_CHAP. I._
ON MAGNETICK
Motions.
Divers things concerning opinions about the magnet-stone, and its variety,
concerning its poles and its known faculties, concerning iron, concerning
the properties of iron, concerning a magnetick substance common to both of
these and to the earth itself, have been spoken briefly by us in the former
book. There remain the magnetical motions, and their fuller philosophy,
shown and demonstrated. These motions are incitements of homogeneal parts
either among themselves or toward the primary conformation of the whole
earth. Aristotle admits only two simple motions of his elements, from the
centre and toward the centre; of light ones upward, heavy ones downward; so
that in the earth there exists one motion only of all its parts towards the
centre of the world,--a rude and inert precipitation. But what of it is
light, and how wrongly it is inferred by the Peripateticks from the simple
motion of the elements, and also what is its heavy part, we will discuss
elsewhere. But now our inquiry must be into the causes of other motions,
depending on its true form, which we have plainly seen in our magnetick
bodies; and these we have seen to be present in the earth and in all its
homogenic parts also. We have noticed that they harmonize with the earth,
and are bound up with its forces. Five movements[106] or differences of
motions are then observed by us: Coition (commonly called attraction), the
{46} incitement to magnetick union; Direction towards the poles of the
earth, and the verticity and continuance of the earth towards the
determinate poles of the world; Variation, a deflexion from the meridian,
which we call a perverted movement; Declination, a descent of the magnetick
pole below the horizon; and circular motion, or Revolution. Concerning all
these we shall discuss separately, and how they all proceed from a nature
tending to aggregation, either by verticity or by volubility. Jofrancus
Offusius[107] makes out different magnetick motions; a first toward a
centre; a second toward a pole at seventy-seven degrees; a third toward
iron; a fourth toward loadstone. The first is not always to a centre, but
exists only at the poles in a straight course toward the centre, if the
motion is magnetick; otherwise it is only motion of matter toward its own
mass and toward the globe. The second toward a pole at seventy-seven
degrees is no motion, but is direction with respect to the pole of the
earth, or variation. The third and fourth are magnetick and are the same.
So he truly recognizes no magnetick motion except the Coition toward iron
or loadstone, commonly called attraction. There is another motion in the
whole earth, which does not exist towards the terrella or towards its
parts; videlicet, a motion of aggregation, and that movement of matter,
which is called by philosophers a right motion, of which elsewhere.
* * * * *