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Title: On the magnet, magnetick bodies also, and on the great magnet
the earth

Adapter: William Gilbert

Translator: Silvanus P. Thompson

Release date: September 26, 2010 [eBook #33810]

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK ON THE
MAGNET, MAGNETICK BODIES ALSO, AND ON THE GREAT
MAGNET THE EARTH ***

VVILLIAM GILBERT

OF COLCHESTER,
PHYSICIAN OF

LONDON.

ON THE MAGNET, MAGNETICK
BODIES ALSO, AND ON

the great magnet the earth; a new Physiology,

demonstrated by many arguments

& experiments.

LONDON

IMPRINTED at the Chiswick Press ANNO

MCM.

PREFACE TO THE CANDID
READER, STUDIOUS OF
THE MAGNETICK
PHILOSOPHY.

learer proofs, in the discovery of secrets, and in the investigation
of the hidden causes of things, being afforded by trustworthy
experiments and by demonstrated arguments, than by the probable
guesses and opinions of the ordinary professors of philosophy: so,
therefore, that the noble substance of that great magnet, our common
mother (the earth), hitherto quite unknown, and the conspicuous and exalted
powers of this our globe, may be the better understood, we have proposed
to begin with the common magnetick, stony, and iron material, and with
magnetical bodies, and with the nearer parts of the earth which we can
reach with our hands and perceive with our senses; then to proceed with

demonstrable magnetick experiments; and so penetrate, for the first time,
into the innermost parts of the earth. For after we had, in order finally to
learn the true substance of the globe, seen and thoroughly examined many
of those things which have been obtained from mountain heights or ocean
depths, or from the profoundest caverns and from hidden mines: we applied
much prolonged labour on investigating the magnetical forces; so
wonderful indeed are they, compared with the forces of all other minerals,
surpassing even the virtues of all other bodies about us. Nor have we found
this our labour idle or unfruitful; since daily during our experimenting, new
and unexpected properties came to light; and our Philosophy hath grown so
much from the things diligently observed, that we have attempted to
expound the interior parts of the terrene globe, and its native substance,
upon magnetick principles; and to reveal to men the earth (our common
mother), and to point it out as if with the finger, by real demonstrations and
by experiments manifestly apparent to the senses. And as geometry ascends
from sundry very small and very easy principles to the greatest and most
difficult; by which the wit of man climbs above the firmament: so our
magnetical doctrine and science first sets forth in convenient order the
things which are less obscure; from these there come to light others that are
more remarkable; and at length in due order there are opened the concealed
and most secret things of the globe of the earth, and the causes are made
known of those things which, either through the ignorance of the ancients or
the neglect of moderns, have remained unrecognized and overlooked. But
why should I, in so vast an Ocean of Books by which the minds of studious
men are troubled and fatigued, through which very foolish productions the
world and unreasoning men are intoxicated, and puffed up, rave and create
literary broils, and while professing to be philosophers, physicians,
mathematicians and astrologers, neglect and despise men of learning: why
should I, I say, add aught further to this so-perturbed republick of letters,
and expose this noble philosophy, which seems new and incredible by
reason of so many things hitherto unrevealed, to be damned and torn to
pieces by the maledictions of those who are either already sworn to the
opinions of other men, or are foolish corruptors of good arts, learned idiots,
grammatists, sophists, wranglers, and perverse little folk? But to you alone,
true philosophizers, honest men, who seek knowledge not from books only
but from things themselves, have I addressed these magnetical principles in
this new sort of Philosophizing. But if any see not fit to assent to these self-

same opinions and paradoxes, let them nevertheless mark the great array of
experiments and discoveries (by which notably every philosophy
flourisheth), which have been wrought out and demonstrated by us with
many pains and vigils and expenses. In these rejoice, and employ them to
better uses, if ye shall be able. I know how arduous it is to give freshness to
old things, lustre to the antiquated, light to the dark, grace to the despised,
credibility to the doubtful; so much the more by far is it difficult to win and
establish some authority for things new and unheard-of, in the face of all
the opinions of all men. Nor for that do we care, since philosophizing, as we
deemed, is for the few. To our own discoveries and experiments we have
affixed asterisks, larger and smaller, according to the importance and
subtlety of the matter. Whoso desireth to make trial of the same
experiments, let him handle the substances, not negligently and carelessly,
but prudently, deftly, and in the proper way; nor let him (when a thing doth
not succeed) ignorantly denounce our discoveries: for nothing hath been set
down in these books which hath not been explored and many times
performed and repeated amongst us. Many things in our reasonings and
hypotheses will, perchance, at first sight, seem rather hard, when they are
foreign to the commonly received opinion; yet I doubt not but that hereafter
they will yet obtain authority from the demonstrations themselves.
Wherefore in magnetical science, they who have made most progress, trust
most in and profit most by the hypotheses; nor will anything readily
become certain to any one in a magnetical philosophy in which all or at
least most points are not ascertained. This nature-knowledge is almost
entirely new and unheard-of, save what few matters a very few writers have
handed down concerning certain common magnetical powers. Wherefore
we but seldom quote antient Greek authors in our support, because neither
by using greek arguments nor greek words can the truth be demonstrated or
elucidated either more precisely or more significantly. For our doctrine
magnetical is at variance with most of their principles and dogmas. Nor
have we brought to this work any pretence of eloquence or adornments of
words; but this only have we done, that things difficult and unknown might
be so handled by us, in such a form of speech, and in such words as are
needed to be clearly understood: Sometimes therefore we use new and
unusual words, not that by means of foolish veils of vocabularies we should
cover over the facts with shades and mists (as Alchemists are wont to do)
but that hidden things which have no name, never having been hitherto

perceived, may be plainly and correctly enunciated. After describing our
magnetical experiments and our information of the homogenick parts of the
earth, we proceed to the general nature of the whole globe; wherein it is
permitted us to philosophize freely and with the same liberty which the
Egyptians, Greeks, and Latins formerly used in publishing their dogmas:
whereof very many errors have been handed down in turn to later authors:
and in which smatterers still persist, and wander as though in perpetual
darkness. To those early forefathers of philosophy, Aristotle, Theophrastus,
Ptolemy, Hippocrates, and Galen, let due honour be ever paid: for by them
wisdom hath been diffused to posterity; but our age hath detected and
brought to light very many facts which they, were they now alive, would
gladly have accepted. Wherefore we also have not hesitated to expound in
demonstrable hypotheses those things which we have discovered by long
experience. Farewell.

TO THE MOST EMINENT AND LEARNED MAN

Dr. William Gilbert,
a distinguished Doctor of Medicine amongst the

Londoners, and Father of Magnetick Philosophy,

an Encomiastic Preface of Edward Wright

on the subject of these books

Magnetical.
hould there by chance be any one, most eminent Sir, who reckons
as of small account these magnetical books and labours of yours,
and thinks these studies of yours of too little moment, and by no
means worthy enough of the attention of an eminent man devoted
to the weightier study of Medicine: truly he must deservedly be judged to be
in no common degree void of understanding. For that the use of the magnet
is very important and wholly admirable is better known for the most part to
men of even the lowest class than to need from me at this time any long
address or commendation. Nor truly in my judgment could you have chosen
any topick either more noble or more useful to the human race, upon which
to exercise the strength of your philosophic intellect; since indeed it has
been brought about by the divine agency of this stone, that continents of
such vast circuit, such an infinite number of lands, islands, peoples, and
tribes, which have remained unknown for so many ages, have now only a
short time ago, almost within our own memory, been quite easily discovered
and quite frequently explored, and that the circuit of the whole terrestrial
globe also has been more than once circumnavigated by our own
countrymen, Drake and Cavendish; a fact which I wish to mention to the
lasting memory of these men. For by the pointing of the iron touched by a
loadstone, the points of South, North, East, and West, and the other
quarters of the world are made known to navigators even under an overcast
sky and in the darkest night; so that thus they always very easily understand
to which point of the world they ought to direct their ship's course; which

before the discovery of this wonderful virtue of the magnetick βορεοδείξις
was clearly impossible. Hence in old times (as is established in histories),
an incredible anxiety and immense danger was continually threatening
sailors; for at the coming on of a tempest and the obscuring of the view of
sun and stars, they were left entirely in ignorance whither they were
making; nor could they find out this by any reasoning or skill. With what joy
then may we suppose them to have been filled, to what feelings of delight
must all shipmasters have given utterance, when that index magnetical first
offered itself to them as a most sure guide, and as it were a Mercury, for
their journey? But neither was this sufficient for this magnetical Mercury;
to indicate, namely, the right way, and to point, as it were, a finger in the
direction toward which the course must be directed; it began also long ago
to show distinctly the distance of the place toward which it points. For since
the index magnetical does not always in every place look toward the same
point of the North, but deviates from it often, either toward the East or
toward the West, yet always has the same deviation in the same place,
whatever the place is, and steadily preserves it; it has come about that from
that deviation, which they call variation, carefully noticed and observed in
any maritime places, the same places could afterwards also be found by
navigators from the drawing near and approach to the same variation as
that of these same places, taken in conjunction with the observation of the
latitude. Thus the Portuguese in their voyages to the East Indies had the
most certain indications of their approach to the Cape of Good Hope; as
appears from the narrations of Hugo van Lynschoten and of the very
learned Richard Hakluyt, our countryman. Hence also the experienced
skippers of our own country, not a few of them, in making the voyage from
the Gulf of Mexico to the islands of the Azores, recognized that they had
come as near as possible to these same islands; although from their sea-
charts they seemed to be about six hundred British miles from them. And so,
by the help of this magnetick index, it would seem as though that
geographical problem of finding the longitude, which for so many centuries
has exercised the intellects of the most learned Mathematicians, were going
to be in some way satisfied; because if the variation for any maritime place
whatever were known, the same place could very readily be found
afterward, as often as was required, from the same variation, the latitude of
the same place being not unknown.

It seems, however, that there has been some inconvenience and hindrance
connected with the observation of this variation; because it cannot be
observed excepting when the sun or the stars are shining. Accordingly this
magnetick Mercury of the sea goes on still further to bless all shipmasters,
being much to be preferred to Neptune himself, and to all the sea-gods and
goddesses; not only does it show the direction in a dark night and in thick
weather, but it also seems to exhibit the most certain indications of the
latitude. For an iron index, suspended on its axis (like a pair of scales),
with the most delicate workmanship so as to balance in æquilibrio, and then
touched and excited by a loadstone, dips to some fixed and definite point
beneath the horizon (in our latitude in London, for example, to about the
seventy-second degree), at which it at length comes to rest. But under the
æquator itself, from that admirable agreement and congruency which, in
almost all and singular magnetical experiments, exists between the earth
itself and a terrella (that is, a globular loadstone), it seems exceedingly
likely (to say the very least), and indeed more than probable, that the same
index (again stroked with a loadstone) will remain in æquilibrio in an
horizontal position. Whence it is evident that this also is very probable, that
in an exceedingly small progress from the South toward the North (or
contrariwise) there will be at least a sufficiently perceptible change in that
declination; so that from that declination in any place being once carefully
observed along with the latitude, the same place and the same latitude may
be very easily recognized afterward, even in the darkest night and in the
thickest mist by a declination instrument. Wherefore to bring our oration at
length back to you, most eminent and learned Dr. Gilbert (whom I gladly
recognize as my teacher in this magnetick philosophy), if these books of
yours on the Magnet had contained nothing else, excepting only this finding
of latitude from magnetick declination, by you now first brought to light,
our shipmasters, Britains, French, Belgians, and Danes, trying to enter the
British Channel or the Straits of Gibraltar from the Atlantick Ocean in dark
weather, would still most deservedly judge them to be valued at no small
sum of gold. But that discovery of yours about the whole globe of the earth
being magnetical, although perchance it will seem to many "most
paradoxical," producing even a feeling of astonishment, has yet been so
firmly defended by you at all points and confirmed by so many experiments
so apposite and appropriate to the matter in hand, in Bk. 2, chap. 34; Bk. 3,
chap. 4 and 12; and in almost the whole of the fifth book, that no room is

left for doubt or contradiction. I come therefore to the cause of the
magnetick variation, which hitherto has distracted the minds of all the
learned; for which no mortal has ever adduced a more probable reason
than that which has now been set forth by you for the first time in these
books of yours on the Magnet. The ὀρθοβορεοδείξις of the index
magnetical in the middle of the ocean, and in the middle of continents (or at
least in the middle of their stronger and more lofty parts), its inclining near
the shore toward those same parts, even by sea and by land, agreeing with
the experiments Bk. 4, chap. 2, on an actual terrella (made after the
likeness of the terrestrial globe, uneven, and rising up in certain parts,
either weak or wanting in firmness, or imperfect in some other way),—this
inclination having been proved, very certainly demonstrates the probability
that that variation is nought else than a certain deviation of the magnetick
needle toward those parts of the earth that are more vigorous and more
prominent. Whence the reason is readily established of that irregularity
which is often perceived in the magnetick variations, arising from the
inæquality and irregularity of those eminences and of the terrestrial forces.
Nor of a surety have I any doubt, that all those even who have either
imagined or admitted points attractive or points respective in the sky or the
earth, and those who have imagined magnetick mountains, or rocks, or
poles, will immediately begin to waver as soon as they have perused these
books of yours on the Magnet, and willingly will march with your opinion.
Finally, as to the views which you discuss in regard to the circular motion
of the earth and of the terrestrial poles, although to some perhaps they will
seem most supposititious, yet I do not see why they should not gain some
favour, even among the very men who do not recognize a sphærical motion
of the earth; since not even they can easily clear themselves from many
difficulties, which necessarily follow from the daily motion of the whole sky.
For in the first place it is against reason that that should be effected by
many causes, which can be effected by fewer; and it is against reason that
the whole sky and all the sphæres (if there be any) of the stars, both of the
planets and the fixed stars, should be turned round for the sake of a daily
motion which can be explained by the mere daily rotation of the earth. Then
whether will it seem more probable, that the æquator of the terrestrial globe
in a single second (that is, in about the time in which any one walking
quickly will be able to advance only a single pace) can accomplish a
quarter of a British mile (of which sixty equal one degree of a great circle

on the earth), or that the æquator of the primum mobile in the same time
should traverse five thousand miles with celerity ineffable; and in the
twinkling of an eye should fly through about five hundred British miles,
swifter than the wings of lightning, if indeed they maintain the truth who
especially assail the motion of the earth). Finally, will it be more likely to
allow some motion to this very tiny terrestrial globe; or to build up with
mad endeavour above the eighth of the fixed sphæres those three huge
sphæres, the ninth (I mean), the tenth, and the eleventh, marked by not a
single star, especially since it is plain from these books on the magnet, from
a comparison of the earth and the terrella, that a circular motion is not so
alien to the nature of the earth as is commonly supposed. Nor do those
things which are adduced from the sacred Scriptures seem to be specially
adverse to the doctrine of the mobility of the earth; nor does it seem to have
been the intention of Moses or of the Prophets to promulgate any
mathematical or physical niceties, but to adapt themselves to the
understanding of the common people and their manner of speech, just as
nurses are accustomed to adapt themselves to infants, and not to go into
every unnecessary detail. Thus in Gen. i. v. 16, and Psal. 136, the moon is
called a great light, because it appears so to us, though it it is agreed
nevertheless by those skilled in astronomy that many of the stars, both of the
fixed and wandering stars, are much greater. Therefore neither do I think
that any solid conclusion can be drawn against the earth's mobility from
Psal. 104, v. 5; although God is said to have laid the foundations of the
earth that it should not be removed for ever; for the earth will be able to
remain evermore in its own and self-same place, so as not to be moved by
any wandering motion, nor carried away from its seat (wherein it was first
placed by the Divine artificer). We, therefore, with devout mind
acknowledging and adoring the inscrutable wisdom of the triune Divinity
(having more diligently investigated and observed his admirable work in
the magnetical motions), induced by philosophical experiments and
reasonings not a few, do deem it to be probable enough that the earth,
though resting on its centre as on an immovable base and foundation,
nevertheless is borne around circularly.
But passing over these matters (concerning which I believe no one has ever
demonstrated anything with greater certainty), without any doubt those
matters which you have discussed concerning the causes of the variation

and of the magnetick dip below the horizon, not to mention many other
matters, which it would take too long to speak of here, will gain very great
favour amongst all intelligent men, and especially (to speak after the
manner of the Chemists) amongst the sons of the magnetick doctrine. Nor
indeed do I doubt that when you have published these books of yours on the
Magnet, you will excite all the diligent and industrious shipmasters to take
no less care in observing the magnetick declination beneath the horizon
than the variation. Since (if not certain) it is at least probable, that the
latitude itself, or rather the effect of the latitude, can be found (even in very
dark weather) much more accurately from that declination alone, than can
either the longitude or the effect of the longitude from the variation, though
the sun itself is shining brightly or all the stars are visible, with the most
skilful employment likewise of all the most exact instruments. Nor is there
any doubt but that those most learned men, Peter Plancius (not more deeply
versed in Geography than in observations magnetical), and Simon Stevinus,
the most distinguished mathematician, will rejoice in no moderate degree,
when they first see these magnetical books of yours, and observe their
λιμενευρετική, or Haven-finding Art, enlarged and enriched by so great
and unexpected an addition; and without doubt they will urge all their own
shipmasters (as far as they can) to observe also everywhere the magnetick
declination below the horizon no less than the variation. May your
Magnetical Philosophy, therefore, most learned Dr. Gilbert, come forth into
the light under the best auspices, after being kept back not till the ninth year
only (as Horace prescribes), but already unto almost a second nine, a
philosophy rescued at last by so many toils, studyings, watchings, with so
much ingenuity and at no moderate expense maintained continuously
through so many years, out of darkness and dense mist of the idle and
feeble philosophizers, by means of endless experiments skilfully applied to
it; yet without neglecting anything which has been handed down in the
writings of any of the ancients or of the moderns, all which you did
diligently peruse and perpend. Do not fear the boldness or the prejudice of
any supercilious and base philosophaster, who by either enviously
calumniating or stealthily arrogating to himself the investigations of others
seeks to snatch a most empty glory. Verily

Envy detracts from great Homer's genius;

but

Whoever thou art, Zoilus, thou hast thy name from him.

May your new physiology of the Magnet, I say (kept back for so many
years), come forth now at length into the view of all, and your Philosophy,
never to be enough admired, concerning the great Magnet (that is, the
earth); for, believe me

(If there is any truth in the forebodings of seers),

these books of yours on the Magnet will avail more for perpetuating the
memory of your name than the monument of any great Magnate placed
upon your tomb.

Interpretation of certain words.[1]

Terrella, a globular loadstone.
Verticity, polar vigour, not περιδίνησις but περιδίνεισιος δύναμις: not a
vertex or πόλος but a turning tendency.
Electricks, things which attract in the same manner as amber.
Excited Magnetick, that which has acquired powers from the loadstone.
Magnetick Versorium, a piece of iron upon a pin, excited by a loadstone.
Non-magnetick Versorium, a versorium of any metal, serving for electrical
experiments.
Capped loadstone, which is furnished with an iron cap, or snout.
Meridionally, that is, along the projection of the meridian.
Paralleletically, that is, along the projection of a parallel.
Cusp, tip of a versorium excited by the loadstone.

Cross, sometimes used of the end that has not been touched and excited by
a loadstone, though in many instruments both ends are excited by the
appropriate termini of the stone.
Cork, that is, bark of the cork-oak.
Radius of the Orbe of the Loadstone, is a straight line drawn from the
summit of the orbe of the loadstone, by the shortest way, to the surface of
the body, which, continued, will pass through the centre of the loadstone.
Orbe of Virtue, is all that space through which the Virtue of any loadstone
extends.
Orbe of Coition, is all that space through which the smallest magnetick is
moved by the loadstone.
Proof, for a demonstration shown by means of a body.
Magnetick Coition: since in magnetick bodies, motion does not occur by an
attractive faculty, but by a concourse or concordance of both, not as if there
were an ἑλκτικὴ δύναμις of one only, but a συνδρομή of both; there is
always a coition of the vigour: and even of the body if its mass should not
obstruct.
Declinatorium, a piece of Iron capable of turning about an axis, excited by a
loadstone, in a declination instrument.

I N D E X O F C H A P T E R S.

Book 1.
Chap. 1. Ancient and modern writings on the Loadstone, with certain
matters of mention only, various opinions, & vanities.
Chap. 2. Magnet Stone, of what kind it is, and its discovery.
Chap. 3. The loadstone has parts distinct in their natural power, & poles
conspicuous for their property.

Chap. 4. Which pole of the stone is the Boreal: and how it is distinguished
from the austral.
Chap. 5. Loadstone seems to attract loadstone when in natural position: but
repels it when in a contrary one, and brings it back to order.
Chap. 6. Loadstone attracts the ore of iron, as well as iron proper, smelted
& wrought.
Chap. 7. What iron is, and of what substance, and its uses.
Chap. 8. In what countries and districts iron originates.
Chap. 9. Iron ore attracts iron ore.
Chap. 10. Iron ore has poles, and acquires them, and settles itself toward the
poles of the universe.
Chap. 11. Wrought iron, not excited by a loadstone, draws iron.
Chap. 12. A long piece of Iron (even though not excited by a loadstone)
settles itself toward North & South.
Chap. 13. Wrought iron has in itself certain parts Boreal & Austral: a
magnetick vigour, verticity, and determinate vertices or poles.
Chap. 14. Concerning other powers of loadstone, & its medicinal
properties.
Chap. 15. The medicinal virtue of iron.
Chap. 16. That loadstone & iron ore are the same, but iron an extract from
both, as other metals are from their own ores; & that all magnetick virtues,
though weaker, exist in the ore itself & in smelted iron.
Chap. 17. That the globe of the earth is magnetick, & a magnet; & how in
our hands the magnet stone has all the primary forces of the earth, while the
earth by the same powers remains constant in a fixed direction in the
universe.

Book 2.

Chap. 1. On Magnetick Motions.
Chap. 2. On the Magnetick Coition, and first on the attraction of Amber, or
more truly, on the attaching of bodies to Amber.
Chap. 3. Opinions of others on Magnetick Coition, which they call
Attraction.
Chap. 4. On Magnetick Force & Form, what it is; and on the cause of the
Coition.
Chap. 5. How the Power dwells in the Loadstone.
Chap. 6. How magnetick pieces of Iron and smaller loadstones conform
themselves to a terrella & to the earth itself, and by them are disposed.
Chap. 7. On the Potency of the Magnetick Virtue, and on its nature capable
of spreading out into an orbe.
Chap. 8. On the geography of the Earth, and of the Terrella.
Chap. 9. On the Æquinoctial Circle of the Earth and of a Terrella.
Chap. 10. Magnetick Meridians of the Earth.
Chap. 11. Parallels.
Chap. 12. The Magnetick Horizon.
Chap. 13. On the Axis and Magnetick Poles.
Chap. 14. Why at the Pole itself the Coition is stronger than in the other
parts intermediate between the æquator and the pole; and on the proportion
of forces of the coition in various parts of the earth and of the terrella.
Chap. 15. The Magnetick Virtue which is conceived in Iron is more
apparent in an iron rod than in a piece of Iron that is round, square, or of
other figure.
Chap. 16. Showing that Movements take place by the Magnetical Vigour
though solid bodies lie between; and on the interposition of iron plates.

Chap. 17. 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.
Chap. 18. An armed Loadstone does not indue an excited piece of Iron with
greater vigour than an unarmed.
Chap. 19. Union with an armed Loadstone is stronger; hence greater
weights are raised; but the coition is not stronger, but generally weaker.
Chap. 20. An armed Loadstone raises an armed Loadstone, which also
attracts a third; which likewise happens, though the virtue in the first be
somewhat small.
Chap. 21. If Paper or any other Medium be interposed, an armed loadstone
raises no more than an unarmed one.
Chap. 22. That an armed Loadstone draws Iron no more than an unarmed
one: and that an armed one is more strongly united to iron is shown by
means of an armed loadstone and a polished Cylinder of iron.
Chap. 23. The Magnetick Force causes motion toward unity, and binds
firmly together bodies which are united.
Chap. 24. A piece of Iron placed within the Orbe of a Loadstone hangs
suspended in the air, if on account of some impediment it cannot approach
it.
Chap. 25. Exaltation of the power of the magnet.
Chap. 26. Why there should appear to be a greater love between iron &
loadstone, than between loadstone & loadstone, or between iron & iron,
when close to the loadstone, within its orbe of virtue.
Chap. 27. The Centre of the Magnetick Virtues in the earth is the centre of
the earth; and in a terrella is the centre of the stone.
Chap. 28. A Loadstone attracts magneticks not only to a fixed point or pole,
but to every part of a terrella save the æquinoctial zone.
Chap. 29. On Variety of Strength due to Quantity or Mass.

Chap. 30. The Shape and Mass of the Iron are of most importance in cases
of coition.
Chap. 31. On long and round stones.
Chap. 32. Certain Problems and Magnetick Experiments about the Coition,
and Separation, and regular Motion of Bodies magnetical.
Chap. 33. On the Varying Ratio of Strength, and of the Motion of coition,
within the orbe of virtue.
Chap. 34. Why a Loadstone should be stronger in its poles in a different
ratio; as well in the Northern regions as in the Southern.
Chap. 35. On a Perpetual Motion Machine, mentioned by authors, by means
of the attraction of a loadstone.
Chap. 36. How a more robust Loadstone may be recognized.
Chap. 37. Use of a Loadstone as it affects iron.
Chap. 38. On Cases of Attraction in other Bodies.
Chap. 39. On Bodies which mutually repel one another.

Book 3.
Chap. 1. On Direction.
Chap. 2. The Directive or Versorial Virtue (which we call verticity): what it
is, how it exists in the loadstone; and in what way it is acquired when
innate.
Chap. 3. How Iron acquires Verticity through a loadstone, and how that
verticity is lost and changed.
Chap. 4. Why Iron touched by a Loadstone acquires an opposite verticity,
and why iron touched by the true Northern side of a stone turns to the North
of the earth, by the true Southern side to the South; and does not turn to the
South when rubbed by the Northern point of the stone, and when by the
Southern to the North, as all who have written on the Loadstone have
falsely supposed.

Chap. 5. On the Touching of pieces of Iron of divers shapes.
Chap. 6. What seems an Opposing Motion in Magneticks is a proper motion
toward unity.
Chap. 7. A determined Verticity and a disponent Faculty are what arrange
magneticks, not a force, attracting them or pulling them together, nor
merely a strongish coition or unition.
Chap. 8. Of Discords between pieces of Iron upon the same pole of a
Loadstone, and how they can agree and stand joined together.
Chap. 9. Figures illustrating direction and showing varieties of rotations.
Chap. 10. On Mutation of Verticity and of Magnetick Properties, or on
alteration in the power excited by a loadstone.
Chap. 11. On the Rubbing of a piece of Iron on a Loadstone in places
midway between the poles, and upon the æquinoctial of a terrella.
Chap. 12. In what way Verticity exists in any Iron that has been smelted
though not excited by a loadstone.
Chap. 13. 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.
Chap. 14. The Placing of a Loadstone above or below a magnetick body
suspended in æquilibrio changes neither the power nor the verticity of the
magnetick body.
Chap. 15. The Poles, Æquator, Centre in an entire Loadstone remain and
continue steady; by diminution and separation of some part they vary and
acquire other positions.
Chap. 16. If the Southern Portion of a Stone be lessened, something is also
taken away from the power of the Northern Portion.
Chap. 17. On the Use and Excellence of Versoria: and how iron versoria
used as pointers in sun-dials, and the fine needles of the mariners' compass,
are to be rubbed, that they may acquire stronger verticity.

Book 4.
Chap. 1. On Variation.
Chap. 2. That the variation is caused by the inæquality of the projecting
parts of the earth.
Chap. 3. The variation in any one place is constant.
Chap. 4. The arc of variation is not changed equally in proportion to the
distance of places.
Chap. 5. An island in Ocean does not change the variation, as neither do
mines of loadstone.
Chap. 6. The variation and direction arise from the disponent power of the
earth, and from the natural magnetick tendency to rotation, not from
attraction, or from coition, or from other occult cause.
Chap. 7. Why the variation from that lateral cause is not greater than has
hitherto been observed, having been rarely seen to reach two points of the
mariners' compass, except near the pole.
Chap. 8. On the construction of the common mariners' compass, and on the
diversity of the compasses of different nations.
Chap. 9. Whether the terrestrial longitude can be found from the variation.
Chap. 10. Why in various places near the pole the variations are much more
ample than in a lower latitude.
Chap. 11. Cardan's error when he seeks the distance of the centre of the
earth from the centre of the cosmos by the motion of the stone of Hercules;
in his book 5, On Proportions.
Chap. 12. On the finding of the amount of variation: how great is the arc of
the Horizon from its arctick to its antarctick intersection of the meridian, to
the point respective of the magnetick needle.
Chap. 13. The observations of variation by seamen vary, for the most part,
and are uncertain: partly from error and inexperience, and the imperfections

of the instruments: and partly from the sea being seldom so calm that the
shadows or lights can remain quite steady on the instruments.
Chap. 14. On the variation under the æquinoctial line, and near it.
Chap. 15. The variation of the magnetick needle in the great Æthiopick and
American sea, beyond the æquator.
Chap. 16. On the variation in Nova Zembla.
Chap. 17. Variation in the Pacifick Ocean.
Chap. 18. On the variation in the Mediterranean Sea.
Chap. 19. The variation in the interior of large Continents.
Chap. 20. Variation in the Eastern Ocean.
Chap. 21. How the deviation of the versorium is augmented and diminished
by reason of the distance of places.

Book 5.
Chap. 1. On Declination.
Chap. 2. Diagram of declinations of the magnetick needle, when excited, in
the various positions of the sphere, and horizons of the earth, in which there
is no variation of the declination.
Chap. 3. An indicatory instrument, showing by the virtue of a stone the
degrees of declination from the horizon of each several latitude.
Chap. 4. Concerning the length of a versorium convenient for declination
on a terrella.
Chap. 5. That declination does not arise from the attraction of the loadstone,
but from a disposing and rotating influence.
Chap. 6. On the proportion of declination to latitude, and the cause of it.
Chap. 7. Explanation of the diagram of the rotation of a magnetick needle.

Chap. 8. Diagram of the rotation of a magnetick needle, indicating
magnetical declination in all latitudes, and from the rotation and
declination, the latitude itself.
Chap. 9. Demonstration of direction, or of variation from the true direction,
at the same time with declination, by means of only a single motion in
water, due to the disposing and rotating virtue.
Chap. 10. On the variation of the declination.
Chap. 11. On the essential magnetick activity sphærically effused.
Chap. 12. Magnetick force is animate, or imitates life; and in many things
surpasses human life, while this is bound up in the organick body.

Book 6.
Chap. 1. On the globe of the earth, the great magnet.
Chap. 2. The Magnetick axis of the Earth persists invariable.
Chap. 3. On the magnetick diurnal revolution of the Earth's globe, as a
probable assertion against the time-honoured opinion of a Primum Mobile.
Chap. 4. That the Earth moves circularly.
Chap. 5. Arguments of those denying the Earth's motion, and their
confutation.
Chap. 6. On the cause of the definite time of an entire rotation of the Earth.
Chap. 7. On the primary magnetick nature of the Earth, whereby its poles
are parted from the poles of the Ecliptick.
Chap. 8. On the Præcession of the Æquinoxes, from the magnetick motion
of the poles of the Earth, in the Arctick & Antarctick circle of the Zodiack.
Chap. 9. On the anomaly of the Præcession of the Æquinoxes, & of the
obliquity of the Zodiack.

WILLIAM GILBERT
ON THE LOADSTONE, BK. I.

CHAP. I.

