( '^14 ) 



4''45"^ P. M. ; an ordinary galvanometer with pointer was used. 



I have chosen from these readings those falling on magnetically 

 very calm days and evincing moreo\er not to have sulFered from 

 disturbances on the line or from other irregidarities. For those same 

 days I have used the observatory-notation during the houi-s of the 

 night (6 P.M.— 5 A.M.). 



Two unknown quantities remained, viz. the ratio of the values 

 of the scale division and the difference of the central position. 



The former I determined one evening during a magnetic storm 

 at the office of the Company by alternately reading the galvanometer 

 and allowing the Observatory to register. The reduction to a 

 same central position I got to a plausible result by using the Sunday 

 notations. For, on those days 1 could use the line already after 12 

 at noon and from a score of magnetically fairly calm Sundays I 

 deduced the difference between the hours 4'/^ and 6 p.m. 



Graphically I then interpolated the 24 values of the hours of 

 the day. 



For the employed magnetically calm days finally was calculated the 

 daily variation of the magnetic component normal to the direction 

 Cheribon-Batavia from the Buitenzorg magnetograms. 



Daily variation of the earth-current Cheribon-Batavia and of the 

 magnetic horizontal component normal to that direction. 



Earth-current in Volt 



per Kilometer X '0—^ 



(Direction Ch.-Bat. =-f) 



Magnetic 



Component in 



I U-^' C. G. S. 



(NE = +) 



! Earth-current in Volt | 

 j per Kilometer X'**""' 

 (Direction Ch.-Bat. =+) 



Magnetic 



Component in 



10-' C. G. S. 



(NE = +j 



1 a. m. 



2 



3 



4 



5 



6 



7 



9 

 10 

 11 



4-; 



— 38 



— 36 



— 40 



— 33 



— 32 



— 22 

 11 

 81 



153 



154 



117 



84 



-tt.l 



- 9.6 



- 9.3 



- 7.9 



- 6.5 



- 3.0 

 3.4 

 8.8 



15.9 

 24.2 

 29.5 

 28.5 



1 p. m. + 33 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



— 6 



— 33 



— 40 



— 32 



— 23 



— 51 



— 60 



— 51 



— 47 



— 46 



— 39 



22 2 



13.9 



3.3 



— 4.5 



— 9.4 

 —10.2 

 — It.O 

 —13.1 

 —13.6 

 —14.6 

 -13.7 

 —12.9 



