( 288 ) 



The mean difference of the dip at 10 a. m. and 4 p. m. in 

 the year beginning December 1, 1868, and ending November 



30, 1869, is 2'.96. Table IV shows that this difference varies 

 in the different months ; perhaps a longer continuation of the 

 observations will show that there exists a regular annual varia- 

 tion of this difference. 



The diurnal variation of the inclination in the Southern He- 

 misphere has, as far as I know, never been deduced from ob- 

 servations with the dip-circle. General sabine deduced the 

 diurnal variation of the inclination at St. Helena (Latitude 

 15°56'41".2 South, Longitude h 22 m 41 s .9 West from Green- 

 wich) from the diurnal variations of the horizontal and of the 

 vertical force observed from January 1, 1843, to December 



31, 1846. As St. Helena is the place of the Southern He- 

 misphere the nearest in Latitude to Batavia, of which the 

 diurnal variation of the inclination is known, I transcribe in 

 Table V General sabine's results j(see e. sabine, Observations 

 at St. Helena. Vol. II, pag. LXIj. 



