( 517 ) 



Magnet, comp. —2.1 —3.7 -5.3 —5.5 —4.9 —4.1 —3.3 —3.4 —4.5 —5.4 

 10-5 c. G. S. 



For the earth-current the maximum comes one hour, the minimum 

 about half an hour earlier. Let us suppose this minimum to belong- 

 to the preceding vibration of' 3'' 30" duration, then the difference in 

 phase is 26''. 



The ratio of the amplitude is 26^.0, whilst I deduced roughly out 

 of the Sunday notation for the great vibration 16.0 when the cable 

 was at my disposal from 0'^ till 4'* p.m. 



So v^^e meet here too with decrease of the ratio between earth- 

 current and corresponding magnetic component together with increase 

 of the duration of the vibration, but by the side of it a much 

 stronger earth-cuT-rent than for the line Cheribon — Batavia. 



Annual inequality in the daily vibration. 



At Batavia the amplitude of the daily vibration of the magnetic 

 force is liable to a single- and a double-yearly inequality, where the 

 maxima are attained in March and September, the minima in January 

 and in June. The two maxima and the two minima are of the same 

 magnitude. 



From the continued measurements at the office of the Intercommunal 

 Telephone Company I could deduce that the variations of the earth- 

 current show the same annual inequality. 



This series of measurements shows two breaks. 



First in January '06 the lines were permanently disturbed and 

 secondly in August '06 errors seem to have slipped into the obser- 

 vations, on account of which repeatedly improbably large values 

 were read. After my having pointed this out, the readings in December 

 next were again serviceable. 



Out of each month I have taken those days which were in the 

 first place magnetically calm and for which in the second place as 

 much as possible complete and useful readings of earth-currents were 

 at hand. 



Of the mean hourvalues for each month was then taken the 

 difference of the smallest and the greatest value. 



The maximum generally fell in with the 8V4 a.m. or 974 a.m. 

 observation, the minimum with that of 3^^ p.m. or 474 p.m. 



These differences expressed in Volt pro kilometer X 10-^ follow here. 

 J. F. M. A. M. J. J. A. S. 0. N. D. 



1905 266 194 208 190 129 127 127 170 173 167 131 



1906 171 177 127 125 109 135 233 (?) 122 



1907 81 118 113 90 88. 



35* 



