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earth-ciiiTent between Cheribon and Batavia, with the aid of the 

 intercommunal telephone-line. The variations were written down 

 photographically, the velocity of' the registering strip amounted to 

 the usual 15 mm. an hour. 



The important results obtained by this method incited me to go 

 on and in the period now come to a close I could at night make 

 use, by the kind cooperation of the officials of the Telegraph Service, 

 of difïerent telegraph-lines (to Anjer, Buitenzorg, Soekaboemi, Billiton, 

 Poerwakarta, Cheribon, Samarang, Soerabaja and Makassar) ; greater 

 velocity of registration was applied too (60 and 240 mm. an hour). 



Besides continuing the different registrations of the earth-current 

 during longer or shorter time to obtain statistic results, I also made 

 experiments. When the registration pointed to a new connection 

 between earth-current and magnetic variation, other registrations of 

 the earth-current were organised to get a closer investigation of that 

 connection. When questions on the influence of wire or groundplate 

 cropped up, it was tried to answer them by experimentation. 



The instrumental arrangement was contrived in such a way, that 

 on a strip 20 cm. wide beside the variations of two earth-current 

 circuits those of the corresponding magnetic components were noted 

 down. Corresponding means here: the component normal to the 

 direction of the earth-current circuit. 



The sensibility was chosen in such a way, that the corresponding 

 variations of earth-current and magnetic force did not differ too 

 much in magnitude. To this end great sensibility of the magnetic 

 variation instruments (up to 0.1 y an mm.) was necessary; as 

 however only the relative position during one night was considered 

 it was easy to arrange those variation instruments quite simply. 



I intend to give a more extensive communication about this at 

 some other time. 



The daily variation. 



The obstacles met with in investigating the daily variation were 

 very great. For the most important part of that variation takes place 

 "about noon, but during the day time the electric field of Batavia is 

 disturbed by the electric tram and moreover I was allowed the use 

 of the lines only at night. 



If still I succeeded in coming to useful results, this is due to the 

 kindness of the Superintendent of the Intercommunal Telephone 

 Company, Mr. S. W. Baints, who allowed hourly readings of the 

 amount of the earth-current to be done at the office of the Company 

 at Batavia. The hours were 8''45"' A. M., 9''45'" A. M. etc. until 



