Chapter VIII: Part I

Chap. I states that the intention or object of the work is to
make known the hitherto hidden nature, occult properties, of
the loadstone, the art of treating the latter, the making of
scientific instruments, and matters of interest to students of
nature, astrologers and sailors.

Chap. II. The investigator in this line should know the natures
of things and understand the motions of the heavenly bodies,
but, above all, he should be assiduous in handiwork for
experimental research.

Chap. III indicates four different requisite qualities of the
loadstone, and tells where they are to be found and how to
select and test them--the best of them being free from flaws, of
great density and of a bluish or celestial colour.

Chap. IV shows how to find in the loadstone the two poles,
one north and the other south, using preferably a globular
magnet,[17] placing thereon a needle or an oblong piece of
iron, and, either drawing lines in the direction taken by the
needle, so that they “may meet at two points, just as all the
meridian circles of the world meet at the two opposite poles
of the world,” or, by merely marking the magnet so that “the
opposite points will be correctly placed just as are the poles
in a sphere.”

Chap. V. In order to find the poles in a stone--which of them is
the North and which the South--take a round wooden vessel shaped
like a skiff (_paropsidis_, _parascidis_), and place
the stone therein, then put the vessel containing the stone into
another large vessel filled with water, so that the first-named
vessel may float into the larger one: “The stone in the first
vessel will be like a sailor in a ship, and the first vessel
may float roomily into the second as does a ship in a river,
and the stone so placed will turn its small vessel acting as
the Northern pole in the direction of the Northern heaven....
If this pole were then turned away a thousand times, a thousand
times would it return to its place by the will of God.”

Chap. VI. Having found which pole is the Northern, mark it so
that it may be known when necessary. Place the stone into a
small vessel, as shown in Chap. V, then hold another stone in
the hand and approach its Northern part to the Southern part of
the stone floating in the vessel, and the floating stone will
follow the other “as if it wished to adhere thereto.... Know
that, as a rule, the Northern part of one stone attracts the
Southern part of another stone and the Southern the Northern.”

Chap. VII. When the needle or oblong piece of iron (alluded to
in Chap. IV) has touched the magnet and been attached to a light
piece of wood or stalk and then placed in a vessel of water,
one part will be turned towards the mariner’s star because it
is near the pole, “the fact being that it does not turn towards
the aforesaid star but towards the pole.” That end of the iron
which has touched the Southern end of the stone turns towards
the Northern quarter of the sky, and _vice versa_.

Chap. VIII. If you wish to attract iron floating on water, hold
the Southern part of a loadstone to the Northern part of the
iron and the iron will follow. But, if you bring the North end
of the stone near the North end of the iron, the latter will
avoid the stone. “If, however, violence is used towards the
ends, so that, for instance, the Southern end of the iron which
was touched with the Northern end of the magnet is now touched
with the Southern end of the magnet ... the power in the iron
will easily be changed, and that will become Southern which was
previously Northern, and the converse.”

Chap. IX. “The Northern part of the magnet attracts the Southern
and the reverse, as has been shown; in which attraction the
magnet is an ‘agent’ of greater power while the ‘patient’
(_i. e._ the other which is acted upon) is, of weaker.” This
is proved by taking a loadstone--marking it, for instance,
AD--dividing, separating it into two parts, and placing one
part (the Northern, marked A, called the “agent”) into water
so that it will float. It will turn “to the North, as before,
for the division does not deprive the parts of the stone of
their properties, if it be homogeneous.” The other part (the
Southern, marked D, called the “patient”) is next to be floated
in a similar manner. When this is done, the other ends of the
two stones should be marked respectively B and C. It will then
be observed that “if the same parts are again brought near each
other, one will attract the other, so that they will be joined
together again at B and C where the division took place. Whence
it is that they become one body with the same natural propensity
as at first. The proof of this is that if they are joined
together they will possess the same oppositions (opposite poles)
they first contained. The ‘agent,’ therefore, as you will see by
experiment, intends to unite its ‘patient’ to itself, and this
takes place on account of the similitude between them.... And,
in the same way, it will happen that if A is joined with D, the
two lines will become one, by virtue of that very attraction,
in this order CD--AB ... there will then remain the identity of
the extreme parts as at first, before they were reunited, for C
will be the North point and B the South point, as B and C were
before.... It is therefore evident, from these observations,
why the Southern parts do attract the Northern, and the reverse,
and why the attraction of the South by the South, and the North
by the North, is not according to Nature.”

Chap. X. “Some weak inquirers have imagined that the power which
the magnet exercises over iron lies in those mineral places in
which the magnet is found ... but it is found in different parts
of the world.... Besides, when iron or the magnet turns towards
the Southern as well as to the Northern quarter, as is evident
from what has already been said, we are compelled to decide
that the attraction is exercised on the poles of the magnet not
only from the locality of its quarry, from which ensues the
evident result that, wheresoever a man may be, the direction
of this stone appears to his eye, according to the position of
his meridian circle. All the meridian circles, however, meet
together at the poles of the globe, wherefore it is that the
poles of the magnet receive their power from the poles of the
world. From this, it manifestly appears that the direction of
the magnet is not towards the mariner’s star, as the meridian
circles do not meet there, but all the poles, for the mariner’s
star is always found beyond the meridian circle of any region
unless it be twice in a complete revolution of the firmament.
Likewise from this, it is manifest that the parts of the magnet
receive their power from the world’s poles ... the whole
magnet from the whole heavens.”[18] Then follows a suggestive
experiment looking towards perpetual motion, by which one may
secure “a wonderful secret” and even “be saved the trouble of
having any clock.” Here, it is given that a _terrella_,
poised on its poles in the meridian, moves circularly with a
complete revolution in twenty-four hours. This is explained by
N. Cabæus in his “Phil. Magn.,” lib. iii. cap. 4.