. Annals of Philosophy. 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 -,,0 ) 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 «•* »?*•
. Annals of Philosophy. 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 -,,0 ) 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
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