128 COSMOS. 



the needle moves in a totally opposite direction from that 

 which it follows in the northern, for while in the south the 

 needle that is pointed southward turns from east to west be- 

 tween morning and noon, the northern point of the needle 

 exhibits a direction from west to east. 



Sabine, to whom we are indebted for an elaborate revi- 

 sion of all these variations, has arranged the horary observa- 

 tions that were carried on for five years at Hobarton (42 53' 

 S. lat., variation 9 57' east,) and Toronto (43 39' N. lat., 

 variation 1 33' west), so that we can draw a distinction 

 between the periods from October to February, and from 

 April to August, since the intermediate months of March 

 and September present, as it were, phenomena of transition. 

 At Hobarton the extremity of the needle which points 

 northwards exhibits two eastern and two western maxima 

 of elongation, 63 so that in the period of the year from Octo- 

 ber to February it moves eastward from 8 or 9 o'clock A.M. 

 till 2 P.M., and then from 2 till 11 P.M., somewhat to the 

 west, from 11 P.M. to 3 A.M. it again turns eastward, and 

 from 3 *o 8 A.M. it goes back to the west. In the period 

 between April and August, the eastern turning hours are 

 later, occurring at 3 P.M. and 4 A.M., whilst the western turn- 

 ing hours fall earlier, namely at 10 A.M. and at 11 P.M. In 

 the northern magnetic hemisphere the motion of the needle 

 westward from 8 A.M. till 1 P.M. is greater in the summer 

 than in the winter, whilst in the southern magnetic hemi- 

 sphere, where the motion has an opposite direction between 

 the above-named turning hours, the quantity of the elon- 

 gation is greater when the sun is in the southern than when 

 it is in the northern signs. 



The question which I discussed seven years ago in the 

 Picture of Nature, 64 whether there may not be a region of 

 the earth, probably between the geographical and magnetic 

 equators, in which there is no horary variation (before the 

 return of the northern extremity of the needle to an oppo- 

 site direction of variation in the same hours), is one which 



63 Sabine, Magn. Observ. made at Hobarton, vol. i (1841 and 1842), 

 pp. xxxv ; 2, 148 ; vol. ii (18431845), pp. iii xxxv, 172344. See 

 also Sabine, Obs. made at St. Helena, and in Phil. Transact, for 1847, 

 pt. i, p. 55, pi. iv, and Phil. Transact, for 1851, pt. ii, p. 36, pi. xxvii. 



64 Cosmos, vol. i, p. 176. 