ANCIENT AND MODERN WRITINGS
on the Loadstone, with certain matters of mention only,
various opinions, & vanities.

t an early period, while philosophy lay as yet rude and
uncultivated in the mists of error and ignorance, few were the
virtues and properties of things that were known and clearly
perceived: there was a bristling forest of plants and herbs, things
metallick were hidden, and the knowledge of stones was unheeded. But no
sooner had the talents and toils of many brought to light certain
commodities necessary for the use and safety of men, and handed them on
to others (while at the same time reason and experience had added a larger
hope), than a thorough examination began to be made of forests and fields,
hills and heights; of seas too, and the depths of the waters, of the bowels of
the earth's body; and all things began to be looked into. And at length by
good luck the magnet-stone was discovered in iron lodes, probably by
smelters of iron or diggers of metals. This, on being handled by metal folk,
quickly displayed that powerful and strong attraction for iron, a virtue not
latent and obscure, but easily proved by all, and highly praised and
commended. And in after time when it had emerged, as it were out of
darkness and deep dungeons, and had become dignified of men on account
of its strong and amazing attraction for iron, many philosophers as well as
physicians of ancient days discoursed of it, in short celebrated, as it were,
its memory only; as for instance Plato in the Io[2], Aristotle in the De
Anima[3], in Book I. only, Theophrastus the Lesbian, Dioscorides, C. Plinius
Secundus, and Julius Solinus[4]. As handed down by them the loadstone
merely attracted iron, the rest of its virtues were all undiscovered. But that

the story of the loadstone might not appear too bare and too brief, to this
singular and sole known quality there were added certain figments and
falsehoods, which in the earliest times, no less than nowadays, used to be
put forth by raw smatterers and copyists to be swallowed of men. As for
instance, that if a loadstone be anointed with garlick, or if a diamond be
near, it does not attract iron[5]. Tales of this sort occur in Pliny, and in
Ptolemy's Quadripartitum; and the errors have been sedulously propagated,
and have gained ground (like ill weeds that grow apace) coming down even
to our own day, through the writings of a host of men, who, to fill put their
volumes to a proper bulk, write and copy out pages upon pages on this, that,
and the other subject, of which they knew almost nothing for certain of their
own experience. Such fables of the loadstone even Georgius Agricola
himself, most distinguished in letters, relying on the writings of others, has
embodied as actual history in his books De Natura Fossilium. Galen noted
its medicinal power in the ninth book of his De Simplicium
Medicamentorum Facultatibus, and its natural property of attracting iron in
the first book of De Naturalibus Facultatibus; but he failed to recognize the
cause, as Dioscorides before him, nor made further inquiry. But his
commentator Matthiolus repeats the story of the garlick and the diamond,
and moreover introduces Mahomet's shrine vaulted with loadstones[6], and
writes that, by the exhibition of this (with the iron coffin hanging in the air)
as a divine miracle, the public were imposed upon. But this is known by
travellers to be false. Yet Pliny relates that Chinocrates the architect had
commenced to roof over the temple of Arsinoe at Alexandria with magnet-
stone[7], that her statue of iron placed therein might appear to hang in space.
His own death, however, intervened, and also that of Ptolemy, who had
ordered it to be made in honour of his sister. Very little was written by the
ancients as to the causes of attraction of iron; by Lucretius and others there
are some short notices; others only make slight and meagre mention of the
attraction of iron: all of these are censured by Cardan for being so careless
and negligent in a matter of such importance and in so wide a field of
philosophizing; and for not supplying an ampler notion of it and a more
perfect philosophy: and yet, beyond certain received opinions and ideas
borrowed from others and ill-founded conjectures, he has not himself any
more than they delivered to posterity in all his bulky works any contribution
to the subject worthy of a philosopher. Of modern writers some set forth its
virtue in medicine only, as [8]Antonius Musa Brasavolus, Baptista

Montanus, Amatus Lusitanus, as before them Oribasius in his thirteenth
chapter De Facultate Metallicorum, Aetius Amidenus, Avicenna, Serapio
Mauritanus, Hali Abbas, Santes de Ardoynis, Petrus Apponensis,
Marcellus[9], Arnaldus. Bare mention is made of certain points relating to
the loadstone in very few words by Marbodeus Callus, Albertus, Matthæus
Silvaticus, Hermolaus Barbarus, Camillus Leonhardus, Cornelius Agrippa,
Fallopius, Johannes Langius, Cardinal Cusan, Hannibal Rosetius Calaber;
by all of whom the subject is treated very negligently, while they merely
repeat other people's fictions and ravings. Matthiolus compares the alluring
powers of the loadstone which pass through iron materials, with the
mischief of the torpedo, whose venom passes through bodies and spreads
imperceptibly; Guilielmus Pateanus in his Ratio Purgantium
Medicamentorum discusses the loadstone briefly and learnedly. Thomas
Erastus[10], knowing little of magnetical nature, finds in the loadstone weak
arguments against Paracelsus; Georgius Agricola, like Encelius[11] and other
metallurgists, merely states the facts; Alexander Aphrodiseus in his
Problemata considers the question of the loadstone inexplicable; Lucretius
Carus, the poet of the Epicurean school, considers that an attraction is
brought about in this way: that as from all things there is an efflux of very
minute bodies, so from the iron atoms flow into the space emptied by the
elements of the loadstone, between the iron and the loadstone, and that as
soon as they have begun to stream towards the loadstone, the iron follows,
its corpuscles being entangled. To much the same effect Johannes Costæus
adduces a passage from Plutarch; Thomas Aquinas[12], writing briefly on
the loadstone in Chapter VII. of his Physica, touches not amiss on its
nature, and with his divine and clear intellect would have published much
more, had he been conversant with magnetick experiments. Plato thinks the
virtue divine. But when three or four hundred years afterwards, the
magnetick movement to North and South was discovered or again
recognized by men, many learned men attempted, each according to the
bent of his own mind, either by wonder and praise, or by some sort of
reasonings, to throw light upon a virtue so notable, and so needful for the
use of mankind. Of more modern authors a great number have striven to
show what is the cause of this direction and movement to North and South,
and to understand this great miracle of nature, and to disclose it to others:
but they have lost both their oil and their pains; for, not being practised in
the subjects of nature, and being misled by certain false physical systems,

they adopted as theirs, from books only, without magnetical experiments,
certain inferences based on vain opinions, and many things that are not,
dreaming old wives' tales. Marsilius Ficinus ruminates over the ancient
opinions, and in order to show the reason of the direction seeks the cause in
the heavenly constellation of the Bear, supposing the virtue of the Bear to
prevail in the stone and to be transferred to the iron. Paracelsus asserted that
there are stars, endowed with the power of the loadstone, which attract to
themselves iron. Levinus Lemnius describes and praises the compass[13],
and infers its antiquity on certain grounds; he does not divulge the hidden
miracle which he propounds. In the kingdom of Naples the Amalfians were
the first (so it is said) to construct the mariners' compass: and as Flavius
Blondus says the Amalfians[14] boast, not without reason, that they were
taught by a certain citizen, Johannes Goia, in the year thirteen hundred after
the birth of Christ. That town is situated in the kingdom of Naples not far
from Salerno, near the promontory of Minerva; and Charles V. bestowed
that principality on Andrea Doria, that great Admiral, on account of his
signal naval services. Indeed it is plain that no invention of man's device
has ever done more for mankind than the compass: some notwithstanding
consider that it was discovered by others previously and used in navigation,
judging from ancient writings and certain arguments and conjectures. The
knowledge of the little mariners' compass seems to have been brought into
Italy by Paolo, the Venetian[15], who learned the art of the compass in the
Chinas about the year MCCLX.; yet I do not wish the Amalfians to be
deprived of an honour so great as that of having first made the construction
common in the Mediterranean Sea. Goropius[16] attributes the discovery to
the Cimbri or Teutons, forsooth because the names of the thirty-two winds
inscribed on the compass are pronounced in the German tongue by all ship-
masters, whether they be French, British, or Spaniards; but the Italians
describe them in their own vernacular. Some think that Solomon, king of
Judæa, was acquaint with the use of the mariners' compass, and made it
known to his ship-masters in the long voyages when they brought back such
a power of gold from the West Indies: whence also, from the Hebrew word
Parvaim[17], Arias Montanus maintains that the gold-abounding regions of
Peru are named But it is more likely to have come from the coast of lower
Æthiopia, from the region of Cephala, as others relate. Yet that account
seems to be less true, inasmuch as the Phœnicians, on the frontier of Judæa,

who were most skilled in navigation in former ages (a people whose talents,
work, and counsel Solomon made use of in constructing ships and in the
actual expeditions, as well as in other operations), were ignorant of
magnetick aid, the art of the mariners' compass: For had it been in use
amongst them, without doubt the Greeks and also Italians and all barbarians
would have understood a thing so necessary and made famous by common
use; nor could matters of much repute, very easily known, and so highly
requisite ever have perished in oblivion; but either the learning would have
been handed down to posterity, or some memorial of it would be extant in
writing. Sebastian Cabot was the first to discover that the magnetick iron
varied[18]. Gonzalus Oviedus[19] is the first to write, as he does in the
Historia, that in the south of the Azores it does not vary. Fernelius in his
book De Abditis Rerum Causis says that in the loadstone there is a hidden
and abstruse cause, elsewhere calling it celestial; and he brings forth
nothing but the unknown by means of what is still more unknown. For
clumsy, and meagre, and pointless is his inquiry into hidden causes. The
ingenious Fracastorio, a distinguished philosopher, in seeking the reason for
the direction of the loadstone, feigns Hyperborean magnetick mountains
attracting magnetical things of iron: this view, which has found acceptance
in part by others, is followed by many authors and finds a place not in their
writings only, but in geographical tables, marine charts, and maps of the
globe: dreaming, as they do, of magnetick poles and huge rocks, different
from the poles of the earth. More than two hundred years earlier than
Fracastorio there exists a little work, fairly learned for the time, going under
the name of one Peter Peregrinus[20], which some consider to have
originated from the views of Roger Bacon, the Englishman of Oxford: In
which book causes for magnetick direction are sought from the poles of the
heaven and from the heaven itself. From this Peter Peregrinus, Johannes
Taisnier of Hainault[21] extracted materials for a little book, and published it
as new. Cardan talks much of the rising of the star in the tail of the Greater
Bear, and has attributed to its rising the cause of the variation: supposing
that the variation is always the same, from the rising of the star. But the
difference of the variation according to the change of position, and the
changes which occur in many places, and are even irregular in southern
regions, preclude the influence of one particular star at its northern rising.
The College of Coimbra[22] seeks the cause in some part of the heaven near
the pole: Scaliger in section CXXXI. of his Exercitationes on Cardan

suggests a heavenly cause unknown to himself, and terrestrial loadstones
nowhere yet discovered. A cause not due to those sideritic mountains named
above, but to that power which fashioned them, namely that portion of the
heaven which overhangs that northern point. This view is garnished with a
wealth of words by that erudite man, and crowned with many marginal
subtilities; but with reasonings not so subtile. Martin Cortes[23] considers
that there is a place of attraction beyond the poles, which he judges to be
the moving heavens. One Bessardus[24], a Frenchman, with no less folly
notes the pole of the zodiack. Jacobus Severtius[25], of Paris, while quoting
a few points, fashions new errors as to loadstones of different parts of the
earth being different in direction: and also as to there being eastern and
western parts of the loadstone. Robert Norman[26], an Englishman, fixes a
point and region respective, not attractive; to which the magnetical iron is
collimated, but is not itself attracted. Franciscus Maurolycus[27] treats of a
few problems on the loadstone, taking the trite views of others, and avers
that the variation is due to a certain magnetical island mentioned by Olaus
Magnus[28]. Josephus Acosta[29], though quite ignorant about the loadstone,
nevertheless pours forth vapid talk upon the loadstone. Livio Sanuto[30] in
his Italian Geographia, discusses at length the question whether the prime
magnetick meridian and the magnetick poles are in the heavens or in the
earth; also about an instrument for finding the longitude: but through not
understanding magnetical nature, he raises nothing but errors and mists in
that so important notion. Fortunius Affaytatus[31] philosophizes foolishly
enough on the attraction of iron, and its turning to the poles. Most recently,
Baptista Porta[32], no ordinary philosopher, in his Magia Naturalis, has
made the seventh book a custodian and distributor of the marvels of the
loadstone; but little did he know or ever see of magnetick motions; and
some things that he noted of the powers which it manifested, either learned
by him from the Reverend Maestro Paolo, the Venetian[33], or evolved from
his own vigils, were not so well discovered or observed; but abound in
utterly false experiments, as will be clear in due place: still I deem him
worthy of high praise for having attempted so great a subject (as he has
done with sufficient success and no mean result in many other instances),
and for having given occasion for further research. All these philosophizers
of a previous age, philosophizing about attraction from a few vague and
untrustworthy experiments, drawing their arguments from the hidden causes

of things; and then, seeking for the causes of magnetick directions in a
quarter of the heavens, in the poles, the stars, constellations, or in
mountains, or rocks, space, atoms, attractive or respective points beyond the
heavens, and other such unproven paradoxes, are whole horizons wrong,
and wander about blindly. And as yet we have not set ourselves to
overthrow by argument those errors and impotent reasonings of theirs, nor
many other fables told about the loadstone, nor the superstitions of
impostors and fabulists: for instance, Franciscus Rueus'[34] doubt whether
the loadstone were not an imposture of evil spirits: or that, placed
underneath the head of an unconscious woman while asleep, it drives her
away from the bed if an adulteress: or that the loadstone is of use to thieves
by its fume and sheen, being a stone born, as it were, to aid theft: or that it
opens bars and locks, as Serapio[35] crazily writes: or that iron held up by a
loadstone, when placed in the scales, added nothing to the weight of the
loadstone, as though the gravity of the iron were absorbed by the force of
the stone: or that, as Serapio and the Moors relate, in India there exist
certain rocks of the sea abounding in loadstone, which draw out all the nails
of the ships which are driven toward them, and so stop their sailing; which
fable Olaus Magnus[36] does not omit, saying that there are mountains in the
north of such great powers of attraction, that ships are built with wooden
pegs, lest the iron nails should be drawn from the timber as they passed by
amongst the magnetick crags. Nor this: that a white loadstone may be
procured as a love potion: or as Hali Abbas[37] thoughtlessly reports, that if
held in the hand it will cure gout and spasms: Or that it makes one
acceptable and in favour with princes, or eloquent, as Pictorio[38] has sung;
Or as Albertus Magnus[39] teaches, that there are two kinds of loadstones,
one which points to the North, the other to the South: Or that iron is
directed toward the Northern stars by an influence imparted by the polar
stars, even as plants follow the sun, as Heliotrope does: Or that there is a
magnet-stone situated under the tail of the Greater Bear, as Lucas Gauricus
the Astrologer stated: He would even assign the loadstone, like the
Sardonyx and onyx, to the planet Saturn, yet at the same time he assigns it
with the adamant, Jasper, and Ruby, to Mars; so that it is ruled by two
planets. The loadstone moreover is said by him to pertain to the sign Virgo;
and he covers many such shameful pieces of folly with a veil of
mathematical erudition. Such as that an image of a bear is engraved on a

loadstone when the Moon faces towards the north, so that when hung by an
iron wire it may conciliate the influence of the celestial Bear, as Gaudentius
Merula[40] relates: Or that the loadstone drew iron and directed it to the
north, because it is superior in rank to iron, at the Bear, as Ficinus writes,
and Merula repeats: Or that by day it has a certain power of attracting iron,
but by night the power is feeble, or rather null: Or that when weak and
dulled the virtue is renewed by goats' blood, as Ruellius[41] writes: Or that
Goats' blood sets a loadstone free from the venom of a diamond, so that the
lost power is revived when bathed in goats' blood by reason of the discord
between that blood and the diamond: Or that it removed sorcery from
women, and put to flight demons, as Arnaldus de Villanova dreams: Or that
it has the power to reconcile husbands to their wives, or to recall brides to
their husbands, as Marbodeus Gallus[42], chorus-leader of vanities, teaches:
Or that in a loadstone pickled in the salt of a sucking fish[43] there is power
to pick up gold which has fallen into the deepest wells, according to the
narratives of Cælius Calcagninus. With such idle tales and trumpery do
plebeian philosophers delight themselves and satiate readers greedy for
hidden things, and unlearned devourers of absurdities: But after the
magnetick nature shall have been disclosed by the discourse that is to
follow, and perfected by our labours and experiments, then will the hidden
and abstruse causes of so great an effect stand out, sure, proven, displayed
and demonstrated; and at the same time all darkness will disappear, and all
error will be torn up by the roots and will lie unheeded; and the foundations
of a grand magnetick philosophy which have been laid will appear anew, so
that high intellects may be no further mocked by idle opinions. Some
learned men there are who in the course of long voyages have observed the
differences of magnetick variation: the most scholarly Thomas Hariot[44],
Robert Hues, Edward Wright, Abraham Kendall, all Englishmen; Others
there are who have invented and produced magnetical instruments, and
ready methods of observation, indispensable for sailors and to those
travelling afar: as William Borough[45] in his little book on the Variation of
the Compass or Magneticall Needle, William Barlowe[46] in his Supply,
Robert Norman in his Newe Attractive. And this is that Robert Norman[47]
(a skilful seaman and ingenious artificer) who first discovered the
declination of the magnetick needle. Many others I omit wittingly; modern
Frenchmen, Germans, and Spaniards, who in books written for the most

part in their native tongues either misuse the placets of others, and send
them forth furbished with new titles and phrases as tricky traders do old
wares with meretricious ornaments; or offer something not worthy of
mention even: and these lay hands on some work filched from other authors
and solicit some one as their patron, or go hunting after renown for
themselves among the inexperienced and the young; who in all branches of
learning are seen to hand on errors and occasionally add something false of
their own.

CHAP. II.

Magnet Stone, of what kind it is, and its
discovery.

oadstone, the stone which is commonly called the Magnet, derives
its name either from the discoverer (though he was not Pliny's
fabulous herdsman[48], quoted from Nicander, the nails of whose
shoes and the tip of whose staff stuck fast in a magnetick field
while he pastured his flocks), or from the region of Magnesia in Macedonia,
rich in loadstones: Or else from the city Magnesia in Ionia in Afia Minor,
near the river Mæander. Hence Lucretius says,

The Magnet's name the observing Grecians drew
From the Magnetick region where it grew.

It is called Heraclean from the city Heraclea, or from the invincible
Hercules, on account of the great strength and domination and power which
there is in iron of subduing all things: it is also called siderite, as being of
iron; being not unknown to the most ancient writers, to the Greeks,
Hippocrates, and others, as also (I believe) to Jewish and Egyptian writers;
For in the oldest mines of iron, the most famous in Asia, the loadstone was
often dug out with its uterine brother, iron. And if the tales be true which are
told of the people of the Chinas, they were not unacquainted in primitive
times with magnetical experiments, for even amongst them the finest

magnets of all are still found. The Egyptians, as Manetho relates, gave it the
name Os Ori: calling the power which governs the turning of the sun Orus,
as the Greeks call it Apollo. But later by Euripides, as narrated by Plato, it
was designated under the name of Magnet. By Plato in the Io, Nicander of
Colophon, Theophrastus, Dioscorides, Pliny, Solinus, Ptolemy, Galen, and
other investigators of nature it was recognized and commended; such,
however, is the variety of magnets and their points of unlikeness in
hardness, softness, heaviness, lightness, density, firmness, and friability of
substance: so great and manifold are the differences in colour and other
qualities, that they have not handed down any adequate account of it, which
therefore was laid aside or left imperfect by reason of the unfavourable
character of the time; for in those times varieties of specimens and foreign
products never before seen were not brought from such distant regions by
traders and mariners as they have been lately, and now that all over the
globe all kinds of merchandise, stones, woods, spices, herbs, metals, and
ore in abundance are greedily sought after: neither was metallurgy so
generally cultivated in a former age. There is a difference in vigour; as
whether it is male or female: for it was thus that the ancients used often to
distinguish many individuals of the same species. Pliny quotes from
Sotacus five kinds; those from Æthiopia, Macedonia, Bœotia, the Troad,
and Asia, which were especially known to the ancients: but we have posited
as many kinds of loadstones as there are in the whole of nature regions of
different kinds of soil. For in all climates, in every province, on every soil,
the loadstone is either found, or else lies unknown on account of its rather
deep site and inaccesible position; or by reason of its weaker and less
obvious strength it is not recognized by us while we see and handle it. To
the ancients the differences were those of colour[49], how they are red and
black in Magnesia and Macedonia, in Bœotia red rather than black, in the
Troad black, without strength: While in Magnesia in Asia they are white,
not attracting iron, and resemble pumice-stone. A strong loadstone of the
kind celebrated so often nowadays in experiments presents the appearance
of unpolished iron, and is mostly found in iron mines: it is even wont to be
discovered in an unbroken lode by itself: Loadstones of this sort are brought
from East India, China, and Bengal, of the colour of iron, or of a dark blood
or liver colour; and these are the finest, and are sometimes of great size, as
though broken off a great rock, and of considerable weight; sometimes
single stones, as it were, and entire: some of these, though of only one

pound weight, can lift on high four ounces of iron or a half-pound or even a
whole pound. Red ones are found in Arabia, as broad as a tile, not equal in
weight to those brought from China, but strong and good: they are a little
darker in the island of Elba in the Tuscan sea, and together with these also
grow white ones, like some in Spain in the mines of Caravaca: but these are
of lesser power. Black ones also are found, of lower strength, such as those
of the iron mines in Norway and in sea-coast places near the strait of
Denmark. Amongst the blue-black or dusky blue also some are strong and
highly commended. Other loadstones are of a leaden colour, fissile and not-
fissile, capable of being split like slates in layers. I have also some like gray
marble of an ashen colour, and some speckled like gray marble, and these
take the finest polish. In Germany there are some perforated like
honeycombs, lighter than any others, and yet strong. Those are metallick
which smelt into the best iron; others are not easily smelted, but are burned
up. There are loadstones that are very heavy, as also others very light; some
are very powerful in catching up pieces of iron, while others are weaker and
of less capacity, others so feeble and barren that they with difficulty attract
ever so tiny a piece of iron and cannot repel an opposite magnetick. Others
are firm and tough, and do not readily yield to the artificer. Others are
friable. Again, there are some dense and hard as emery, or loose-textured
and soft as pumice; porous or solid; entire and uniform, or varied and
corroded; now like iron for hardness, yea, sometimes harder than iron to cut
or to file; others are as soft as clay. Not all magnets can be properly called
stones; some rather represent rocks; while others exist rather as metallick
lodes; others as clods and lumps of earth. Thus varied and unlike each other,
they are all endowed, some more, some less, with the peculiar virtue. For
they vary according to the nature of the soil, the different admixture of
clods and humours, having respect to the nature of the region and to their
subsidence in this last-formed crust of the earth, resulting from the
confluence of many causes, and the perpetual alternations of growth and
decline, and the mutations of bodies. Nor is this stone of such potency rare;
and there is no region wherein it is not to be found in some sort. But if men
were to search for it more diligently and at greater outlay, or were able,
where difficulties are present, to mine it, it would come to hand
everywhere, as we shall hereafter prove. In many countries have been found
and opened mines of efficacious loadstones unknown to the ancient writers,
as for instance in Germany, where none of them has ever asserted that

loadstones were mined. Yet since the time when, within the memory of our
fathers, metallurgy began to flourish there, loadstones strong and
efficacious in power have been dug out in numerous places; as in the Black
Forest beyond Helceburg; in Mount Misena not far from
Schwartzenberg[50]; a fairly strong kind between Schneeberg and Annaberg
in Joachimsthal, as was noticed by Cordus: also near the village of Pela in
Franconia. In Bohemia it occurs in iron mines in the Lessa district and other
places, as Georgious Agricola and several other men learned in metallurgy
witness. In like manner in other countries in our time it is brought to light;
for as the stone remarkable for its virtues is now famous throughout the
whole world, so also everywhere every land produces it, and it is, so to
speak, indigenous in all lands. In East India, in China, in Bengal near the
river Indus it is common, and in certain maritime rocks: in Persia, Arabia,
and the islands of the Red Sea; in many places in Æthiopia, as was formerly
Zimiri, of which Pliny makes mention. In Asia Minor around Alexandria
and the Troad; in Macedonia, Bœotia, in Italy, the island of Elba, Barbary;
in Spain still in many mines as aforetime. In England quite lately a huge
power of it was discovered in a mine belonging to Adrian Gilbert,
gentleman[51]; also in Devonshire and the Forest of Dean; in Ireland, too,
Norway, Denmark, Sweden, Lapland, Livonia, Prussia, Poland, Hungary.
For although the terrestrial globe, owing to the varied humours and natures
of the soil arising from the continual succession of growth and decay, is in
the lapse of time efflorescing through all its ambit deeper into its surface,
and is girt about with a varied and perishable covering, as it were with a
veil; yet out of her womb ariseth in many places an offspring nigher to the
more perfect body and makes its way to the light of day. But the weak and
less vigorous loadstones, enfeebled by the flow of humours, are visible in
every region, in every strath. It is easy to discover a vast quantity of them
everywhere without penetrating mountains or great depths, or encountering
the difficulties and hardships of miners; as we shall prove in the sequel. And
these we shall take pains so to prepare by an easy operation that their
languid and dormant virtue shall be made manifest. It is called by the
Greeks[52] ἑράκλιος, as by Theophrastus, and μαγνῆτις; and μάγνης, as by
Euripides, as quoted by Plato in the Io: by Orpheus[53] too μαγνῆοσα, and
σιδερίτης as though of iron: by the Latins magnes, Herculeus; by the
French aimant[54], corruptly from adamant; by the Spaniards piedramant:

by the Italians calamita[55]; by the English loadstone and adamant
stone[56], by the Germans magness[57] and siegelstein: Among English,
French, and Spaniards it has its common name from adamant; perhaps
because they were at one time misled by the name sideritis being common
to both: the magnet is called σιδερίτης from its virtue of attracting iron: the
adamant is called σιδερίτης from the brilliancy of polished iron. Aristotle
designates it merely by the name of the stone:[58] Ἔοικε δὲ καὶ θαλῆς ἐξ
ὧν ἀπομνημονεύουσι, κινητικόν τι τὴν ψυχὴν ὑπολαβεῖν, ἔιπερ τὸν
λίθον ἔφη ψυχὴν ἔχειν, ὅτι τὸν σίδηρον κινεῖ: De Anima, Lib. I. The
name of magnet is also applied to another stone differing from siderite,
having the appearance of silver; it is like Amianth in its nature; and since it
consists of laminæ (like specular stone)[59], it differs in form: in German
Katzensilber and Talke[60].

CHAP. III.

The Loadstone has parts distinct in their natural
power, & poles conspicuous for their property.

he stone itself manifests many qualities which, though known
afore this, yet, not having been well investigated, are to be briefly
indicated in the first place so that students may understand the
powers of loadstone and iron, and not be troubled at the outset
through ignorance of reasonings and proofs. In the heaven astronomers
assign a pair of poles for each moving sphere: so also do we find in the
terrestrial globe natural poles preeminent in virtue, being the points that
remain constant in their position in respect to the diurnal rotation, one
tending to the Bears and the seven stars; the other to the opposite quarter of
the heaven. In like manner the loadstone has its poles, by nature northern
and southern, being definite and determined points set in the stone, the
primary boundaries of motions and effects, the limits and governors of the
many actions and virtues. However, it must be understood that the strength
of the stone does not emanate from a mathematical point, but from the parts
themselves, and that while all those parts in the whole belong to the whole,

the nearer they are to the poles of the stone the stronger are the forces they
acquire and shed into other bodies: these poles are observant of the earth's
poles, move toward them, and wait upon them. Magnetick poles can be
found in every magnet, in the powerful and mighty (which Antiquity used
to call the masculine) as well as in the weak, feeble and feminine; whether
its figure is due to art or to chance, whether long, flat, square, three-
cornered, polished; whether rough, broken, or unpolished; always the
loadstone
* contains and shows its poles. But since the spherical form, which
is also the most perfect, agrees best with the earth, being a globe, and is
most suitable for use and experiment, we accordingly wish our principal
demonstrations by the stone to be made with a globe-shaped magnet as
being more perfect and adapted for the purpose. Take, then, a powerful
loadstone, solid, of a just size, uniform, hard, without flaw[61]; make of it a
globe upon the turning tool used for rounding crystals and some other
stones, or with other tools as the material and firmness of the stone requires,
for sometimes it is difficult to be worked. The stone thus perpared is a true,
homogeneous offspring of the earth and of the same shape with it:
artificially possessed of the orbicular form which nature granted from the
beginning to the common mother earth: and it is a physical corpuscle
imbued with many virtues, by means of which many abstruse and neglected
truths in philosophy buried in piteous darkness may more readily become
known to men. This round stone is called by us a μικρόγη or Terrella[62].
To find, then, the poles conformable to the earth's, take the round stone in
hand, and place upon the stone a needle or wire of iron: the ends of the iron
move upon their own centre and suddenly stand still. Mark the stone with
ochre or with chalk where the wire lies and sticks: move the middle or
centre of the wire to another place, and so on to a third and a fourth, always
marking on the stone along the length of the iron where it remains at rest:
those lines show the meridian circles, or the circles like meridians on the
stone, or terrella, all of which meet as will be manifest at the poles of the
stone. By the circles thus continued the poles are made out, the Boreal as
well as the southern, and in the middle space betwixt these a great circle
may be drawn for an æquator, just as Astronomers describe them in the
heavens and on their own globes, or as Geographers do on the terrestrial
globe: for that line so drawn on this our terrella is of various uses in our
demonstrations and experiments magnetical. Poles are also found in a round
stone by a versorium, a piece of iron touched with a loadstone, and placed

upon a needle or point firmly fixed on a foot so as to turn freely about in the
following way:[63]

On the stone A B the versorium is placed in such a way that the versorium
may remain in equilibrium: you will mark with chalk the course of the iron
when at rest: Move the instrument to another spot, and again make note of
the direction and aspect: do the same thing in several places, and from the
concurrence of the lines of direction you will find one pole at the point A,
the other at B. A versorium placed near the stone also indicates the true
pole; when at right angles it eagerly beholds the stone and seeks the pole
itself directly, and is turned in a straight line through the axis to the centre
of the stone. For instance, the versorium D faces toward A and F, the pole
and centre,
* whereas E does not exactly respect either the pole A or the
centre F[64]. A bit of rather fine iron wire, of the length of a barley-corn, is
placed on the stone, and is moved over the regions and surface of the stone,
until it rises to the perpendicular[65]: for it stands erect at the actual pole,
whether Boreal or austral; the further from the pole, the more it inclines
from the vertical. The poles thus found you shall mark with a sharp file or
gimlet.

CHAP. IIII.

Which pole of the stone is the Boreal: & how it is
distinguished from the austral.

ne pole of the earth turns toward the constellation of the Cynosure,
and constantly regards a fixed point in the heaven (except so far as
it changes by the fixed stars being shifted in longitude, which
motion we recognize as existing in the earth, as we shall hereafter
prove): While the other pole turns to the opposite face of heaven, unknown
to the ancients, now visible on long voyages, and adorned with
multitudinous stars: In the same way the loadstone has the property and
power of directing itself North and South (the earth herself consenting and
contributing force thereto) according to the conformation of nature, which
arranges the movements of the stone towards its native situation. Which
thing is proved thus: Place a magnetick stone (after finding the poles) in a
round wooden vessel, a Bowl or dish, at the same time place it together
with the vessel (like a sailor in a skiff) upon water in some large vessel or
cistern, so that it may be able to float freely in the middle, nor touch the
edge of it, and where the air is not disturbed by winds, which would thwart
the natural movement of the stone. Hereupon the stone placed as it were in
a ship, in the middle of the surface of the still and unruffled water, will at
once put itself in motion along with the vessel that carries it, and revolve
circularly, until its austral pole points to the north, and its boreal pole to the
south. For it reverts from the contrary position to the poles: and although by
the first too-vehement impulse it over-passes the poles; yet after returning
again and again, it rests at length at the poles, or at the meridian (unless
because of local reasons it is diverted some little from those points, or from
the meridional line, by some sort of variation[66], the cause of which we will
hereafter state). However often you move it away from its place, so often by
virtue of nature's noble dower does it seek again those sure and determined
goals; and this is so, not only if the poles have been disposed in the vessel
evenly with the plane of the horizon, but also in the case of one pole,
whether austral or boreal, being raised in the vessel ten, or twenty, or thirty,
or fifty
* or eighty degrees, above the plane of the horizon, or lowered
beneath it: Still you shall see the boreal part of the stone seek the south, and
the austral part seek the north; So much so that if the pole of the stone shall
be only one degree distant from the Zenith and highest point of the heaven,
in the case of a spherical stone, the whole stone revolves until the pole
occupies its own site; though not in the absolutely direct line, it will yet
tend toward those parts, and come to rest in the meridian of the directive
action. With a like impulse too it is borne if the austral pole have been

raised toward the upper quarters, the same as if the Boreal had been exalted
above the Horizon. But it is always to be noted that, though there are
various kinds of unlikeness in the stones, and one loadstone may far surpass
another in virtue and efficiency; yet all hold to the same limits, and are
borne*toward the same points. Further it is to be remembered that all who
before our time wrote of the poles of the stone, and all the craftsmen and
navigators, have been very greatly in error in considering the part of the
stone which tended to the north as the north pole of the stone, and that
which verged toward the south, the south pole, which we shall hereafter
prove to be false. So badly hitherto hath the whole magnetick philosophy
been cultivated, even as to its foundation principles.

CHAP. V.

Loadstone seems to attract Loadstone when in natural
position: but repels it when in a contrary one, and brings
it back to order.

irst of all we must declare, in familiar language, what are the
apparent and common virtues of the stone; afterward numerous
subtilities, hitherto abstruse and unknown, hidden in obscurity, are
to be laid open, and the causes of all these (by the unlocking of
nature's secrets) made evident, in their place, by fitting terms and devices. It
is trite and commonplace that loadstone draws iron; in the same way too
does loadstone attract loadstone. Place the stone which you have seen to
have poles clearly distinguished, and marked austral and boreal, in its vessel
so as to float; and let the poles be rightly arranged with respect to the plane
of the horizon, or, at any rate not much raised or awry: hold in your hand
another stone the poles of which are also known; in such a way that its
austral pole may be toward the boreal pole of the one that is swimming, and
near it, sideways: for the floating stone forthwith follows the other stone
(provided it be within its force and dominion) and does not leave off nor
forsake it until it adhæres; unless by withdrawing your hand, you cautiously
avoid contact. In like manner if you set the boreal pole of the one you hold

in your hand opposite the austral pole of the swimming stone, they rush
together and follow each other in turn. For contrary poles allure contrary. If,
however, you apply in the same way the northern to the northern, and the
austral to the austral pole, the one stone puts the other to flight, and it turns
aside as though a pilot were pulling at the helm and it makes sail in the
opposite ward as one that ploughs the sea, and neither stands anywhere, nor
halts, if the other is in pursuit. For stone disposeth stone; the one turns the
other around, reduces it to range, and brings it back to harmony with itself.
When, however, they come together and are conjoined according to the
order of nature, they cohære firmly mutually. For instance, if you were to
set the boreal pole of that stone which is in your hand before the tropic of
Capricorn of a round floating loadstone (for it will be well to mark out on
the round stone, that is the terrella, the mathematical circles as we do on a
globe itself), or before any point between the æquator and the austral pole;
at once the swimming stone revolves, and so arranges itself that its austral
pole touches the other's boreal pole, and forms a close union with it. In the
same way, again, at the other side of the æquator, with the opposite poles,
you may produce similar results; and thus by this art and subtilty we exhibit
attraction, repulsion, and circular motion for attaining a position of
agreement and for declining hostile encounters. Moreover 'tis in one and the
same stone that we are thus able to demonstrate all these things and also
how the same part of one stone may on division become either boreal or
austral. Let A D be an oblong stone, in which A is the northern, D the
southern pole; cut this into two equal parts, then set part A in its vessel on
the water[67], so as to float.

And you will then see[68] that A the northern point will turn to the south, as
before; in like manner also the point D will move to the north, in the
divided stone, as in the whole one. Whereas, of the parts B and C, which

were before continuous, and are now divided, the one is southern B, the
other northern C. B draws C, desirous to be united, and to be brought back
into its pristine continuity: for these which are now two stones were formed
out of one: and for this cause C of the one turning itself to B of the other,
they mutually attract each other, and when freed from obstacles and
relieved of their own weight, as upon the surface of water, they run together
and are conjoined. But if you direct the part or point A to C in the other
stone, the one repels or turns away from the other: for so were nature
perverted, and the form of the stone perturbed, a form that strictly keeps the
laws which it imposed upon bodies: hence, when all is not rightly ordered
according to nature, comes the flight of one from the other's perverse
position and from the discord, for nature does not allow of an unjust and
inequitable peace, or compromise: but wages war and exerts force to make
bodies acquiesce well and justly. Rightly arranged, therefore, these
mutually attract each other; that is, both stones, the stronger as well as the
weaker, run together, and with their whole forces tend to unity, a fact that is
evident in all magnets, not in the Æthiopian only, as Pliny supposed. The
Æthiopian magnets if they be powerful, like those brought from China,
because all strong ones show the effect more quickly and more plainly,
attract more strongly in the parts nearest the pole, and turn about until pole
looks directly at pole. The pole of a stone more persistently attracts and
more rapidly seizes the corresponding part (which they term the adverse
part) of another stone; for instance, North pulls South; just so it also
summons iron with more vehemence, and the iron cleaves to it more firmly
whether it have been previously excited by the magnet, or is untouched. For
thus, not without reason hath it been ordained by nature, that the parts
nearer to the pole should more firmly attract: but that at the pole itself
should be the seat, the throne, as it were, of a consummate and splendid
virtue, to which magnetical bodies on being brought are more vehemently
attracted, and from which they are with utmost difficulty dislodged. So the
poles are the parts which more particularly spurn and thrust away things
strange and alien perversely set beside them.

CHAP. VI.

Loadstone attracts the ore of iron, as well as iron
proper, smelted and wrought.

* rincipal and manifest among the virtues of the magnet, so much
and so anciently commended, is the attraction of iron; for Plato
states that the magnet, so named by Euripides, allures iron, and
that it not only draws iron rings but also indues the rings with
power to do the same as the stone; to wit, draw other rings, so that
sometimes a long chain of iron objects, nails or rings is formed, some
hanging from others. The best iron (like that which is called acies from its
use, or chalybs from the country of the Chalybes) is best and strongly
drawn by a powerful loadstone; whereas the less good sort, which is
impure, rusty, and not thoroughly purged from dross, and not wrought in
second furnaces, is more feebly drawn; and yet more weakly when covered
and defiled with thick, greasy, and sluggish humours. It also draws ores of
iron, those that are rich and of iron colour; the poorer and not so productive
ores it does not attract, except they be prepared with some art. A loadstone
loses some attractive virtue, and, as it were, pines away with age, if exposed
too long to the open air instead of being laid in a case with filings or scales
of iron. Whence it should be buried in such materials; for there is nothing
that plainly resists this exhaustless virtue which does not destroy the form
of the body, or corrode it; not even if a thousand adamants were conjoined.
Nor do I consider that there is any such thing as the Theamedes[69], or that it
has a power opposite to that of the loadstone. Although Pliny, that eminent
man and prince of compilers (for it is what others had seen and discovered,
not always or mainly his own observations, that he has handed down to
posterity) has copied from others the fable now made familiar by repetition:
That in India there are two mountains near the river Indus; the nature of one
being to hold fast all that is iron, for it consists of loadstone; the other's
nature being to repel it, for it consists of the Theamedes. Thus if one had
iron nails in one's boots, one could not tear away one's foot on the one
mountain, nor stand still on the other. Albertus Magnus writes that a
loadstone had been found in his day which with one part drew to itself iron,
and repelled it with its other end; but Albertus observed the facts badly; for
every loadstone attracts with one end iron that has been touched with a
loadstone, and drives it away with the other; and draws iron that been

touched with a loadstone more powerfully than iron that has not been so
touched.

