It was not
till 1808, four years after my return from America that the observations
made by M. de Rossel were published in the 'Voyage de l'Entrecasteaux', t.
ii., p. 287 , 291, 321, 480, and 644. Up to the present day it is still
usual, in all the tables of magnetic intensity which have been published in
Germany (Hausteen, 'Magnet. der Erde', 1819, s. 71; Gauss, 'Beob. des
Magnet. Vereins', 1838, s. 36-39; Erman, 'Physikal. Beob.', 1841, s.
529-579), in England (Sabine, 'Report on Magnet. Intensity', 1838, p. 43-62;
'Contributions to Terrestrial Magnetism', 1843), and in France (Becquerel,
'Traite de Electr. et de Magnet.', t. vii., p. 354-367), to reduce the
oscillations observed in any part of the Earth to the standard of force
which I found on the magnetic equator in Northern Peru, so that, according
to the unit thus arbitrarily assumed, the intensity of the magnetic force at
Paris is put down as 1.348. The observations made by Lamanon in the
unfortunate expedition of La Perouse, during the stay at Teneriffe (1785),
and on the voyage to Macao (1787), are still older than those of Admiral
Rossel. They were sent to the Academy of Sciences, and it is known that
they were in the possession of Condorcet in the July of 1787 (Becquerel, t.
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