310 Scientific Intelligence. 



satisfactorily explained as due to changes of the position of the 

 earth's axis in relation to the sun, or, in other words, the variation 

 of the sun's declination. There are, however, other phenomena, 

 such as magnetic disturbances and auroras, which have been 

 explained differently. 



Thus, in regard to this seasonal variation Mr. Ellis* has written, 

 "The related physical circumstance is that at the equinoxes, when 

 disturbance is more frequent, the whole surface of the earth 

 comes under the influence of the sun, whilst at the solstices, when 

 magnetic disturbance is less frequent, a portion ot the surface 

 remains for a considerable period in shadow." 



The object of the present communication is to put forward 

 anotfier possible cause. 



It has been previously pointed outf that a very close relation- 

 ship exists between the epochs of occurrence of prominences in 

 the polar regions of the sun and Ellis's "great" magnetic dis- 

 turbances. This synchronism showed that either the polar prom- 

 inences themselves, or the disturbances thus indicated in these 

 polar regions, were the origin of these " great " magnetic storms, 

 or that they were caused by a more general stirring-up of a 

 greater extent in latitude of the solar atmosphere. 



A further investigation]; indicated, however, that in all proba- 

 bility it was either the actual polar prominences themselves, or 

 the activity in the solar polar regions, that initiated these mag- 

 netic disturbances, for it was there pointed out that the presence 

 of polar prominence activity-tracks synchronized with the appear- 

 ances of large " polar " coronal streamers. Here we have, an 

 indication of a local cause and effect. 



It will be gathered then, that, even as regards terrestrial mag- 

 netic phenomena, considerable importance must be attached to 

 action taking place in the regions about the solar poles. 



Since the axis on which the sun rotates is inclined to the plane 

 of the ecliptic, there will be times throughout the course of a 

 year when the solar polar regions will be exposed most and least 

 to the earth. 



It should be expected, then, that if the polar regions of the 

 sun have any action, as above suggested, the effects of the 

 action on the earth should vary according to the positions of the 

 solar poles relative to the earth. 



The actual inclination of the sun's axis being 82° 45', and the 

 longitude of the ascending node being 74° 25', or the tilt of the 

 axis being in the direction of about 19 hours in right ascension, 

 it follows that, in each year, the south pole of the sun is most 

 turned towards the earth in the beginning of March (about the 

 6th), and the north pole most towards the earth in the beginning 

 of September (about the 5th). At the two intermediate epochs, 



* Monthly Notices, vol. Ixi, p. 540. 



f Proc. Koy. Soc, vol. lxxi, p. 244; also Monthly Notices, E.A.S., vol. 

 lxiii, Appendix I, p. 6. 



% Monthly Notices, E.A.S., vol. lxiii, p. 481. 



