On the Iron Cap of a Loadstone, with which
it is armed at the pole (for the sake of the
_virtue) and on the efficacy of the same._
Conceive a small round plate, concave in shape, of the breadth of a digit
to be applied to the convex polar surface of a loadstone and skilfully
attached; or a piece of iron shaped like an acorn, rising from the base
into an obtuse cone, hollowed out a little and fitted to the surface of the
stone, to be tied to the loadstone. Let the iron be the best steel,
smoothed, shining, and even. A loadstone with such an appliance, which
before only bore four ounces of iron, will now raise twelve. But the
greatest force of a combining or rather united nature is seen {87} when two
loadstones, armed with iron caps, are so joined by their concurrent
(commonly called contrary) ends, that they mutually * attract and raise one
another. In this way a weight of twenty ounces is raised, when either stone
unarmed would only allure four ounces of iron. Iron unites to an armed
loadstone more firmly than to a loadstone; and on that account raises
greater weights, because the pieces of iron stick more pertinaciously to
one that is armed. For by the near presence of the magnet they are cemented
together, and since the armature[173] conceives a magnetick vigour 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.
* * * * *