CHAP. VII.

What Iron is, and of what substance,
and its uses.

or that now we have declared the origin and nature of the
loadstone, we think it necessary first to add a history of iron and to
indicate the hitherto unknown forces of iron, before this our
discourse goes on to the explanation of magnetick difficulties and
demonstrations, and to deal with the coitions and harmonies of loadstone
with iron. Iron is by all reckoned in the class of metals, and is a metal livid
in colour, very hard, glows red-hot before it melts, being most difficult of
fusion, is beaten out under the hammer, and is very resonant. Chemists say
that if a bed of fixed earthy sulphur be combined with fixed earthy
quicksilver, and the two together are neither pure white but of a livid
whiteness, if the sulphur prevail, iron is formed. For these stern masters of
metals who by many inventions twisting them about, pound, calcine,
dissolve, sublime, and precipitate, decide that this metal, both on account of
the earthy sulphur and of the earthy mercury, is more truly a son of the earth
than any other; they do not even think gold or silver, lead, tin, or copper
itself so earthy; for that reason it is not smelted except in the hottest
furnaces, with bellows; and when thus fused, on having again grown hard it
is not melted again without heavy labour; but its slag with the utmost
difficulty. It is the hardest of metals, subduing and breaking all things, by
reason of the strong concretion of the more earthy matter. Wherefore we
shall better understand what iron is, when we shall declare what are the
causes and substance of metals, in a different way from those who before
our time have considered them. Aristotle takes the material of the metals to
be vapour. The chemists in chorus pronounce their actual elements to be
sulphur and quicksilver. Gilgil Mauritanus gives it as ashes moistened with
water. Georgius Agricola makes it out to be water and earth mixed; nor, to

be sure, is there any difference between his opinion and the position taken
by Mauritanus. But ours is that metals arise and effloresce at the summits of
the earth's globe, being distinguished each by its own form, like some of the
other substances dug out of it, and all bodies around us. The earth's globe
does not consist of ashes or inert dust. Nor is fresh water an element, but a
more simple consistency of evaporated fluids of the earth. Unctuous bodies,
fresh water devoid of properties, quicksilver and sulphur, none of these are
principia of metals: these latter, things are the results of a different nature,
they are neither constant nor antecedent in the course of the generation of
metals. The earth emits various humours, not begotten of water nor of dry
earth, nor from mixtures of these, but from the substance of the earth itself:
these humours are not distinguished by contrary qualities or substance, nor
is the earth a simple substance, as the Peripateticks dream. The humours
proceed from vapours sublimated from great depths; all waters are extracts
and, as it were, exudations from the earth. Rightly then in some measure
does Aristotle make out the matter of metals to be that exhalation which in
continuance thickens in the lodes of certain soils: for the vapours are
condensed in places which are less hot than the spot whence they issued,
and by help of the nature of the soils and mountains, as in a womb, they are
at fitting seasons congealed and changed into metals: but it is not they alone
which form ores, but they flow into and enter a more solid material, and so
form metals. So when this concreted matter has settled down in more
temperate beds, it begins to take shape in those tepid places, just as seed in
the warm womb, or as the embryo acquires growth: sometimes the vapour
conjoins with suitable matter alone: hence some metals are occasionally
though rarely dug up native, and come into existence perfect without
smelting: but other vapours which are mixed with alien soils require
smelting in the way that the ores of all metals are treated, which are rid of
all their dross by the force of fires, and being fused flow out metallick, and
are separated from earthy impurities but not from the true substance of the
earth. But in so far as that it becomes gold, or silver, or copper, or any other
of the existing metals, this does not happen from the quantity or proportion
of material, nor from any forces of matter, as the Chemists fondly imagine;
but when the beds and region concur fitly with the material, the metals
assume forms from the universal nature by which they are perfected; in the
same manner as all the other minerals, plants, and animals whatever:
otherwise the species of metals would be vague and undefined, which are

even now turned up in such scanty numbers that scarce ten kinds are
known. Why, however, nature has been so stingy as regards the number of
metals, or why there should be as many as are known to man, it is not easy
to explain; though the simple-minded and raving Astrologers refer the
metals each to its own planet. But there is no agreement of the metals with
the planets, nor of the planets with the metals, either in numbers or in
properties. For what connexion is there of iron with Mars? unless it be that
from the former numerous instruments, particularly swords and engines of
war, are fashioned. What has copper to do with Venus? or how does tin, or
how does spelter correspond with Jupiter? They should rather be dedicated
to Venus. But this is old wives' talk. Vapour is then a remote cause in the
generation of the metals; the fluid condensed from vapours is a more
proximate one, like the blood and semen in the generation of animals. But
those vapours and juices from vapours pass for the most part into bodies
and change them into marcasites and are carried into lodes (for we have
numerous cases of wood so transmuted), the fitting matrices of bodies,
where they are formed as metals. They enter most often into the truer and
more homogeneal substance of the globe, and in the process of time a vein
of iron results; loadstone is also produced, which is nought else than a noble
kind of iron ore: and for this reason, and on account of its substance being
singular, alien from all other metals, nature very rarely, if ever, mixes with
iron any other metal, while the other metals are very often minutely mixed,
and are produced together. Now when that vapour or those juices happen to
meet, in fitting matrices, with efflorescences deformed from the earth's
homogenic substance, and with divers precipitates (the forms working
thereto), the remainder of the metals are generated (a specifick nature
affecting the properties in that place). For the hidden primordial elements of
metals and stones lie concealed in the earth, as those of herbs and plants do
in its outer crust. For the soil dug out of a deep well, where would seem to
be no suspicion of a conception of seed, when placed on a very high tower,
produces, by the incubation of sun and sky, green herbage and unbidden
weeds; and those of the kind which grow spontaneously in that region, for
each region produces its own herbs and plants, also its own metals.
[70]Here corn exults, and there the grape is glad,

Here trees and grass unbidden verdure add.
So mark how Tmolus yields his saffrone store,

But ivory is the gift of Indian shore;
With incense soft the softer Shebans deal;
The stark Chalybeans' element is steel:
With acrid castor reek the Pontic wares,
Epirus wins the palm of Elian mares.

But what the Chemists (as Geber, and others) call fixed earthy sulphur in
iron is nothing else than the homogenic earth-substance concreted by its
own humour, amalgamated with a double fluid: a metallick humour is
inserted along with a small quantity of the substance of the earth not devoid
of humour. Wherefore the common saying that in gold there is pure earth,
but in iron mostly impure, is wrong; as though there were indeed such a
thing as natural earth, and that the globe itself were (by some unknown
process of refining) depurate. In iron, especially in the best iron, there is
earth in its own nature true and genuine; in the other metals there is not so
much earth as that in place of earth and precipitates there are consolidated
and (so to speak) fixed salts, which are efflorescences of the globe, and
which differ also greatly in firmness and consistency: In the mines their
force rises up along with a twofold humour from the exhalations, they
solidify in the underground spaces into metallic veins: so too they are also
connate by virtue of their place and of the surrounding bodies, in natural
matrices, and take on their specific forms. Of the various constitutions of
loadstones and their diverse substances, colours, and virtues, mention has
been made before: but, now having stated the cause and origin of metals,
we have to examine ferruginous matter not as it is in the smelted metal, but
as that from which the metal is refined. Quasi-pure iron is found of its
proper colour and in its own lodes; still, not as it will presently be, nor as
adapted for its various uses. It is sometimes dug up covered with white silex
or with other stones. It is often the same in river sand, as in Noricum. A
nearly pure ore of iron is now often dug up in Ireland, which the smiths,
without the labours of furnaces, hammer out in the smithy into iron
implements. In France iron is very commonly smelted out of a liver-
coloured stone, in which are glittering scales; the same kind[71] without the
scales is found in England, which also they use for craftsmen's ruddle[72]. In
Sussex in England[73] is a rich dusky ore and also one of a pale ashen hue,
both of which on being dried for a time, or kept in moderate fires, presently
acquire a liver-colour; here also is found a dusky ore square-shaped with a

black rind of greater hardness. An ore having the appearance of liver is
often variously intermingled with other stones: as also with the perfect
loadstone which yields the best of iron. There is also a rusty ore of iron, one
of a leaden hue tending to black, one quite black, or black mixed with true
cobalt: there is another sort mixed either with pyrites, or with sterile
plumbago. One kind is also like jet, another like bloodstone. The emery
used by armourers, and by glaziers for glass-cutting, called amongst the
English Emerelstone, by the Germans Smeargel, is ferruginous; albeit iron
is extracted from it with difficulty, yet it attracts the versorium. It is now
and then found in deep iron and silver diggings. Thomas Erastus says he
had heard from a certain learned man of iron ores, of the colour of iron, but
quite soft and fatty, which can be smoothed with the fingers like butter, out
of which excellent iron can be smelted: somewhat the same we have seen
found in England, having the aspect of Spanish soap. Besides the
numberless kinds of stony ores, iron is extracted from clay, from clayey
earth, from ochre, from a rusty matter deposited from chalybeate waters; In
England iron is copiously extracted in furnaces often from sandy and clayey
stones which appear to contain iron not more than sand, marl, or any other
clay soils contain it. Thus in Aristotle's book De Mirabilibus
Auscultationibus[74], "There is said" (he states) "to be a peculiar formation
of Chalybean and Misenian iron, for instance the sort collected from river
gravel; some say that after being simply washed it is smelted in the furnace;
others declare that it and the sediment which subsides after several
washings are cast in and purified together by the fire; with the addition of
the stone pyrimachus which is found there in abundance." Thus do
numerous sorts of things contain in their various substances notably and
abundantly this element of iron and earth. However, there are many stones,
and very common ones, found in every soil, also earths, and various and
mixed materials, which do not hold rich substances, but yet have their own
iron elements, and yield them to skilfully-made fires, yet which are left
aside by metallick men because they are less profitable; while other soils
give some show of a ferruginous nature, yet (being very barren) are hardly
ever smelted down into iron; and being neglected are not generally known.
Manufactured irons differ very greatly amongst themselves. For one kind is
tenacious in its nature, and this is the best; one is of medium quality:
another is brittle, and this is the worst. Sometimes the iron, by reason of the
excellency of the ore, is wrought into steel, as to-day in Noricum. From the

finest iron, too, well wrought and purged from all dross, or by being
plunged in water after heating, there issues what the Greeks call στόμωμα;
the Latins acies; others aciarium, such as was at times called Syrian,
Parthian, Noric, Comese, Spanish; elsewhere it is named from the water in
which it is so often plunged, as at Como in Italy[75], Bambola and Tarazona
in Spain. Acies fetches a much larger price than mere iron. And owing to its
superiority it better accords with the loadstone, from which more powerful
quality it is often smelted, and it acquires the virtues from it more quickly,
retains them longer at their full, and in the best condition for magnetical
experiments. After iron has been smelted in the first furnaces, it is afterward
wrought by various arts in large worksteads or mills, the metal acquiring
consistency when hammered with ponderous blows, and throwing off the
dross. After the first smelting it is rather brittle and by no means perfect.
Wherefore with us (English) when the larger military guns are cast, they
purify the metal from dross more fully, so that they may be stronger to
withstand the force of the firing; and they do this by making it pass again
(in a fluid state) through a chink, by which process it sheds its recremental
matter. Smiths render iron sheets tougher with certain liquids, and by blows
of the hammer, and from them make shields and breastplates that defy the
blows of battle-axes. Iron becomes harder through skill and proper
tempering, but also by skill turns out in a softer condition and as pliable as
lead. It is made hard by the action of certain waters into which while
glowing it is plunged, as at Bambola and Tarazona in Spain: It grows soft
again, either by the effect of fire alone, when without hammering and
without water, it is left to cool by itself; or by that of grease into which it is
plunged; or (that it may the better serve for various trades) it is tempered
variously by being skilfully besmeared. Baptista Porta expounds this art in
book 13 of his Magia Naturalis. Thus this ferric and telluric nature is
included and taken up in various bodies of stones, ores, and earths; so too it
differs in aspect, in form, and in efficiency. Art smelts it by various
processes, improves it, and turns it, above all material substances, to the
service of man in trades and appliances without end. One kind of iron is
adapted for breastplates, another serves as a defence against shot, another
protects against swords and curved blades (commonly called scimitars),
another is used for making swords, another for horseshoes. From iron are
made nails, hinges, bolts, saws, keys, grids, doors, folding-doors, spades,
rods, pitchforks, hooks, barbs, tridents, pots, tripods, anvils, hammers,

wedges, chains, hand-cuffs, fetters, hoes, mattocks, sickles, baskets,
shovels, harrows, planes, rakes, ploughshares, forks, pans, dishes, ladles,
spoons, spits, knives, daggers, swords, axes, darts, javelins, lances, spears,
anchors, and much ship's gear. Besides these, balls, darts, pikes,
breastplates, helmets, cuirasses, horseshoes, greaves, wire, strings of
musical instruments, chairs, portcullises, bows, catapults, and (pests of
human kind) cannon, muskets, and cannon-balls, with endless instruments
unknown to the Latins: which things I have rehearsed in order that it may
be understood how great is the use of iron, which surpasses a hundred times
that of all the other metals; and is day by day being wrought by metal-
workers whose stithies are found in almost every village. For this is the
foremost of metals, subserving many and the greatest needs of man, and
abounds in the earth above all other metals, and is predominant. Wherefore
those Chemists are fools[76] who think that nature's will is to perfect all
metals into gold; she might as well be making ready to change all stones to
diamonds, since diamond surpasses all in splendour and hardness, because
gold excels in splendour, gravity, and density, being invincible against all
deterioration. Iron as dug up is therefore, like iron that has been smelted, a
metal, differing a little indeed from the primary homogenic terrestrial body,
owing to the metallick humour it has imbibed; yet not so alien as that it will
not, after the manner of refined matter, admit largely of the magnetick
forces, and may be associated with that prepotent form belonging to the
earth, and yield to it a due submission.

CHAP. VIII.

In what countries and districts iron
originates.

lenty of iron mines exist everywhere, both those of old time
recorded in early ages by the most ancient writers, and the new
and modern ones. The earliest and most important seem to me to
be those of Asia. For in those countries which abound naturally in
iron, governments and the arts flourished exceedingly, and things needful

for the use of man were discovered and sought after. It is recorded to have
been found about Andria, in the region of the Chalybes near the river
Thermodon in Pontus; in the mountains of Palestine which face Arabia; in
Carmania: in Africa there was a mine of iron in the Isle of Meroe; in Europe
in the hills of Britain, as Strabo writes; in Hither Spain, in Cantabria.
Among the Petrocorii and Cubi Biturges[77] (peoples of Gaul), there were
worksteads in which iron used to be wrought. In greater Germany near
Luna, as recorded by Ptolemy; Gothinian iron is mentioned by Cornelius
Tacitus; Noric iron is celebrated in the verses of poets; and Cretan, and that
of Eubœa; many other iron mines were passed over by these writers or
unknown to them; and yet they were neither poor nor scanty, but most
extensive. Pliny[78] says that Hither Spain and all the district from the
Pyrenees is ferruginous, and on the part of maritime Cantabria washed by
the Ocean (says the same writer) there is (incredible to relate) a
precipitously high mountain wholly composed of this material. The most
ancient mines were of iron rather than of gold, silver, copper or lead; since
mainly this was sought because of the demand; and also because in every
district and soil they were easy to find, not so deep-lying, and less beset by
difficulties. If, however, I were to enumerate modern iron workings, and
those of this age and over Europe only, I should have to write a large and
bulky volume, and sheets of paper would run short quicker than the iron,
and yet for one sheet they could furnish a thousand worksteads. For
amongst minerals, no material is so ample; all metals, and all stones distinct
from iron, are outdone by ferric and ferruginous matter. For you will not
readily find any region, and scarcely any country district over the whole of
Europe (if you search at all deeply), that does not either produce a rich and
abundant vein of iron or some soil containing or slightly charged with
ferruginous stuff; and that this is true any expert in the arts of metals and
chemistry will easily find. Beside that which has ferruginous nature, and the
metallick lode, there is another ferric substance which does not yield the
metal in this way because its thin humour is burnt out by fierce fires, and it
is changed into an iron slag like that which is separated from the metal in
the first furnaces. And of this kind is all clay and argillaceous earth, such as
that which apparently forms a large part of the whole of our island of
Britain: all of which, if subjected very vehemently to intense heat, exhibits
a ferric and metallick body, or passes into ferric vitreous matter, as can be
easily seen in buildings in bricks baked from clay, which, when placed next

the fires in the open kilns (which our folk call clamps)[79] and burned,
present an iron vitrification, black at the other end. Moreover all those
earths as prepared are drawn by the magnet, and like iron are attracted by it.
So perpetual and ample is the iron offspring of the terrestrial globe.
Georgius Agricola says that almost all mountainous regions are full of its
ores, while as we know a rich iron lode is frequently dug in the open
country and plains over nearly the whole of England and Ireland; in no
other wise than as, says he, iron is dug out of the meadows at the town of
Saga in pits driven to a two-foot depth. Nor are the West Indies without
their iron lodes, as writers tell us; but the Spaniards, intent upon gold,
neglect the toilsome work of iron-founding, and do not search for lodes and
mines abounding in iron. It is probable that nature and the globe of the earth
are not able to hide, and are evermore bringing to the light of day, a great
mass of inborn matter, and are not invariably obstructed by the settling of
mixtures and efflorescences at the earth's surface. It is not only in the
common mother (the terrestrial globe) that iron is produced, but sometimes
also in the air from the earth's exhalations, in the highest clouds. It rained
iron in Lucania, the year in which M. Crassus was slain. The tale is told,
too, that a mass of iron, like slag, fell from the air in the Nethorian forest,
near Grina, and they narrate that the mass was many pounds in weight; so
that it could neither be conveyed to that place, on account of its weight, nor
be brought away by cart, the place being without roads. This happened
before the civil war waged between the rival dukes in Saxony. A similar
story, too, comes to us from Avicenna. It once rained iron in the
Torinese[80], in various places (Julius Scaliger telling us that he had a piece
of it in his house), about three years before that province was taken over by
the king. In the year 1510 in the country bordering on the river Abdua (as
Cardan writes[81] in his book De Rerum Varietate) there fell from the sky
1200 stones, one weighing 120 pounds, another 30 or 40 pounds, of a rusty
iron colour and remarkably hard. These occurrences being rare are regarded
as portents, like the showers of earth and stones mentioned in Roman
history. But that it ever rained other metals is not recorded; for it has never
been known to rain from the sky gold, silver, lead, tin, or spelter[82].
Copper, however, has been at some time noticed to fall from the sky, and
this is not very unlike iron; and in fact cloud-born iron of this sort, or
copper, are seen to be imperfectly metallick, incapable of being cast in any
way, or wrought with facility. For the earth hath of her store plenty of iron

in her highlands, and the globe contains the ferric and magnetick element in
rich abundance. The exhalations forcibly derived from such material may
well become concreted in the upper air by the help of more powerful
causes, and hence some monstrous progeny of iron be begotten.

CHAP. IX.

Iron ore attracts iron ore.

* rom various substances iron (like all the rest of the metals) is
extracted: such substances being stones, earth, and similar
concretions which miners call veins because it is in veins[83], as it
were, that they are generated. We have spoken above of the variety
of these veins. If a properly coloured ore of iron and a rich one (as miners
call it) is placed, as soon as mined, upon water in a bowl or any small vessel
(as we have shown before in the case of a loadstone), it is attracted by a
similar piece of ore brought near by hand, yet not so powerfully and quickly
as one loadstone is drawn by another loadstone, but slowly and feebly. Ores
of iron that are stony, cindery, dusky, red, and several more of other colours,
do not attract one another mutually, nor are they attracted by the loadstone
itself, even by a strong one, no more than wood, or lead, silver, or gold.
Take those ores and burn, or rather roast them, in a moderate fire, so that
they are not suddenly split up, or fly asunder, keeping up the fire ten or
twelve hours, and gently increasing it, then let them grow cold, skill being
shown in the direction in which they are placed: These ores thus prepared a
loadstone will now draw, and they now show a mutual sympathy, and when
skilfully arranged run together by their own forces.

CHAP. X.

*

Iron ore has poles, and acquires them, and settles
itself toward the poles of the universe.

eplorable is man's ignorance in natural science, and modern
philosophers, like those who dream in darkness, need to be
aroused, and taught the uses of things and how to deal with them,
and to be induced to leave the learning sought at leisure from
books alone, and that is supported only by unrealities of arguments and by
conjectures. For the knowledge of iron (than which nothing is in more
common use), and that of many more substances around us, remains
unlearned; iron, a rich ore of which, placed in a vessel upon water, by an
innate property of its own directs itself, just like the loadstone, North and
South, at which points it rests, and to which, if it be turned aside, it reverts
by its own inherent vigour. But many ores, less perfect in their nature,
which yet contain amid stone or earthy substances plenty of iron, have no
such motion; but when prepared by skilful treatment in the fires, as shown
in the foregoing chapter, they acquire a polar vigour (which we call
verticity[84]); and not only the iron ores in request by miners, but even earth
merely charged with ferruginous matter, and many rocks, do in like manner
tend and lean toward those portions of the heavens, or more truly of the
earth, if they be skilfully placed, until they reach the desired location, in
which they eagerly repose.

CHAP. XI.

* Wrought Iron, not excited by a loadstone,
draws iron.

rom the ore, which is converted, or separated, partly into metal,
partly into slag, by the intense heat of fires, iron is smelted in the
first furnaces in a space of eight, ten, or twelve hours, and the
metal flows away from the dross and useless matter, forming a
large and long mass, which being subjected to a sharp hammering is cut into
parts, out of which when reheated in the second hearth of the forge, and

again placed on the anvil, the smiths fashion quadrangular lumps, or more
specially bars which are bought by merchants and blacksmiths, from which
in smithies usually it is the custom to fashion the various implements. This
iron we term wrought, and its attraction by the loadstone is manifest to all.
But we, by more carefully trying everything[85], have found out that iron
merely, by itself alone, not excited by any loadstone, not charged by any
alien forces, attracts other iron; though it does not so eagerly snatch and
suddenly pluck at it as would a fairly strong loadstone; this you may know
thus: A small piece of cork, the size of a hazel-nut, rounded, is traversed by
an iron wire up to the middle of the wire: when set swimming on still water
apply to one end of it, close (yet so as not to touch), the end of another iron
wire; and wire draws wire, and one follows the other when slowly drawn
back, and this goes on up to the proper boundaries. Let A be the cork with
the iron wire, B one end of it raised a little above the surface of the water, C
the end of the second wire, showing the way in which B is drawn by C. You
may prove it in another way in a larger body. Let a long bright iron rod
(such as is made for hangings and window curtains) be hung in balance by a
slender silken cord: to one end of this as it rests in the air bring a small
oblong mass of polished iron, with its proper end at the distance of half a
digit. The balanced iron turns itself to the mass; do you with the same
quickness draw back the mass in your hand in a circular path about the
point of equilibrium of the suspension; the end of the balanced iron follows
after it, and turns in an orbit.

CHAP. XII.

* A long piece of Iron, even though not excited by a
loadstone, settles itself toward North and South.

very good and perfect piece of iron, if drawn out in length, points
North and South, just as the loadstone or iron rubbed with a
magnetical body does; a thing that our famous philosophers have
little understood, who have sweated in vain to set forth the
magnetick virtues and the causes of the friendship of iron for the stone. You
may experiment with either large or small iron works, and either in air or in
water. A straight piece of iron six feet long of the thickness of your finger is
suspended (in the way described in the foregoing chapter) in exact
æquipoise by a strong and slender silken cord. But the cord should be cross-
woven of several silk filaments, not twisted simply in one way; and it
should be in a small chamber with all doors and windows closed, that the
wind may not enter, nor the air of the room be in any way disturbed; for
which reason it is not expedient that the trial should be made on windy
days, or while a storm is brewing. For thus it freely follows its bent, and
slowly moves until at length, as it rests, it points with its ends North and
South, just as iron touched with a loadstone does in shadow-clocks, and in
compasses, and in the mariners' compass. You will be able, if curious
enough, to balance all at the same time by fine threads a number of small
rods, or iron wires, or long pins with which women knit stockings; you will
see that all of them at the same time are in accord, unless there be some
error in this delicate operation: for unless you prepare everything fitly and
skilfully, the labour will be void. Make trial of this thing in water also,
which is done both more certainly and more easily. Let an iron wire two or

three digits long, more or less, be passed through a round cork, so that it
may just float upon water; and as soon as you have committed it to the
waves, it turns upon its own centre, and one end tends to the North, the
other to the South; the causes of which you will afterwards find in the laws
of the direction. This too you should understand, and hold firmly in
memory,
* that as a strong loadstone, and iron touched with the same, do not
invariably point exactly to the true pole but to the point of the variation; so
does a weaker loadstone, and so does the iron, which directs itself by its
own forces only, not by those impressed by the stone; and so every ore of
iron, and all bodies naturally endowed with something of the iron nature,
and prepared, turn to the same point of the horizon, according to the place
of the variation in that particular region (if there be any variation therein),
and there abide and rest.

CHAP. XIII.

*
Wrought iron has in itself certain parts Boreal and Austral:
A magnetick vigour, verticity, and determinate
vertices, or poles.

ron settles itself toward the North and South; not with one and the
same point toward this pole or that: for one end of the piece of ore
itself and one extremity also of a wrought-iron wire have a sure and
constant destination to the North, the other to the South, whether
the iron hang in the air, or float on water, be the iron large rods or thinner
wires. Even if it be a little rod, or a wire ten or twenty or more ells in
length; one end as a rule is Boreal, the other Austral. If you cut off part of
that wire, and if the end of that divided part were Boreal, the other end
(which was joined to it) will be Austral. Thus if you divide it into several
parts, before making an experiment on the surface of water, you can
recognize the vertex[86]. In all of them a Boreal end draws an Austral and
repels a Boreal, and contrariwise, according to the laws magnetical. Yet
herein wrought iron differs from the loadstone and from its own ore,
inasmuch as in an iron ball of any size, such as those used for artillery or

cannon, or bullets used for carbines or fowling-pieces, verticity is harder to
acquire and is less apparent than in a piece of loadstone, or of ore itself, or
than in a round loadstone. But in long and extended pieces of iron a power
is at once discerned; the causes of which fact, and the methods by which it
acquires its verticity and its poles without use of a loadstone, as well as the
reasons for all the other obscure features of verticity, we shall set forth in
describing the motion of direction.

CHAP. XIIII.

Concerning other powers of loadstone, and its
medicinal properties.

ioscorides prescribes loadstone to be given with sweetened water,
three scruples' weight, to expel gross humours. Galen writes that a
like quantity of bloodstone avails. Others relate that loadstone
perturbs the mind and makes folk melancholick, and mostly kills.
Gartias ab Horto[87] thinks it not deleterious or injurious to health. The
natives of East India tell us, he says, that loadstone taken in small doses
preserves youth. On which account the aged king, Zeilam, is said to have
ordered the pans in which his victuals were cooked to be made of loadstone.
The person (says he) to whom this order was given told me so himself.
There are many varieties of loadstone produced by differences in the
mingling of earths, metals, and juices; hence they are altogether unlike in
their virtues and effects, due to propinquities of places and of agnate bodies,
and arising from the pits themselves as it were from the matrices being soul.
One loadstone is therefore able to purge the stomach, and another to check
purging, to cause by its fumes a serious shock to the mind, to produce a
gnawing at the vitals, or to bring on a grave relapse; in case of which ills
they exhibit gold and emerald, using an abominable imposture for lucre.
Pure loadstone may, indeed, be not only harmless, but even able to correct
an over-fluid and putrescent state of the bowels and bring them back to a
better temperament; of this sort usually are the oriental magnets from
China, and the denser ones from Bengal, which are neither misliking nor

unpleasant to the actual senses. Plutarch and Claudius Ptolemy[88], and all
the copyists since their time, think that a loadstone smeared with garlick
does not allure iron. Hence some suspect that garlick is of avail against any
deleterious power of the magnet: thus in philosophy many false and idle
conjectures arise from fables and falsehoods. Some physicians[89] have that
a loadstone has power to extract the iron of an arrow from the human body.
But it is when whole that the loadstone draws, not when pulverized and
formless, buried in plasters; for it does not attract by reason of its material,
but is rather adapted for the healing of open wounds, by reason of
exsiccation, closing up and drying the sore, an effect by which the arrow-
heads would rather be retained in the wounds. Thus vainly and
preposterously do the sciolists look for remedies while ignorant of the true
causes of things. The application of a loadstone for all sorts of headaches no
more cures them (as some make out) than would an iron helmet or a steel
cap. To give it in a draught to dropsical persons is an error of the ancients,
or an impudent tale of the copyists, though one kind of ore may be found
which, like many more minerals, purges the stomach; but this is due to
some defect of that ore and not to any magnetick property. Nicolaus puts a
large quantity of loadstone into his divine plaster[90], just as the
Augsburgers do into a black plaster[91] for fresh wounds and stabs; the
virtue of which dries them up without smart, so that it proves an efficacious
medicament. In like manner also Paracelsus to the same end mingles it in
his plaster for stab wounds[92].

CHAP. XV.

The Medicinal Virtue of Iron.[93]

ot foreign to our present purpose will it be to treat briefly also of
the medicinal virtue of iron: for it is a prime remedial for some
diseases of the human body, and by its virtues, both those that are
natural and those acquired by suitable preparation, it works
marvellous changes in the human body, so that we may the more surely
recognize its nature through its medicinal virtue and through certain

manifest experiments. So that even those tyros in medicine who abuse this
most famous medicament may learn to prescribe it with better judgment for
the healing of the sick, and not, as too often they use it, to their harm. The
best iron, Stomoma, or Chalybs, Acies, or Aciarium, is reduced to a fine
powder by a file; the powder is steeped in the sharpest vinegar, and dried in
the sun, and again soused in vinegar, and dried; afterwards it is washed in
spring water or other suitable water, and dried; then for the second time it is
pulverized and reduced on porphyry, passed through a very fine sieve, and
put back for use. It is given chiefly in cases of laxity and over-humidity of
the liver, in enlargement of the spleen, after due evacuations; for which
reason it restores young girls when pallid, sickly, and lacking colour, to
health and beauty; since it is very siccative, and is astringent without harm.
But some who in every internal malady always talk of obstruction of the
liver and spleen, think it beneficial in those cases because it removes
obstructions, mainly trusting to the opinions of certain Arabians[94]:
wherefore they administer it to the dropsical and to those suffering from
tumour of the liver or from chronic jaundice, and to persons troubled with
hypochondrical melancholia or any stomachic disorder, or add it to
electuaries, without doubt to the grievous injury of many of their patients.
Fallopius commends it prepared in his own way for tumours of the spleen,
but is much mistaken; for loadstone is pre-eminently good for spleens
relaxed with humour, and swollen; but it is so far from curing spleens
thickened into a tumour that it mightily confirms the malady. For those
drugs which are strong siccatives and absorb humour force the viscera when
hardened into a tumour more completely into a quasi-stony body. There are
some who roast iron in a closed oven with fierce firing, and burn it strongly,
until it turns red, and they call this Saffron of Mars; which is a powerful
siccative, and more quickly penetrates the intestines. Moreover they order
violent exercise, that the drug may enter the viscera while heated and so
reach the place affected; wherefore also it is reduced to a very fine flour;
otherwise it only sticks in the stomach and in the chyle and does not
penetrate to the intestines. As a dry and earthy medicament, then, it is
shown by the most certain experiments to be, after proper evacuations, a
remedy for diseases arising from humour (when the viscera are charged and
overflowing with watery rheum). Prepared steel is a medicament proper for
enlarged spleen. Iron waters too are effectual in reducing the spleen,
although as a rule iron is of a frigid and astringent efficiency, not a laxative;

but it effects this neither by heat nor by cold, but from its own dryness when
mixed with a penetrative fluid: it thus disperses the humour, thickens the
villi, hardens the tissues, and contracts them when lax; while the inherent
heat in the member thus strengthened, being increased in power, dissipates
what is left. Whereas if the liver be hardened and weakened by old age or a
chronic obstruction, or the spleen be shrivelled and contracted to a schirrus,
by which troubles the fleshy parts of the limbs grow flaccid, and water
under the skin invades the body, in the case of these conditions the
introduction of iron accelerates the fatal end, and considerably increases the
malady. Amongst recent writers there are some who in cases of drought of
the liver prescribe, as a much lauded and famous remedy, the electuary of
iron slag, described by Rhazes[95] in his ninth book ad Almansorem, Chap.
63, or prepared filings of steel; an evil and deadly advice: which if they do
not some time understand from our philosophy, at least everyday
experience, and the decline and death of their patients, will convince them,
even the sluggish and lazy. Whether iron be warm or cold is variously
contended by many. By Manardus, Curtius, Fallopius and others, many
reasons are adduced on both sides; each settles it according to his own
sentiment. Some make it to be cold, saying that iron has the property of
refrigerating, because Aristotle in his Meteorologica would put iron in the
class of things which grow concreted in cold by emission of the whole of
their Heat: Galen, too, says that iron has its consistency from cold; also that
it is an earthy and dense body. Further that iron is astringent, also that
Chalybeate water quenches thirst: and they adduce the cooling effect of
thermal iron waters. Others, however, maintain that it is Warm, because of
Hippocrates making out that waters are warm which burst forth from places
where iron exists. Galen says that in all metals there is considerable
substance, or essence, of fire. Paolo[96] affirms that iron waters are warm.
Rhazes will have it that iron is warm and dry in the third degree. The
Arabians think that it opens the spleen and liver; wherefore also that iron is
warm. Montagnana recommends it in cold affections of the uterus and
stomach. Thus do the smatterers cross swords together, and puzzle inquiring
minds by their vague conjectures, and wrangle for trifles as for goats' wool,
when they philosophize, wrongly allowing and accepting properties: but
these matters will appear more plainly by and by when we begin to discuss
the causes of things; the clouds being dispersed that have so darkened all
Philosophy. Filings, scales, and slag of iron are, as Avicenna makes out, not

wanting in deleterious power (haply when they are not well prepared or are
taken in larger quantity than is fit), hence they cause violent pain in the
bowels, roughness of the mouth and tongue, marasmus, and shrivelling of
the limbs. But Avicenna wrongly[97] and old-womanishly makes out that the
proper antidote to this iron poison is loadstone to the weight of a drachm
taken as a draught in the juice of mercurialis or of Beet; for loadstone is of a
twofold nature, usually malefiant and pernicious, nor does it resist iron,
since it attracts it; nor when drunk in a draught in the form of powder does
it avail to attract or repel, but rather inflicts the same evils.

CHAP. XVI.

