Professor EUas Loom is. 435 



zone oi moderate breadth and of oval form, enclosing the 

 North Pole of the earth, and also the North Magnetic Pole. 

 Ir was therefore mnch farther south in the Western hemi- 

 sphere than in the Eastern. Along the central line of this 

 belt there are more than eighty auroras annually, hut on going 

 either north or south from the central line of that belt the 

 number diminishes. 



In 1S70 Professor Loom is published a paper of importance 

 relating to terrestrial magnetism, in which he showed its 

 connection and that of the aurora with spots on the 

 sun. That the spots on the sun had periods of maximum 

 and minimum development had long been known. Lamont 

 had noticed a periodicity in the magnetic diurnal variations. 

 Sabine and Wolf and Gauthier had noticed that the two peri- 

 odicities were allied. The connection of the period of solar 

 spots with conjunction and opposition of certain planets had 

 been shown by De La Rue and Stewart. Professor Loomis 

 undertook an exhaustive examination of the facts that tended 

 to confirm or refute the propositions that had been advanced. 

 He confirmed and added to the conclusions of Messrs. De La Rue 

 and Stewart. He also brought together such facts as were rele- 

 vant to the question, and he showed that the regular diurnal vari- 

 ation of the magnetic needle was entirely independent of the 

 solar spots, but that those disturbances that were excessive in 

 amount were almost exactly proportional to the spotted surface 

 of the sun. He also showed that great disturbances of the 

 earth's magnetism are accompanied by unusual disturbances on 

 the sun's surface on the very day of the storm. 



Various forms of periodicity in the aurora have frequently 

 been suggested. Professor Loomis, from all available accounts 

 of the aurora, was able to show that while in the center of the 

 zone of greatest auroral frequency auroras might be visible 

 nearly every night, and hence that periodicity could not easily 

 be shown by means of numbers of auroras recorded in such 

 places, yet that such periodicity was distinctly traceable at 

 places where the average number seen was about twenty or 

 twenty-five a year. The times of maxima and minima of the solar 

 spots were seen to correspond in a remarkable manner with 

 the maxima and minima in the frequency of auroral displays 



