1865.] 99 [Chase. 



II. "At the hour of 6 or 7, in the morning, the annual variation 

 is a maximum, disappearing at a quarter before 10 A. M., and reach- 

 ing a second (secondary) maximum value at 1 P. M. It almost dis- 

 appears soon after 5 p. M., and a third still smaller maximum is reached 

 after 9 P. 31. Half an hour before midnight, the annual variation 

 again disappears. At (and before and after) the principal maximum, 

 between 6 and 7 in the morning, the annual variation causes the 

 north end of the magnet to be deflected to the east in summer, and 

 to the west in winter; at 1 P. M., the deflections are to the west in 

 summer, and to the east in winter. The range of the diurnal mo- 

 tion is thus increased in summer, and diminished in winter; the 

 magnet being deflected in suuimer more to the east in the morning 

 hours, and more to the west in the afternoon hours, or having greater 

 elongations than it would have if the sun mov^ed in the equator. In 

 winter, the converse is the case." [Ibid. p. 12. Compare St. Hel. 

 Obs., 2, cxviii; Toronto Obs. 1, xiv, and 2, xvi.] 



III. "According to the same authority" [Gen. Sabine], "the an- 

 nual variation is the same in both hemispheres, the north end of the 

 magnet being deflected to the east in the forenoon, the sun having 

 north declination; when in the (^tM)'ftaZ variation, the north end of 

 the magnet at that time of the day is deflected to the east in the 

 northern hemisphere, and to the west in the southern hemisphere. 

 In other words, in regard to direction, the law of the annual varia- 

 tion is the same, and that of the diurnal variation the opposite, in 

 passing from the northern to the southern magnetic hemisphere." 

 [Ibid. p. 13. Comp. St. Hel. Obs., 2, Ixxx, cxviii.] 



IV. " The regular progression of the monthly values is a feature 

 of the annual variation deserving particular notice. There is no 

 sudden transition from the positive to the negative side, or vice versa, 

 at or near the time of the equinoxes (certainly not at the vernal 

 equinox); on the contrary, the annual variation seems to be regular 

 in its progressive changes. The method here pursued is entirely 

 diS'erent from that employed by Gen. Sabine for the same end, but 

 the results are, nevertheless, in close accordance." It has been 

 found that the tran.sition takes place "ten days after either equinox, 

 and also that the turning-points occur ten days after the solstices." 

 [Ibid. p. 14. Comp. St. Hel. Obs., 2, cxx.] 



V. " The general character of the diurnal motion ... is 

 nearly the same throughout the year; the most eastern deflection is 

 reached a quarter before 8 o'clock in the morning (about a quarter 

 of an hour earlier in summer, and half an hour later in winter); 



