EVIDENCE OF VERTICAL MAGNETIC FORCE. 77 



SECTION V. 



ON TERRESTRIAL MAGNETISM, AS ACTING IN THE 

 VERTICAL AT EACH PLACE OF OBSERVATION; AND 

 ON THE COMBINATION OF THE HORIZONTAL AND 

 VERTICAL FORCES, AND THE TOTAL TERRESTRIAL 

 MAGNETIC FORCE AT EACH PLACE OF OBSERVATION. 



35. First evidence of the existence of a vertical 

 magnetic force. 



When a needle is prepared, in the unmagnetized 

 state, for mounting in a compass, with its center of 

 gravity very little below its point of support, and is 

 adjusted to horizontally ; on being magnetized, its red 

 end (in northern latitudes) dips considerably. This 

 proves that (in northern latitudes) the terrestrial hori- 

 zontal magnetic force towards the north is accompaDied 

 with a vertical force downwards, and the terrestrial 

 horizontal force towards the south is accompanied with 

 a vertical force upwards. 



. When the same compass is carried into southern 

 latitudes, the blue end dips. This proves that, while 

 the sign of the terrestrial .horizontal force in the north 

 direction or in the south direction has not changed, the 



