It
would seem from the controversy of Henry Bond (the author of 'The Longitude
Found', 1676) with Beckborrow, that this view in some measure influenced
Halley in his theory of four magnetic poles. See my 'Examen Critique de
l'Hist. de la Geographie', t. iii., p. 60.
The bold conjecture hazarded one hundred and twenty-eight years since by
Halley,* that the Aurora Borealis was a magnetic phenomenon, has acquired
empirical certainty from Faraday's brilliant discovery of the evolution of
light by magnetic forces.
[footnote] *Halley, in the 'Philosophical Transactions', vol. xxix. (for
1714-1716), No. 341.
The northern light is preceded by premonitory signs. Thus, in the morning
before the occurrence of the phenomenon, the irregular horary course of the
magnetic needle generally indicates a disturbance of the equilibrium in the
distribution of
p 194
terrestrial magnetism.*
[footnote] *[The Aurora Borealis of October 24th, 1847, which was one of
the most brilliant ever known in this country, was preceded by great
magnetic disturbance. On the 22d of October the maximum of the west
declination was 23 degrees 10'; on the 23d the position of the magnet was
continually changing, and the extreme west declinations were between 22
degrees 44' and 23 degrees 37';on the night between the 23d and 24th of
October, the changes of position were very large and very frequent, the
magnet at times moving across the field so rapidly that a difficulty was
experienced in following it.
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