( 787 ) 



was different in the Northcoaslplain to that in the mountains. If this 

 were so, then the earth-current in the Preanger country, where the 

 Southline runs in a niveau of =b 600 M. between numerous volcanoes 

 would have to show the same peculiarity. To prove this it was for- 

 tunately not necessary for me to remove with my instruments, but 

 I could suftice by making the following connection. 



Earth at Buitenzorg — Galvanometer — Observatory — Batavia — Bui- 

 tenzorg — Tasikmalaja — Earth at that point. Buitenzorg is situated 

 at the N.W.-foot of the mountains and Tasikmalaja at the East foot. 

 Both places lie still at a height of ± 300 M. above the sea. 



Loss by isolation along the poles on the there-and-back line 

 Buitenzorg — Batavia — Buitenzorg could not bring the earth-current 

 out of the plain between Buitenzorg and Batavia into the line, and 

 could only cause a part of the Preangercurrent to flow away. That 

 loss could thus not falsify the result. 



The current between Buitenzorg and Tasikmalaja really proved to 

 possess the above mentioned character, i.e. it showed a much stronger 

 increase when the duration of the oscillation decreased than the 



If loss by isolation is the cause of the inequality of the current 

 between Batavia and Semarang round the North and the South, 

 then that loss will be smaller in the dry season than in the wet one. 

 And, indeed, I found that this was the case as the figures below 

 will indicate. 



Duration of 



half an 

 oscillation 



U.G min. 



1.0 „ 



1.4 „ 



5.0 „ 



11.5 .. 



18-21 Juni 1907 



Ampl. Sem.-Bat. current 

 in Volt. p. K.M. 



Ampl. 



X 



43 



35 

 31 

 18 

 13 



in dynes 



Duration of 



half an 

 oscillation 



0.5 min. 



0.8 „ 

 1.5 „ 



5.5 „ 



8.6 „ 

 21.8 „ 



December 1907 



Ampl. Sem.-Bat. current 

 in Volt, per K.M. 



Ampl. 



X 

 62 

 48 

 50 

 24 

 23 

 13 



in dynes 



These characteristic differences treated above can perhaps afford 

 an occasion to find an explanation of the nature and the cause of the 