That loadstone & iron ore are the same, but iron an
extract from both, as other metals are from their own
ores; & that all magnetick virtues, though
weaker, exist in the ore itself & in
smelted iron.

itherto we have declared the nature & powers of the loadstone, &
also the properties & essence of iron; it now remains to show their
mutual affinities, & kinship, so to speak, & how very closely
conjoined these substances are. At the highest part of the terrestrial
globe, or at its perishable surface & rind, as it were, these two bodies
usually originate & are produced in one and the same matrix, as twins in
one mine. Strong loadstones are dug up by themselves, weaker ones too
have their own proper vein. Both are found in iron mines. Iron ore most
often occurs alone, without strong loadstone (for the more perfect are rarely
met with). Strong loadstone is a stone resembling iron; out of it is usually
smelted the finest iron, which the Greeks call stomoma, the Latins acies, the
Barbarians (not amiss) aciare, or aciarium. This same stone draws, repels,
controls other loadstones, directs itself to the poles of the world, picks up
smelted iron, and works many other wonders, some already set forth by us,
but many more which we must demonstrate more fully. A weaker loadstone,

however, will exhibit all these powers, but in a lesser degree; while iron ore,
& also wrought iron (if they have been prepared) show their strength in all
magnetick
* experiments not less than do feeble and weak loadstones; & an
inert piece of ore, & one possessed of no magnetick properties, & just
thrown out[98] of the pit, when roasted in the fire & prepared with due art
(by the elimination of humours & foreign excretions) awakes, and becomes
in power
* & potency a magnet, occasionally a stone or iron ore is mined,
which attracts forthwith without being prepared: for native iron of the right
colour attracts and governs iron magnetically. One form then belongs to the
one mineral, one species, one self-same essence. For to me there seems to
be a greater difference, & unlikeness, between the strongest loadstone, & a
weak one which scarce can attract a single chip of iron; between one that is
stout, strong, metallick, & one that is soft, friable, clayey; amidst such
variety of colour, substance, quality, & weight; than there is on the one hand
between the best ore, rich in iron, or iron that is metallick from the
beginning, and on the other the most excellent loadstone. Usually, too, there
are no marks to distinguish them, and even metallurgists cannot decide
between them, because they agree together in all respects. Moreover we see
that the best loadstone and the ore of iron are both as it were distressed by
the same maladies & diseases, both run to old age in the same way &
exhibit the same marks of it, are preserved & keep their properties by the
same remedies & safeguards; & yet again the one increases the potency of
the other, & by artfully devised adjuncts marvellously intensifies, & exalts
it. For both are impaired by the more acrid juices as by poisons, & the aqua
fortis of the Chemists inflicts on both the same wounds, and when exposed
too long to harm from the atmosphere, they both alike pine away, so to
speak, & grow old; each is preserved by being kept in the dust & scrapings
of the other; & when a fit piece of steel or iron is adjoined above its pole,
the loadstone's vigour is augmented through the firm union. The loadstone
is laid up in iron filings, not that iron is its food; as though loadstone were
alive and needed feeding, as Cardan philosophizes[99]; nor yet that so it is
delivered from the inclemency of the weather (for which cause it as well as
iron is laid up in bran by Scaliger; mistakenly, however, for they are not
preserved well in this way, and keep for years their own fixed forms): nor
yet, since they remain perfect by the mutual action of their powders, do
their extremities waste away, but are cherished & preserved, like by like.
For just as in their own places, in the mines, bodies like to each other

endure for many ages entire and uncorrupt, when surrounded by bodies of
the same stuff, as the lesser interior parts in a great mass: so loadstone and
ore of iron, when inclosed in a mound of the same material, do not exhale
their native humour, do not waste away, but retain their soundness. A
loadstone lasts longer in filings of smelted iron, & a piece of iron ore
excellently also in dust of loadstone; as also smelted iron in filings of
loadstone & even in those of iron. Then both these allied bodies have a true
& just form of one & the same species; a form which until this day was
considered by all, owing to their outward unlikeness & the inequality of the
potency that is the same innate in both, to be different & unlike in kind; the
smatterers not understanding that the same powers, though differing in
strength, exist in both alike. And in fact they both are true & intimate parts
of the earth, & as such retain the prime natural properties of mutually
attracting, of moving, & of disposing themselves toward the position of the
world, and of the terrestrial globe; which properties they also impart to each
other, and increase, confirm, receive, and retain each other's forces. The
stronger fortifies the weaker, not as though aught were taken away from its
own substance, or its proper vigour, nor because any corporeal substance is
imparted, but the dormant virtue of the one is aroused by the other, without
loss. For if with a single small stone you touch a thousand bits of iron for
the use of mariners[100], that loadstone attracts iron no less strongly than
before; with the same stone weighing one pound, any one will be able to
suspend in the air a thousand pounds of iron. For if any one were to fix high
up on the walls so many iron nails of so great a weight, & were to apply to
them the same number of nails touched, according to the art, by a loadstone,
they would all be seen to hang in the air through the force of one small
stone. So this is not solely the action, labour, or outlay of the loadstone; but
the iron, which is in a sense an extract from loadstone, and a fusion of
loadstone into metal, & conceives vigour from it, & by proximity
strengthens the magnetick faculties, doth itself, from whatever lode it may
have come, raise its own inborn forces through the presence & contact of
the stone, even when solid bodies intervene. Iron that has been touched, acts
anew on another piece of iron by contact, & adapts it for magnetick
movements, & this again a third. But if you rub with a loadstone any other
metal, or wood, or bones, or glass, as they will not be moved toward any
particular and determinate quarter of heaven, nor be attracted by any
magnetick body, so they are able not to impart any magnetick property to

other bodies or to iron itself by attrition, & by infection. Loadstone differs
from iron ore, as also from some weaker magnets, in that when molten in
the furnace into a ferric & metallick fused mass, it does not so readily flow
& dissolve into metal; but is sometimes burnt to ashes in large furnaces; a
result which it is reasonable to suppose arises from its having some kind of
sulphureous matter mixed with it, or from its own excellence & simpler
nature, or from the likeness & common form which it has with the common
mother, the Great Magnet. For earths, and iron stones, magnets abounding
in metal, are the more imbued & marred with excrementitious metallick
humours, and earthy corruptions of substance, as numbers of loadstones are
weaker from the mine; hence they are a little further remote from the
common mother, & are degenerate, & when smelted in the furnace undergo
fusion more easily, & give out a more certain metallick product, & a metal
that is softer, not a tough steel. The majority of loadstones (if not unfairly
burnt[101]) yield in the furnace a very excellent iron. But iron ore also agrees
in all those primary qualities with loadstone; for both, being nearer and
more closely akin to the earth above all bodies known to us, have in
themselves a magnetick substance, & one that is more homogenic, true &
cognate with the globe of the earth; less infested & spoiled by foreign
blemish; less confused with the outgrowths of earth's surface, & less
debased by corrupt products. And for this reason Aristotle in the fourth
book of his Meteora seems not unfairly to separate iron from all the rest of
the metals. Gold, he says, silver, copper, tin, lead, belong to water; but iron
is of the earth. Galen, in the fourth chapter of De Facultatibus Simplicium
Medicamentorum, says that iron is an earthy & dense body. Accordingly a
strong loadstone is on our showing especially of the earth: the next place is
occupied by iron ore or weaker loadstone; so the loadstone is by nature and
origin[102]** of iron, and it and magnetick iron are both one in kind. Iron
ore yields iron in furnaces; loadstone also pours forth iron in the furnaces,
but of a much more excellent sort, that which is called steel or blade-edge;
and the better sort of iron ore is a weak loadstone, the best loadstone being
a most excellent ore of iron, in which, as is to be shown by us, the primary
properties are grand and conspicuous. Weaker loadstone or iron ore is that
in which these properties are more obscure, feeble, and are scarce
perceptible to the senses.

CHAP. XVII.

That the globe of the earth is magnetick, & a magnet; &
how in our hands the magnet stone has all the primary
forces of the earth, while the earth by the
same powers remains constant in a
fixed direction in the
universe.

rior to bringing forward the causes of magnetical motions, &
laying open the proofs of things hidden for so many ages, & our
experiments (the true foundations of terrestrial philosophy), we
have to establish & present to the view of the learned our New &
unheard of doctrine about the earth; and this, when argued by us on the
grounds of its probability, with subsequent experiments & proofs, will be as
certainly assured as anything in philosophy ever has been considered &
confirmed by clever arguments or mathematical proofs. The terrene mass,
which together with the vasty ocean produces the sphærick figure &
constitutes our globe, being of a firm & constant substance, is not easily
changed, does not wander about, & fluctuate with uncertain motions, like
the seas, & flowing waves: but holds all its volume of moisture in certain
beds & bounds, & as it were in oft-met veins, that it may be the less
diffused & dissipated at random. Yet the solid magnitude of the earth
prevails & reigns supreme in the nature of our globe. Water, however, is
attached to it, & as an appendage only, & a flux emanating from it; whose
force from the beginning is conjoined with the earth through its smallest
parts, and is innate in its substance. This moisture the earth as it grows hot
throws off freely when it is of the greatest possible service in the generation
of things. But the thews and dominant stuff of the globe is that terrene body
which far exceeds in quantity all the volume of flowing streams and open
waters (whatever vulgar philosophers may dream of the magnitudes and
proportions of their elements), and which takes up most of the whole globe
and almost fills it internally, and by itself almost suffices to endow it with
sphærick shape. For the seas only fill certain not very deep or profound
hollows, since they rarely go down to a depth of a mile and generally do not

exceed a hundred or 50 fathoms. For so it is ascertained by the observations
of seamen when by the plumb-line and sinker its abysms are explored with
the nautical sounder; which depths relatively to the dimensions of the globe,
do not much deform its globular shape. Small then appears to be that
portion of the real earth that ever emerges to be seen by man, or is turned
up; since we cannot penetrate deeper into its bowels, further than the
wreckage of its outer efflorescence, either by reason of the waters which
gush up in deep workings, as through veins, or for want of a wholesome air
to support life in the miners, or on account of the vast cost that would be
incurred in pumping out such huge workings[103], and many other
difficulties; so that to have gone down to a depth of four hundred, or (which
is of rarest occurrence) of five hundred fathoms[104] as in a few mines,
appears to all a stupendous undertaking. But it is easy to understand how
minute, how almost negligibly small a portion that 500 fathoms is of the
earth's diameter, which is 6,872 miles. It is then parts only of the earth's
circumference and of its prominences that are perceived by us with our
senses; and these in all regions appear to us to be either loamy, or clayey, or
sandy, or full of various soils, or marls: or lots of stones or gravel meet us,
or beds of salt, or a metallick lode, and metals in abundance. In the sea and
in deep waters, however, either reefs, and huge boulders, or smaller stones,
or sands, or mud are found by mariners as they sound the depths. Nowhere
does the Aristotelian element of earth come to light; and the Peripateticks
are the sport of their own vain dreams about elements. Yet the lower bulk of
the earth and the inward parts of the globe consist of such bodies; for they
could not have existed, unless they had been related to and exposed to the
air and water, and to the light and influences of the heavenly bodies, in like
manner as they are generated, and pass into many dissimilar forms of
things, and are changed by a perpetual law of succession. Yet the interior
parts imitate them, and betake themselves to their own source, on the
principle of terrene matter, albeit they have lost the first qualities and the
natural terrene form, and are borne towards the earth's centre, and cohære
with the globe of the earth, from which they cannot be wrenched asunder
except by force. But the loadstone and all magneticks, not the stone only,
but every magnetick homogenic substance, would seem to contain the
virtue of the earth's core and of its inmost bowels, and to hold within itself
and to have conceived that which is the secret and inward principle of its
substance; and it possesses the actions peculiar to the globe of attracting,

directing, disposing, rotating, stationing itself in the universe, according to
the rule of the whole, and it contains and regulates the dominant powers of
the globe; which are the chief tokens and proofs of a certain distinguishing
combination, and of a nature most thoroughly conjoint. For if among actual
bodies one sees something move and breathe, and experience sensations,
and be inclined and impelled by reason, will one not, knowing and seeing
this, conclude that it is a man or something rather like a man, than that it is
a stone or a stick? The loadstone far excels all other bodies known to us in
virtues and properties pertaining to the common mother: but those
properties have been far too little understood or realized by philosophers:
for to its body bodies magnetical rush in from all sides and cleave to it, as
we see them do in the case of the earth. It has poles, not mathematical
points, but natural termini of force excelling in primary efficiency by the
co-operation of the whole: and there are poles in like manner in the earth
which our forefathers sought ever in the sky: it has an æquator, a natural
dividing line between the two poles, just as the earth has: for of all lines
drawn by the mathematicians on the terrestrial globe, the æquator is the
natural boundary, and is not, as will hereafter appear, merely a
mathematical circle. It, like the earth, acquires Direction and stability
toward North and South, as the earth does; also it has a circular motion
toward the position of the earth, wherein it adjusts itself to its rule: it
follows the ascensions and declinations of the earth's poles, and conforms
exactly to the same, and by itself raises its own poles above the horizon
naturally according to the law of the particular country and region, or sinks
below it. The loadstone derives temporary properties, and acquires its
verticity from the earth, and iron is affected by the verticity of the globe
even as iron is by a loadstone: Magneticks are conformable to and are
regulated by the earth, and are subject to the earth in all their motions. All
its movements harmonize with, and strictly wait upon, the geometry and
form of the earth, as we shall afterwards prove by most conclusive
experiments and diagrams; and the chief part of the visible earth is also
magnetical, and has magnetick motions, although it be disfigured by
corruptions and mutations without end. Why then do we not recognize this
the chief homogenic substance of the earth, likest of substances to its inner
nature and closest allied to its very marrow? For none of the other mixed
earths suitable for agriculture, no other metalliferous veins, nor stones, nor
sand, nor other fragments of the earth which have come to our view possess

such constant and peculiar powers. And yet we do not assume that the
whole interior of this globe of ours is composed of stones or iron (although
Franciscus Maurolycus, that learned man, deems the whole of the earth's
interior to consist of solid stone). For not every loadstone that we have is a
stone, it being sometimes like a clod, or like clay and iron either firmly
compacted together out of various materials, or of a softer composition, or
by heat reduced to the metallick state; and the magnetick substance by
reason of its location and of its surroundings, and of the metallick matrix
itself, is distinguished, at the surface of the terrene mass, by many qualities
and adventitious natures, just as in clay it is marked by certain stones and
iron lodes. But we maintain that the true earth is a solid substance,
homogeneous with the globe, closely coherent, endowed with a primordial
and (as in the other globes of the universe) with a prepotent form; in which
position it persists with a fixed verticity, and revolves with a necessary
motion and an inherent tendency to turn, and it is this constitution, when
true and native, and not injured or disfigured by outward defects, that the
loadstone possesses above all bodies apparent to us, as if it were a more
truly homogenic part taken from the earth. Accordingly native iron which
sui generis (as metallurgists term it), is formed when homogenic parts of
the earth grow together into a metallick lode; Loadstone being formed when
they are changed into metallick stone, or a lode of the finest iron, or steel:
so in other iron lodes the homogenic matter that goes together is somewhat
more imperfect; just as many parts of the earth, even the high ground, is
homogenic but so much more deformate. Smelted iron is fused and smelted
out of homogenic stuffs, and cleaves to the earth more tenaciously than the
ores themselves. Such then is our earth in its inward parts, possessed of a
magnetick homogeneal nature, and upon such more perfect foundations as
these rests the whole nature of things terrestrial, manifesting itself to us, in
our more diligent scrutiny, everywhere in all magnetick minerals, and iron
ores, in all clay, and in numerous earths and stones; while Aristotle's simple
element, that most empty terrestrial phantom of the Peripateticks, a rude,
inert, cold, dry, simple matter, the universal substratum, is dead, devoid of
vigour, and has never presented itself to any one, not even in sleep, and
would be of no potency in nature. Our philosophers were only dreaming
when they spoke of a kind of simple and inert matter. Cardan does not
consider the loadstone to be any kind of stone, "but a sort of perfected
portion of some kind of earth that is absolute; a token of which is its

abundance, there being no place where it is not found. And there is" (he
says) "a power of iron in the wedded Earth which is perfect in its own kind
when it has received fertilizing force from the male, that is to say, the stone
of Hercules" (in his book De Proportionibus). And later: "Because" (he
says) "in the previous proposition I have taught that iron is true earth." A
strong loadstone shows itself to be of the inward earth, and upon
innumerable tests claims to rank with the earth in the possession of a
primary form, that by which Earth herself abides in her own station and is
directed in her courses. Thus a weaker loadstone and every ore of iron, and
nearly all clay, or clayey earth, and numerous other sorts (yet more, or less,
owing to the different labefaction of fluids and slimes), keep their
magnetick and genuine earth-properties open to view, falling short of the
characteristic form, and deformate. For it is not iron alone (the smelted
metal) that points to the poles, nor is it the loadstone alone that is attracted
by another and made to revolve magnetically; but all iron ores, and other
stones, as Rhenish slates and the black ones from Avignon (the French call
them Ardoises) which they use for tiles, and many more of other colours
and substances, provided they have been prepared; as well as all clay,
grit[105], and some sorts of rocks, and, to speak more clearly, all the more
solid earth that is everywhere apparent; given that that earth be not fouled
with fatty and fluid corruptions; as mud, as mire, as accumulations of putrid
matter; nor deformate by the imperfections of sundry admixtures; nor
dripping with ooze, as marls; all are attracted by the loadstone, when simply
prepared by fire, and freed from their refuse humour; and as by the
loadstone so also by the earth herself they are drawn and controlled
magnetically, in a way different from all other bodies; and by that inherent
force settle themselves according to the orderly arrangement and fabric of
the universe and of the Earth, as will appear later. Thus every part of the
earth which is removed from it exhibits by sure experiments every impulse
of the magnetick nature; by its various motions it observes the globe of the
earth and the principle common to both.

BOOK SECOND.

CHAP. I.

ON MAGNETICK
Motions.

ivers things concerning opinions about the magnet-stone, and its
variety, concerning its poles and its known faculties, concerning
iron, concerning the properties of iron, concerning a magnetick
substance common to both of these and to the earth itself, have
been spoken briefly by us in the former book. There remain the magnetical
motions, and their fuller philosophy, shown and demonstrated. These
motions are incitements of homogeneal parts either among themselves or
toward the primary conformation of the whole earth. Aristotle admits only
two simple motions of his elements, from the centre and toward the centre;
of light ones upward, heavy ones downward; so that in the earth there exists
one motion only of all its parts towards the centre of the world,—a rude and

inert precipitation. But what of it is light, and how wrongly it is inferred by
the Peripateticks from the simple motion of the elements, and also what is
its heavy part, we will discuss elsewhere. But now our inquiry must be into
the causes of other motions, depending on its true form, which we have
plainly seen in our magnetick bodies; and these we have seen to be present
in the earth and in all its homogenic parts also. We have noticed that they
harmonize with the earth, and are bound up with its forces. Five
movements[106] or differences of motions are then observed by us: Coition
(commonly called attraction), the incitement to magnetick union; Direction
towards the poles of the earth, and the verticity and continuance of the earth
towards the determinate poles of the world; Variation, a deflexion from the
meridian, which we call a perverted movement; Declination, a descent of
the magnetick pole below the horizon; and circular motion, or Revolution.
Concerning all these we shall discuss separately, and how they all proceed
from a nature tending to aggregation, either by verticity or by volubility.
Jofrancus Offusius[107] makes out different magnetick motions; a first
toward a centre; a second toward a pole at seventy-seven degrees; a third
toward iron; a fourth toward loadstone. The first is not always to a centre,
but exists only at the poles in a straight course toward the centre, if the
motion is magnetick; otherwise it is only motion of matter toward its own
mass and toward the globe. The second toward a pole at seventy-seven
degrees is no motion, but is direction with respect to the pole of the earth, or
variation. The third and fourth are magnetick and are the same. So he truly
recognizes no magnetick motion except the Coition toward iron or
loadstone, commonly called attraction. There is another motion in the whole
earth, which does not exist towards the terrella or towards its parts;
videlicet, a motion of aggregation, and that movement of matter, which is
called by philosophers a right motion, of which elsewhere.

CHAP. II.

On the Magnetick Coition, and first on the
Attraction of Amber, or more truly, on the
Attaching of Bodies to Amber.

elebrated has the fame of the loadstone and of amber ever been in
the memoirs of the learned. Loadstone and also amber do some
philosophers invoke when in explaining many secrets their senses
become dim and reasoning cannot go further. Inquisitive
theologians also would throw light on the divine mysteries set beyond the
range of human sense, by means of loadstone and amber; just as idle
Metaphysicians, when they are setting up and teaching useless phantasms,
have recourse to the loadstone as if it were a Delphick sword, an illustration
always applicable to everything. But physicians even (with the authority of
Galen), desiring to confirm the belief in the attraction of purgative
medicines by means of the likeness of substance and the familiarities of the
juices—truly a vain and useless error—bring in the loadstone as witness as
being a nature of great authority and of conspicuous efficacy and a
remarkable body. So in very many cases there are some who, when they are
pleading a cause and cannot give a reason for it, bring in loadstone and
amber as though they were personified witnesses. But these men (apart
from that common error) being ignorant that the causes of magnetical
motions are widely different from the forces of amber, easily fall into error,
and are themselves the more deceived by their own cogitations. For in other
bodies a conspicuous force of attraction manifests itself otherwise than in
loadstone; like as in amber, concerning which some things must first be
said, that it may appear what is that attaching of bodies, and how it is
different from and foreign to the magnetical actions; those mortals being
still ignorant, who think that inclination to be an attraction, and compare it
with the magnetick coitions. The Greeks call it ἤλεκτρον[108] because it
attracts straws to itself, when it is warmed by rubbing; then it is called
ἅρπαξ[109]; and χρυσοφόρον from its golden colour. But the Moors call it
Carabe[110], because they are accustomed to offer the same in sacrifices and
in the worship of the Gods. For Carab signifies to offer in Arabic; so
Carabe, an offering: or seizing chaff, as Scaliger quotes from Abohalis, out
of the Arabic or Persian language. Some also call it Amber, especially the
Indian and Ethiopian amber, called in Latin Succinum, as if it were a
juice[111]. The Sudavienses or Sudini[112] call it geniter, as though it were
generated terrestrially. The errors of the ancients concerning its nature and
origin having been exploded, it is certain that amber comes for the most
part from the sea, and the rustics collect it on the coast after the more
violent storms, with nets and other tackle; as among the Sudini of Prussia;

and it is also found sometimes on the coast of our own Britain. It seems,
however, to be produced also in the soil and at spots of some depth, like
other bitumens; to be washed out by the waves of the sea; and to become
concreted more firmly from the nature and saltness of the sea-water. For it
was at first a soft and viscous material; wherefore also it contains enclosed
and entombed in pieces of it, shining in eternal sepulchres, flies, grubs,
gnats, ants; which have all flown or crept or fallen into it when it first
flowed forth in a liquid state[113]. The ancients and also more recent writers
recall (experience proving the same thing), that amber attracts straws and
chaff[114]. The same is also done by jet[115], which is dug out of the earth in
Britain, in Germany, and in very many lands, and is a rather hard concretion
from black bitumen, and as it were a transformation into stone. There are
many modern authors[116] who have written and copied from others about
amber and jet[117] attracting chaff, and about other substances generally
unknown; with whose labours the shops of booksellers are crammed. Our
own age has produced many books about hidden, abstruse, and occult
causes and wonders, in all of which amber and jet are set forth as enticing
chaff; but they treat the subject in words alone, without finding any reasons
or proofs from experiments, their very statements obscuring the thing in a
greater fog, forsooth in a cryptic, marvellous, abstruse, secret, occult, way.
Wherefore also such philosophy produces no fruit, because very many
philosophers, making no investigation themselves, unsupported by any
practical experience, idle and inert, make no progress by their records, and
do not see what light they can bring to their theories; but their philosophy
rests simply on the use of certain Greek words, or uncommon ones; after
the manner of our gossips and barbers nowadays, who make show of certain
Latin words to an ignorant populace as the insignia of their craft, and snatch
at the*popular favour. For it is not only amber and jet (as they suppose)
which entice small bodies[118]; but Diamond, Sapphire, Carbuncle, Iris
gem[119], Opal, Amethyst, Vincentina, and Bristolla (an English gem or
spar)[120], Beryl, and Crystal[121] do the same. Similar powers of attraction
are seen also to be possessed by glass (especially when clear and lucid), as
also by false gems made of glass or Crystal, by glass of antimony, and by
many kinds of spars from the mines, and by Belemnites. Sulphur also
attracts, and mastick, and hard sealing-wax[122] compounded of lac
tinctured of various colours. Rather hard resin entices, as does

orpiment[123], but less strongly; with difficulty also and indistinctly under a
suitable dry sky[124], Rock salt, muscovy stone, and rock alum. This one
may see when the air is sharp and clear and rare in mid-winter, when the
emanations from the earth hinder electricks less, and the electrick bodies
become* more firmly indurated; about which[125] hereafter. These substances
draw everything, not straws and chaff only , but all metals, woods,
leaves, stones, earths, even water and oil, and everything which is subject to
our senses, or is solid; although some write that amber does not attract
anything but chaff and certain twigs; (wherefore Alexander Aphrodiseus
falsely declares the question of amber to be inexplicable, because it attracts
dry chaff only, and not basil leaves[126]), but these are the utterly false and
disgraceful tales of the writers. But in order that you may be able clearly to
test how such attraction occurs[127], and what those materials[128] are which
thus entice other bodies (for even if bodies incline towards some of these,
yet on account of weakness they seem not to be raised by them, but are
more easily turned), make yourself a versorium of any metal you like, three
or four digits in length, resting rather lightly on its point of support after the
manner of a magnetick needle, to one end of which bring up a piece of
amber or a smooth and polished gem which has been
gently rubbed; for the versorium turns forthwith. Many
things are thereby seen to attract, both those which are
formed by nature alone, and those which are by art
prepared, fused, and mixed; nor is this so much a singular property of one
or two things (as is commonly supposed), but the manifest nature of very
many, both of simple substances, remaining merely in their own form, and
of compositions, as of hard sealing-wax, & of certain other mixtures
besides, made of unctuous stuffs. We must, however, investigate more fully
whence that tendency arises, and what those forces be, concerning which a
few men have brought forward very little, the crowd of philosophizers
nothing at all. By Galen three kinds of attractives in general were
recognized in nature: a First class of those substances which attract by their
elemental quality, namely, heat; the Second is the class of those which
attract by the succession of a vacuum; the Third is the class of those which
attract by a property of their whole substance, which are also quoted by
Avicenna and others. These classes, however, cannot in any way satisfy us;
they neither embrace the causes of amber, jet, and diamond, and of other

similar substances (which derive their forces on account of the same virtue);
nor of the loadstone, and of all magnetick substances, which 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, 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. They are very general
qualities or kinships of a substance, and yet are not to be assigned as true
causes, and, if I may say so, those philosophizers utter some resounding

words; but about the thing itself prove nothing in particular. Nor does this
attraction accredited to amber arise from any singular quality of the
substance or kinship, since by more thorough research we find the same
effect in very many other bodies; and all bodies, moreover, of whatever
quality, are allured by all those bodies. Similarity also is not the cause;
because all things around us placed on this globe of the earth, similar and
dissimilar, are allured by amber and bodies of this kind; and on that account
no cogent analogy is to be drawn either from similarity or identity of
substance. But neither do similars mutually attract one another, as stone
stone, flesh flesh, nor aught else outside the class of magneticks and
electricks. Fracastorio would have it that "things which mutually attract one
another are similars, as being of the same species, either in action or in right
subjection. Right subjection is that from which is emitted the emanation
which attracts and which in mixtures often lies hidden on account of their
lack of form, by reason of which they are often different in act from what
they are in potency. Hence it may be that hairs and twigs move towards
amber and towards diamond, not because they are hairs, but because either
there is shut up in them air or some other principle, which is attracted in the
first place, and which bears some relation and analogy to that which attracts
of itself; in which diamond and amber agree through a principle common to
each." Thus far Fracastorio. Who if he had observed by a large number of
experiments that all bodies are drawn to electricks except those which are
aglow and aflame, and highly rarefied, would never have given a thought to
such things. It is easy for men of acute intellect, apart from experiments and
practice, to slip and err. In greater error do they remain sunk who maintain
these same substances to be not similar, but to be substances near akin; and
hold that on that account a thing moves towards another, its like, by which
it is brought to more perfection. But these are ill-considered views; for
towards all electricks all things move[130] except such as are aflame or are
too highly rarefied, as air, which is the universal effluvium of this globe and
of the world. Vegetable substances draw moisture by which their shoots are
rejoiced and grow; from analogy with that, however, Hippocrates, in his De
Natura Hominis, Book I., wrongly concluded that the purging of morbid
humour took place by the specifick force of the drug. Concerning the action
and potency of purgatives we shall speak elsewhere. Wrongly also is
attraction inferred in other effects; as in the case of a flagon full of water,
when buried in a heap of wheat, although well stoppered, the moisture is

drawn out; since this moisture is rather resolved into vapour by the
emanation of the fermenting wheat, and the wheat imbibes the freed vapour.
Nor do elephants' tusks attract moisture, but drive it into vapour or absorb
it. Thus then very many things are said to attract, the reasons for whose
energy must be sought from other causes. Amber in a fairly large mass
allures,
* if it is polished; in a smaller mass or less pure it seems not to attract
without friction. But very many electricks (as precious stones and some
other substances) do not attract at all unless rubbed. On the other hand
many*gems, as well as other bodies, are polished, yet do not allure, and by
no amount of friction are they aroused; thus the emerald, agate, carnelian,
pearls, jasper, chalcedony, alabaster, porphyry, coral, the marbles,
touchstone, flint, bloodstone, emery[131], do not acquire any power; nor do
bones, or ivory, or the hardest woods, as ebony, nor do cedar, juniper, or
cypress; nor do metals, silver, gold, brass, iron, nor any loadstone, though
many of them are finely polished and shine. But on the other hand there are
some other polished substances of which we have spoken before, toward
which, when they have been rubbed, bodies incline. This we shall
understand only when we have more closely looked into the prime origin of
bodies. It is plain to all, and all admit, that the mass of the earth, or rather
the structure and crust of the earth, consists of a twofold material, namely,
of fluid and humid matter, and of material of more consistency and dry.
From this twofold nature or the more simple compacting of one, various
substances take their rise among us, which originate in greater proportion
now from the earthy, now from the aqueous nature. Those substances which
have received their chief growth from moisture, whether aqueous or fatty,
or have taken on their form by a simpler compacting from them, or have
been compacted from these same materials in long ages, if they have a
sufficiently firm hardness, if rubbed after they have been polished and when
they remain bright with the friction—towards those substances everything,
if presented to them in the air, turns, if its too heavy weight does not
prevent it. For amber has been compacted of moisture, and jet also. Lucid
gems are made of water; just as Crystal[132], which has been concreted from
clear water, not always by a very great cold, as some used to judge, and by
very hard frost, but sometimes by a less severe one, the nature of the soil
fashioning it, the humour or juices being shut up in definite cavities, in the
way in which spars are produced in mines. So clear glass is fused out of
sand, and from other substances, which have their origin in humid juices.

