110 COSMOS. 



small intermediate variation between 7 and 9 A.M. (Sabine, 

 Carte Obs. 18411850, 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, Greenwich, 

 and St. Petersburg, whilst in like manner the minima of the 

 turning hours all fall in the afternoon or evening, although 

 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 annual mean of the in- 

 clinations was for 9 A.M. : 68 5 6'. 8, and for 3 P.M.: 68 58M. 

 "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 

 1 1. 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 fo.'rce is very remarkable. If, on the other hand, we 

 compare Hobarton and Toronto in respect to the order in 

 whicli 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 

 follows only 2 hours after the principal minimum of the 

 inclination, whilst the delay in the maximum amounts to 

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

 minimum of intensity precedes the principal maximum of 

 inclination by 8 hours, whilst the maximum of intensity 

 differs only by 2 hours from the minimum of inclination. 36 

 36 Total intensity at Hobartou, max. 5h. 30m. P.M., miu. 8h. 30m, A.M.J 



