On a Perpetual Motion Machine, mentioned
by authors, by means of the attraction
_of a loadstone_.
Cardan writes[183] that out of iron and the Herculean stone can be made a
perpetual motion machine; not that he himself had ever seen one, but only
conceived the idea from an account by Antonius de Fantis[184], of Treves.
Such a machine he describes, Book 9, _De Rerum Varietate_. But they have
been little practised in magnetick experiments who forge such things as
that. For no magnetick attraction can be greater (by any skill or by any
kind of instrument) than the retention. Things which are joined and those
which are approaching near are retained with a greater force than those
which are enticed and set in motion, and are moved; and that coition is, as
we have shown above, a motion of both, not an attraction of one. Such a
machine Peter Peregrinus feigned many centuries before or else depicted one
which he had received from others, and one which was much better fitted for
the purpose. Johannes Taysnier published it also, spoiled by wretched
figures, and copied out the whole theory of it word for word. O that the
gods would at length bring to a miserable end such fictitious, crazy,
deformed labours, with which the minds of the studious are blinded!
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{108} CHAP. XXXVI.
How a more robust Loadstone may be
_recognized_.
Very powerful loadstones sometimes lift into the air a weight of iron equal
to their own; a weak one barely attracts a slender wire. Those therefore
are more robust which appeal to and retain larger bodies, if there is no
defect in their form, or the pole of the stone is not suitably moved up.
Moreover, when placed in a boat a keener influence turns its own poles
round more quickly to the poles of the earth or the limits of variation on
the horizon. One which performs its function more feebly indicates a defect
and an effete nature. There must always be a similar preparation, a similar
figure, and a like size; for in such as are very dissimilar and unlike, the
experiment is doubtful. The method of testing the strength is the same also
with a versorium in a place somewhat remote from a loadstone; for the one
which is able to turn the versorium round at the greater distance, that one
conquers and is held the more potent. Rightly also is the force of a
loadstone weighed in a balance by B. Porta; a piece of loadstone is placed
in one scale-pan, in the other just as much weight of something else, so
that the scale-pans hang level. Soon a piece of iron lying on the table is
adjusted so that it sticks to the loadstone placed in the scale, and they
cling together most perfectly, according to their friendly points; into the
other scale-pan sand is gradually thrown, and that until the scale in which
the loadstone is placed is separated from the iron. Thus by weighing the
weight of sand, the magnetick force becomes known. Similarly also it will
be pleasing to try with another stone, in equilibrium, the weight of the
sand being observed, and to find out the stronger by means of the weights
of sand. Such is the experiment of Cardinal Cusan in his _De
Staticis_[185], from whom it would seem that B. Porta learnt the
experiment. The better loadstones turn themselves round more quickly toward
the poles or points of variation; then they also lead along and turn round
more quickly, according to the greater quantity and mass of wood, a boat
and other stuff. In a declination instrument, the more powerful force of a
loadstone is looked for and required. Those therefore are more lively when
they get through their work readily, and pass through and come back again
with speed, and swiftly at length settle at their own point. Languid and
effete ones move more sluggishly[186], settle more tardily, adhære more
uncertainly, and are easily disturbed from their possession.
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{109} CHAP. XXXVII.
Use of a Loadstone as it affects
_iron._
By magnetick coition we test iron ore in a blacksmith's forge. It is burnt,
broken in pieces, washed and dried, in which way it lays down its alien
humours; in the bits collected from the washing is placed a loadstone,
which attracts the iron dust to itself; this, being brushed off with
feathers, is received in a crucible, and the loadstone is again placed in
the bits collected from the washing, and the dust wiped off, as long as any
remains which it will attract to itself. This is then heated in the
crucible along with _sal nitri_[187] until it is liquid, and from this a
small mass of iron is cast. But if the loadstone draws the dust to itself
quickly and readily, we conjecture that the iron ore is rich; if slowly,
poor; if it seems altogether to reject it, there is very little iron in it
or none at all. In like manner iron dust can be separated from another
metal. Many tricks there are also, when iron is secretly applied to lighter
bodies, and, being attracted by the motion of a loadstone which is kept out
of sight, causes movements which are amazing to those who do not know the
cause. Very many such indeed every ingenious mechanician will perform by
sleight of hand, as if by incantations and jugglery[188].
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