Why no other Body, excepting a magnetick, is imbued
_with verticity by being rubbed on a loadstone; and why no_
body is able to instil and excite that virtue,
_unless it be a magnetick._
Ligneous substances floating on water never by their own strength turn
round toward the poles of the earth, save by chance. So wires of gold,
silver, brass, tin, lead, or glass, pushed through corks and floating, have
no sure direction; and for this reason they do not show poles or points of
variation when rubbed with a loadstone. For those things which do not of
themselves incline toward the poles and obey the earth are also not ruled
by {143} the touch of a loadstone; for the magnetick vigour has no entrance
into their inward parts; neither is the magnetick form received by them,
nor are their forms magnetically excited; nor, if it did enter, would it
effect anything, because in those bodies (mixed up with various kinds of
efflorescent humours and forms, corrupted from the original property of the
earth) there are no primary qualities. But those prime qualities of iron
are excited by the juxtaposition of a loadstone, just as brute animals or
men, when they are awakened out of sleep, move and put forth their
strength. Here one must marvel at a demonstrable error of B. Porta, who,
while rightly opposing a very old falsehood about the diamond, in speaking
of a power contrary to that of the loadstone, introduces another still
worse opinion; that forsooth iron, when touched by a diamond, turns to the
north. "If" (he says) "you rub a steel-Needle on a Diamond, and then put it
in a Boat, or thrust it through a reed, or hang it up by a Thread, it will
presently turn to the North, almost as well as if it had been touched with
the Loadstone; but something more faintly. And, what is worth noting, the
contrary part will turn the iron to the South: and when I had tried this in
many steel-Needles, and put them all into the Water, I found, that they all
stood equi-distant, pointing to the North." This indeed would * be contrary
to our magnetick rules. For this reason we made an experiment with seventy
excellent diamonds, in the presence of many witnesses, on a large number of
spikes and wires, with the most careful precautions, floating (thrust, of
course, through their corks) on the surface of water; never, however, could
we observe this. He was deceived by the verticity acquired from the earth
(as stated above) in the spike or wire of iron itself, and the iron itself
turned aside to its own definite pole; and he, being ignorant of this,
thought it was done by the diamond. But let the investigators of natural
phenomena take heed that they are not the more deceived by their own badly
observed experiments, and disturb the commonwealth of letters with their
errors and stupidities. Diamond is sometimes designated by the name of
_Sideritis_, not because it is made of iron or because it draws iron, but
on account of its lustre, resembling flashing steel; with such a lustre do
the choicest pieces of diamond shine; hence by very many writers many
qualities are imputed to diamond which really belong to siderite loadstone.
* * * * *
{144} CHAP. XIIII.
The Placing of a Loadstone above or below a magnetick
body suspended in æquilibrium changes neither the power
_nor the verticity of the magnetick body._
Quietly to pass this over would be improper, because a recent error arising
from a defective observation of Baptista Porta must be overthrown; on which
he (by an unfortunate repetition) even writes three chapters, namely, the
18th, the 31st, and the 42nd. For if a loadstone or a piece of magnetick
iron, hanging in æquilibrium or floating on water, is attracted and
disposed toward certain definite points, when you bring above it a piece of
iron or another loadstone, it will not, if you afterward put the same[215]
below it, turn round to the contrary parts; but the same ends of the iron
or the loadstone will always be directed toward the same ends of the stone,
even if the loadstone or the iron is suspended in any way in æquilibrium or
is poised on a needle, so that it can turn round freely. He was deceived by
the irregular shape of some stone, or because he did not arrange the
experiment suitably. Wherefore he is led astray by a vain opinion, and
thinks he may infer that, just as a stone has an arctic and antarctic pole,
so also it has a western and an eastern, and an upper and a lower pole. So
from foolish ideas conceived and admitted arise other fallacies.
* * * * *