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equinoxes ; these form the epochs when the transition from the cha- 

 racters of the one semiannual group to those of the other commences, 

 the transition being completed a very few days after the September 

 equinox, but somewhat less rapidly after the March equinox. Like the 

 changes in the induced magnetism of ships, which follow immediately 

 the changes in the terrestrial magnetism corresponding to the ship's 

 altered geographical position, but complete the change only after in- 

 tervals of time of greater or less duration, so the changes which we 

 are here considering appear to commence at the equinoxial epochs, 

 but to require a greater or less interval of time for their completion." 



The divergence of the semiannual groups at the different hours 

 from a mean march in the year has been shown in figs. 1, 2 and 3 by 

 their comparison with the latter projected as straight lines, because 

 the accordance of the divergence at the three stations is seen thereby 

 in its simplest form. In another diagram the lines thus projected as 

 straight lines were exhibited in their true Declination values, and com- 

 pared with a Zero-line representing at each station the mean Decli- 

 nation in the year. " In the previous comparison of the annual varia- 

 tions at the three stations with each other, it was shown that there 

 is no inversion, or contrariety, between the phenomena at Toronto and 

 Hobarton as representatives of opposite hemispheres, the same semi- 

 annual group diverging (during the hours of the day when the cha- 

 racters are most marked) in the same direction at the same hours at 

 both stations. But markedly opposite characteristics are shown when 

 we compare the divergences of the mean diurnal variation in the 

 year from the zero-line at different stations ; these divergences, so 

 far from according with each other at the two stations, present a 

 strong contrast throughout; the divergence at Toronto being to the 

 east at the hours when at Hobarton it is to the west, and vice versa. 

 St. Helena, moreover, which agrees with both the other stations in 

 the divergences of the semiannual groups, differs from both in those 

 of the mean of the whole year. The phenomena of the solar annual 

 variation superimposed upon those of the solar diurnal variation, 

 and those of the solar diurnal variation itself, are in this respect 

 contradistinguished by important differences. 



" To have completed the view of the solar variations of the Decli- 

 nation at St. Helena would have required a notice of the so-called 

 irregular disturbances of that element, which are now known to have 