But the dross of metals, as also metals, stones, rocks, woods, contain earth
rather,* or are mixed with a good deal of earth; and therefore they do not
attract. Crystal, mica, glass, and all electricks do not attract if they are burnt
or roasted; for their primordial supplies of moisture perish by heat, and are
changed and exhaled. All things therefore which have sprung from a
predominant moisture and are firmly concreted, and retain the appearance
of spar and its resplendent nature in a firm and compact body, allure all
bodies, whether humid or dry. Those, however, which partake of the true
earth-substance or are very little different from it, are seen to attract also,
but from a far different reason, and (so to say) magnetically; concerning
these we intend to speak afterwards. But those substances which are more
mixed of water and earth, and are produced by the equal degradation of
each element (in which the magnetick force of the earth is deformed and
remains buried; while the watery humour, being fouled by joining with a
more plentiful supply of earth, has not concreted in itself but is mingled
with earthy matter), can in no way of themselves attract or move from its
place anything which they do not touch. On this account metals, marbles,
flints, woods, herbs, flesh, and very many other things can neither allure nor
solicit any body either magnetically or electrically. (For it pleases us to call
that an
* electrick force, which hath its origin from the humour.) But
substances consisting mostly of humour, and which are not very firmly
compacted by nature (whereby do they neither bear rubbing, but either melt
down and become soft, or are not levigable, such as pitch, the softer kinds
of resin, camphor, galbanum, ammoniack[133], storax, asafœtida, benzoin,
asphaltum, especially in rather warm weather) towards them small bodies
are not
* borne; for without rubbing most electricks do not emit their peculiar
and native exhalation and effluvium. The resin turpentine when liquid does
not attract; for it cannot be rubbed; but if it has hardened into a mastick it
does attract. But now at length we must understand why small bodies turn
towards those substances which have drawn their origin from water; by
what force and with what hands (so to speak) electricks seize upon kindred
natures. In all bodies in the world two causes or principles have been laid
down, from which the bodies themselves were produced, matter and
form[134]. Electrical motions become strong from matter, but magnetick
from form chiefly; and they differ widely from one another and turn out
unlike, since the one is ennobled by numerous virtues and is prepotent; the
other is ignoble and of less potency, and mostly restrained, as it were,

within certain barriers; and therefore that force must at times be aroused by
attrition or friction, until it is at a dull heat and gives off an effluvium and a
polish is induced on the body. For spent air, either blown out of the mouth
or given
* off from moister air, chokes the virtue. If indeed either a sheet of
paper or a piece of linen be interposed, there will be no movement. But a
loadstone, without friction or heat, whether dry or suffused with moisture,
as well in air as in water, invites magneticks, even with the most solid
bodies interposed, even planks of wood or pretty thick slabs of stone or
sheets* of metal. A loadstone appeals to magneticks only; towards electricks
all things move. A loadstone[135] raises great weights; so that if there is a
loadstone weighing two ounces and strong, it attracts half an ounce or a
whole ounce. An electrical substance only attracts very small weights; as,
for instance, a piece of amber of three ounces weight, when rubbed, scarce
raises a fourth part of a grain of barley. But this attraction of amber and of
electrical substances must be further investigated; and since there is this
particular affection of matter, it may be asked why is amber rubbed, and
what affection is produced by the rubbing, and what causes arise which
make it lay hold on everything? As a result of friction it grows slightly
warm and becomes smooth; two results which must often occur together. A
large polished fragment of amber or jet attracts indeed, even without
friction, but less strongly; but if it be brought gently near a flame or a live
coal, so that it equally becomes warm, it does not attract small bodies
because* it is enveloped in a cloud from the body of the flaming substance,
which emits a hot breath, and then impinges upon it vapour from a foreign
body which for the most part is at variance with the nature of amber.
Moreover the spirit of the amber which is called forth is enfeebled by alien
heat; wherefore it ought not to have heat excepting that produced by motion
only and friction, and, as it were, its own, not sent into it by other bodies.
For as the igneous heat emitted from any burning substance cannot be so
used that electricks may acquire their force from it; so also heat from the
solar *rays does not fit an electrick by the loosening of its right material,
because it dissipates rather and consumes it (albeit a body which has been
rubbed retains its virtue longer exposed to the rays of the sun than in the
shade; because in the shade the effluvia are condensed to a greater degree
and more quickly). Then again the fervour from the light of the Sun aroused
*
by means of a burning mirror confers no vigour on the heated amber[136];
indeed * it dissipates and corrupts all the electrick effluvia. Again, burning

sulphur and hard wax, made from shell-lac, when aflame do not allure; for
heat from friction resolves bodies into effluvia, which flame consumes
away. For it is impossible for solid electricks to be resolved into their own
true effluvia otherwise than by attrition, save in the case of certain
substances which by reason of innate vigour emit effluvia constantly. They
are rubbed with bodies which do not befoul their surface, and which
produce a polish, as pretty stiff silk or a rough wool rag which is as little
soiled as possible, or the dry palm. Amber also is rubbed with amber, with
diamond, and with glass, and numerous other substances. Thus are
electricks manipulated. These things being so, what is it which moves? Is it
the body itself, inclosed within its own circumference? Or is it something
imperceptible to us, which flows out from the substance into the ambient
air? Somewhat as Plutarch opines, saying in his Quæstiones Platonicæ[137]:
That there is in amber something flammable or something having the nature
of breath, and this by the attrition of the surface being emitted from its
relaxed pores attracts bodies. And if it be an effusion does it seize upon the
air whose motion the bodies follow, or upon the bodies themselves? But if
amber allured the body itself, then what need were there of friction, if it is
bare and smooth? Nor does the force arise from the light which is reflected
from a smooth and polished body; for a Gem of Vincent's rock[138],
Diamond, and clear glass, attract when they are rough; but not so
powerfully and quickly, because they are not so readily cleansed from
extraneous moisture on the surface, and are not rubbed equally so as to be
copiously resolved at that part. Nor does the sun by its own beams of light
and its rays, which are of capital importance in nature, attract bodies in this
way; and yet the herd of philosophizers considers that humours are attracted
by the sun, when it is only denser humours that are being turned into
thinner, into spirit and air; and so by the motion of effusion they ascend into
the upper regions, or the attenuated exhalations are raised up from the
denser air. Nor does it seem to take place from the effluvia attenuating the
air, so that bodies impelled by the denser air penetrate towards the source of
the rarefaction; in this case both hot and flaming bodies would also allure
other bodies; but not even the lightest chaff, or any versorium moves
towards a flame. If there is a flow and rush of air towards the body, how can
a small diamond of the size of a pea[139] summon towards itself so much air,
that it seizes hold of a biggish long body placed in equilibrio (the air about
one or other very small part of an end being attracted)? It ought also to have

slopped or moved more slowly, before it came into contact with the body,
especially if the piece of amber was rather broad and flat, from the
accumulation of air on the surface of the amber and its flowing back again.
If it is because the effluvia are thinner, and denser vapours come in return,
as in breathing, then the body would rather have had a motion toward the
electrick a little while after the beginning of the application; but when
electricks
* which have been rubbed are applied quickly to a versorium then
especially at once they act on the versorium, and it is attracted more when
near them. But if it is because the rarefied effluvia produce a rarefied
medium, and on that account bodies are more prone to slip down from a
denser to a more attenuated medium; they might have been carried from the
side in this way or downwards, but not to bodies above them; or the
attraction and apprehension of contiguous bodies would have been
momentary only. But with a single friction jet and amber draw and attract
bodies to them strongly and for a long time, sometimes for the twelfth part
of an hour, especially in clear weather. But if the mass of amber be rather
large, and the surface polished, it attracts without friction. Flint is rubbed
and emits by attrition an inflammable matter that turns into sparks and heat.
Therefore the denser effluvia of flint producing fire are very far different
from electrical effluvia, which on account of their extreme attenuation do
not take fire, nor are fit material for flame. Those effluvia are not of the
nature of breath, for when emitted they do not propel anything, but are
exhaled without sensible resistance and touch bodies. They are highly
attenuated humours much more subtile than the ambient air; and in order
that they may occur, bodies are required produced from humour and
concreted with a considerable degree of hardness. Non-electrick bodies are
not resolved into humid effluvia, and those effluvia mix with the common
and general effluvia of the earth, and are not peculiar. Also besides the
attraction of bodies, they retain them longer. It is probable therefore that
amber* does exhale something peculiar to itself, which allures bodies
themselves, not the intermediate air. Indeed it plainly does draw the body
itself in the case of a spherical drop of water standing on a dry surface; for a
piece of amber applied to it at a suitable distance pulls the nearest parts out
of their
* position and draws it up into a cone; otherwise, if it were drawn by
means of the air rushing along, the whole drop would have moved. That it
does not attract the air is thus demonstrated: take a very thin wax candle,
which makes a very small and clear flame; bring up to this, within two

digits or any convenient distance, a piece of amber or jet, a broad flat piece,
well prepared
* and skilfully rubbed, such a piece of amber as would attract
bodies far and wide, yet it does not disturb the flame; which of necessity
would have occurred, if the air was disturbed, for the flame would have
followed the current of air. As far as the effluvia are sent out, so far it
allures; but as a body approaches, its motion is accelerated, stronger forces
drawing it; as also in the case of magneticks and in all natural motion; not
by attenuating or by expelling the air, so that the body moves down into the
place of the air which has gone out[140]; for thus it would have allured only
and would not have retained; since it would at first also have repelled
approaching bodies just as it drives the air itself; but indeed a particle, be it
ever so small, does not avoid the first application made very quickly after
rubbing. An effluvium exhales from amber and is emitted by rubbing:
pearls, carnelian, agate, jasper, chalcedony, coral, metals, and other
substances of that kind, when they are rubbed, produce no effect. Is there
not also something which is exhaled from them by heat and attrition? Most
truly; but from grosser bodies more blended with the earthy nature, that
which is exhaled is gross and spent; for even towards very many electricks,
if they
* are rubbed too hard, there is produced but a weak attraction of
bodies, or none at all; the attraction is best when the rubbing has been
gentle and very quick; for so the finest effluvia are evoked. The effluvia
arise from the subtile diffusion of humour, not from excessive and turbulent
violence; especially in the case of those substances which have been
compacted from unctuous matter, which when the atmosphere is very thin,
when the North winds, and amongst us (English) the East winds, are
blowing, have a surer and firmer effect, but during South winds and in
damp*weather, only a weak one; so that those substances which attract with
difficulty in clear weather, in thick weather produce no motion at all; both
because in grosser air lighter substances move with greater difficulty; and
especially because the effluvia are stifled, and the surface of the body that
has been rubbed is affected by the spent humour of the air, and the effluvia
are stopped at their very starting. On that account in the case of amber, jet,
and sulphur, because they do not so easily take up moist air on their surface
and are much more plenteously set free, that force is not so quickly
suppressed as in gems, crystal, glass, and substances of that kind which
collect on their surface the moister breath which has grown heavy. But it
may be asked why does amber allure water, when water placed on its

surface removes its action? Evidently because it is one thing to suppress it
at its *very start, and quite another to extinguish it when it has been emitted.
So also thin and very fine silk, in common language Sarcenet, placed
quickly* on the amber, after it has been rubbed, hinders the attraction of the
body; but if it is interposed in the intervening space, it does not entirely
obstruct it. Moisture also from spent air, and any breath blown from the
mouth, as well as water put on the amber, immediately extinguishes its
force. But oil, which is light and pure, does not hinder it; for although
amber* be rubbed with a warm finger dipped in oil, still it attracts. But if that
amber, after the rubbing, is moistened with aqua vitæ or spirits of wine, it
does not attract; for it is heavier than oil, denser, and when added to oil
sinks beneath it. For oil is light and rare, and does not resist the most
delicate effluvia. A breath therefore, proceeding from a body which had
been compacted from humour or from a watery liquid, reaches the body to
be attracted; the body that is reached is united with the attracting body, and
the one body lying near the other within the peculiar radius of its effluvia
makes one out of two; united, they come together into the closest accord,
and this is commonly called attraction. This unity, according to the opinion
of Pythagoras, is the principle of all things, and through participation in it
each several thing is said to be one. For since no action can take place by
means of matter unless by contact, these electricks are not seen to touch,
but, as was necessary, something is sent from the one to the other,
something which may touch closely and be the beginning of that
incitement. All bodies are united and, as it were, cemented together in some
way by moisture; so that a wet body, when it touches another body, attracts
it, if it is small. So wet bodies on the surface of water attract wet bodies.
But the peculiar electrical effluvia, which are the most subtile material of
diffuse humour, entice corpuscles. Air (the common effluvium of the earth)
not only unites the disjointed parts, but the earth calls bodies back to itself
by means of the intervening air; otherwise bodies which are in higher places
would not so eagerly make for the earth. Electrical effluvia differ greatly
from air; and as air is the effluvium of the earth, so electricks have their
own effluvia and properties, each of them having by reason of its peculiar
effluvia a singular tendency toward unity, a motion toward its origin and
fount, and toward the body emitting the effluvia. But those substances
which by attrition emit a gross or vapourous or aeriform effluvium produce
no effect; for either such effluvia are alien to the humour (the uniter of all

things), or being very like common air are blended with the air and
intermingle with the air, wherefore they produce no effect in the air, and do
not cause motions different from those so universal and common in nature.
In like* manner bodies strive to be united and move on the surface of water,
just as the rod C, which is put a little way under
water. It is plain that the rod E F, which floats on
the water by reason of the cork H, and only has
its wet end F above the surface of the water, is
attracted by the rod C, if the rod C is wet a little
above the surface of the water; they are suddenly united, just as a drop
adjoining a drop is attracted. So a wet thing on the surface of water seeks
union with a wet thing, since the surface of the water is raised on both; and
they immediately flow together, just like drops or bubbles. But they are in
much greater proximity than electricks, and are united by their clammy
natures.
* If, however, the whole rod be dry above the water, it no longer
attracts, but drives away the stick E F. The same is seen in those bubbles
also which are made on water. For we see one drive towards another, and
the quicker the nearer they are. Solids are impelled towards solids by the
medium of liquid: for example, touch the end of a versorium with the end of
a rod on which a drop of water is projecting; as soon as the versorium
touches* the top of the droplet, immediately it is joined strongly by a swift
motion to the body of the rod. So concreted humid things attract when a
little resolved into air (the effluvia in the intermediate space tending to
produce unity); for water has on wet bodies, or on bodies wet with abundant
moisture on the top of water, the force of an effluvium. Clear air is a
convenient medium for an electrical effluvium excited from concreted
humour. Wet bodies projecting above the surface of water (if they are near)
run together so that they may unite; for the surface of the water is raised
around wet substances. But a dry thing is not impelled to a wet one, nor a
wet to a dry, but seems to run away. For if all is dry above the water, the
surface of the water close to it does not rise, but shuns it, the wave sinking
around a dry thing. So neither does a wet thing move towards the dry rim of
a vessel; but it seeks a wet rim. A B is the surface
of the water; C D two rods, which stand up wet
above the water; it is manifest that the surface of
the water is raised at C and D along with the
rods; and therefore the rod C, by reason of the

water standing up (which seeks its level and unity), moves with the water to
D. On E, on the other hand, a wet rod, the water also rises; but on the dry
rod F the surface is depressed; and as it drives to depress also the wave
rising on E in its neighbourhood, the higher wave at E turns away from
F[141]; for it does not suffer itself to be depressed. All electrical attraction
occurs through an intervening humour; so it is by reason of humour that all
things mutually come together; fluids indeed and aqueous bodies on the
surface of water, but concreted things, if they have been resolved into
vapour, in air;—in air indeed, the effluvium of electricks being very rare,
that it may the better permeate the medium and not impel it by its motion;
for if that effluvium had been thick, as that of air, or of the winds, or of
saltpetre burnt by fire, as the thick and foul effluvia given out with very
great force, from other bodies, or air set free from humour by heat rushing
out through a pipe (in the instrument of Hero of Alexandria, described in his
book Spiritalia), then the effluvium would drive everything away, not allure
it. But those rarer effluvia take hold of bodies and embrace them as if with
arms extended, with the electricks to which they are united; and they are
drawn to the source, the effluvia increasing in strength with the proximity.
But what is that effluvium from crystal, glass, and diamond, since these are
bodies of considerable hardness and firmly concreted? In order that such an
effluvium should be produced, there is no need of any marked or
perceptible flux[142] of the substance; nor is it necessary that the electrick
should be abraded, or worn away, or deformed. Some odoriferous
substances are fragrant for many years, exhaling continually, yet are not
quickly consumed. Cypress wood as long as it is sound, and it lasts a very
long time indeed, is redolent; as many learned men attest from experience.
Such an electrick only for a moment, when stimulated by friction, emits
powers far more subtile and more fine beyond all odours; yet sometimes
amber, jet, sulphur, when they are somewhat easily let free into vapour, also
pour out at the same time an odour; and on this account they allure with the
very gentlest rubbing, often even without rubbing; they also excite more
strongly, and retain hold for a longer time, because they have stronger
effluvia
* and last longer. But diamond, glass, rock-crystal, and numerous
others of the harder and firmly concreted gems first grow warm: therefore
at first they are rubbed longer, and then they also attract strongly; nor are
they otherwise set free into vapour. Everything rushes towards
electricks[143] excepting flame, and flaming bodies, and the thinnest air. Just

as they do not draw flame, in like manner they do not affect a versorium, if
on any side it is very near to a flame, either the flame of a lamp or of any
burning matter. It is manifest indeed that the effluvia are destroyed by flame
and igneous
* heat; and therefore they attract neither flame nor bodies very
near a flame. For electrical effluvia have the virtue of, and are analogous
with, extenuated humour; but they will produce their effect, union and
continuity, not by the external impulse of vapours, not by heat and
attenuation of heated bodies, but by their humidity itself attenuated into its
own peculiar
* effluvia. Yet they entice smoke sent out by an extinguished
light; and the more that smoke is attenuated in seeking the upper regions,
the less strongly is it turned aside; for things that are too rarefied are not
drawn* to them; and at length, when it has now almost vanished, it does not
incline towards them at all, which is easily seen against the light. When in
fact the smoke has passed into air, it is not moved, as has been
demonstrated before. For air itself, if somewhat thin, is not attracted in any
way, unless on account of succeeding that which has vacated its place, as in
furnaces and such-like, where the air is fed in by mechanical devices for
drawing it in. Therefore an effluvium resulting from a non-fouling friction,
and one which is not changed by heat, but which is its own, causes union
and coherency, a prehension and a congruence towards its source, if only
the body to be attracted is not unfitted for motion, either by the
surroundings of the bodies or by its own weight. To the bodies therefore of
the electricks themselves small bodies are borne. The effluvia extend out
their virtue—effluvia which are proper and peculiar to them, and sui
generis, differing from common air, being produced from humour, excited
by a calorifick motion from attrition and attenuation. And as if they were
material rays[144], they hold and take up chaff, straws, and twigs, until they
become extinct or vanish away: and then they (the corpuscles) being loosed
again, attracted by the earth itself, fall down to the earth. The difference
between Magneticks and Electricks[145] is that all magneticks run together
with mutual forces; electricks only allure; that which is allured is not
changed
* by an implanted force, but that which has moved up to them
voluntarily rests upon them by the law of matter. Bodies are borne towards
electricks in a straight line towards the centre of the electrick; a loadstone
draws a loadstone directly at the poles only, in other parts obliquely and
transversely, and in this way also they adhere and hang to one another.
Electrical motion is a motion of aggregation of matter; magnetical motion is

one of disposition and conformation. The globe of the earth is aggregated
and cohæres by itself electrically. The globe of the earth is directed and
turned magnetically; at the same time also it both cohæres, and in order that
it may be solid, is in its inmost parts cemented together.

CHAP. III.

Opinions of others on Magnetick Coition,
which they call Attraction.

iscussion having now been made concerning electricks, the causes
of magnetick coition must be set forth. We say coition, not
attraction[146]. The word attraction unfortunately crept into
magnetick philosophy from the ignorance of the ancients; for there
seems to be force applied where there is attraction and an imperious
violence dominates. For, if ever there is talk about magnetick attraction, we
understand thereby magnetick coition, or a primary running together. Now
in truth it will not be useless here first briefly to set forth the views given by
others, both the ancient and the more modern writers. Orpheus in his
hymns[147] narrates that iron is attracted by loadstone as the bride to the
arms of her espoused. Epicurus holds that iron is attracted by a loadstone
just as straws by amber; "and," he adds, "the Atoms and indivisible particles
which are given off by the stone and by the iron fit one another in shape; so
that they easily cling to one another; when therefore these solid particles of
stone or of iron strike against one another, then they rebound into space,
being brought against one another by the way, and they draw the iron along
with them." But this cannot be the case in the least; since solid and very
dense substances interposed, even squared blocks of marble, do not obstruct
this power, though they can separate atoms from atoms; and the stone and
the iron would be speedily dissipated into such profuse and perpetual
streams of atoms. In the case of amber, since there is another different
method of attracting, the Epicurean atoms cannot fit one another in shape.
Thales, as Aristotle writes, De Anima, Bk. I., deemed the loadstone to be
endowed with a soul of some sort, because it had the power of moving and

drawing iron towards it. Anaxagoras also held the same view. In the Timæus
of Plato there is an idle fancy[148] about the efficacy of the stone of
Hercules. For he says that "all flowings of water, likewise the fallings of
thunderbolts, and the things which are held wonderful in the attraction of
Amber, and of the Herculean stone, are such that in all these there is never
any attraction; but since there is no vacuum, the particles drive one another
mutually around, and when they are dispersed and congregated together,
they all pass, each to its proper seat, but with changed places; and it is
forsooth, on account of these intercomplicated affections that the effects
seem to arouse the wonder in him who has rightly investigated them."
Galen does not know why Plato should have seen fit to select the theory of
circumpulsion rather than that of attraction (differing almost on this point
alone from Hippocrates), though indeed it does not agree in reality with
either reason or experiment. Nor indeed is either the air or anything else
circumpelled; and the bodies themselves which are attracted are carried
towards the attracting substance not confusedly, or in an orbe. Lucretius, the
poet of the Epicurean sect, sang his opinion of it thus:
[149]
First, then, know,
Ceaseless effluvia from the magnet flow,—
Effluvia, whose superior powers expel
The air that lies between the stone and steel.
A vacuum formed, the steely atoms fly
In a link'd train, and all the void supply;
While the whole ring to which the train is join'd
The influence owns, and follows close behind. &c.

Such a reason Plutarch also alleges in the Quæstiones Platonicæ: That that
stone gives off heavy exhalations, whereby the adjacent air, being impelled
along, condenses that which is in front of it; and that air, being driven round
in an orbe and reverting to the place it had vacated, drags the iron forcibly
along with it. The following explanation of the virtues of the loadstone and
of amber is propounded by Johannes Costæus of Lodi[150]. For he would
have it that "there is mutual work and mutual result, and therefore the
motion is partly due to the attraction of the loadstone and partly to a
spontaneous movement on the part of the iron: For as we say that vapours
issuing from the loadstone hasten by their own nature to attract the iron, so

also the air repelled by the vapours, whilst seeking a place for itself, is
turned back, and when turned back, it impels the iron, lifts it up, as it were,
and carries it along; the iron being of itself also excited somehow. So by
being drawn out and by a spontaneous motion, and by striking against
another substance, there is in some way produced a composite motion,
which motion would nevertheless be rightly referred to attraction, because
the terminus from which this motion invariably begins is the same terminus
at which it ends, which is the characteristic proper of an attraction." There is
certainly a mutual action, not an operation, nor does the loadstone attract in
that way; nor is there any impulsion. But neither is there that origination of
the motion by the vapours, and the turning of them back, which opinion of
Epicurus has so often been quoted by others. Galen errs in his De
Naturalibus Facultatibus, Book I., chap. 14, when he expresses the view
that whatever agents draw out either the venom of serpents or darts also
exhibit the same power as the loadstone. Now of what sort may be the
attraction of such medicaments (if indeed it may be called attraction) we
shall consider elsewhere. Drugs against poisons or darts have no relation to,
no similitude with, the action of magnetical bodies. The followers of Galen
(who hold that purgative medicaments attract because of similitude of
substance) say that bodies are attracted on account of similitude, not
identity, of substance; wherefore the loadstone draws iron, but iron does not
draw iron. But we declare and prove that this happens in primary bodies,
and in those bodies that are pretty closely related to them and especially like
in kind one to another, on account of their identity; wherefore also
loadstone draws loadstone and likewise iron iron; every really true earth
draws earth; and iron fortified by a loadstone within the orbe of whose
virtue it is placed draws iron more strongly than it does the loadstone.
Cardan asks why no other metal is attracted by any other stone; because (he
replies) no metal is so cold as iron; as if indeed cold were the cause of the
attraction, or as if iron were much colder than lead, which neither follows
nor is deflected towards a loadstone. But that is a chilly story, and worse
than an old woman's tale. So also is the notion that the loadstone is alive
and that iron is its food. But how does the loadstone feed on the iron, when
the filings in which it is kept are neither consumed nor become lighter?
Cornelius Gemma, Cosmographia, Bk. X.[151], holds that the loadstone
draws iron to it by insensible rays, to which opinion he conjoins a story of a
sucking fish and another about an antelope. Guilielmus Puteanus[152]

derives it, "not from any property of the whole substance unknown to any
one and which cannot be demonstrated in any way (as Galen, and after him
almost all the physicians, have asserted), but from the essential nature of the
thing itself, as if moving from the first by itself, and, as it were, by its own
most powerful nature and from that innate temperament, as it were an
instrument, which its substance, its effective nature uses in its operations, or
a secondary cause and deprived of its intermediary"; so the loadstone
attracts the iron not without a physical cause and for the sake of some good.
But there is no such thing in other substances springing from some material
form; unless it were primary, which he does not recognize. But certes good
is shown to the loadstone by the stroke of the iron (as it were, association
with a friend); yet it cannot either be discovered or conceived how that
disposition may be the instrument of form. For what can temperament do in
magnetical motions, which must be compared with the fixed, definite,
constant motions of the stars, at great distances in case of the interposition
of very dense and thick bodies? To Baptista Porta[153] the loadstone seems a
sort of mixture of stone and iron, in such a way that it is an iron stone or
stony iron. "But I think" (he says) "the Loadstone is a mixture of stone and
iron, as an iron stone, or a stone of iron. Yet do not think the stone is so
changed into iron, as to lose its own Nature, nor that the iron is so drowned
in the stone, but it preserves itself; and whilst one labours to get the victory
of the other, the attraction is made by the combat between them. In that
body there is more of the stone than of iron; and therefore the iron, that it
may not be subdued by the stone, desires the force and company of iron;
that being not able to resist alone, it may be able by more help to defend
itself.... The Loadstone draws not stones, because it wants them not, for
there is stone enough in the body of it; and if one Loadstone draw another,
it is not for the stone, but for the iron that is in it." As if in the loadstone the
iron were a distinct body and not mixed up as the other metals in their ores!
And that these, being so mixed up, should fight with one another, and
should extend their quarrel, and that in consequence of the battle auxiliary
forces should be called in, is indeed absurd. But iron itself, when excited by
a loadstone, seizes iron no less strongly than the loadstone. Therefore those
fights, seditions, and conspiracies in the stone, as if it were nursing up
perpetual quarrels, whence it might seek auxiliary forces, are the ravings of
a babbling old woman, not the inventions of a distinguished mage. Others
have lit upon sympathy as the cause. There may be fellow-feeling, and yet

the cause is not fellow-feeling; for no passion can rightly be said to be an
efficient cause. Others hold likeness of substance, many others insensible
rays as the cause; men who also in very many cases often wretchedly
misuse rays, which were first introduced in the natural sciences by the
mathematicians. More eruditely does Scaliger[154] say that the iron moves
toward the loadstone as if toward its parent, by whose secret principles it
may be perfected, just as the earth toward its centre. The Divine
Thomas[155] does not differ much from him, when in the 7th book of his
Physica he discusses the reasons of motions. "In another way," he says, "it
may be said to attract a thing, because it moves it to itself by altering it in
some way, from which alteration it happens that when altered it moves
according to its position, and in this manner the loadstone is said to attract
iron. For as the parent moves things whether heavy or light, in as far as it
gives them a form, by means of which they are moved to their place; so also
the loadstone gives a certain quality to the iron, in accordance with which it
moves towards it." This by no means ill-conceived opinion this most
learned man shortly afterwards endeavoured to confirm by things which
had obtained little credence respecting the loadstone and the adverse forces
of garlick. Cardinal Cusan[156] also is not to be despised. "Iron has," he
says, "in the loadstone a certain principle of its own effluence; and whilst
the loadstone by its own presence excites the heavy and ponderous iron, the
iron is borne by a wonderful yearning, even above the motion of nature (by
which in accordance with its weight it ought to tend downwards) and moves
upwards, in uniting itself with its own principle. For if there were not in the
iron a certain natural foretaste of the loadstone itself, it would not move to
the loadstone any more than to any other stone; and unless there were in the
stone a greater inclination for iron than for copper, there would not be that
attraction." Such are the opinions expressed about the loadstone attracting
(or the general sense of each), all dubious and untrustworthy. But those
causes of the magnetical motions, which in the schools of the Philosophers
are referred to the four elements and the prime qualities, we relinquish to
the moths and the worms.

CHAP. IIII.

On Magnetick Force & Form, what it is; and on the
cause of the Coition.

elinquishing the opinions of others on the attraction of loadstone,
we shall now show the reason of that coition and the translatory
nature of that motion. Since there are really two kinds of bodies,
which seem to allure bodies with motions manifest to our senses,
Electricks and Magneticks, the Electricks produce the tendency by natural
effluvia from humour; the Magneticks by agencies due to form, or rather by
the prime forces. This form is unique, and particular, not the formal cause
of the Peripateticks, or the specifick in mixtures, or the secondary form; not
the propagator of generating bodies, but the form of the primary and chief
spheres and of those parts of them which are homogeneous and not
corrupted, a special entity and existence, which we may call a primary and
radical and astral form; not the primary form of Aristotle, but that unique
form, which preserves and disposes its own proper sphere. There is one
such in each several globe, in the Sun, the moon, and the stars; one also in
the earth, which is that true magnetick potency which we call the primary
vigour. Wherefore there is a magnetick nature peculiar to the earth and
implanted in all its truer parts in a primary and astonishing manner; this is
neither derived nor produced from the whole heaven by sympathy or
influence or more occult qualities, nor from any particular star; for there is
in the earth a magnetick vigour of its own, just as in the sun and moon there
are forms of their own, and a small portion of the moon settles itself in
moon-manner toward its termini and form; and a piece of the sun to the sun,
just as a loadstone to the earth and to a second loadstone by inclining itself
and alluring in accordance with its nature. We must consider therefore about
the earth what magnetical bodies are, and what is a magnet; then also about
the truer parts of it, which are magnetical, and how they are affected as a
result of the coition. A body which is attracted by an electrick is not
changed by it, but remains unshaken and unchanged, as it was before, nor
does it excel any the more in virtue. A loadstone draws magnetical
substances, which eagerly acquire power from its strength, not in their
extremities
* only, but in their inward parts and their very marrow. For when
a rod of iron is laid hold of, it is magnetically excited in the end by which it
is laid hold of, and that force penetrates even to the other extremity, not
through its surface only, but through the interior and all through the middle.

Electrical bodies have material and corporeal effluvia. Is any such
magnetical effluvium given off, whether corporeal or incorporeal? or is
nothing at all given off that subsists? If it really has a body, that body must
be thin and spiritual, since it is necessary that it should be able to enter into
iron. Or what sort of an exhalation is it that comes from lead, when
quicksilver which is bright and fluid is bound together by the odour merely
and vapour of the lead, and remains, as it were, a firm metal? But even
gold, which is exceedingly solid and dense, is reduced to a powder by the
thin vapour of lead. Or, seeing that, as the quicksilver has entrance into
gold, so the magnetical odour has entrance into the substance of the iron,
how does it change it in its essential property, although no change is
perceptible to our senses in the bodies themselves? For without ingression
into the body, the body is not changed, as the Chemists not incorrectly
teach. But if indeed these things resulted from a material ingression, then if
strong and dense and thick substances had been interposed between the
bodies, or if magnetical substances had been inclosed in the centres of the
most solid and the densest bodies, the iron particles would not have suffered
anything from the loadstone. But none the less they strive to come together
and are changed. Therefore there is no such conception and origin of the
magnetick powers; nor do the very minute portions of the stone exist, which
have been wrongly imagined to exist by Baptista Porta, aggregated, as it
were, into hairs, and arising from the rubbing of the stone which, sticking to
the iron, constitute its strength. Electrick effluvia are not only impeded by
any dense matter, but also in like manner by flames, or if a small flame is
near, they do not allure. But as iron is not hindered by any obstacle from
receiving force or motion from a loadstone, so it will pass through the midst
of flames to the body of the loadstone and adhære to the stone. Let there be
a flame or a candle near the stone; bring up a short piece of iron wire, and
when it has come near, it will penetrate through the midst of the flames to
the stone;
* and a versorium turns towards the loadstone nor more slowly nor
less eagerly through the midst of flames than through open air. So flames
interposed do not hinder the coition. But if the iron itself became heated by
a great heat, it is demonstrable that it would not be attracted. Bring a
strongly ignited rod of iron near a magnetized versorium; the versorium
remains
* steady and does not turn towards such iron; but it immediately
turns towards it, so soon as it has lost somewhat of its heat. When a piece of
iron has been touched by a loadstone, if it be placed in a hot fire until it is

perfectly
* red hot and remain in the fire some considerable time, it will lose
that magnetick strength it had acquired. Even a loadstone itself through a
longish stay in the fire, loses the powers of attracting implanted and innate
in it, and any other magnetick powers. And although certain veins of
loadstone exhale when burnt a dark vapour of a black colour, or of a
sulphurous foul odour, yet that vapour was not the soul, or the cause of its
attraction of iron (as Porta thinks), nor do all loadstones whilst they are
being baked or burnt smell of or exhale sulphur. It is acquired as a sort of
inborn defect from a rather impure mine or matrix. Nor does anything
analogous penetrate into the iron from that material corporeal cause, since
the iron conceives the power of attracting and verticity from the loadstone,
even if glass or gold or any other stone be interposed. Then also cast iron
acquires the power of attracting iron, and verticity, from the verticity of the
earth, as we shall afterwards plainly demonstrate in Direction. But fire
destroys the magnetick virtues in a stone, not because it takes away any
parts specially attractive, but because the consuming force of the flame
mars by the demolition of the material the form of the whole; as in the
human body the primary faculties of the soul are not burnt, but the charred
body remains without faculties. The iron indeed may remain after the
burning is completed and is not changed into ash or slag; nevertheless (as
Cardan not inaptly says) burnt iron is not iron, but something placed outside
its nature until it is reduced. For just as by the rigour of the surrounding
air[157] water is changed from its nature into ice; so iron, glowing in fire, is
destroyed by the violent heat, and has its nature confused and perturbed;
wherefore also it is not attracted by a loadstone, and even loses that power
of attracting in whatever way acquired, and acquires another verticity when,
being, as it were, born again, it is impregnated by a loadstone or the earth,
or when its form is revived, not having been dead but confused, concerning
which many things are manifest in the change of verticity. Wherefore
Fracastorio[158] does not confirm his opinion, that the iron is not altered;
"for if it were altered," he says, "by the form of the loadstone, the form of
the iron would have been spoiled." This alteration is not generation, but the
restitution and reformation of a confused form. There is not therefore
anything corporeal which comes from the loadstone or which enters the
iron, or which is sent back from the iron when it is stimulated; but loadstone
disposes loadstone by its primary form; iron, however, which is closely
related to it, loadstone at the same time recalls to its conformate strength,

and settles it; on account of which it rushes to the loadstone and eagerly
conforms itself to it (the forces of each in harmony bringing them together).
The coition also is not vague or confused, not a violent inclination of body
to body, no rash and mad congruency; no violence is here applied to the
bodies; there are no strifes or discords; but there is that concord (without
which the universe would go to pieces), that analogy, namely, of the perfect
and homogeneous parts of the spheres of the universe to the whole, and a
mutual concurrency of the principal forces in them, tending to soundness,
continuity, position, direction, and to unity. Wherefore in the case of such
wonderful action and such a stupendous implanted vigour (diverse from
other natures) the opinion of Thales of Miletus[159] was not very absurd, nor
was it downright madness, in the judgment of Scaliger, for him to grant the
loadstone a soul; for the loadstone is incited, directed, and orbitally moved
by this force, which is all in all, and, as will be made clear afterwards, all in
every part; and it seems to be very like a soul. For the power of moving
itself seems to point to a soul; and the supernal bodies, which are also
celestial, divine, as it were, are thought by some to be animated, because
they move with admirable order. If two loadstones be set one over against
the other, each in a boat, on the surface of water, they do not immediately
run together, but first they turn towards one another, or the lesser conforms
to the greater, by moving itself in a somewhat circular manner, and at
length, when they are disposed according to their nature, they run together.
In smelted iron which has not been excited by a magnet there is no need for
such an apparatus; since it has no verticity, excepting what is adventitious
and acquired, and that not stable and confirmed (as is the case with
loadstone, even if the iron has been smelted from the best loadstone), on
account of the confusion of the parts by fire when it flowed as a liquid; it
suddenly acquires polarity and natural aptitude by the presence of the
loadstone, by a powerful mutation, and by a conversion into a perfect
magnet, and by an absolute metamorphosis; and it flies to the body of the
magnet as if it were a real piece of loadstone. For a loadstone has no power,
nor can a perfect loadstone do anything which iron when excited by
loadstone cannot perform, even when it has not been touched but only
placed in its vicinity. For when first it is within the orbe of virtue of the
loadstone, though it may be some distance away, yet it is immediately
changed, and has a renovated form, formerly indeed dormant and inert in
body, now lively and strong, which will be clearly apparent in the

demonstrations of Direction. So the magnetick coition is a motion of the
loadstone and of the iron, not an action of one[160]; an ἐντελέχεια, of each,
not ἔργον; a συνεντελέχεια or conjoint action, rather than a sympathy.
There is properly no such thing as magnetick antipathy. For the flight and
declination of the ends, or an entire turning about, is an action of each
towards unity by the conjoint action and συνεντελέχεια of both. It has
therefore newly put on the form, and on account of this being roused, it
then, in order that it may more surely acquire it, rushes headlong on the
loadstone, not with curves and turnings, as a loadstone to a loadstone. For
since in a loadstone both verticity and the power disponent have existed
through many ages, or from the very beginnings, have been inborn and
confirmed, and also the special form of the terrestrial globe cannot easily be
changed by another loadstone, as iron is changed; it happens from the
constant nature of each, that one has not the sudden power over another of
changing its verticity, but that they can only mutually come to agreement
with each
* other. Again, iron which has been excited by a loadstone, if that
iron on account of obstacles should not be able to turn round immediately in
accordance with its nature, as happens with a versorium, is laid hold of,
when a loadstone approaches, on either side or at either end. Because, just
as it can implant, so it can suddenly change the polarity and turn about the
formal energies to any part whatever. So variously can iron be transformed
when its form is adventitious and has not yet been long resident in the
metal. In the case of iron, on account of the fusion of the substance when
magnetick ore or iron is smelted, the virtue of its primary form, distinct
before, is now confused; but an entire loadstone placed near it again sets up
its primal activity; its adjusted and arranged form joins its allied strength
with the loadstone; and both mutually agree and are leagued together
magnetically in all their motions towards unity, and whether joined by
bodily contact or adjusted within the orbe, they are one and the same. For
when iron is smelted out of its own ore, or steel (the more noble kind of
iron) out of its ore, that is, out of loadstone, the material is loosed by the
force of the fire, and flows away, and iron as well as steel flow out from
their dross and are separated from it; and the dross is either spoiled by the
force of the fire and rendered useless, or is a kind of dregs of a certain
imperfection and of mixture in the prominent parts of the earth. The
material therefore is a purified one, in which the metallick parts, which are
now mixed up by the melting, since those special forces of its form are

confused and uncertain, by the approach of a loadstone are called back to
life, as if to a kind of disponent form and integrity. The material is thus
awakened and moves together into unity, the bond of the universe and the
essential for its conservation. On this account and by the purging of the
material into a cleaner body, the loadstone gives to the iron a greater force
of attracting
* than there is in itself. For if iron dust or an iron nail be placed
over a large loadstone, a piece of iron joined to it takes away the filings and
nail from the loadstone and retains them so long as it is near the loadstone;
wherefore iron attracts iron more than loadstone does, if it have been
conformed by a loadstone and remains within the orbe of its communicated
form. A piece of iron even, skilfully placed near the pole of a loadstone, lifts
up more than the loadstone. Therefore the material of its own ore is better,
and by the force of fire steel and iron are re-purged; and they are again
impregnated by the loadstone with its own forms; therefore they move
towards it by a spontaneous approach as soon as they have entered within
the orbe of the magnetick forces, because they were possessed by it before,
connected and united with it in a perfect union; & they have immediately an
absolute continuity within that orbe, & have been joined on account of their
harmony, though their bodies may have been disjoined. For the iron is not
taken possession of and allured by material effluvia, after the manner of
electricks, but only by the immaterial action of its form or an incorporeal
progression, which in a piece of iron as its subject acts and is conceived, as
it were, in a continuous homogeneous body, and does not need more open
ways. Therefore (though the most solid substances be interposed) the iron is
still moved and attracted, and by the presence of loadstone the iron moves
and attracts the loadstone itself, and by mutual forces a concurrency is made
towards unity, which is commonly called attraction of the iron. But those
formal forces pass out and are united to one another by meeting together; a
force also, when conceived in the iron, begins to flow out without delay.
But Julius Scaliger, who by other examples contends that this theory is
absurd, makes in his 344th Exercise a great mistake. For the virtues of
primary bodies are not to be compared with bodies formed from and mixed
with them. He would now have been able (had he been still alive) to discern
the nature of effused forms in the chapter on forms effused by spherical
magneticks. But if iron is injured somewhat by rust, it is affected either only
slightly or not at all by the stone. For the metal is spoiled when eaten away
and deformed by external injuries or by lapse of time (just as has been said

about the loadstone), and it loses its prime qualities which are conjoined to
its form; or, being worn out by age, retains them in a languid and weak
condition; indeed it cannot be properly re-formed, when it has been
corrupted. But a powerful and fresh loadstone attracts sound and clean
pieces of iron, and those pieces of iron (when they have conceived strength)
have a powerful attraction for other iron wires and iron nails, not only one
at a time, but even successively one behind another, three, four or five, end
to end, sticking and hanging in order like a chain. The loadstone, however,
would not attract the last one following in such a row, if there were no nails
between. A loadstone placed as at A draws a nail
or a bar B; similarly behind B it draws C; and
after C, D. But the nails B and C being removed,
the loadstone A, if it remain at the same distance, does not raise the nail D
into the air. This occurs for this reason: because in the case of a continuous
row of nails the presence of the loadstone A, besides its own powers, raises
the magnetick natures of the iron works B and C, and makes them, as it
were, forces auxiliary to itself. But B and C, like a continuous magnetical
body, extend as far as D the forces by which D is taken and conformed,
though they are weaker than those which C receives from B. And those iron
nails indeed from that contact only, and from the presence of the loadstone
even without contact, acquire powers which they retain in their own bodies,
as will be demonstrated most clearly in the passage on Direction. For not
only whilst the stone is present does the iron assume these powers, and take
them, as it were, vicariously from the stone, as Themistius lays down in his
8th book on Physicks[161]. The best iron, when it has been melted down
(such is steel), is allured by a loadstone from a greater distance, is raised
though of greater weight, is held more firmly, assumes stronger powers than
the common and less expensive, because it is cast from a better ore or
loadstone, imbued with better powers. But what is made from more impure
ore turns out weaker and is moved more feebly. As to Fracastorio's[162]
statement that he saw a piece of loadstone draw a loadstone by one of its
faces, but not iron; by another face iron, but not loadstone; by another both;
which he says is an indication that in one part there is more of the
loadstone, in another more of the iron, in another both equally, whence
arises that diversity of attraction; it is most incorrect and badly observed on
the part of Fracastorio, who did not know how to apply skilfully loadstone
to loadstone. A loadstone draws iron and also a loadstone, if both are

suitably arranged and free and unrestrained. That is removed more quickly
from its position and place which is lighter; for the heavier bodies are in
weight, the more they resist; but the lighter both moves itself to meet the
heavier and is allured by the other.

