Magnetic perturbations (storms), which occasionally recurred at the
same hour on several successive nights, led me even then to desire extremely
that similar apparatus should be used to the east and west of Berlin, in
order to distinguish general terrestrial phenomena from those which are mere
local disturbances, depending on the inequality of heat in different parts
of the Earth, or on the cloudiness of the atmosphere. My departure to
Paris, and the long period of political disturbance that involved the whole
of the west of Europe, prevented my wish from being then accomplished.
(OErsted's great discovery (1820) of the intimate connection between
electricity and magnetism again excited a general interest (which had long
flagged) in the periodical variations of the electro-magnetic tension of the
Earth. Arago, who many years previously had commenced in the Observatory at
Paris, with a new and excellent declination instrument by Gambey, the
longest uninterrupted series of horary observations which we possess in
Europe, showed by a comparison with simultaneous observations of
perturbation made at Kasan, what advantages might be obtained from
corresponding measurements of declination. When I returned to Berlin, after
an eighteen years' residence in France, I had a small magnetic house erected
in the autumn of 1828, not only with the view of carrying on the work
commenced in 1806, but more with the object that simultaneous observations
at hours previously determined might be made at Berlin, Paris, and Freiburg,
at a depth of 35 fathoms below the surface.
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