hich obtain their
virtue by a very dissimilar and alien influence from them, derived from
other sources. Wherefore also it is fitting that we find other causes of
the motions, or else we must wander (as in darkness), with these men, and
in no way reach the goal. Amber truly does* not allure by heat, since if
warmed by fire and brought near straws, it does not attract them, whether
it be tepid, or hot, or glowing, or even when forced into the flame. Cardan
(as also Pictorio) reckons that this happens in no different way[129] than
with the cupping-glass, by the force of fire. Yet the attracting force of
the cupping-glass does not really come from the force of fire. But he had
previously said that the dry substance wished to imbibe fatty humour, and
therefore it was borne towards it. But these statements are at variance
with one another, and also foreign to reason. For if amber had moved
towards its food, or if other bodies had inclined towards amber as towards
provender, there would have been a diminution of the one which was
devoured, just as there would have been a growth of the other which was
sated. Then why should an attractive force of fire be looked for in amber?
If the attraction existed from heat, why should not very many other bodies
also attract, if warmed by fire, by the sun, or by friction? Neither can
the attraction be on account of the dissipating of the air, when it takes
place in open air (yet Lucretius the poet adduces this as the reason for
magnetical motions). Nor in the cupping-glass can heat or fire attract by
feeding on air: in the cupping-glass air, having been exhausted into flame,
{50} when it condenses again and is forced into a narrow space, makes the
skin and flesh rise in avoiding a vacuum. In the open air warm things
cannot attract, not metals even or stones, if they should * be strongly
incandescent by fire. For a rod of glowing iron, or a flame, or a candle,
or a blazing torch, or a live coal, when they are brought near to straws,
or to a versorium, do not attract; yet at the same time they manifestly
call in the air in succession; because they consume it, as lamps do oil.
But concerning heat, how it is reckoned by the crowd of philosophizers, in
natural philosophy and in _materia medica_ to exert an attraction otherwise
than nature allows, to which true attractions are falsely imputed, we will
discuss more at length elsewhere, when we shall determine what are the
properties of heat and cold.