[footnote] *As the first demand for the establishment of these
observatories (a net-work of stations, provided with similar instruments)
proceeded from me, I did not dare to cherish the hope that I should live
long enough to see the time when both hemispheres should be uniformly
covered with magnetic houses under the associated activity of able
physicists and astronomers. This has, however, been accomplished, and
chiefly through the liberal and continued support of the Russian and British
governments.
[footnote continues] In the years 1806 and 1807, I and my friend and
fellow-laborer, Herr Oltmanns, while at Berlin, observed the movements of
the needle, especially at the times of the solstices and equinoxes, from
hour to hour, and often from half hour to half hour, for five or six days
and nights uninterruptedly. I had persuaded myself that continuous and
uninterrupted observations of several days and nights (observatio perpetua)
were preferable to the single observations of many months. The apparatus, a
Prony's magnetic telescope, suspended in a glass case by a thread devoid of
torsion, allowed angles of seven or eight seconds to be read off on a
finely-divided scale, placed at a proper distance, and lighted at night by
lamps.
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