( 247 ) 



Accordingly il is no wonder thai the currents bear a different 

 type in the mountainous Preanger compared with those ofthecoast- 

 plains; but I utterly fail to explain this difference, just as it has 

 been found. 



All that has become known till now points to the next step, 

 which should be taken in this research, viz. that the earth-connections 

 should be brought to a depth of, say one or more kilometers under 



the surface of the earth, but, alas this is impossible. 



It is true I had the intention to make use of two artesian wells 

 to be bored recently at Serang and Batavia, but the considerations, 

 that first the mantle of these holes consisted of iron, the depth was 

 only 0,2 a 0,3 K.M., and besides the wire connecting the two did 

 not possess the necessary isolation, frightened me out of this burden- 

 some experiment. 



I think it advisable to continue the registration in the old way, 

 but to take into account the geological formation in the first place. 



Dr. L. Steiner of Budapest has directed my attention to the fact, 

 that I have erroneously applied the formula A = 0.81/ — (c.f. 



1 st Coiiim. Proc. Jan. 25, 1908. p. 515) on the harmonic terms of 

 the daily variation for the earthcurrent between Batavia and Cheribon. 



Indeed a calculating error has curiously given rise to an apparent 

 agreement between the observed values and those computed by 

 means of the formula. 



Dr. Steiner deduced the following expression 



A 1 

 _ —3.9 



J/ 7' 0-8 



This formula gives the following values 



A 7'o.2 



or - = 3.9 



M T 



Amplitude 



