Steel dust (when the pole of a loadstone is placed near) is cemented * into
one body; but when it desires coition with the loadstone, the mass is split
and it rises in conglomerated parts.

But if there is a loadstone beneath the paper, the mass is split in the
same way and many portions result, each of which consists of very many
parts, and remains cemented together, as individual bodies. Whilst the
lower parts of these pursue greedily the pole of the loadstone placed
directly beneath, even they also are raised up as magnetick wholes, just as
a small iron wire of the length of a grain or two grains of barley is
raised up, both when the loadstone is moved near both beneath and above.

* * * * *

{105} CHAP. XXXIIII.

Why a Loadstone should be stronger in its poles
in a different ratio; as well in the Northern
_regions as in the Southern_.

The extraordinary magnetick virtue of the earth is * remarkably
demonstrated by the subtility of the following magnetical experiment. Let
there be given a terrella of no contemptible power, or a long loadstone
with equal cones as polar extremities; but in any other shape which is not
exactly round error is easy, and the experiment difficult. In the Northern
regions, raise the true North pole of the terrella above the horizon
straight toward the zenith; it is demonstrable that it raises up a larger
iron spike on its North pole, than the South pole of the same terrella is
able to raise, when turned in the same way toward the highest point of the
sky. The same thing is shown by a small terrella placed in the same way
above a larger.

[Illustration]

Let _a b_ be the earth or a somewhat large terrella, also _a b_ a smaller
terrella. There is set up above the Northern pole of the smaller terrella a
spike larger than the pole _b_ of the smaller terrella can raise, if it is
turned round to the higher parts. And the pole _a_ of the {106} smaller
terrella has its strength from the larger, declining from the Zenith to the
plane of the horizon or to the level. But now, if, * leaving the terrella
disposed in the same way, you bring a piece of iron to the lower and
Southern pole, it will attract and retain a greater weight than the Boreal
pole could, if it were turned round to the lower parts. Which thing is
demonstrated thus: let A be the earth or a terrella; E the Boreal pole or
some place in some great latitude; B a rather large terrella above the
earth