TERRESTRIAL MAGNETISM. 107 



dip of the north end of the needle at Toronto being 75 15', 

 and that of the south end at Hobarton 70 34', and the 

 total force in absolute measure 13'90 at Toronto, and 13'56 

 at Hobarton. Of these two so well-chosen stations, the 

 Canadian shows, according to Sabine's investigation, ( ll9 ) 

 four, and that of Yan Diemen Island only two, turning- 

 points in the diurnal variation of the total force. At Toronto 

 there appears to be a principal maximum at 5 h., and a prin- 

 cipal minimum between 15 h. and 16 h. ; with a weaker 

 secondary maximum varying in different months from 18 h. 

 to 20 h., and a weaker secondary minimum at 22 h. or 23 h. 

 At Hobarton, on the other hand, the intensity of the force 

 follows a single progression from a maximum between 5 h. 

 and 6 h. to a minimum between 20 h. and 21 h. ; although 

 the inclination at that station has, as at Toronto, four 

 turning-points. ( ]2 ) By combining the variations of incli- 

 nation with those of the horizontal force, Sabine has found 

 that at both stations the total force is greatest from October 

 to February, and least from April to August ; October to 

 February being months of winter at Toronto, and of summer 

 at Hobarton ; and April to August being months of summer 

 at Toronto and winter at Hobarton. He thence infers that 

 it is not to differences of temperature that we should ascribe 

 these variations, and suggests that the increase of the total 

 magnetic force in both hemispheres during the months 

 when the Sun is in the southern signs, may be caused by the 

 greater proximity of the Earth in that portion of her orbit to 

 the Sun acting as a magnetic body.( 121 ) At Hobarton, the 

 intensity of the force is in the summer of that station in 

 absolute measure 13'574, and in winter 13'54<3. The 

 secular change of the total magnetic force rests as yet on 



