In this portion of the earth, in northern Asia,
between the mountains of Werchojansk, Jakutsk, and the northern Korea, the
isogonic lines form a remarkable closed system. This oval configuration*
recurs regularly and over a great extent of the South Sea, almost as far as
the meridian of Pitcairn and the group of the Marquesas Islands, between 20
degrees north and 45 degrees
p 183
south lat.
[footnote] *To determine whether the two oval systems of isogonic lines, so
singularly included each within itself, will continue to advance for
centuries in the same inclosed form, or will unfold and expand themselves,
is a question of the highest interest in the problem of the physical causes
of terrestrial magnetism. In the Eastern Asiatic nodes the declination
increases from without inward, while in the node or oval system of the South
Sea the opposite holds good; in fact, at the present time, in the whole
South Sea to the east of the meridian of Kamt-schatka, there is no line
where the declination is null, or, indeed, in which it is less than 2
degrees (Erman, in Pogg., 'Annal.', bd. xxxi, 129). Yet Cornelius Schouten,
on Easter Sunday, 1616, appears to have found the declination null somewhere
to the southeast of Nukahiva, in 15 degrees south lat.
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