OF THE AURORA BOREALIS. 21 



appearances exhibited by a strong electric spark in traversing a space of rarefied 

 air, in what is called the auroral tube." Having very recently performed this expe- 

 riment, in a dark room, with a powerful electric machine and a tube four feet in 

 length and two inches in diameter, I was well prepared for making the comparison. 

 Although I am not a believer in the hypothesis which ascribes the origin of the aurora 

 borealis to electricity, yet the supposition that the aurora derives its illumination 

 from the passage of electricity through it, was favored by this remarkable display 

 of the phenomenon. 1 The aurora of November 17th was equally distinguished 

 for its superior brilliancy and great extent. In respect to extent, I know not that 

 it was ever surpassed, being seen in extraordinary magnificence and splendor hi 

 Asia, Europe, and America. We have accounts of it from Odessa, long. 31° E., 

 to San Francisco, long. 122° W., through 153° of longitude; and from 46° to 21° 

 of north latitude; making from north to south a breadth of 25°. Nor is there any 

 reason to suppose that these were the actual limits of the exhibition. "We should 

 not, perhaps, exceed the truth if we should assert that this aurora was seen in a 

 zone of 30° in breadth, reaching half round the globe. The Rev. Chester S. Lyman, 

 who has described its appearance at San Francisco, 2 was informed by an old Califor- 

 nian that it was the first time he had ever witnessed anything of the kind ; and 

 the same was probably the case with most of those who saw it on the Island of 

 Cuba. 



Previous to this return of the aurora, splendid exhibitions of the phenomenon 

 had become so unfrecptent as to induce the belief that the secular period, which 

 was supposed to have commenced in 1827, was over; and after this exhibition, so 

 long a period of comparative repose followed, that we again supposed that no more 

 of the highest forms of the aurora would be witnessed by the present generation ; 

 but the recurrence of three grand displays in the month of September, 1851, on 

 the 3d, the Gth, and the 29th, has again excited doubts respecting the end of this 

 period. 3 But, meanwhile, the most important facts we have assembled, respecting 

 the progress, so far, of the period under review, may be reserved for future use, and 

 it may add to their value to reduce a few of the leading facts to the tabular form. 



1 New Haven Palladium, for April 7, 1848. 

 3 Amer. Jour., New Series, VII, 293. 



3 The almost total disappearance of auroras of the higher class for several years past, must be 

 obvious to every observer. 



