286 Aurora Borealis of November 14, 1837. 



It is stated by M. Wartmann, of Geneva, in the Bihliotheque 

 Universelle for October, 1836, that " an ilhistrious philosopher, 

 M. Arago, has often announced in advance, the early appearance 

 of an Aurora Borealis ; being apprised of its approach by the ex- 

 traordinary oscillations of the magnetic needle, which is regularly 

 observed every day at the Royal Observatory of Paris ; and that 

 the event has confirmed his prediction on the same day, though 

 frequently the phenomenon has occurred at such a distance as not 

 to be observable at Paris." It would hence appear, that auroral 

 action has beeti detected during the day, by the aid of the needle : 

 and it is quite probable that the light would also have been 

 observed in the absence of the sun. 



Although the Aurora undoubtedly manifests itself, on many 

 occasions, contemporaneously in places situated in every direction 

 from the pole, there is no reason to believe that its intensity is, in 

 the same latitude, every where the same at any given moment ; 

 nor that its successive Jits come on, or reach their height, in dif- 

 ferent longitudes precisely at the same time. There is great rea- 

 son, however, for the contrary opinion ; as is manifest, indeed, 

 from the various accounts which we have condensed in the pres- 

 ent article. 



Nor does it seem that the disturbing influence of the Aurora 

 upon the magnetic needle is similar in different longitudes. There 

 are three observations, of the four recorded in the extract above 

 cited from Loudon's Magazine, which we are able to compare 

 with corresponding observations made in New Haven. After ma- 

 king ample allowance both ways, for possible errors in time, we 

 are able nevertheless to say with positiveness, that, while the nee- 

 dle in New Haven was deflected to the east ; in Brookfield, near 

 Manchester, its disturbance was in the contrary direction ; the 

 ordinary variation in both places being westward. 



Not only are the causes of the Aurora as yet a sealed book to 

 us, but we have not been able to ascertain, otherwise than con- 

 jecturally, the altitude of the illuminated substance above the 

 earth's surface. It is even a question whether this substance is 

 within or beyond the limits of the atmosphere. The question is 

 one which it is exceedingly difficult to settle. To identify posi- 

 tively, particular beams seen from diflerent situations, is not so 

 simple a matter as it may seem. The same beams observed from 

 different points of view, may present very different phases ; while 



