On the 8th of January, being in the latitude of 30 degrees 25 minutes
south, and in the longitude of 192 degrees 20 minutes, we observed the
variation of the needle to be 90 degrees towards the east, and as we had
a high rolling sea from the south-west, I conjectured there could not be
any land hoped for on that side. On the 12th we found ourselves in 30
degrees 5 minutes south latitude, and in 195 degrees 27 minutes of
longitude, where we found the variation 9 degrees 30 minutes to the east,
a rolling sea from the south-east and from the south-west. It is very
plain, from these observations, that the position laid down by Dr.
Halley, that the motion of the needle is not governed by the poles of the
world, but by other poles, which move round them, is highly probable, for
otherwise it is not easy to understand how the needle came to have, as
our author affirms it had, a variation of near 27 degrees to the west, in
the latitude of 45 degrees 47 minutes, and then gradually decreasing till
it had no variation at all; after which it turned east, in the latitude
of 42 degrees 37 minutes, and so continued increasing its variation
eastwardly to this time.

CHAPTER VIII: OBSERVATIONS ON, AND EXPLANATION OF, THE VARIATION OF THE
COMPASS.

On the 16th we were in the latitude of 26 degrees 29 minutes south, and
in the longitude of 199 degrees 32 minutes, the variation of the needle
being 8 degrees. Here we are to observe that the eastern variation
decreases, which is likewise very agreeable to Doctor Halley's
hypothesis; which, in few words, is this: that a certain large solid body
contained within, and every way separated from the earth (as having its
own proper motion), and being included like a kernel in its shell,
revolves circularly from east to west, as the exterior earth revolves the
contrary way in the diurnal motion, whence it is easy to explain the
position of the four magnetical poles which he attributes to the earth,
by allowing two to the nucleus, and two to the exterior earth. And, as
the two former perpetually alter the situation by their circular motion,
their virtue, compared with the exterior poles, must be different at
different times, and consequently the variation of the needle will
perpetually change. The doctor attributes to the nucleus an European
north pole and an American south one, on account of the variation of
variations observed near these places, as being much greater than those
found ne