java. The inequality was, that as the corresponding magnetic variations 

 became shorter the earth-current vai"iations increased more in ampli- 

 tude for the volcanic southern part than for the alluvial and diluvial 

 northern part. 



This great difference in earth-current must become much less for 

 the deeper strata; proof of this is found in the equality of (he 

 magnetic variations at Batavia situated on the Northcoast of Java 

 and at Buitenzorg on the q,(\^q of the >olcanic part. 



But the possibility for a difference when a current is suddenly 



ij See the following |);iper : Earth-ciureut registration at Batavia, 2"f^ commu- 

 nication. 



