MAGNETIC INCLINATION. 109 



double progression of the inclination, while at one part of 

 the northern hemisphere, which corresponds exactly with 

 the position of Hobarton, namely, Toronto, in Canada, both 

 the elements of intensity and inclination exhibit a double 

 progression. 3 * At the Cape of Good Hope there is only one 

 maximum and one minimum of inclination. The horary 

 periodical variations of the magnetic dip are as follows : 



I. Northern Hemisphere. 



Greenwich: Maxim. 9 A.M.; minim. 3 P.M. (Airy, Obsero. 

 in 1845, p. 21 ; in 1846, p. 113 ; in 1847, p. 247). Inclin. 

 in the last named year about 9 A.M. on an average 68 59' 3", 

 but at 3 P.M. it was 68 58' 6". In the monthly variation, 

 the maximum falls between April and June and the mini- 

 mum between October and December. 



Paris : Maxim. 9 A.M. ; minim. 6 P.M. This simple pro- 

 gression from Paris and Greenwich is repeated at the Cape 

 of Good Hope. 



St. Petersburg : Maxim. 8 A.M.; minim. 10 P.M. Varia- 

 tion of the inclination the same as at Paris, Greenwich, and 

 Pekin ; less in the cold months, and the maxima more closely 

 dependent on time than the minima. 



Toronto : Principal maxim. 10 A.M. ; principal minim. 

 4 P.M. ; secondary maxim. 10 P.M.; secondary minim. 6 A.M. 

 (Sabine, Tor. 18401842, vol. i, p. Ixi.) 



II. Southern Hemisphere. 



Hobarton, Van Diemen's Land : principal minim. 6 A.M.; 

 principal maxim. 11 . 30. A.M. ; secondary minim. 5 P.M. ; second- 

 ary maxim. 10 P.M. (Sabine, Hob., vol. i, p. Ixvii.) The incli- 

 nation is greater in the summer when the sun is in the southern 

 zodiacal signs, 70 36'. 74 ; it is smaller in winter when the 

 sun is in the northern signs, 7034 / .66. The annual mean 

 taken from the observations of six years gives 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 

 h. 34 m. P.M. ; maxim. 8 h. 34 m. P.M., with an exceedingly 



85 Sabine, Hobarton, vol. i, pp. Ixvii, Ixix. 



