On the late Exceptional Season. 57 



magnetic conditions of tlie earth have been unusually 

 frequent, that it not unnaturally suggests itself that there 

 may possibly be some connection between the sun's 

 condition and these climatic changes. 



We know that during these spot periods the sun's surface 

 is often teeming with spots frequently of large dimensions. 

 Spots and penumbrte, sometimes cover from a 60th even to 

 as much as a 30th of the sun's visible hemisphere ; and it can 

 easily be imagined that the modification, if not obliteration, of 

 so much sun force, must largely afiect the conditions of the 

 earth and its atmosphere, although in what manner or to 

 what extent remains to be ascertained. The influence of 

 these changes is evident enough so far as the earth's 

 magnetism is concerned, and instances are on record where 

 a rapid change on the sun's surface has been accompanied 

 by almost simultaneous quivers of the earth's magnetism. 

 It is, moreover, now pretty well established that our 

 maximum of magnetic disturbances agrees with the 

 maximum of sun spots recurring about every ten years, and 

 the probable relation between large disturbances of the 

 earth's magnetism and the state of the weather has already 

 been several times suggested. 



Some years ago. Dr. Balfour Stewart suggested that 

 " Aurora displays might be secondary electric currents due 

 to small but rapid changes, caused by some unknown 

 influence in the magnetism of the earth;" he compared the 

 earth and its atmosphere to a Ruhmkorffs machine, the moist 

 upper strata of the earth as well as the upper strata of the 

 atmosphere composing the secondary conductors in which 

 currents will take place whenever the magnetism of the 

 earth changes from any cause." 



' He further states, " These views would appear to be con- 

 firmed by the very interesting records of earth currents 

 obtained by Mr. Airy at the Greenwich Observatory, in which 

 it is found that during times of very great magnetic disturb- 

 ance, there are strong earth currents alternating from positive 

 to negative, the curves lying nearly equally on both sides of 

 the Zero." In the Phil. Mag. of Feb. 1870, Dr. Balfour 

 Stewart, referring again to this subject, says, " A further 

 development of this idea has lately occurred to me, in 

 consequence of a remark of my friend Mr. Lockyer, that the 

 Zodiacal light may possibly be a terrestrial phenomenon, and 

 may therefore be somehow connected with the phenomena 

 of terrestrial magnetism. For not only will secondary 



