ON THE DIUENAL 

 VARIATION OF THE INCLINATION 



OF THE 



MAGNET AT BATAVIA. 



BY 



P. A. BERGSMA. 



The observations, the results of which are communicated in 

 this paper, have all been made on the same spot in the Mag- 

 netical Observatorj at Batavia. This Observatory is a wooden 

 building, in the construction of which no iron has been used; 

 it is situated in a private garden at a distance of about forty 

 mètres from the nearest of the surrounding buildings. The geo- 

 graphical position of the Observatory is: Latitude 6° 11' O 11 

 South, Longitude 7 h 7 m 19 s East from Greenwich. 



The instrument with which the observations have been made, 

 is a 3-inch dip-circle of Barrow; for all the observations the 

 same needie has been used. Each observation of the inclmation 

 with this instrument takes about forty minutes. An observa- 

 tion begun twenty minutes before the full hour, ends at about 

 twenty minutes after the full hour; the result given by this 

 observation is then accepted as being the value of the dip at 

 the full hour. 



Three different sets of observations have been made. 



The first set was made from May 29, 1868, to August 22, 

 1868; it comprises observations made on twelve different days 

 every hour from 7 a. m. until 5 p. m. ; by these observations 

 eleven values of the dip were obtained on each day. When I 

 began this set of observations, I intended to continue thein at 

 least for a year; but at the end of three months I was obli- 

 ged to discontinue them, from beimg too trying to the eyes. 



