MAGNETIC INTENSITY. 129 



it would seem from recent experiments, and more especially 

 since Sabine's ingenious discussions of the observations made 

 at Singapore (1 11' K lat.), at St. Helena (15 56' S. lat.), 

 and at the Cape of Good Hope (33 56' S. lat.), must be an- 

 swered in the negative. No point has hitherto been dis- 

 covered, at which the needle does not exhibit a horary 

 D'otion, and since the erection of magnetic stations, the im- 

 portant and very unexpected fact has been evolved, that 

 there are places in the southern magnetic hemisphere, at 

 which the horary variations of the dipping needle alter- 

 nately participate in the phenomena (types) of both 

 hemispheres. The island of St. Helena lies very near the 

 line of weakest magnetic intensity, in a region where this 

 line divaricates very widely from the geographical equator 

 and from the line of no inclination. At St. Helena, the 

 movement of the end of the needle which points to the 

 north is entirely opposite in the months from May to Sep- 

 tember from the direction which it follows in the analogous 

 hours from October to February. It has been found after five 

 years' horary observations, that during the winter of the 

 southern hemisphere, in the above-named periods of the 

 year, while the sun is in the northern signs, the northern 

 point of the needle has the greatest eastern variation at 

 7 A.M., from which hour, as in the middle latitudes of Europe 

 and North America, it moves westward till 10 A.M. and re- 

 mains very nearly stationary until 2 P.M. At other parts of 

 the year, on the other hand, namely from October till 

 February, (which constitutes the summer of the southern 

 hemisphere and when the sun is in the southern signs and 

 therefore nearest to the earth) the greatest western elonga- 

 tion of the needle falls about 8 A.M., showing a movement 

 from west to east until noon, precisely in accordance with 

 the type of Hobarton (42 53 S. lat.)," and of other districts 

 of the middle parts of the southern hemisphere. At the 

 time of the equinoxes, or soon afterwards, as for instance in 

 March and April, as well as in September and October, the 

 course of the needle fluctuates on individual days, showing 

 periods of transition from one type to another, from that of 

 the northern to that of the southern hemisphere. 66 



*' Sabine, Observations made at the Magn. and Meteor. Observatory at 

 St. Helena in 1840- -1845, vol. i, p. 30, and in the Phil. Transact, for 



VOL. V. K 