CHAP. V.

How the Power dwells in the
Loadstone.

hat a loadstone attracts loadstone, iron and other magnetical
bodies, has been shown above in the previous book, and also with
what strength the magnetick coition is ordered; but now we must
inquire how that vigour is disposed in a magnetick substance. And
indeed an analogy must be inferred from a large loadstone. Any magnetick
substance joins itself with a loadstone strongly, if the loadstone itself is
strong; but more weakly, when it is somewhat imperfect or has been
weakened by some flaw. A loadstone does not draw iron equally well with
every part; or a magnetick substance does not approach every part of a
loadstone alike; because a loadstone has its points, that is its true poles, in
which an exceptional virtue excels. Parts nearer the pole are stronger, those
far away more weak, and yet in all the power is in a certain way equal. The
poles of a terrella are A, B; the æquinoctial is C, D. At A and B the alluring
force seems greatest.

At C and D there is no force alluring magnetick ends to the body, for the
forces tend toward both poles. But direction is powerful on the æquator. At

C, D, the distances are equal from both poles; therefore iron which is at C,
D, when it is allured in contrary ways, does not adhære with constancy; but
it remains and is joined to the stone, if only it incline to the one or other
side. At E there is a greater power of alluring than at F, because E is nearer
the pole. This is not so because there is really greater virtue residing at the
pole, but since all the parts are united in the whole, they direct their forces
towards the pole. From the forces flowing from the plane of the æquinoctial
towards the pole, the power increases. A fixed verticity exists at the pole, so
long as the loadstone remains whole; if it is divided or broken, the verticity
obtains
* other positions in the parts into which it is divided. For the verticity
always changes in consequence of any change in the mass, and for this
cause, if the terrella be divided from A to B, so that there are two stones, the
poles will not be A, B, in the divided parts, but F, G, and H, I.

Although these stones now are in agreement with one another, so that F
would not seek H, yet if A was previously the boreal pole[163], F is now
boreal, and H also boreal; for the verticity is not changed (as Baptista Porta
incorrectly affirms in the fourth chapter of his seventh book); since, though
F and H do not agree, so that the one would incline to the other, yet both
turn to the same point of the horizon. If the hemisphere H I be divided into
two quadrants, the one pole takes up its position in H, the other in I. The
whole mass of the stone, as I have said, retains the site of its vertex
constant; and any part of the stone, before it was cut out from the block[164],
might have been the pole or vertex. But concerning this more under
Direction. It is important now to comprehend and to keep firmly in mind
that the vertices are strong on account of the force of the whole, so that (the
command being, as it were, divided by the æquinoctial) all the forces on
one side tend towards the north; but those of an opposite way towards the
south, so long as the parts are united, as in the following demonstration.

For so, by an infinite number of curves from every point of the equator
dividing the sphere into two equal parts, and from every point of the surface
from the æquator towards the North, and from the æquator towards the
Southern pole, the whole force tends asunder toward the poles. So the
verticity is from the æquinoctial circle towards the pole in each direction.
Such is the power reposed in the undivided stone. From A vigour is sent to
B, from A, B, to C, from A, B, C, to D, and from them likewise to E. In like
manner from G to H, and so forth, as long as the whole is united. But if a
piece A B be cut out (although it is near the æquator), yet it will be as strong
in its magnetical actions as C D or D E, if torn away from the whole in
equal quantity. For no part excels in special worth in the whole mass except
by what is owing to the other adjoining parts by which an absolute and
perfect whole is attained.

Diagram of Magnetic Vigour
transmitted from the plane of the Æquator
to the peripherery of the terella
or of the earth

HEQ is a terrella, E a pole, M the centre, HMQ the æquinoctial plane. From
every point of the æquinoctial plane vigour extends to the periphery, but by
various methods; for from A the formal force is transmitted towards C, F, N,
E, and to every point from C up to E, the pole; but not towards B; so neither
from G towards C. The power of alluring is not strengthened in the part
FHG from that which is in GMFE, but FGH increases the force in the
eminence FE. So no force rises from the internal parts, from the lines
parallel to the Axis above those parallels, but always inwards from the
parallels to the pole. From every point of the plane of the equator force
proceeds to the pole E, but the point F has its powers only from GH, and N
from OH; but the pole E is strengthened from the whole plane HQ.
Wherefore in it the mighty power excels (just as in a palace); but in the
intermediate intervals (as in F) only so much force of alluring is exerted as
the portion HG of the plane can contribute.

CHAP. VI.

How magnetick pieces of Iron and smaller
loadstones conform themselves to a terrella & to
the earth itself, and by them are
disposed.

oition of those bodies which are divided, and do not naturally
cohære, if they are free, occurs through another kind of motion. A
terrella sends out in an orbe its powers in proportion to its vigour
and quality. But when iron or any other magnetick of convenient
magnitude comes within its orbe of virtue, it is allured; but the nearer it
comes to the body, the more quickly it runs up to it. They move towards the
magnet,
* not as to a centre, nor towards its centre. For they only do this in
the case of the poles themselves, when namely that which is being allured,
and the pole of the loadstone, and its centre, are in the same straight line.
But in the intervening spaces they tend obliquely, just as is evident in the
following figure, in which it is shown how the influence is extended to the
adjoining magneticks within the orbe; in the case of the poles straight out.

The nearer the parts are to the æquinoctial, the more obliquely are
magneticals allured; but the parts nearer the poles appeal more directly, at
the poles quite straight. The principle of the turning of all loadstones, of
those which are round and those which are long, is the same, but in the case
of the long ones the experiment is easier. For in whatever form they are the
verticity exists, and there are poles; but on account of bad and unequal
form, they are often hindered by certain evils. If the stone were long, the
vertex is at the ends, not on the sides; it allures more strongly at the vertex.
For the parts bring together stronger forces to the pole in right lines than
oblique. So the stone and the earth conform their magnetick motions by
their nature.

CHAP. VII.

On the Potency of the Magnetick Virtue, and on
its nature capable of spreading out into an orbe.

rom about a magnetical body the virtue magnetical is poured out
on every side around in an orbe; around a terrella; in the case of
other shapes of stones, more confusedly and unevenly. But yet
there exists in nature no orbe or permanent or essential virtue
spread through the air, but a magnet only excites magneticks at a convenient
distance from it. And as light comes in an instant (as the opticians teach), so

much more[165] quickly is the magnetick vigour present within the limits of
its strength; and because its activity is much more subtile than light, and
does not consent with a non-magnetick substance, it has no intercourse with
air, water, or any non-magnetick; nor does it move a magnetick with any
motion by forces rushing upon it, but being present in an instant, it invites
friendly bodies. And as light strikes an object, so a loadstone strikes a
magnetick body and excites it. And just as light does not remain in the air
above vapours and effluvia, and is not reflected from those spaces, so
neither is the magnetick ray held in air or water. The appearances of things
are apprehended in an instant in mirrors and in the eye by means of light; so
the magnetick virtue seizes upon magneticks. Without the more intangible
and shining bodies, the appearances of things are not seized or reflected; so
without magnetical objects the magnetick power is not perceived, nor are
the forces thus conceived sent back again to the magnetick substance. In
this, however, the magnetick power excels light, in that it is not hindered by
any opaque or solid substance, but proceeds freely, and extends its forces on
every side. In a terrella and globe-shaped loadstone the magnetick power is
extended outside the body in an orbe; in a longer one, however, not in an
orbe, but it is extended in an ambit conformably to the shape of the stone.
As in the somewhat long stone A, the vigour is extended to the ambient
limit F C D, equidistant on every side from the stone A.

CHAP. VIII.

On the geography of the Earth,
and of the Terrella.

esiring that what follows may be better understood, we must now
say something also about magnetick circles and limits.
Astronomers, in order to understand and observe methodically the
motion of the planets and the revolution of the heavens, and to
describe with more accuracy the celestial attire of the fixed stars, settled
upon certain circles and definite limits in the sky (which geographers also
imitate), so that the varied face of the earth and the beauty of its districts
might be delineated. But we, in a way differing from them, recognize those
limits and circles, and have found very many fixed by nature, not merely
conceived by the imagination, both in the earth and in our terrella. The earth
they mark out[166] chiefly by means of the æquator and the poles; and those
limits indeed have been arranged and marked out by nature. The meridians
also indicate straight paths from pole to pole through distinct points on the
æquator; by which way the magnetick virtue directs its course and moves.
But the tropics and arctic circles, as also the parallels, are not natural limits
placed on the earth; but all parallel circles indicate a certain agreement of
the lands situated in the same latitude, or diametrically opposite. All these
the Mathematicians use for convenience, painting them on globes and
maps. In like manner also in a terrella all these are required; not, however,
in order that its exterior appearance may be geographically delineated, since
the loadstone may be perfect, even, and uniform on all sides. And there are
no upper and lower parts in the earth, nor are there in a terrella; unless
perchance some one considers those parts superior which are in the
periphery, and those inferior which are situated more towards the centre.

CHAP. IX.

On the Æquinoctial Circle of the Earth
and of a Terrella.

As conceived by astronomers the æquinoctial circle is equidistant from both
poles, cutting the world in the middle, measures the motions of their
primum mobile or tenth sphere, and is named the zone of the primum
mobile. It is called æquinoctial, because when the sun stands in it (which

must happen twice in the year) the days are equal to the nights. That circle
is also spoken of as æquidialis, wherefore it is called by the Greeks
ἰσημερινός. In like manner it is also properly called Æquator, because it
divides the whole frame of the earth between the poles into equal parts. So
also an æquator may be rightly assigned to a terrella, by which its power is
naturally divided, and by the plane of which permeating through its centre,
the whole globe is divided into equal parts both in quantity and strength (as
if by a transverse septum) between verticities on both sides imbued with
equal vigour.

CHAP. X.

Magnetick Meridians of the Earth.

eridians have been thought out by the geographer, by means of
which he might both distinguish the longitude and measure the
latitude of each region. But the magnetick meridians are infinite,
running in the same direction also, through fixed and opposite
limits on the æquator, and through the poles themselves. On them also the
magnetick latitude is measured, and declinations are reckoned from them;
and the fixed direction in them tends to the poles, unless it varies from some
defect and the magnetick is disturbed from the right way. What is
commonly called a magnetick meridian is not really magnetick, nor is it
really a meridian, but it is understood to pass through the termini of the
variation on the horizon. The variation is a depraved deviation from a
meridian, nor is it fixed and constant in various places on any meridian.

CHAP. XI.

Parallels.

n parallel circles the same strength and equal power are perceived
everywhere, when various magneticks are placed on one and the
same parallel either on the earth or on a terrella. For they are
distant from the poles by equal intervals and have equal tendencies
of declination, and they are attracted and held, and they come together with
like forces; just as those regions which are situated under the same parallel,
even if they differ in longitude, yet we say possess the same quantity of
daylight and a climate equally tempered.

CHAP. XII.

The Magnetick Horizon.

orizon is the name given to the great circle, separating the things
which are seen from those which are not seen; so that a half part of
the heaven always is open and easily seen by us, half is always
hidden. This seems so to us on account of the great distance of the
star-bearing orbe: yet the difference is as great as may arise from the ratio
of the semi-diameter of the earth compared with the semi-diameter of the
starry heaven, which difference is in fact not perceived by our senses. We
maintain, however, that the magnetick horizon is a plane level throughout
touching the earth or a terrella in the place of some one region, with which
plane the semi-diameter, whether of the earth or of the terrella, produced to
the place of the region, makes right angles on every side. Such a plane is to
be considered in the earth itself and also in the terrella, for magnetick
proofs and demonstrations. For we consider the bodies themselves only, not
the general appearances of the world. Therefore not with the idea of outlook
(which varies with the elevations of the lands), but taking it as a plane
which makes equal angles with the perpendicular, we accept in magnetick
demonstrations a sensible horizon or boundary, not that which is called by
Astronomers the rational horizon.

CHAP. XIII.

On the Axis and Magnetick Poles.

et the line be called the axis which is drawn in the earth (as in a
terrella) through the centre to the poles. They are called πόλοι by
the Greeks from πολεῖν, to turn, and by the Latins they are also
called Cardines or Vertices; because the world rotates and is
perpetually carried around them. We are about to show, indeed, that the
earth and a terrella are turned about them by a magnetick influence. One of
them in the earth, which looks towards the Cynosure, is called Boreal and
Arctic; the other one, opposite to this, is called Austral and Antarctic. Nor
do these also exist on the earth or on a terrella for the sake of the turning
merely; but they are also limits of direction and position, both as respects
destined districts of the world, and also for correct turnings among
themselves.

CHAP. XIIII.

Why at the Pole itself the Coition is stronger than in
the other parts intermediate between the æquator and the pole;
and on the proportion of forces of the coition in
various parts of the earth and of the terrella.

bservation has already been made that the highest power of alluring
exists in the pole, and that it is weaker and more languid in the
parts adjacent to the æquator. And as this is apparent in the
declination, because that disponent and rotational virtue has an
augmentation as one proceeds from the Æquator towards the poles: so also
the coition of magneticks grows increasingly fresh by the same steps, and in
the same proportion. For in the parts more remote from the poles the
loadstone does not draw magneticks straight down towards its own viscera;
but they tend obliquely and they allure obliquely. For as the smallest chords

in a circle differ from the diameter, so much do the forces of attracting
differ between themselves in different parts of the terrella. For since
attraction is coition towards a body, but magneticks run together by their
versatory tendency, it comes about that in the diameter drawn from pole to
pole the body appeals directly, but in other places less directly. So the less
the magnetick is turned toward the body, the less, and the more feebly, does
it approach and adhære. Just as if A B were the poles
and a bar of iron or a magnetick fragment C is allured at
the part E; yet the end laid hold of does not tend
towards the centre of the loadstone, but verges obliquely
towards the pole; and a chord drawn from that end
obliquely as the attracted body tends is short; therefore
it has less vigour and likewise less inclination. But as a
greater chord proceeds from a body at F, so its action is
stronger; at G still longer; longest at A, the pole (for the diameter is the
longest way) to which all the parts from all sides bring assistance, in which
is constituted, as it were, the citadel and tribunal of the whole province, not
from any worth of its own, but because a force resides in it contributed from
all the other parts, just as all the soldiers bring help to their own
commander. Wherefore also a slightly longer stone attracts more than a
spherical one, since the length from pole to pole is extended, even if the
stones are both from the same mine and of the same weight and size. The
way from pole to pole is longer in a longer stone, and the forces brought
together from other parts are not so scattered as in a round magnet and
terrella, and in a narrow one they agree more and are better united, and a
united stronger force excels and is preeminent. A much weaker office,
however, does a plane or oblong stone perform, when the length is extended
according to the leading of the parallels, and the pole stops neither on the
apex nor in the circle and orbe, but is spread over the flat. Wherefore also it
invites a friend wretchedly, and feebly retains him, so that it is esteemed as
one of an abject and contemptible class, according to its less apt and less
suitable figure.

CHAP. XV.

* The Magnetick Virtue which is conceived in Iron is
more apparent in an iron rod than in a piece of iron that
is round, square, or of other figure.

uly was it said before that the longer magnet attracts the greater
weight of iron[167]; so also in a longish piece of iron which has
been touched the magnetick force conceived is stronger when the
poles exist at the ends. For the magnetick forces which are driven
from the whole in every part into the poles are not scattered but united in
the narrow ends. In square and other angular figures the influence is
dissipated, and does not proceed in straight lines or in convenient arcs.
Suppose also an iron globe have the shape of the earth, yet for the same
reasons it drags magnetick substances less; wherefore a small iron sphere,
when excited, draws another piece of iron more sluggishly than an excited
rod of equal weight.

CHAP. XVI.

Showing that Movements take place by the Magnetical
Vigour though solid bodies lie between; and on
the interposition of iron plates.

loat a piece of iron wire on the surface of water by transfixing it
through a suitable cork; or set a versatory piece of iron on a pin or
in a seaman's compass (a magnet being brought near or moved
about underneath), it is put into a state of motion; neither the
water, nor the vessel, nor the compass-box offering resistance in any way.
Thick boards do not obstruct[168], nor earthen vessels nor marble vases, nor
the metals themselves; nothing is so solid as to carry away or impede the
forces excepting an iron plate. Everything which is interposed (even though
it is very dense) does not carry away its influence or obstruct its path, or
indeed in any way hinder, diminish, or retard it. But all the force is not
suppressed by an iron plate, but it is in some measure diverted aside. For

when the vigour passes into the middle of an iron plate within the orbe of
the magnetick virtue or placed just opposite the pole of the stone, that virtue
is scattered in very large measure towards its extremities; so that the edges
of a small
* round plate of suitable size allure iron wires on every side. This is
also apparent in the case of a long iron wand, which, when it has been
touched
* by a magnet in the middle, has a like verticity at either end.

B is a loadstone, C D a long rod magnetized in the middle A; E being the
Boreal pole; C is an Austral end or pole; in like manner also the end D is
another Austral pole. But observe here the exactness with which a
versorium touched by a pole, when a round plate is interposed, turns
towards
* the same pole in the same way as before the interposition, only
weaker; the plate not standing in the way, because the vigour is diverted
through the edges of the small plate, and passes out of its straight course,
but yet the plate retains in the middle the same verticity, when it is in the
neighbourhood of that pole, and close to it; wherefore the versorium tends
towards the plate, having been touched by the same pole. If a loadstone is
rather weak, a versorium hardly turns when a plate is put in between; for the
vigour of the rather weak loadstone, being diffused through the extremities,
passes* less through the middle. But if the plate has been touched in this way
by a pole in the middle and has been removed from the stone outside its
orbe of virtue, then you will see the point of the same versorium tend in the
contrary direction and desert the centre of the small plate, which formerly it
desired; for outside the orbe of virtue it has an opposite verticity, in the
vicinity the same; for in the vicinity it is, as it were, a part of the loadstone,
and has the same pole.

A is an iron plate near the pole, B a versorium which tends with its point
towards the centre of the small plate, which has been touched by the pole of
the loadstone C. But if the same small plate be placed outside the orbe of
magnetick virtue, the point will not turn towards its centre, but the cross E
of the same versorium does. But an iron globe interposed (if it is not too
large)*attracts the point of the iron on the other side of the stone. For the
verticity of that side is the same as that of the adjoining pole of the stone.
And this turning of the cusp (that is, of the end touched by that pole) as well
as of the cross-end, at a greater distance, takes place with an iron globe
interposed,
* which would not happen at all if the space were empty, because
the magnetick virtue is passed on and continued through magnetick bodies.

A is a terrella, B an iron globe; between the two bodies is F, a versorium
whose point has been excited by the pole C. In the other figure A is a
terrella, C its pole, B an iron globe; where the versorium tends towards C,
the pole of the terrella, through the iron globe. So a versorium placed
between a terrella and an iron globe vibrates more forcibly towards the pole
of the terrella; because the loadstone sends an instantaneous verticity into
the opposite globe. There is the same efficiency in the earth, produced from
the same cause. For if a revolvable needle is shut up in a rather thick gold
box (this metal indeed excels all others in density) or a glass or stone box,
nevertheless that magnetick needle has its forces connected and united with
the influences of the earth, and the iron will turn freely and readily
(unhindered
* by its prison) to its desired points, North and South. It even
does this when shut up in iron caverns, if they are sufficiently spacious.
Whatever bodies are produced among us, or are artificially forged from
things which are produced, consist of matter of the terrestrial globe; nor do
those bodies hinder the prime forces of nature which are derived from their
primary form, nor can they resist them except by contrary forms. But no

forms of mixed bodies are inimical to the primary implanted earth-nature,
although some often do not agree[169] with one another. But in the case of
all those substances which have a material cause for their inclining (as
amber, jet, sulphur), their action is impeded by the interposition of a body
(as paper, leaves, glass, or the like) when that way is impeded and
obstructed, so that that which exhales[170] cannot reach the corpuscle to be
allured. Terrestrial and magnetick coition and motion, when corporeal
impediments are interposed, is demonstrated also by the efficiencies of
other chief bodies due to their primary form. The moon (more than all the
stars) agrees with internal parts of the earth on account of its nearness and
similarity in form. The moon produces the movements of the waters and the
tides of the sea; twice it fills up the shores and empties them whilst it moves
from a certain definite point in the sky back to the same point in a daily
revolution. This motion of the waters is incited and the seas rise and fall no
less when the moon is below the horizon and in the lowest part of the
heavens, than if it had been raised at a height above the horizon. So the
whole mass of the earth interposed[171] does not resist the action of the
moon, when it is below the earth; but the seas bordering on our shores, in
certain positions of the sky when it is below the horizon, are kept in motion,
and likewise stirred by its power (though they are not struck by its rays nor
illuminated by its light), rise, come up with great force, and recede. But
about the reason of the tides anon[172]; here let it suffice to have merely
touched the threshold of the question. In like manner nothing on the earth
can be hidden from the magnetick disposition of the earth or of the stone,
and all magnetical bodies are reduced to order by the dominant form of the
earth, and loadstone and iron show sympathy with a loadstone though solid
bodies be interposed.

CHAP. XVII.

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.

onceive 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 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.

CHAP. XVIII.

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

than an unarmed.

* uppose 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.

CHAP. XIX.

Union with an armed Loadstone is stronger;
hence greater weights are raised; but the
coition is not stronger[176], but
generally weaker.

n 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.

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.

agnets armed cohære firmly when duly joined, and
accord into one; and though the first be rather weak, yet
the second one adhæres to it not only by the strength of
the first, but of the second, which mutually give helping
hands; also to the second a third often adheres and in the case of
robust stones, a fourth to the third.

CHAP. XXI.

* If Paper or any other Medium be interposed,
an armed loadstone raises no more than an
unarmed one.

bservation has shown above that an armed loadstone does not
attract at a greater distance than an unarmed one; yet raises iron in
greater quantity, if it is joined to and made continuous with the
iron. But if Paper be placed between, that intimate cohæsion of the
metal is hindered, nor are the metals cemented together at the same time by
the operation of the magnet.

CHAP. XXII.

*
That an armed Loadstone draws Iron no more than an
unarmed one: And that an armed one is more strongly united

to iron is shown by means of an armed loadstone
and a polished cylinder of iron.

f a cylinder be lying on a level surface, of too great a
weight for an unarmed loadstone to lift, and (a piece of
paper being interposed) if the pole of an armed
loadstone be joined to the middle of it; if the cylinder
were drawn from there by the loadstone, it would follow rolling;
but if no medium were interposed, the cylinder would be drawn
along firmly united with the armed loadstone, and in no wise
rolling. But if the same loadstone be unarmed, it will draw the
cylinder rolling with the same speed as the armed loadstone with
the paper between or when it was wrapped in paper.
Armed* loadstones of diverse weights, of the same ore vigour
and form, cling and hang to pieces of iron of a convenient size and
proportionate figure with an equal proportion of strength. The same is
apparent
* in the case of unarmed stones. A suitable piece of iron being
applied
* to the lower part of a loadstone, which is hanging from a magnetick
body, excites its vigour, so that the loadstone hangs on more firmly. For a
pendent loadstone clings more firmly to a magnetick body joined to it
above with a hanging piece of iron added to it, than when lead or any other
non-magnetick body is hung on.
A loadstone,
* whether armed or unarmed, joined by its proper pole to the
pole of another loadstone, armed or unarmed, makes the loadstone raise a
greater weight by the opposite end[177]. A piece of iron also applied to the
pole of a magnet produces the same result, namely, that the other pole will
carry a greater weight of iron; just as a loadstone with a piece of iron
superposed on it (as in this figure) holds up a piece of iron below, which it
cannot* hold, if the upper one be removed. Magneticks in conjunction make
one magnetick. Wherefore as the mass increases, the magnetick vigour is
also augmented.
An armed
* loadstone, as well as an unarmed one, runs more readily to a
larger piece of iron and combines more firmly with a larger piece than with
a lesser one.

CHAP. XXIII.

Magnetick Force causes motion towards unity,
and binds firmly together bodies which are united.

agnetick fragments cohære within their strength well and
harmoniously together. Pieces of iron in the presence of a loadstone
* (even if they are not touching the loadstone) run together, seek one
another anxiously and embrace one another, and when joined are as
if they* were cemented. Iron filings or the same reduced to powder inserted
in paper tubes, placed upon a stone meridionally or merely brought rather
close to it, coalesce into one body, and so many parts suddenly are
concreted
* and combine; and the whole company of corpuscles thus
conspiring together affects another piece of iron and attracts it, as if it
constituted one integral rod of iron; and above the stone it is directed
toward * the North and South. But when they are removed a long way from
the stone, the particles (as if loosed again) are separated and move apart
singly. In this way also the foundations of the world are connected and
joined and cemented together magnetically. So let Ptolemy of Alexandria,
and his followers, and those philosophers of ours, be the less terrified if the
earth do move round in a circle, nor threaten its dissolution.
Iron filings, after being heated for a long time, are attracted by a loadstone,
yet not so strongly or from so great a distance as when not heated. A
loadstone loses some of its virtue by too great a heat; for its humour is set
free, whence its peculiar nature is marred. Likewise also, if iron filings are
well burnt in a reverberatory furnace and converted into saffron of Mars,
they are not attracted by a loadstone; but if they are heated, but not
thoroughly burnt, they do stick to a magnet, but less strongly than the
filings themselves not acted upon by fire. For the saffron has become totally
deformate, but the heated metal acquires a defect from the fire, and the
forces in the enfeebled body are less excited by a loadstone; and, the nature
of the iron being now ruined, it is not attracted by a loadstone.

CHAP. XXIIII.

A piece of Iron placed within the Orbe of a
Loadstone hangs suspended in the air, if on account
of some impediment it cannot approach it.

ithin the magnetick orbe a piece of iron moves towards the more
powerful points of the stone, if it be not hindered by force or by
the material of a body placed between them; either it falls down
from above, or tends sideways or obliquely, or flies up above.
But if the iron cannot reach the stone on account of some obstacle, it
cleaves to it and remains there, but with a less firm and constant connection,
since at greater intervals or distances the alliance is less amicable.
Fracastorio, in the eighth chapter of his De Sympathia, says that a piece of
iron is suspended in the air, so that it can be moved neither up nor down, if
a loadstone be placed above which is able to draw the iron up just as much
as the iron itself inclines downwards with equal force; for thus the iron
would be supported in the air: which thing is absurd; because the force of a
magnet is always the stronger the nearer it is. So that when a piece of iron is
raised a very little from the earth by the force of the magnet, it needs must
be drawn steadily on towards the magnet (if nothing else come in the way)
and cleave to it. Baptista Porta suspends a piece of iron in the air[178] (a
magnet being fixed above), and, by no very subtile process, the iron is
detained by a slender thread from its lower part, so that it cannot rise up to
the stone. The iron is raised upright by the magnet, although the magnet
does not
* touch the iron, but because it is in its vicinity; but when the whole
iron on account of its greater nearness is moved by that which erected it,
immediately it hurries with a swift motion to the magnet and cleaves to it.
For by approaching the iron is more and more excited, and the coition
grows stronger.

CHAP. XXV.

Exaltation of the power of the Magnet.

ne loadstone far surpasses another in power, since one draws iron
of almost its own weight, another can hardly stir some shreds.
Whatever things, whether animals or plants, are endowed with life
need some sort of nourishment, by which their strength not only
persists but grows firmer and more vigorous. But iron is not, as it seemed to
Cardan and to Alexander Aphrodiseus, attracted by the loadstone in order
that it may feed on shreds of it, nor does the loadstone take up vigour from
iron filings as if by a repast on victuals. Since Porta had doubts on this and
resolved to test it, he took a loadstone of ascertained weight, and buried it in
iron filings of not unknown weight; and when he had left it there for many
months, he found the stone of greater weight, the filings of less. But the
difference was so slender that he was even then doubtful as to the truth.
What was done by him does not convict the stone of voracity, nor does it
show any nutrition; for minute portions of the filings are easily scattered in
handling. So also a very fine dust is insensibly born on a loadstone in some
very slight quantity, by which something might have been added to the
weight of the loadstone but which is only a surface accretion and might
even be wiped off with no great difficulty. Some think that a weak and
sluggish stone can bring itself back into better condition, and that a very
powerful one also might present it with the highest powers. Do they acquire
strength like animals when they eat and are sated? Is the medicine prepared
by addition or subtraction? Is there anything which can re-create this
primary form or bestow it anew? And, certes, nothing can do this which is
not magnetical. Magneticks can restore a certain soundness to magneticks
(when not incurable); some can even exalt them beyond their proper
strength; but when a body is at the height of perfection in its own nature, it
is not capable of being strengthened further. So that that imposture of
Paracelsus, who affirms that the force and virtue can be increased and
transmuted tenfold, turns out to be the more infamous. The method of
effecting this is as follows, viz., you make it semi-incandescent in a fire of
charcoal (that is, you heat it very hot), so that it does not become red-hot,
however, and immediately slake it, as much indeed as it can imbibe, in oil
of saffron of Mars, made from the best Carynthian steel. "In this way you

will be able so to strengthen a loadstone that it can draw a nail out of a wall
and accomplish many other like wonderful things, which are not possible
for a common loadstone." But a loadstone thus slaked in oil not only does
not gain power, but suffers also a certain loss of its inborn strength. A
loadstone is improved if polished and rubbed with steel. Buried in filings of
the best iron or of pure steel, not rusty, it preserves its strength. Sometimes
also a somewhat good and strong one gains some strength when it is rubbed
on the pole of another, on the opposite
part, and receives virtue. In all these
experiments it is an advantage to observe
the pole of the earth, and to adjust
according to magnetick laws the stone
which we wish to strengthen; which we
shall set forth below. A somewhat
powerful and fairly large loadstone
increases the strength of a loadstone as it
does of
* iron. A loadstone being placed over the boreal pole of a loadstone,
the boreal pole becomes stronger, and an iron rod (like an arrow) sticks to
the boreal pole A, but not at all to the pole B. The pole A also, when it is at
the top in a right line with the axis of both loadstones joined in accordance
with magnetick laws, raises the rod to the perpendicular, which it cannot do
if the large loadstone be removed, on account of its own weaker strength.
But as a small iron globe, when placed above the pole of a terrella, raises
the rod
* to the perpendicular, so, when placed at the side, the rod is not
directed towards the centre of the globe, but is raised obliquely and cleaves
anywhere, because the pole in a round piece of iron is always the point
which is joined most closely to the pole of the terrella and is not constant as
in a smaller terrella. The parts of the earth, as of all magneticks, are in
agreement and take delight in their mutual proximity; if placed in the
highest power, they do not harm their inferiors, nor slight them; there is a
mutual love among them all, a perennial good feeling. The weaker
loadstones are re-created by the more powerful, and the less powerful cause
no harm to the stronger. But a powerful one attracts and turns a somewhat
strong one more than it does an impotent one. Because a strenuous one
confers a stronger activity, and itself hastens, flies up to the other, and
solicits it more keenly; therefore there is a more certain and a stronger co-
action and cohærency.

