These lines are not parallel to
lines of equal inclination (isoclinic line), and the intensity of the force
is not at its minimum at the magnetic equator, as has been supposed, nor is
it even equal at all parts of it. If we compare Erman's observations in the
southern part of the Atlantic Ocean, where a faint zone (0.706) extends from
Angola over the island of St. Helena to the Brazilian coast, with the most
recent investigations of the celebrated navigator James Clark Ross, we shall
find that on the surface of our planet the force increases almost in the
relation of 1:3 toward the magnetic south pole, where Victoria Land extends
from Cape Crozier toward the volcano Erebus, which has been raised to an
elevation of 12,600 feet above the ice.*
[footnote] *From the observations hitherto collected, it appears that the
maximum of intensity for the whole surface of the Earth is 2.052, and the
minimum 0.706. Both phenomena occur in the southern hemisphere; the former
in 73 degrees 47' S. lat., and 169 degrees 30'E. long. from Paris, near
Mount Crozier, west-northwest of the south magnetic pole, at a place where
Captain James Ross found the inclination of the needle to be 87 degrees 11'
(Sabine, 'Contributions to Terrestrial Magnetism', 1843, No.
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