1814.] 



On the Aurora Borealis. 431 



Height in 

 Place. Observer. English Miles. 



C Upsala Bergman ? g66 



(_ Hernosand Gisler • • • 5 



C Upsala Bergman ? 666 



£ Hernosand Gisler 5 



C Upsala Bergman \ 534 



£ Hernosand Gisler J 



C Upsala Bergman \334 



(_ Hernosand Gisler J 



C Hernosand Gisler \ „o . 



> Lidkb'ping Bergman f 



C Vienna Hell "1 -,, 



) Hernosand Gisler J 



C Hernosand Gisler 1 „o « 



£ Enkoping Bergman j 



( Hernosand Gisler "» G ^~ 



{_ Mariestadt Berirman J 



•7«, * o* [&: :::::: & : : ::■: }™ 



17G4, 22 Feb. Upsala Bergman 254 



1784, 23 Feb. London Cavendish 62 



«•* » ■*• [&;::::::: c^Ui.;".:::} 150 * 



From this table it is obvious that the height of the cylindrical 

 luminous bodies, which constitute the Aurora Borealis, varies very 

 considerably at different times ; but that they are always situated 

 beyond the sensible atmosphere which surrounds the earth. 



7. During the prevalence of the Aurora Borealis the magnetic 

 needle is frequently observed to become unsteady. 



These are the facts respecting the Aurora Borealis that seem to be 

 perfectly authenticated. There are some other curious observations 

 on it, which were made by Rilter; but I forbear to state them, be- 

 cause 1 do not know how far their accuracy can be depended on. 



It is quite obvious from the preceding detail that the Aurora 

 Borealis is connected with the magnetism of the earth ; that the 

 luminous cylinders arc in fact magnets parallel to the magnetic axis 

 of the earth, and pointing to the northern magnetic pole of the 

 earth. Hence the position of the beams constituting the Aurora 

 varies with the declination of the needle, as becomes quite obvious 

 when we compare together the different observations of Aurone 

 made at different times. 



The connection between the Aurora Borealis and magnetism was 

 seen bv Dr. Halley, who in his first paper on the subject, printed 

 in the Philosophical Transactions for 1716, endeavours to explain 



• This table, except the last two bcighu, i« taken from Bergman, Opine, t. 291. 