CHAP. XXVI.

Why there should appear to be a greater love between
iron and loadstone, than between loadstone and loadstone, or
between iron and iron, when close to the loadstone,
within its orbe of virtue.

agnet attracts magnet, not in every part and on every side with
equal conditions, as iron, but at one and a fixed point; therefore the
poles of both must be exactly disposed, otherwise they do not
cleave together duly and strongly. But this disposition is not easy
and expeditious; wherefore a loadstone seems not to conform to a
loadstone, when nevertheless they agree very well together. A piece of iron
by the sudden impression of a loadstone is not only allured by the stone, but
is renewed, its forces being drawn forth; by which it follows and solicits the
loadstone with no less impulse, and even leads another piece of iron
captive. Let there be a small iron spike above a loadstone clinging firmly to
it; if you apply an unmagnetized rod of iron to the spike, not, however, so
that it touches the stone, you will see the spike when it has touched the iron,
leaving the loadstone, follow the rod, try to grasp it by leaning toward it,
and (if it should touch it) cleave firmly to it: for a piece of iron, when united
and joined to another piece of iron placed within the orbe of virtue of the
loadstone, draws it more strongly than does the loadstone itself. The natural
magnetick virtue, confused and dormant in the iron, is aroused by the
loadstone, is linked to the loadstone, and rejoices with it in its primary
form; then smelted iron becomes a perfect magnetick, as robust as the
loadstone itself. For as the one imparts and stirs, so the other conceives, and
being stirred remains in virtue, and pours back the forces also by its own
activity. But since iron is more like iron than loadstone, and the virtue in
both pieces of iron is exalted by the proximity of the loadstone, so in the
loadstone itself, in case of equal strength, likeness of substance prevails,
and iron gives itself up rather to iron, and they are united by their very
similar homogenic powers. Which thing happens not so much from a

coition, as from a firmer unition; and a knob or snout of steel, fixed
skilfully on the pole of the stone, raises greater weights of iron than the
stone of itself could. When steel or iron is smelted from loadstone or iron
ore, the slag and corrupt substances are separated from the better by the
fusion of the material; whence (in very large measure) that iron contains the
nature of the earth, purified from alien flaw and blemish, and more
homogenic and perfect, though deformed by the fusion. And when that
material indeed is provoked by a loadstone, it conceives the magnetick
virtues, and within their orbe is raised in strength more than the weaker
loadstone, which with us is often not free from some admixture of
impurities.

CHAP. XXVII.

* The Centre of the Magnetick Virtues in the earth
is the centre of the earth; and in a terrella
is the centre of the stone.

ays of magnetick virtue spread out in every direction in an orbe;
the centre of this orbe is not at the pole (as Baptista Porta reckons,
Chap. 22), but in the centre of the stone and of the terrella. So also
the centre of the earth is the centre of the magnetick motions of the
earth; though magneticks are not borne directly toward the centre by
magnetical motion, except when they are attracted by the true pole. For
since the formal power of the stone and of the earth does not promote
anything but the unity and conformity of disjoined bodies, it comes about
that everywhere at an equal distance from the centre or from the
circumference, just as it seems to attract perpendicularly at one place, so at
another it is able even to dispose and to turn, provided the stone is not
uneven in virtue. For if at the distance C from the pole D the stone is able to
allure*a versorium, at an equally long interval above the æquator at A that
stone can also direct and turn the versorium. So the very centre and middle
of the terrella is the centre of its virtue, and from this to the circumference

of the orbe (at equal intervals on every side) its magnetick virtues are
emitted.

CHAP. XXVIII.

A Loadstone attracts magneticks not only to a
fixed point or pole, but to every part of a
terrella save the æquinoctial zone.

oitions are always more powerful when poles are near poles, since
in them by the concordancy of the whole there exists a stronger
force; wherefore the one embraces the other more strongly. Places
declining from the poles have attractive forces, but a little weaker
and languid in the ratio of their distance; so that at length on the æquinoctial
circle they are utterly enervated and evanescent. Neither do even the poles
attract as mathematical points; nor do magneticks come into conjunction by
their own poles, only on the poles of a loadstone. But coition is made on
every part of the periphery, both Northern and Southern, by virtue
emanating from the whole body; magneticks nevertheless incline languidly
towards magneticks in the parts bordering on the æquator, but quickly in
places nearer the pole. Wherefore not the poles, not the parts alone nearest
to the pole allure and invite magneticks, but magneticks are disposed and
turned round and combine with magneticks in proportion as the parts facing
and adjoined unite their forces together, which are always of the same
potency in the same parallel, unless they are distributed otherwise from
causes of variation.

CHAP. XXIX.

On Variety of Strength due to Quantity
or Mass.

uite similar in potency are those stones which are of the same mine,
and not corrupted by adjacent ores or veins. Nevertheless that
which excels in size shows greater powers, since it seizes greater
weights and has a wider orbe of virtue. For a loadstone weighing
one ounce does not lift a large nail as does one weighing a pound, nor does
it rule so widely, nor extend its forces; and if from a loadstone of a pound
weight a portion is taken away, something of its power will be seen to go
also; for when a portion is abstracted the virtue is lessened. But if that part
is properly
* applied and united to it, though it is not fastened to nor grown
into it, yet by the application it obtains its pristine power and its vigour
returns. Sometimes, however, when a part is taken away, the virtue turns out
to be *stronger on account of the bad shape of the stone, namely, when the
vigour is scattered through inconvenient angles. In various species the ratio
is various, for one stone of a drachm weight draws more than another of
twenty pounds. Since in very many the influence is so effete that it can
hardly be perceived, those weak stones are surpassed by prepared pieces of
clay. But, it may be asked[179], if a stone of the same species and goodness
weighing a drachm would seize upon a drachm of iron, would a stone of an
ounce weight seize on an ounce, a pound on a pound, and so on? And this is
indeed true; for it both strains and remits its strength proportionately, so that
if a loadstone, one drachm of which would attract one drachm of iron, were
in equal proportion applied either to a suitably large obelisk or to an
immense pyramid of iron, it would lift it directly in such proportion and
would draw it towards itself with no greater effort of its nature or trouble
than a loadstone of a drachm weight embraces a drachm. But in all such
experiments as this let the vigour of the magnets be equal; let there be also a
just proportion in all of the shapes of the stones, and let the shape of the
iron to be attracted be the same, and the goodness of the metal, and let the
position of the poles of the loadstones be most exact. This is also no less

true in the case of an armed loadstone than of an unarmed one. For the sake
of experiment, let there be given a loadstone of eight ounces weight, which
when armed lifts twelve ounces of iron; if you cut off from that loadstone a
certain
* portion, which when it has been reduced to the shape of the former
whole one is then only of two ounces, such a loadstone armed lifts a piece
of iron applied to it of three ounces, in proportion to the mass. In this
experiment also the piece of iron of three ounces ought to have the same
shape as the former one of twelve ounces; if that rose up into a cone, it is
necessary that this also in the ratio of its mass should be given a pyramidal
shape proportioned to the former.

CHAP. XXX.

The Shape and Mass of the Iron are of most
importance in coition.

bservation has shown above that the shape and mass of the
loadstone have great influence in magnetick coitions; likewise also
the shape and mass of the iron bodies give back more powerful and
steady forces. Oblong iron rods are both drawn more quickly to a
loadstone and cleave to it with greater obstinacy than round or square
pieces, for the same reasons which we have proven in the case of the
loadstone. But, moreover, this is also worthy of observation, that a smaller
piece of iron, to which is hung a weight of another material, so that it is
altogether in weight equal to another large whole piece of iron of a right
weight
* (as regards the strength of the loadstone), is not lifted by the
loadstone as the larger piece of iron would be. For a smaller piece of iron
does not join with a loadstone so firmly, because it sends back less strength,
and only that which is magnetick conceives strength; the foreign material
hung on cannot acquire magnetick forces.

CHAP. XXXI.

On Long and Round Stones.

ieces of iron join more firmly with a long stone than with a round
one, provided that the pole of the stone is at the extremity and end
of its length; because, forsooth, in the case of a long stone, a
magnetick is directed at the end straight towards the body in which
the virtue proceeds in straighter lines and through the longer diameter. But a
somewhat long stone has but little power on the side, much less indeed than
* one. It is demonstrable[180], indeed, that at A and B the coition is
a round
stronger in a round stone than at C and D, at like distances from the pole.

CHAP. XXXII.

Certain Problems and Magnetick Experiments about
the Coition, and Separation, and regular Motion
of bodies magnetical.

* qual loadstones come together with equal incitation.
* Also magnetick bodies of iron, if alike in all respects, come
together when excited with similar incitation.
Furthermore,
* bodies of iron not excited by a loadstone, if they are alike and
not weighed down by their bulk, move towards one another with equal
motion.
Two loadstones, disposed on the surface of some water in suitable skiffs, if
they are drawn up suitably within their orbes of virtue, incite one another
mutually
* to an embrace. So a proportionate piece of iron in one skiff hurries

with the same speed towards the loadstone as the loadstone itself in its boat
strives towards the iron. From their own positions, indeed, they are so borne
together, that they are joined and come to rest at length in the middle of the
space.* Two iron wires magnetically excited, floating in water by means of
suitable pieces of cork, strive to touch and mutually strike one another with
their corresponding ends, and are conjoined.
Coition
* is firmer and swifter than repulsion and separation in equal
magnetick substances. That magnetick substances are more sluggishly
repelled than they are attracted is manifest in all magnetical experiments in
the case of stones floating on water in suitable skiffs; also in the case of iron
wires or rods swimming (transfixed through corks) and well excited by a
loadstone, and in the case of versoria. This comes about because, though
there is one faculty of coition, another of conformation or disposition,
repulsion and aversion is caused merely by something disposing; on the
other hand, the coming together is by a mutual alluring to contact and a
disposing, that is, by a double vigour.
A disponent vigour is often only the precursor of coition, in order that the
bodies may stand conveniently for one another before conjunction;
wherefore also they are turned round to the corresponding ends, if they can
[not][181] reach them through the hindrances.

If a loadstone be divided through a meridian into two equal parts, the
separate
* parts mutually repel one another, the poles being placed directly
opposite one another at a convenient and equal distance. They repel one
another also with a greater velocity than when pole is put opposite pole
incongruously. Just as the part B of the loadstone, placed almost opposite
the part A, repels it floating in its skiff, because D turns away from F, and E
from C; but if B is exactly joined with A again, they agree and become one

body magnetical; but in proximity they raise enmities. But if one part of the
stone is turned round, so that C faces D and F faces E, then A pursues B
within its orbe until they are united.
The Southern parts of the stone avoid the Southern parts, and the Northern
parts the Northern. Nevertheless, if by force you move up the Southern cusp
of a piece of iron too near the Southern part of the stone, the cusp is seized
and both are linked together in friendly embraces: because it immediately
reverses the implanted verticity of the iron, and it is changed by the
presence of the more powerful stone, which is more constant in its forces
than the iron. For they come together according to their nature, if by
reversal and mutation true conformity is produced, and just coition, as also
regular direction. Loadstones of the same shape, size, and vigour, attract
one another mutually with like efficacy, and in the opposite position repel
one another mutually with a like vigour.
Iron rods
* not touched, though alike and equal, do yet often act upon one
another with different forces; because as the reasons of their acquired
verticity, also of their stability and vigour, are different, so the more
strongly they are excited, the more vigorously do they incite.
Pieces* of iron excited by one and the same pole mutually repel one another
by those ends at which they were excited; then also the opposite ends to
those in these iron pieces raise enmities one to another.
In versoria
* whose cusps have been rubbed, but not their cross-ends, the
crosses mutually repel one another, but weakly and in proportion to their
length.
In like
* versoria the cusps, having been touched by the same pole of the
loadstone, attract the cross-ends with equal strength.
In a somewhat
* long versorium the cross-end is attracted rather weakly by
the cusp of a shorter iron versorium; the cross of the shorter more strongly
by the cusp of the longer, because the cross of the longer versorium has a
weak verticity, but the cusp has a stronger.
The cusp
* of a longer versorium drives away the cusp of a shorter one more
vehemently than the cusp of the shorter the cusp of the longer, if the one is
free upon a pin, and the other is held in the hand; for though both were

equally excited by the same loadstone, yet the longer one is stronger at its
cusp on account of its greater mass.
The Southern
* end of an iron rod which is not excited attracts the Northern,
and the Northern the Southern; moreover, also the Southern parts repel the
Southern, and the Northern the Northern.
If magnetick substances are divided or in any way broken in pieces, each
part has a Northern and a Southern end.
A versorium
* is moved as far off by a loadstone when an obstacle is put in
the way, as through air and an open medium.
Rods *rubbed upon the pole of a stone strive after the same pole and follow
it. Therefore Baptista Porta errs when he says, chapter 40[182], "If you put
that part to it from which it received its force, it will not endure it, but
drives it from it, and draws to it the contrary and opposite part."
The principles of turning round and inclining are the same in the case of
loadstone to loadstone, of loadstone to iron, of iron also to iron.
When magnetick substances which have been separated by force and
dissected into parts flow together into a true union and are suitably
connected, the body becomes one, and one united virtue, nor have they
diverse ends.
The separate
* parts assume two opposite poles, if the division has not been
made along a parallel: if the division has been made along a parallel, they
are able to retain one pole in the same site as before.
Pieces of iron which have been rubbed and excited by a loadstone are more
surely and swiftly seized by a loadstone at fitting ends than such as have not
been rubbed.
If a spike
* is set up on the pole of a loadstone, a spike or style of iron placed
on the upper end is strongly cemented to it, and draws away the erect spike
from the terrella when motion is made.
If to the
* lower end of the erect spike the end of another spike is applied, it
does not cohære with it, nor do they unite together.

As a rod of iron draws away a piece of iron from a terrella, so is it also with
a minute loadstone and a lesser terrella, though weaker in strength.

The piece of iron C comes into conjunction with the terrella A, and the
vigour in it is magnetically exalted and excited, both in the adjoining end
and in the other also which is turned away through its conjunction with the
terrella. The end that is turned away also conceives vigour from the
loadstone B; likewise the pole D of that loadstone is powerful on account of
its suitable aspect and the nearness of the pole E of the terrella. Several
causes therefore concur why the piece of iron C should cleave to the terrella
B, to which it is joined more firmly than to the terrella A; the vigour excited
in the rod, the vigour also excited in the stone B, and the strength implanted
in B concur; therefore D is more firmly cemented magnetically with C than
E with C.
But if you were to turn the vertex F round to the iron C, C would not
adhære to F as formerly to D; for stones so arranged being within the orbe
of virtue are placed contrary to natural order; wherefore F does not receive
power from E.
Two loadstones
* or excited pieces of iron, duly cohæring, fly asunder on the
approach of another more powerful loadstone or magnetized piece of iron.
Because the new-comer repels the other with its opposing face, and
dominates it, and ends the relationship of the two which were formerly
joined. So the forces of the other are lessened and succumb; but if it
conveniently could, being diverted of its association with the weaker, and
rolling round, it would turn about to the stronger. Wherefore also magnetick
bodies suspended in the air fall when a loadstone is brought near them with
an opposing face, not (as Baptista Porta teaches) because the faculty of both
those which were joined before grows faint and torpid, for no face can be

hostile to both the ends which cohære, but to one only; and when the
stronger loadstone, coming fresh with opposing face, impels this further
from it, it is put to flight by the friendly reception of the former.

CHAP. XXXIII.

On the Varying Ratio of Strength, and of the Motion
of coition, within the orbe of virtue.

hould a very large weight, which at a very small distance is drawn
towards a loadstone, be divided into ever so many equal parts, and
should the radius of the orbe of magnetick attraction be divided
into the same number of parts, the like named parts of the weight
will correspond to the intermediate parts of the radius.
The orbe of virtue extends more widely than the orbe of motion of any
magnetick; for the magnetick is affected at its extremity, even if it is not
moved with local motion, which effect is produced by the loadstone being
brought nearer. A small versorium also is turned when a good distance off,
even if at the same distance it would not flow towards the loadstone, though
free and disengaged from impediment.
The swiftness of the motion of a magnetick body to a loadstone is
dependent on either the power of the loadstone, on its mass, on its shape, on
the medium, or on its distance within the magnetick orbe.
A magnetick
* moves more quickly towards a more powerful stone than
towards a sluggish one in proportion to the strength, and [as appears] by a
comparison of the loadstones together. A lesser mass of iron also is carried
more quickly towards a loadstone, just as also one that is a little longer in
shape. The swiftness of magnetick motion towards a loadstone is changed
by reason of the medium; for bodies are moved more quickly in air than in
water, and in clear air than in air that is thick and cloudy.
By reason of the distance, the motion is quicker in the case of bodies near
together than when they are far off. At the limits of the orbe of virtue of a

terrella a magnetick is moved feebly and slowly. At very short distances
close to the terrella the moving impetus is greatest.
A loadstone
* which in the outmost part of its orbe of virtue hardly moves a
versorium when one foot removed from it, doth, if a long piece of iron is
joined to it, attract and repel the versorium more strongly with its opposite
poles when even three feet distant. The result is the same whether the
loadstone is armed or unarmed. Let the iron be a suitable piece of the
thickness of the little finger.
For the vigour of the loadstone excites verticity in the iron and proceeds in
the iron and through the iron much further than it extends through the air.
The vigour
* proceeds even through several pieces of iron (joined to one
another end to end), not so regularly, however, as through one continuous
solid.
Dust of steel placed upon paper rises up when a loadstone is moved near
above it in a sort of steely hairiness; but if the loadstone is placed below,
such a hairiness is likewise raised.
Steel *dust (when the pole of a loadstone is placed near) is cemented into
one body; but when it desires coition with the loadstone, the mass is split
and it rises in conglomerated parts.
But if there is a loadstone beneath the paper, the mass is split in the same
way and many portions result, each of which consists of very many parts,
and remains cemented together, as individual bodies. Whilst the lower parts
of these pursue greedily the pole of the loadstone placed directly beneath,
even they also are raised up as magnetick wholes, just as a small iron wire
of the length of a grain or two grains of barley is raised up, both when the
loadstone is moved near both beneath and above.

CHAP. XXXIIII.

Why a Loadstone should be stronger in its poles
in a different ratio; as well in the Northern
regions as in the Southern.

* he extraordinary magnetick virtue of the earth is remarkably
demonstrated by the subtility of the following magnetical
experiment. Let there be given a terrella of no contemptible power,
or a long loadstone with equal cones as polar extremities; but in
any other shape which is not exactly round error is easy, and the experiment
difficult. In the Northern regions, raise the true North pole of the terrella
above the horizon straight toward the zenith; it is demonstrable that it raises
up a larger iron spike on its North pole, than the South pole of the same
terrella is able to raise, when turned in the same way toward the highest
point of the sky. The same thing is shown by a small terrella placed in the
same way above a larger.

Let a b be the earth or a somewhat large terrella, also a b a smaller terrella.
There is set up above the Northern pole of the smaller terrella a spike larger
than the pole b of the smaller terrella can raise, if it is turned round to the
higher parts. And the pole a of the smaller terrella has its strength from the
larger, declining from the Zenith to the plane of the horizon or to the level.
But now,
* if, leaving the terrella disposed in the same way, you bring a piece
of iron to the lower and Southern pole, it will attract and retain a greater
weight than the Boreal pole could, if it were turned round to the lower parts.
Which thing is demonstrated thus: let A be the earth or a terrella; E the
Boreal pole or some place in some great latitude; B a rather large terrella
above the earth or a smaller terrella on the top of a larger; D its Southern
pole. It is manifest that D (the Southern pole) attracts a larger piece of iron,

C, than F (the Boreal pole) will be able to, if it is turned round downward to
the position D, toward the earth or the terrella in the Northern regions.

Magneticks acquire strength through magneticks, if they are properly
placed according to their nature, in near neighbourhood and within the orbe
of virtue. Wherefore when a terrella is placed on the earth or on a terrella,
so that its Southern pole is turned round toward the Northern pole, its
Northern pole, however, turned away from the Northern pole, the influence
and strength of its poles are increased. And so the Northern pole of a terrella
in such a position lifts up a larger spike than the Southern pole, if the
Southern pole is turned away. Similarly the Southern pole in a proper and
natural arrangement, acquiring strength from the earth or from a larger
terrella,
* attracts and retains larger rods of iron. In the other part of the
terrestrial globe toward the South, as also in the Austral portion of a terrella,
the reasoning is converse; for the Southern pole of the terrella being turned
away is more robust, as also the Northern pole when turned round. The
more a region on the earth is distant from the æquinoctial (as also in a larger
terrella), the larger is the accession of strength perceived; near the æquator,
indeed, the difference is small, but on the æquator itself null; at the poles
finally it is greatest.

CHAP. XXXV.

On a Perpetual Motion Machine, mentioned
by authors, by means of the attraction
of a loadstone.

ardan 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!

CHAP. XXXVI.

How a more robust Loadstone may be
recognized.

ery 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.

CHAP. XXXVII.

Use of a Loadstone as it affects
iron.

y 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].

CHAP. XXXVIII.

On Cases of Attraction in other Bodies.

ery often the herd of philosophizers and plagiarists repeat from the
records of others in natural philosophy opinions and errors about
the attractions of various bodies; as that Diamond attracts iron, and
snatches it away from a magnet; that there are various kinds or
magnets, some which attract gold, others silver, brass, lead; even some
which attract flesh, water, fishes. The flame of sulphur is said to seek iron
and stones; so white naphtha is said to attract fire. I have said above that
inanimate natural bodies do not attract, and are not attracted by, others on
the earth, excepting magnetically or electrically. Wherefore it is not true

that there are magnets which attract gold or other metals; because a
magnetick substance draws nothing but magnetick substances. Though
Fracastorio says that he has shown a magnet drawing silver; if this were
true, it must have happened on account of iron skilfully mixed with that
silver or concealed in it, or else because nature (as she does sometimes, but
rarely) had mixed iron with the silver; iron indeed is rarely mixed with
silver by nature; silver with iron very rarely or never. Iron is mixed with
silver by forgers of false coin or from the avarice of princes in the coining
of money, as was the case with the denarius of Antony[189], provided that
Pliny is recording a true incident. So Cardan (perhaps deceived by others)
says that there is a certain kind of loadstone which draws silver; he adds a
most foolish test of this: "If therefore" (he says) "a slender rod of silver be
steeped in that in which a versatory needle has stood, it will turn toward
silver (especially toward a large quantity) although it be buried; by this
means anyone will be able easily to dig up concealed treasures." He adds
that "it should be very good stone, such as he has not yet seen." Nor indeed
will either he or anyone else ever see such a stone or such an experiment.
Cardan brings forward an attraction of flesh, wrongly so named and very
dissimilar from that of the loadstone; for his magnes creagus or flesh-
magnet, from the experiment that it sticks to the lips, must be hooted out
from the assembly of loadstones, or by all means from the family of things
attractive. Lemnian earth, ruddle, and very many minerals do this, and yet
they are fatuously said to attract. He will have it that there is another
loadstone, as it were, a third species, into which, if a needle is driven and
afterwards stuck into the body, it is not felt. But what has attraction to do
with stupefaction, or stupor with a Philosopher's intellect, when he is
discoursing about attraction? There are many stones, both found in nature
and made by art, which have the power of stupefying. Sulphur flame is said
by some to attract, because it consumes certain metals by its power of
penetration. So white naphtha attracts flame, because it gives off and
exhales an inflammable vapour, on which account it is kindled at some
distance, just as the smoke of a recently extinguished candle takes fire again
from another flame; for fire creeps to fire through an inflammable medium.
Why the sucking fish Echineis or the Remora should stay ships has been
variously treated by Philosophers, who are often accustomed to fit this fable
(as many others) to their theories, before they find out whether the thing is
so in nature. Therefore, in order that they may support and agree with the

fatuities of the ancients, they put forward even the most fatuous
ratiocinations and ridiculous problems, cliffs that attract, where the sucking
fish tarry, and the necessity of some vacuum, I know not what, or how
produced. Pliny and Julius Solinus make mention of a stone
Chatochitis[190]. They say that it attracts flesh, and keeps hold of the hands,
just as a loadstone does iron, and amber chaff. But that happens only from a
stickiness and from glue contained in it, since it sticks more easily to the
hands when they are warm. Sagda or Sagdo[191], of the colour of a sard, is a
precious stone mentioned by Pliny, Solinus, Albertus, and Evax[192]; they
describe its nature and relate, on the authority of others, that it specially
attracts wood to itself. Some even babble that woods cannot be wrenched
away except they are cut off. Some also narrate that a stone is found which
grows pertinaciously into ships, in the same way as certain testacea on long
voyages. But a stone does not draw because it sticks; and if it drew, it would
certainly draw shreds electrically, Encelius saw in the hands of a sailor such
a stone of feeble virtue, which would hardly attract even the smallest twigs;
and in truth, not of the colour of the sard. So Diamond, Carbuncle, Crystal,
and others do attract. I pass over other fabulous stones; Pantarbe, about
which Philostratus writes that it draws other stones to itself; Amphitane
also, which attracts gold. Pliny in his origin of glass will have it that a
loadstone is an attractor of glass, as well as of iron. For in his method of
preparing glass, when he has indicated its nature, he subjoins this about
loadstone. "Soon (such is the astute and resourceful craft) it was not content
to have mixed natron; loadstone also began to be added, since it was
thought to attract to itself the liquor of glass (as it does iron)." Georgius
Agricola writes that to the material of glass (sand and natron) one part also
of loadstone is added. "Because that force is believed, in our times just as in
former times, to attract the liquor of glass to itself, as it attracts iron to
itself, purges it when drawn, and makes clear glass from green or muddy;
but the fire afterwards burns up the loadstone." It is true indeed that some
sort of magnes (as the magnesia of the glass-makers imbued with no
magnetick virtues) is sometimes put in and mixed with the material of the
glass; not, however, because it attracts glass. But when a loadstone is burnt,
it does not lay hold of iron at all, nor is iron when red-hot allured by any
loadstone; and loadstone also is burnt up by more powerful fires and loses
its attractive potency. Nor is this a function of loadstone alone in the glass
furnaces; but also of certain pyrites and of some easily combustible iron

ores, which are the only ones used by our glass-makers, who make clear,
bright glass. They are mixed with the sand, ashes, and natron (just as they
are accustomed to make additions in the case of metallick ores whilst they
are smelted), so that when the material slows down into glass, the green and
muddy colour of the glass may be purged by the penetrating heat. For no
other material becomes so hot, or bears the fire for such a convenient time,
until the material of the glass is perfectly fluid, and is at the same time burnt
up by that ardent fire. It happens, however, sometimes, that on account of
the magnetick stone, the magnesia, or the ore, or the pyrites, the glass has a
dusky colour, when they resist the fire too much and are not burnt up, or are
put in in too great quantity. Wherefore manufacturers are seeking for a
stone suitable for them, and are observing also more diligently the
proportion of the mixture. Badly therefore did the unskilful philosophy of
Pliny impose upon Georgius Agricola and the more recent writers, so that
they thought the loadstone was wanted by glass-makers on account of its
magnetick strength and attraction. But Scaliger in De Subtilitate ad
Cardanum, in making diamond attract iron, when he is discussing
magneticks, wanders far from the truth, unless it be that diamond attracts
iron electrically, as it attracts wood, straws, and all other minute bodies
when it is rubbed. Fallopius reckons that quicksilver draws metals by
reason of an occult property, just as a loadstone iron, amber chaff. But when
quicksilver enters metals, it is wrongly called attraction. For metals imbibe
quicksilver, just as clay water; nor do they do this unless they are touching,
for quicksilver does not allure gold or lead to itself from afar, but they
remain motionless in their places.

CHAP. XXXIX.

On Bodies which mutually repel one another.

riters who have discoursed on the forces of bodies which attract
others have also spoken about the powers of bodies which repel,
but especially those who have instituted classes for natural
objects on the basis of sympathy and antipathy. Wherefore it

would seem necessary for us to speak also about the mutual strife of bodies,
so that published errors should not creep further, and be received by all to
the ruin of true philosophy. They say that, just as like things attract for the
sake of preservation, so unlike and contrary things for the same purpose
mutually repel and put one another to flight. This is evident in the reaction
of many things, but it is most manifest in the case of plants and animals,
which attract kindred and familiar things, and in like manner reject foreign
and unsuitable things. But in other bodies there is not the same reason, so
that when they are separated, they should come together by mutually
attracting one another. Animals take food (as everything which grows), and
draw it into their interior; they absorb the nourishment by certain parts and
instruments (through the action and operation of the anima). They enjoy by
natural instinct only the things set in front of them and near them, not things
placed afar off; and this without any alien force or motion. Wherefore
animals neither attract any bodies nor drive them away. Water does not
repel oil (as some think) because the oil floats on water; nor does water
repel mud, because the mud, if mixed in water, settles down in time. This is
a separation of unlike bodies or such as are not perfectly mixed as respects
the material; the separated bodies nevertheless remain joined without any
natural strife. Wherefore a muddy sediment settles quietly on the bottom of
vessels, and oil remains on the top of the water and is not sent further away.
A drop of water remains intact on a dry surface, and is not expelled from
the dry substance. Wrongly therefore do those who discourse on these
matters infer an antipathy (that is, the force of repelling by contrary
passions); for there is no repelling force in them; and repulsion comes[193]
from action, not from passion. But their greek vocables please them too
much. We, however, must inquire whether there is any body which drives
anything else further off without material impetus, as a loadstone attracts.
But a loadstone seems even to repel loadstone. For the pole of one
loadstone repels the pole of another, which does not agree with it according
to nature; by repelling, it turns it round in an orbit so that they may exactly
agree according to their nature. But if a somewhat weak loadstone, floating
freely on water, cannot readily be turned round on account of impediments,
the whole loadstone is repelled and sent further away from the other. All
electricks attract all things: they never repel or propel anything at all[194]. As
to what is related about certain plants (as about the cucumber, which turns
aside when oil is applied to it), there is a material change from the vicinity,

not a hidden antipathy. But when they show a candle flame put against a
cold solid substance (as iron) turn away to the side, and allege antipathy as
the cause, they say nothing. The reason of this they will see clearer than the
day, when we discourse on what heat is[195]. But Fracastorio's opinion that a
loadstone can be found, which would drive iron away, on account of some
opposing principle lurking in the iron, is foolish.

BOOK THIRD.

CHAP. I.

ON DIRECTION.

n referring to the earlier books it will be found shown that a
loadstone has its poles, and that a piece of iron has also poles, and
rotation, and a certain verticity; finally, that the loadstone and the
iron direct their poles toward the poles of the earth. Now, however,
we must make clear the causes of these things and their admirable
workings, pointed out indeed before, but not proven. All those who have
written before us about these rotations have left us their opinions so briefly,
so meagrely, and with such hesitating judgment that they seem hardly likely
ever to persuade anyone, or even to be able to satisfy themselves; and all
their petty reasons are rejected by the more prudent as useless, uncertain,
and absurd, being supported by no proofs or arguments; whence also
magnetick science, being all the more neglected and not understood, has
been in exile. The true austral pole of a loadstone, not the boreal (as all
before* us used to think), if the loadstone is placed in its boat on the surface
of water, turns to the North; in the case of a piece of iron also, whether it

has been excited by a loadstone or not, the southern end moves toward the
North. An oblong piece of iron of three or four digits' length[196], when
skilfully rubbed with a loadstone, quickly turns north and south. Wherefore
mechanicians, taking a piece of iron prepared in this way, balance it on a
pin in a box, and fit it up with the requisites of a sun-dial; or they prepare
the versorium out of two curved pieces of iron with their ends touching one
another, so that the motion may be more constant. In this way the mariners'
versorium is arranged, which is an instrument beneficial, useful, and
auspicious to sailors for indicating, like a good genius, safety and the right
way. But it must be understood on the threshold of this argument (before we
proceed further) that these pointings of the loadstone or of iron are not
perpetually made toward the true poles of the world, do not always seek
those fixed and definite points, or remain on the line of the true meridian;
but usually diverge some distance to the East or to the West. Sometimes
also at certain places on land or sea they do indicate exactly the true poles.
This discrepancy is called the Variation of the iron or of the loadstone; and
since this is brought about by other causes, and is merely a certain
disturbance and perversion of the true direction, we are directing our
attention in this place to the true direction of the compass and of the
magnetick iron (which would be equally toward the true poles and on the
true meridian everywhere on the earth, unless other obstacles and an
untoward pervertency hindered it). Of its variation and the cause of the
perversion we shall treat in the next book. Those who wrote about the world
and about natural philosophy a century ago, especially those remarkable
elementary philosophers, and all those who trace their knowledge and
training to them down to our own times, those men, I say, who represented
the earth as always at rest and, as it were, a useless weight, placed in the
centre of the universe at an equal distance from the sky on every side, and
its nature to be simple, imbued only with the qualities of dryness and cold,
sought diligently for the causes of all things and of all effects in the
heavens, the stars, the planets, in fire, air, waters and substances of mixed
natures. Never indeed did they recognize that the terrestrial globe had,
besides dryness and cold, some special, effective, and predominant
properties, strengthening, directing, and moving the globe itself through its
whole mass and its very deepest vitals; nor did they ever inquire whether
there were any such. For this reason the crowd of philosophizers, in order to
discover the reasons of the magnetical motions, called up causes lying

remote and far away. And one man seems to me beyond all others worthy of
censure, Martin Cortes, who, since there was no cause which could satisfy
him in the whole of nature, dreamed that there was a point of magnetical
attraction beyond the heavens, which attracted iron. Peter Peregrinus thinks
that the direction arises from the poles of the sky. Cardan thought that the
turning of iron was caused by a star in the tail of the Great Bear; Bessard,
the Frenchman, opines that a magnetick turns toward the pole of the
zodiack. Marsilius Ficinus will have it that the loadstone follows its own
Arctick pole; but that iron follows the loadstone, straws amber; whilst this
perhaps follows the Antarctick pole—a most foolish dream. Others have
recourse to I know not what magnetick rocks and mountains. Thus it is
always customary with mortals, that they despise things near home, whilst
foreign and distant things are dear and prized. But we study the earth itself
and observe in it the cause of so great an effect. The earth, as the common
mother, has these causes inclosed in her innermost parts; in accordance with
her rule, position, condition, verticity, poles, æquator, horizons, meridians,
centre, circumference, diameter, and the nature of the whole interior of her
substance, must all magnetical motions be discussed. The earth has been
ordered by the highest Artificer and by nature in such a way that it should
have parts dissimilar in position, bounds of the whole and complete body,
ennobled by certain functions, by which it might itself remain in a definite
direction. For just as a loadstone, when it is floated on water in a suitable
vessel, or is hung by slender threads in the air, by its implanted verticity
conforms its poles to the poles of the common mother in accordance with
magnetick laws; so if the earth were to deviate from its natural direction and
its true position in the universe, or if its poles were to be drawn aside (if this
were possible) toward the sun-rising or the sun-setting or toward any other
points whatsoever in the visible firmament, they would return again to the
north and south by magnetical motion, and would settle at the same points
at which they are now fixed. The reason why the terrestrial globe seems to
remain more steadily with the one pole toward those parts and directed
toward the Cynosure, and why its pole diverges by 23 degrees 29 minutes,
with a certain variation not sufficiently investigated as yet by Astronomers,
from the poles of the ecliptick, depends on its virtue magnetical. The causes
of the precession of the æquinoxes and the progression of the fixed stars,
and of the change, moreover, in the declinations of the sun and of the
tropicks, must be sought from magnetick influences; so that neither that

absurd motion of trepidation of Thebit Bencora[197], which is at great
variance with observations, nor the monstrous superstructures of other
heavens, are any longer needed. A versatory iron turns to the position of the
earth, and if disturbed ever so often returns always to the same points. For
in the far regions of the north, in a latitude of 70 or 80 degrees (to which at
the milder seasons of the year our sailors are accustomed to penetrate
without injury from the cold); in the regions halfway between the poles; on
the æquator in the torrid zone; and again in all the maritime places and
lands of the south, in the highest latitude which has thus far been reached,
always the iron magnetick finds its way, and points to the poles in the same
manner (excepting for the difference of variation); on this side of the
æquator (where we live), and on the other side to the south, less well
known, but yet in some measure explored by sailors: and always the lily of
the compass points toward the North. This we have had confirmed by the
most eminent captains, and also by very many of the more intelligent
sailors. These facts have been pointed out to me and confirmed by our most
illustrious Sea-god, Francis Drake, and by another circumnavigator of the
globe, Thomas Candish; our terrella also indicates the same thing. This is
demonstrated in the case of the orbicular stone, whose
poles are A and B; an iron wire CD, which is placed
upon the stone, always points directly along the meridian
toward the poles AB, whether the centre of the wire is on
the central line or æquator of the stone, or on any other
part situated between the æquator and the poles, as at H,
G, F, E. So the cusp of a versorium on this side of the
æquator
* points toward the north; on the other side the cross is always
directed toward the south; but the cusp or lily[198] does not, as some one has
thought, turn toward the south beyond the æquator. Some inexperienced
people indeed, who in distant parts beyond the æquator have seen the
versorium sometimes become more sluggish and less prompt, thought that
the distance from the arctick pole or from the magnetick rocks was the
cause of this. But they are very much mistaken; for it is as powerful[199],
and adjusts itself as quickly to the meridian or to the point of variation in
the southern as in the northern parts of the earth. Yet sometimes the motion
appears slower, namely, when the supporting pin by lapse of time and long
voyaging has become somewhat blunt, or the magnetick iron parts have
lost, by age or rust, some of their acquired vigour. This may also be shown

experimentally by the versatory iron of a small sun-dial placed on a very
short pin set perpendicular to the surface of the stone, for the iron when
touched by a loadstone points toward the poles of the stone and leaves the
poles of the earth; for the general and remoter cause is overcome by the
particular and powerful cause which is so near at hand. Magnetick bodies
have of themselves an inclination toward the position of the earth and are
influenced by a terrella. Two equal stones of equal strength adjust
themselves to a terrella in accordance with magnetick laws. The iron
conceives vigour from the loadstone and is influenced by the magnetical
motions. Wherefore true direction is the motion of a magnetick body in
regard to the verticity of the earth, the natures of both agreeing and working
together toward a natural position and unity. For indeed we have found out
at length, by many experiments and in many ways, that there is a disposing
nature, moving them together by reason of their various positions by one
form that is common to both, and that in all magnetick substances there is
attraction and repulsion. For both the stone[200] and the magnetick iron
arrange themselves by inclination and declination, according to the
common position of their nature and the earth. And the force of the earth by
the virtue of the whole, by attracting toward the poles, and repelling,
arranges all magneticks which are unfixed and loose. For in all cases all
magneticks conform themselves to the globe of the earth in the same ways
and by the same laws by which another loadstone or any magneticks do to a
terrella.[201]

CHAP. II.

