THE AURORA. 5 



that the magnetic needle not only swayed responsively 

 to auroras observable in the immediate neighbourhood, 

 but to auroras in progress hundreds or even thousands 

 of miles away. Nay, as inquiry progressed, it was 

 discovered that the needles in our northern observa- 

 tories are swayed by influences associated even with the 

 occurrence of auroras around the southern polar regions. 



In fact, not only have the difficulties pointed out 

 (very properly, it need hardly be remarked) by Sir 

 David Brewster been wholly removed ; but it has 

 been found that a much closer bond of sympathy 

 exists between the magnetised needle and the auroral 

 streamers than even Arago had supposed. It is not 

 merely the case that while an auroral display is in 

 progress the needle is subject to unusual disturbance, 

 but the movements of the needle are actually synchro- 

 nous with the waving movements of the mysterious 

 streamers. An aurora may be in progress in the north 

 of Europe, or even in Asia or America, and as the 

 coloured banners wave to and fro, the tiny needle, 

 watched by patient observers at Greenwich or Paris, 

 will respond to every phase of the display. 



And I may notice in passing that two very interesting 

 conclusions follow from this peculiarity. First, every 

 magnetic needle over the whole earth must be simulta- 

 neously disturbed ; and secondly, the auroral streamers 

 which wave across the skies of one country must move 

 synchronously with those which are visible in the skies 

 of another country, even though thousands of miles 

 may separate the two regions. 



