246 THE ALRORA BOREALlS. 



intensity. This is proved by the fact that in the polar regions it almost 

 constantly illuminates the sky, and thus renders the cheerlessness of the 

 long absence of the sun the more tolerable. 



The question whether there are periods or cycles of greater and less 

 intensity : that is whether during a part of a century or during several 

 centuries together the auroras occur in greater numbers and are charac- 

 terized by greater splendor and magnitude, has not been satisfactorily 

 answered. But the prevailing opinion among philosophers is that there 

 are such cycles. The great magnificence of a number which have been 

 particularly noticed and recorded within the last quarter of a century 

 has favored the opinion that we have just passed through the period of 

 maximum activity ; and the silence of Grecian and Roman philosophers 

 as well as of all antiquity, has been deemed sufficient proof of the al- 

 most entire absence of auroral phenomena, at least during the immense 

 period in which Greece and Rome were the representatives of the learn- 

 ing and science of the world. With the exception of a few atmospheric 

 phenomena mentioned by Aiistotle, Seneca, and Pliny, such as "a bloody 

 appearance of the heavens," that of "fire descending to the earth," and 

 "a light seen in the night time equal to the brightness of day," which 

 may be referred to the aurora borealis, "the whole of antiquity is abso- 

 lutely silent on this subject." ft is only within about a century and a 

 half that we have frequent' records of its occurrence. But this silence 

 may be accounted for without the supposition that it was a less frequent 

 and splendid phenomenon then than now. The ancients knew abso- 

 lutely nothing of those regions in which the aurora usually displays it- 

 self, their attention was but little directed to the noticing of and account- 

 ing for any atmospheric phenomena whatever in a rational manner, and 

 they saw every thing, even the few auroras which might be witnessed 

 by them in their particular regions, in the distorted light of their idola- 

 trous systems, and no doubt looked upon them merely as prodigies. — 

 Besides, if even in this age of enlightienment of the masses, nineteen- 

 twentieths of the people see only a few of the more splendid auroras, 

 and permit the impression made by them soon to be effaced from their 

 minds, and we are dependent upon the diligence of a few scientific men, 

 Avho have devoted themselves to the observation of the heavens, for the 

 records which we have, what could we expect else than that from the 

 Grecians and Romans, possessed of fewer facilities and motives for re- 

 cording and transmitting such information to future times, we should 

 derive nothing definite or valuable upon this subject, though the heavens 

 may always, as now, have been occasionally glowing with auroral light. 

 And it is also not a little remarkable that the frequency and splendor of 



