108 COSMOS. 



70° 36'-01. (Sabine, Hob., vol. ii., p. xliv.). Moreover, the 

 intensity at Hobarton is greater from October to February 

 than from April to August, p. xlvi. 



Cape of Good Hope: Simple progression, the minim, 

 being Oh. 34m. P.M.; maxim. 8h. 34m. P.M., with an ex- 

 ceedingly small intermediate variation between 7 and 9 A.M. 

 (Sabine, Cape Obs., 1841-1850, p. liii.). 



The phenomena of the turning hours of the maximum of 

 the inclinations expressed in the time of the place fall with 

 remarkable regularity between 8 and 10 A.M. for places in 

 the northern hemisphere, such as Toronto, Paris, Green- 

 wich, and St. Petersburg, while in like manner the minima 

 of the turning hours all fall in the afternoon or evening, al- 

 though not within equally narrow limits (at 4, 6, and 10 

 P.M.). It is so much the more remarkable, that in the 

 course of very accurate observations made at Greenwich 

 during five years there was one year, 1845, in which the 

 epochs of the maxima and minima were reversed. The an- 

 nual mean of the inclinations was for 9 A.M. : 68° 56'-8, 

 and for 3 P.M. : 68° 58'a. 



When we compare together the stations of Toronto and 

 Hobarton, which exhibit a corresponding geographical posi- 

 tion on either side of the equator, we find that there is at 

 Hobarton a great difference in the turning hours of the prin- 

 cipal minimum of inclination (at 4 o'clock in the afternoon 

 and 6 o'clock in the morning), although such is not the case 

 in the turning hours of the principal maximum (10 and 

 11.30 A.M.). The period of the principal minimum (6 A.M.) 

 at Hobarton coincides with that of the secondary minimum 

 at Toronto. The principal and secondary maxima occur at 

 both places at the same hours, between 10 and 11.30 A.M. 

 and 10 P.M. The four turning hours of the inclination occur 

 almost precisely the same at Toronto as at Hobarton, only 

 in a reversed order (4 or 5 P.M., 10 P.M., 6 A.M., and 10 or 

 11.30 A.M.). This complicated effect of the internal terres- 

 trial force is very remarkable. If, on the other hand, we 

 compare Hobarton and Toronto in respect to the order in 

 which the turning hours of the alterations of intensity and 

 inclination occur, we shall find that at the former place in 

 the southern hemisphere the minimum of the intensity fol- 

 lows only two hours after the principal minimum of the in- 

 clination, while the delay in the maximum amounts to six 

 hours ; while in the northern hemisphere, at Toronto, the 

 minimum of intensity precedes the principal maximum of 



