from its
presence and the other conjoined piece of iron is at the same time endued
with vigour from the presence of the loadstone, they are firmly bound
together. Therefore by the mutual contact of strong pieces of iron, the
cohesion is strong. Which thing is also made clear and is exhibited by
means of rods sticking together, Bk. 3, chap 4[174]; and also when the
question of the concretion of iron dust into a united body was discussed.
For this reason a piece of iron set near a loadstone draws away any
suitable piece of iron from the loadstone, if only it touch the iron;
otherwise it does not snatch it away, though in closest proximity. For
magnetick pieces of iron within the orbe of virtue, or near a loadstone, do
not rush together with a greater endeavour[175] than the iron and the
magnet; but joined they are united more strongly and, as it were, cemented
together, though the substance remain the same with the same forces acting.

* * * * *

CHAP. XVIII.

An armed Loadstone does not endow an
excited piece of Iron with greater vigour
_than an unarmed_.

Suppose there are two pieces of iron, one of * which has been excited by an
armed loadstone, the other by one unarmed; and let there be applied to one
of them another piece of iron of a weight just proportional to its
strength, it is manifest that the remaining one in like manner raises the
same and no more. Magnetick versoria also touched by an armed loadstone
turn with the same velocity and constancy towards the poles of the earth as
those magnetized by the same loadstone unarmed.

* * * * *

{88} CHAP. XIX.

Union with an armed Loadstone is stronger;
_hence greater weights are raised; but the_
coition is not stronger[176], but
_generally weaker_.

An armed magnet raises a greater weight, as is manifest to all; but a piece
of iron moves towards a stone at an equal, or rather greater, distance when
it * is bare, without an iron cap. This must be tried with two pieces of
iron of the same weight and figure at an equal distance, or with one and
the same versorium, the test being made first with an armed, then with an
unarmed loadstone, at equal distances.

* * * * *

[Illustration]

CHAP. XX.

*

An armed Loadstone raises an armed Loadstone,
_which also attracts a third; which likewise_
happens, though the virtue in the first
_be somewhat small_.

Mag