( ^^^ ) 



nection with Cheribon I immediately closed the new one, in con- 

 sequence of which the depolarisation-current passed through the second 

 galvanometer. 



I actually found the polarisation with its characteristic qualities, 

 but its intensity was hardly more than a few percents of the chief 

 current and thus really too small to serve as cause of difference in 

 phase and change in ratio of amplitudes. 



After this investigation I have placed a set of non-polarising ground- 

 plates (amalgamated zinc plates immersed in a solution of Zn SO^ in 

 porous pots) ^) on the garden of the Observatory, and repaired to 

 Cheribon to place a corresponding set there. The repetition of the 

 experiment described above showed really the non-appearance of 

 polarisation. 



After this I connected one of the two telephone wires between 

 Batavia and Cheribon with the old polarising ground-plates, the 

 other with the new non-polarising ones, and allo^ved the two earth- 

 currents to register simultaneously on the same strip with the same 

 sensibility and a velocity of registration of 24 cm. an hour together 

 with the magnetic component. The experiment could hardly have 

 been taken more accurately. 



As I expected the result for the difference in phase was a very 

 slight influence in the sense mentioned above; for the ratio of 

 amplitude I found for 07ie night also a very small influence in the 

 expected direction, but during two other nights a somewhat greater 

 difference in opposite sense. I think I must attribute those last 

 influences to the unavoidable inaccuracy of the determination of the 

 values of the scale division (by switching on a cell of known E. M. F.). 



At any rate I had proved sufficiently that the current of polari- 

 sation was not the cause of the found phenomena, so I can take 

 those phenomena to be real. 



Connection between earth-curreut and magnetic force. 



If we wish to investigate more closely the connection between 

 the variation of earth-current and magnetic component it is necessary 

 to regard the variations of the latter quite by themselves. 



The general rule holds at Batavia that the two horizontal compo- 

 nents change simultaneously, i. e. that generally between the turning- 

 points of X and Y only a small difference in time exists and that 

 on the other hand Z generally has a difference of phase of 90^ with 

 X and Y. 



Ad. Schmidt (Met. Zeitschrift 1899) has pointed out, that the 



1) C. A. Brander, Inaugural Dissertation, Helsingfors, 1888. 