The Directive or Versorial Virtue (which we call
verticity): what it is, how it exists in the loadstone;
and in what way it is acquired when innate.

irective force, which is also called by us verticity, is a virtue which
spreads by an innate vigour from the æquator in both directions
toward the poles. That power, inclining in both directions towards
the termini, causes the motion of direction, and produces a

constant and permanent position in Nature, not only in the earth itself but
also in all magneticks. Loadstone is found either in veins of its own or in
iron mines, when the homogeneous substance of the earth, either having or
assuming a primary form, is changed or concreted into a stony substance,
which besides the primary qualities of its nature has various dissimilitudes
and differences in different quarries and mines, as if from different
matrices, and very many secondary qualities and varieties in its substance.
A loadstone which is dug out in this breaking up of the earth's surface and
of protuberances upon it, whether formed complete in itself (as sometimes
in China) or in a larger vein, is fashioned by the earth and follows the nature
of the whole. All the interior parts of the earth mutually conspire together in
combination and produce direction toward north and south. But those
magnetical bodies which come together in the uppermost parts of the earth
are not true united parts of the whole, but appendages and parts joined on,
imitating the nature of the whole; wherefore when floating free on water,
they dispose themselves just in the same way as they are placed in the
terrestrial
* system of nature. We had a large loadstone of twenty pounds
weight, dug up and cut out of its vein, after we had first observed and
marked its ends; then after it was dug out, we placed it in a boat on water,
so that it could turn freely; then immediately the face which had looked
toward the north in the quarry began to turn to the north on the waves and at
length settled toward that point. For that face which looked toward the north
in the quarry is the southern, and is attracted by the northern parts of the
earth, in the same way as pieces of iron which
acquire their verticity from the earth. About this
point we intend to speak afterwards[202] under
change of verticity. But there is a different rotation of
the internal parts of the earth, which are perfectly
united to the earth and which are not separated from
the true substance of the earth by the interposition of
bodies as are loadstones in the upper portion of the
earth, which is maimed, corrupt, and variable. Let A B be a piece of
magnetick ore; between which and the uniform globe of the earth lie
various soils or mixtures which separate the ore to a certain extent from the
globe of the true earth. It is therefore influenced by the forces of the earth
just in the same way as C D, a piece of iron, in the air. So the face B of
some ore or of that piece of it is moved toward the Boreal pole G, just as

the extremity C of the iron, not A or D. But the condition of the piece E F is
different, which piece is produced in one connected mass with the whole,
and is not separated from it by any earthy mixture. For if the part E F were
taken out and floated freely in a boat by itself, it is not E that would be
directed toward the Boreal pole, but F. So in those substances which acquire
their verticity in the air, C is the southern part and is seen to be attracted by
the Boreal pole G. In the case of others which are found in the upper
unstable portion of the earth, B is the south, and in like manner inclines
toward the Boreal pole. But if those pieces deep down which are produced
along with the earth are dug up, they turn about on a different plan. For F
turns *toward the Boreal parts of the earth, because is the southern part; E
toward the south, because it is the northern. So of a magnetick body, C D,
placed close to the earth, the end C turns toward the Boreal pole; of one that
is adnate to it B A, B inclines to the North; of one that is innate in it, E F, E
turns toward the southern pole; which is confirmed by the following
demonstration, and comes about of necessity according
to all magnetick laws. Let there be a terrella with poles A
B; from its mass cut out a small part E F; if this be
suspended by a fine thread above the hole or over some
other place, E does not seek the pole A but the pole B,
and F turns to A; very differently from a rod of iron C D;
because C, touching some northern part of the terrella,
being magnetically carried away makes a turn round to A, not to B. And yet
here it* should be observed, that if the pole A of the terrella were moved
toward the earth's south, the end E of the piece cut out by itself, if not
brought too near to the stone, would also move of itself toward the south.
But the end C of the piece of iron, placed beyond its orbe of virtue, will turn
toward the north. The part E F of the terrella, whilst in the mass, produced
the same direction as the whole; but when it is separated and suspended by
a thread, E turns to B, and F to A. So parts having the same verticity with
the whole, when separated, are impelled in the contrary direction; for
contrary parts solicit contrary parts. Nor yet is this a true contrariety, but the
highest concordancy, and the true and genuine conformation of bodies
magnetical in the system of nature, if they shall have been divided and
separated: for the parts thus divided should be raised some distance from
the whole, as will be made clear afterwards. Magnetick substances seek a
unity as regards form; they do not so much respect their own mass.

Wherefore the part F E is not attracted into its former
bed; but when once it is unsettled and at a distance, it
* is solicited by the opposite pole. But if the small piece
F E is placed back again in its bed or brought close to,
without any substances intervening, it acquires its
former combination, and, as a part of the whole once
more united, accords with the whole and sticks readily
in its former position; and E remains toward A, and F
toward B, and they settle steadily in their mother's lap.
The reasoning is the same when the stone is divided
into equal parts through the poles. A spherical stone is
divided into two equal parts along the axis
A B; *whether therefore the surface A B is
in the one part facing upward (as in the
former diagram) or lying on its face in both
parts *(as in the latter), the end A tends
toward B. But it must also be understood
that the point A is not carried with a
definite aim always toward the point B,
because in consequence of the division the
verticity proceeds to other points, as to F G, as appears in the fourteenth
chapter of this book. And L M are now the axes in each, and A B is no
longer the axis; for magnetick bodies, as soon as they are divided, become
single magnetick wholes; and they have vertices in accordance with their
mass, new poles arising at each end in consequence of the division. Yet the
axis and the poles always follow the leading of a meridian; because that
force passes along the meridians of the stone from the æquator to the poles,
by an everlasting rule, the inborn virtue of the substance agreeing thereto
from the long and lasting position and the facing of a suitable substance
toward the poles of the earth; by whose strength continued through many
centuries it has been fashioned; toward fixed and determined parts of which
it has remained since its origin firmly and constantly turned.

CHAP. III.

How Iron acquires Verticity through
a Loadstone, and how that verticity
is lost and changed.

riction between an oblong piece of iron and a loadstone imparts to
the former magnetick virtues, which are not corporeal nor inherent
and persistent in any body, as we showed in the discussion on
coition. It is plain that the iron, when it has been rubbed hard with
one end and applied to the stone for a pretty long time, receives no stony
nature, acquires no weight; for if, before the iron is touched by the stone,
you weigh
* it in a small and very exact goldsmith's balance, you will see
after the rubbing that it has exactly the same weight, neither diminished nor
increased. But if you wipe the iron with cloths after it has been touched, or
wash it in water, or scour it with sand or on a grindstone, still it in nowise
lays aside its acquired strength. For the force is spread through the whole
body and conceived in the inmost parts, and cannot in any way be washed
or wiped away. Let an experiment then be made in fire, that untamed tyrant
of nature. Take a piece of iron of the length of a palm and the thickness of a
goosequill pen; let this iron be passed through a suitable round cork and
placed on the surface of water, and observe the end which turns to the north;
rub this particular end with the true southern end of a loadstone; the iron so
rubbed * turns toward the south. Remove the cork, and place the end which
was excited in the fire until the iron is just red-hot; when it is cooled, it will
retain the strength of the loadstone and the verticity, though it will not be so
prompt, whether because the force of the fire had not yet continued long
enough to overcome all its strength, or because the whole iron was not
heated to redness, for the virtue is diffused through the whole. Remove the
cork a second time, and putting the whole iron in the fire, blow the fire with
the bellows, so that it may be all aglow, and let it remain a little longer time
red-hot; when cooled (so, however, that, whilst it is cooling, it does not rest
in one position), place it again on the water with the cork, and you will see
that it*has lost the verticity which it had acquired from the stone. From these
experiments it is clear how difficult it is for the property of polarity
implanted by the loadstone to be destroyed. But if a small loadstone had
remained as long in the same fire, it would have lost its strength. Iron,
because it does not so easily perish, and is not so easily burnt up as very
many loadstones, retains its strength more stably, and when it is lost can

recover it again from a loadstone; but a loadstone when burnt does not
revive.* But now that iron, which has been deprived of its magnetick form,
moves in a different way from any other piece of iron, for it has lost its
polar nature; and whereas before the touch of the loadstone it may have had
a motion toward the north, and after contact toward the south; now it turns
to no *definite and particular point; but afterwards, very slowly and after a
long time, it begins to turn in a doubtful fashion toward the poles of the
earth (having acquired some power from the earth). I have said that the
cause of direction was twofold, one implanted in the stone and iron, but the
other in the earth, implanted by the disponent virtue; and for that reason
(the distinction of poles and the verticity in the iron having now been
destroyed) a slow and weak directive power is acquired anew from the
verticity of the earth. We may see, therefore, with what difficulty and only
by the application of hot fires and by long ignition of the iron heated to
softness, the imparted magnetick virtue is eradicated. When this ignition has
overcome the acquired polarity, and it has been now completely subdued
and not awakened again, that iron is left unsettled and utterly incapable of
direction. But we must further inquire how iron remains affected by
verticity. It is manifest that it strongly affects and changes the nature of the
iron, because the presence of a loadstone attracts the iron to itself with an
altogether wonderful readiness. Nor is it only the part that is rubbed, but on
account of the rubbing (on one end only) the whole iron is affected together,
and gains by it a permanent though an unequal power. This is demonstrated
as follows.
* Rub an iron wire on the end so that it is excited, and it will turn
towards the north; afterward cut off some portion of it; you will see that it
still turns toward the north (as before), but more feebly. For it must be
understood that the loadstone excites a steady verticity in the whole iron (if
the rod be not too long) more vigorous throughout the whole mass in a
shorter bar, and as long as the iron remains touching the loadstone a little
stronger. But when the iron is separated from contact with it, then it
becomes much weaker, especially in the end that was not touched. Just as a
long rod, one end of which is placed in the fire and heated, grows
exceedingly hot at that end, less so in the parts adjoining and in the middle,
whilst at the other end it can be held in the hand, and that end is only warm;
so the magnetical vigour diminishes from the excited end to the other end;
but it is present there instantly, and does not enter after an interval of time
nor successively, as the heat in the iron; for as soon as a piece of iron has

been touched by a loadstone it is excited throughout its whole length. For
the sake
* of experiment, let there be a rod of iron 4 or 5 digits long,
untouched by a loadstone; as soon as you touch one end only with a
loadstone, the opposite end immediately, or in the twinkling of an eye, by
the power that it has conceived, repels or attracts a versorium, if it be
applied to it ever so quickly.

CHAP. IIII.

Why Iron touched by a Loadstone acquires an opposite
verticity, and why iron touched by the true Northern side of a
stone
turns to the North of the earth, by the true Southern side
to the South; and does not turn to the South when rubbed
by the Northern point of the stone, and when by
the Southern to the North, as all who have
written on the loadstone have
falsely supposed.

emonstration has already been given that the northern part of a
loadstone does not attract the northern part of another stone, but
the southern, and repels the northern part of another stone from its
northern side when it is applied[203] to it. That general magnet, the
terrestrial globe, disposes iron touched by a loadstone in the same way, and
likewise magnetick iron stirs this same iron by its implanted strength, and
excites motion and controls it. For whether the comparison and experiment
has been made between loadstone and loadstone, or loadstone and iron, or
iron and
* iron, or the earth and loadstone, or the earth and iron conformed by
the earth or strengthened by the power of a loadstone, the strength and
inclinations of each must mutually harmonize and accord in the same way.
But the reason must be sought, why a piece of iron when touched by a
loadstone acquires a disposition to motion toward the opposite pole of the
earth, and not toward that pole of the earth to which that pole of that

loadstone turned by which it was excited. It has been pointed out that iron
and loadstone are of one primary nature; when the iron is joined to the
loadstone, they become, as it were, one body, and not only is the end of the
iron changed, but the remaining parts also are affected along with it. A, the
north pole of a loadstone, is placed against the cusp of a piece of iron; the
cusp of the iron has now become the southern part of the iron, because it is
touching the northern part of the stone; the cross-end
of the iron has become the northern. For if that
contiguous magnetick substance be separated from
the pole of the terrella, or from the parts near the
pole, the one end (or the end which, whilst the
connection was kept up, was touching the northern
part of the stone) is the southern, whilst the other is the northern. So also if
a versorium excited by a loadstone be divided into ever so many parts
(however small), those parts when separated will, it is clear, arrange
themselves in the same disposition as that in which they were disposed
before, when they were undivided. Wherefore whilst the cusp remains over
the northern pole A, it is not the southern end, but is, as it were, part of a
whole; but when it is taken away from the stone, it is the southern end,
because when rubbed it tended toward the northern parts of the stone, and
the cross (the other end of the versorium) is the northern end. The loadstone
and the iron make one body; B is the south pole of the whole; C (that is, the
cross) is the northern end of the whole; divide the iron also at E, and E will
be the southern end with respect to the cross; and E will likewise be the
northern end in respect to B. A is the true northern pole of the stone and is
attracted by the southern pole of the earth. The end of the iron which is
touched by the true boreal part of the stone becomes the southern end, and
turns to A, the north [pole] of the stone, if it be near; or if it be some
distance from the stone it turns to the north [pole] of the earth. So always
iron which is touched (if it is free and unrestrained) tends to the opposite
part of the earth from that part to which the loadstone that touched it tends.
Nor does
* it make any difference how it is rubbed, whether straight up or
slanting in some way. For in any case the verticity flows into the iron,
provided it is touched by either end. Wherefore all the cusps at B acquire
the same verticity, after they are separated, but opposite to that pole of the
stone; wherefore also they are united to the loadstone at the pole B; and all
the crosses in the present figure have the opposite verticity to the pole E,

and are moved and laid hold of by E when they are
in a convenient position. It is exactly the same in the
case of the long stone F H divided at G; F and H
always move, both in the whole and in the divided
stone, to opposite poles of the earth, and O and P
mutually attract one another, the one of them being
the northern, the other the southern. For, supposing
H to have been the southern in the whole stone and F the northern, P will be
the northern with respect to H in the divided stone, and O the southern with
respect to F. So also F and H mutually incline to a connection, if they are
turned a very little toward one another, and run together at length and join.
But supposing the division of the stone to have been meridional (that is,
according to the line of a meridian, not of any parallel circle), then they turn
round, and A attracts B, and the end B is attracted to
A and attracts A, until, being turned round, they are
connected and cemented together; because
magnetick attraction is not made along the parallels,
but meridionally. For this reason pieces of iron
placed* on a terrella whose poles are A B, near the æquator along parallels,
do not combine or stick together firmly:
But if applied to one another along a
* meridian they are immediately joined
firmly together, not only on and near the
stone, but even at some distance within the
force of the controlling orbe. Thus they are
joined and cemented together at E, but not
at C in the other figure. For the opposite
ends C and F meet and adhære together in
the case of the iron just in the same way as A and B before in the case of the
stone. But they are opposite ends, because the pieces of iron proceed from
the opposite sides and poles of the terrella; and C in reference to the
northern
* pole A is southern, and F is boreal in reference to the southern pole
B. In like manner also they are cemented together, if the rod C (being not
too long[204]) be moved further toward A, and F toward B, and they be
joined together over the terrella, like A and B of the divided stone above.
But now
* if the cusp A, which has been touched by a loadstone, be the
southern end, and you were to touch and rub with this the cusp of another

iron needle B, which has not been touched, B will be northern, and will
point to the south. But if you were to touch with the northern point B any
other iron needle, still new, on its cusp, this again will be southern, and will
turn to the north. The iron not only receives the necessary strength from the
loadstone, if it be a good loadstone, but also imparts its acquired strength to
another piece of iron, and the second to a third (always in strict accordance
with magnetick laws). In all these demonstrations of ours it should always
be borne in mind that the poles of a stone, as well as those of iron, whether
touched or untouched, are always in fact and by nature opposite to the pole
toward which they point and are so designated by us, as we have laid down
above.* For in them all it is always the northern which tends to the south,
either of the earth or of the stone, and the southern which tends to the north
of the stone. Northern parts are attracted by the southern of the earth; so in
the boat they tend toward the south. A piece of iron touched by the northern
parts of a loadstone becomes south at the one end and tends always (if it is
near and within the orbe of the loadstone) to the north of the stone, and if it
be free and left to itself at some distance from the stone, it tends to the
northern part of the earth. The northern pole A of a loadstone turns to G, the
south of the earth; a versorium touched at its cusp by the part A follows A,
because it has become southern. But the versorium C, placed farther away
from *the loadstone, turns its cusp to F, the north of the earth, because the
cusp has become southern by contact with the boreal part of the stone. So
the ends touched by the northern part of the stone are made southern, or are
excited with a southern polarity, and tend toward the north of the earth;
those touched by the southern pole are made northern, or are excited with a
northern force, and turn to the south of the earth.

CHAP. V.

On the Touching of pieces of Iron
of divers shapes.

ars of iron, when touched by a loadstone, have one end north, the
other south, and in the middle is the limit of verticity, like the
æquinoctial circle on the globe of a terrella or on an iron globe.
* But when an iron ring is rubbed on one side on a loadstone, then
the one pole is on the place that was in contact, whilst the other is at the
opposite point; and the magnetick power divides the ring into two parts by a
natural distinction which, though not in shape, yet in power and effect is
like an æquator. But if a thin straight rod be bent into a ring without any
welding or union of the ends, and be touched in the middle by a loadstone,
both ends will be of the same verticity. Let a ring be taken which is whole
and continuous,
* and which has been touched by a loadstone at one place,
and let it be divided afterward at the opposite point and straightened out,
both ends
* will also be of the same verticity, no otherwise than a thin rod
touched in the middle or a ring not cohærent at the joint.

CHAP. VI.

What seems an Opposing Motion in Magneticks
is a proper motion toward unity.

n things magnetical nature always tends to unity, not merely to
confluence and agglomeration, but to harmony; in such a way that
the rotational and disponent faculty should not be disturbed, as is
variously shown in the following example. Let C D be an entire
body of some magnetick substance, in which C tends to B, the north of the
earth, and D to the south, A. Then[205] divide it in the middle in its æquator,
and it will be E that is tending toward A, and F tending toward B. For just
as in the undivided body, so in the divided, nature aims at these bodies
being*united; the end E again joins with F harmoniously and eagerly and
they stick together, but E is never joined to D, nor F to C; for then C must
be turned contrary to nature toward A, the south, or D toward B, the north,
which is foreign to them and incongruous. Separate the stone in the place
where it is cut and turn D round to C; they harmonize and combine
excellently. For D is tending to the south, as before, and C to the north; E
and F, parts which were cognate in the ore, are now widely separated, for
they do not move together on account of material affinity, but they take
their motion and inclination from their form. So the ends, whether joined or
divided, tend magnetically in the same way to the earth's poles in the first
figure where there is one whole, or divided as in the second figure; and F E
in the second figure is a perfect magnetick joined together into one body
and C D, just as it was primarily produced in its ore, and F E in its boat,
turn in
* this way to the poles of the earth and are conformed to them. This
harmony of the magnetick form is shown also in the forms of vegetables.
Let A*B be a twig from a branch of osier or other tree which sprouts easily.
Let A be the upper part, B the lower part toward the root; divide it at C D; I
say that the end D, if grafted again to C by the primer's art, grows to it; just
as also if B is grafted to A, they grow together and germinate. But D being
grafted on A, or C on B, they are at variance, and never grow into one
another, but one of them dies on account of the inverted and inharmonious
arrangement, since the vegetative force, which moves in one way, is now
impelled in opposite directions.

CHAP. VII.

A determined Verticity and a disponent Faculty are what
arrange magneticks, not a force, attracting or pulling them
together, nor merely strongish coition or unition.

n the neighbourhood of the æquinoctial A there is no coition of the
ends of a piece of iron with the terrella; at the poles there is the
strongest. The greater the distance from the æquinoctial, the
stronger is the coition with the stone itself, and with any part of it,
not with its pole alone. Yet pieces of iron are not raised up on account of
some peculiar attracting force or a stronger combined force, but on account
of that common directing or conforming and rotating force; nor indeed is a
spike *in the part about B, even one that is very small and of no weight[206],
raised up to the perpendicular by the strongest terrella, but cleaves to it
obliquely. Also just as a terrella attracts magnetick bodies variously with
dissimilar forces, so also an iron snout placed on the stone obtains a
different
* potency in proportion to the latitude, just as a snout at L by its
firmer connection resists a greater weight more stoutly than one at M, and

at M than at N. But neither does the snout raise the spike to the
perpendicular except at the poles, as is shown in the figure. A snout at L
may hold and lift from the earth two ounces of iron in one piece; yet it is
not strong enough to raise an iron wire of two grains weight to the
perpendicular,
* which would happen if the verticity arose on account of a
stronger attraction, or rather coition or unition.

CHAP. VIII.

Of Discords between pieces of Iron upon the same pole
of a loadstone, and how they can agree and
stand joined together.

uppose two iron wires or a pair of needles stuck on the pole of a
terrella; though they ought to stand perpendicularly, they mutually
* repel one another at the upper end, and produce the appearance of a
fork; and if one end be forcibly impelled toward the other, the other
declines and bends away from association with it, as in the following figure.
A and B, iron spikes, adhære obliquely[207] upon the pole
on account of their nearness to one another; either alone
would otherwise stand erect and perpendicular. For the
extremities A B, being of the same verticity, mutually
abhor and fly one another. For if C be the northern pole of
the terrella, A and B are also northern ends; but the ends
which* are joined to and held at the pole C are both
southern. But if those spikes be a little longer (as, for
example, of two digits length) and be joined by force, they adhære together
and unite in a friendly style, and are not separated without force. For they
are magnetically welded, and there are now no longer two distinct ends, but
one end and one body; no less than a wire which is doubled and set up
perpendicularly. But here is seen also another subtile point, that if those
spikes* were shorter, not as much as the breadth of one digit, or even the
length of a barleycorn, they are in no way willing to harmonize or to stand
straight up at the same time, because naturally in shorter wires the verticity

is stronger in the ends which are distant from the terrella and the magnetick
discord more vehement than in long ones. Wherefore they in no way admit
of an intimate association and connection.

Likewise if those lighter pieces of iron or iron wires be suspended, hanging,
as A *and B, from a very fine silk thread, not twisted but braided, distant
from the stone the length of a single barleycorn, then the opposing ends, A
and B, being situated within the orbe of virtue above the pole, keep a little
away from one another for the same reason; except when they are very near
the pole of the stone C, the stone then attracting them more strongly toward
one end.

CHAP. IX.

Figures illustrating direction and showing varieties
of rotations.

assing from the probable cause of motion
toward fixed points (according to magnetick
laws and principles), it remains for us to
indicate those motions. Above a round
loadstone (whose poles are A, B) let a versatory needle
be placed whose cusp has been excited by the pole A;
that cusp is certainly directed toward A, and is strongly

attracted by A; because, having been touched by A, it is in true harmony
with A, and combines with it; and yet it is called contrary, because when the
versorium is separated from the stone, it is seen to be moved toward the
opposite part of the earth to that toward which the pole A of the loadstone is
moved. For if A be the northern pole of the terrella, the cusp is the southern
end of the needle, of which the other end (namely, the cross) is pointed to
B; so B is the southern pole of the loadstone, but the cross is the northern
end of the versorium. So also the cusp is attracted by E, F, G, H, and by
every*part of a meridian, from the æquator toward the pole, by the faculty
disponent; and when the versorium is on the same parts of the meridian, the
cusp is directed toward A. For it is not the point A that turns the versorium
toward it, but the whole loadstone; as also the whole earth does, in the
turning of loadstones to the earth.

Figures illustrating magnetick directions in a right sphere[208] of stone, and
in the right sphere of the earth, as well as the polar directions to the
perpendicular of the poles. All these cusps have been touched by the pole
A; all the cusps are turned toward A, excepting that one which is repelled
by B.

Figures illustrating horizontal directions above the body of a loadstone. All
the cusps that have been made southern by rubbing on the boreal pole, or
some place round the northern pole A, turn toward the pole A, and turn

away from the southern pole B, toward which all the crosses look. I call the
direction horizontal, because it is arranged along the plane of the horizon;
for nautical
* and horological instruments are so constructed that the iron
hangs or is supported in æquilibrium on the point of a sharp pin, which
prevents the dipping of the versorium, about which we intend to speak later.
And in this way it is of the greatest use to man, indicating and
distinguishing all the points of the horizon and the winds. Otherwise on
every oblique sphere (whether of stone or the earth) versoria and all
magnetick substances would have a dip by their own nature below the
horizon; and at the poles the directions would be perpendicular, which
appears in our discussion On Declination.

A round stone (or terrella) cut in two at the æquator; and all the cusps have
been touched by the pole A. The points at the centre of the earth, and
between the two parts of the terrella which has been cut in two through the
plane of the æquator, are directed as in the present[209] diagram. This would
also happen in the same way if the division of the stone were through the
plane of a tropick, and the mutual separation of the divided parts and the
interval between them were the same as before, when the loadstone was
divided through the plane of the æquator, and the parts separated. For the
cusps are repelled by C, are attracted by D; and the versoria are parallel, the
poles or the verticity in both ends mutually requiring it.

Half a* terrella by itself and its directions, unlike the directions of the two
parts close to one another as shown in the figure above. All the cusps have
been touched by A; all the crosses below except the middle one tend toward
the loadstone, not straight, but obliquely; because the pole is in the middle
of the plane which before was the plane of the æquator. All cusps touched
by places distant from the pole move toward the pole (exactly the same as if
they had been rubbed upon the pole itself), not toward the place where they
were rubbed, wherever that may have been in the undivided stone in some
latitude between the pole and the æquator. And for this reason there are only
two distinctions of regions, northern and southern, in the terrella, just as in
the general terrestrial globe, and there is no eastern nor western place; nor
are there any eastern or western regions, rightly speaking; but they are
names used in respect of one another toward the eastern or western part of
the sky. Wherefore it does not appear that Ptolemy did rightly in his
Quadripartitum, making eastern and western districts and provinces, with
which he improperly connects the planets, whom the common crowd of
philosophizers and the superstitious soothsayers follow.

CHAP. X.

On Mutation of Verticity and of Magnetick
Properties, or on alteration in the power
excited by a loadstone.

riction with a loadstone gives to a piece of iron a verticity strong
enough; not, however, so stable that the iron may not by being
rubbed on the opposite part (not only with a more powerful
loadstone, but with the same) be changed and deprived of all its
former verticity, and indued with a new and opposite one. Take a piece of
iron wire and rub each end of the wire equally with one and the same pole
of a loadstone, and let it be passed through a suitable cork and place it on
water. Then truly one end of the wire will be directed toward that pole of
the earth toward which that end of the stone will not turn. But which end of
the iron wire will it be? That certainly which was rubbed last. Rub the other

end of * this again with the same pole, and immediately that end will turn
itself in the opposite direction. Again touch the former end of the iron wire
only with the same pole of the loadstone as before; and that[210] end, having
gained the command, immediately changes to the contrary side. So you will
be able to change the property of the iron frequently, and that end of the
wire rules which has been touched the last. Now then merely hold the
boreal pole of the stone for some time near the boreal part of the wire which
was last touched, so that it does not touch, but so that it is removed from it
by one,* two, or even three digits, if the stone have been pretty strong; and
again it will change its property and will turn round to the contrary side;
which will also happen (albeit rather more feebly) even if the loadstone be
removed to a distance of four digits. You will be able to do the same thing,
moreover, with both the austral and the boreal part of the stone in all these
experiments. Verticity may likewise be acquired and changed when thin
plates*of gold, silver, and glass are interposed between the stone and the end
of the iron or iron wire, if the stone were rather strong, even if the
intermediate lamina is not touched either by the iron or the stone. And these
changes of verticity take place in smelted iron. Indeed what the one pole of
the stone implants and excites, the other disturbs and extinguishes, and
confers a new force. For it does not require a stronger loadstone to take
away the weaker and sluggish virtue and to implant the new one; nor is iron
inebriated by the equal strength of loadstones, and made utterly uncertain
and neutral, as Baptista Porta teaches; but by one and the same loadstone, or
by loadstones endowed with equal power and might, its strength is, in
accordance with magnetick rules, turned round and changed, excited,
repaired, or disturbed. But a loadstone itself, by being rubbed on another,
whether a larger or a more powerful stone, is not disturbed from its own
property and verticity, nor does it turn round toward the opposite direction
in its boat, or to the other pole opposite to that to which it inclines by its
own nature and implanted verticity. For strength which is innate and has
been implanted for a very long time abides more firmly, nor does it easily
yield from its ancient holding; and that which has grown for a long time is
not all of a sudden brought to nothing, without the destruction of the
substance
* containing it. Nevertheless in a long interval of time a change
does take place; in one year, that is to say, or two, or sometimes in a few
months; doubtless when a weaker loadstone remains lying by a stronger one
contrary to the order of nature, namely, with the northern pole of one

loadstone adjoined to the northern pole of another, or the southern to the
southern. For so the weaker strength gradually declines with the lapse of
time.

CHAP. XI.

On the Rubbing of a piece of Iron on a Loadstone
in places midway between the poles, and upon
the æquinoctial of a terrella.

elect a piece of iron wire of three digits length, not touched by a
loadstone (but it will be better if its acquired verticity be rather
weak or have been damaged in some way); touch it and rub it on
the æquator of a terrella, exactly on the æquinoctial line in the
direction of its length, on the one end, or the ends only, or in all its parts;
place *the wire touched in this way on water in a cork fitted for it; it will
swim about doubtfully on the waves without any acquired verticity, and the
verticity previously implanted will be disturbed. If, however, it float by
chance toward the poles, it will be checked a little by the poles of the earth,
and will at length by the influence of the earth be indued with verticity.

CHAP. XII.

In what way Verticity exists in any Iron that has
been smelted though not excited by a lodestone.

aving thus far[211] demonstrated natural and inborn causes and
powers acquired by means of the stone, we will now examine the
causes of magnetick virtues in smelted iron that has not been
excited by a stone. Loadstone and iron furnish and exhibit to us wonderful
subtilities. It has been repeatedly shown above that iron not excited by a
stone turns north and south; further that it has verticity, that is, special and
peculiar polar distinctions, just as a loadstone, or iron which has been
rubbed upon a loadstone. This indeed seemed to us at first wonderful and
incredible; the metal of iron from the mine is smelted in the furnace; it runs
out of the furnace, and hardens into a great mass; this mass is divided in
great worksteads, and is drawn into iron bars, from which smiths again
construct many instruments and necessary pieces of iron-work. Thus the
same mass is variously worked up and transformed into very many
similitudes. What is it, then, which preserves its verticity, and whence is it
derived? So take this first from the above[212] smithy. Let the blacksmith
beat out upon his anvil a glowing mass of iron of two or three ounces
weight into an iron spike of the length of a span of nine inches. Let the
smith*be standing with his face to the north, his back to the south, so that
the hot iron on being struck has a motion of extension to the north; and let
him so complete his work with one or two heatings of the iron (if that be
required); let him always, however, whilst he is striking the iron, direct and
beat out the same point of it toward the north, and let him lay down that end
toward the north. Let him in this way complete two, three, or more pieces of
iron, nay, a hundred or four hundred; it is demonstrable that all those which
are thus beaten out toward the north, and so placed whilst they are cooling,

turn round on their centres; and floating pieces of iron (being transfixed, of
course, through suitable corks) make a motion in the water, the determined
end being toward the north. In the same way also pieces of iron acquire
verticity from their direction whilst they are being beaten out and
hammered
* or drawn out, as iron wires are accustomed to do toward some
point of the horizon between east and south or between south and west, or
in the opposite direction. Those, however, which are pointed or drawn out
rather*toward the eastern or western point, conceive hardly any verticity or
a very undecided one. That verticity is especially acquired by being beaten
out. But a somewhat inferior iron ore, in which no magnetick powers are
apparent,
* if put in a fire (its position being observed to be toward the poles
of the world or of the earth) and heated for eight or ten hours, then cooled
away from the fire, in the same position towards the poles, acquires a
verticity in accordance with the position of its heating and cooling. Let a
rod of* cast iron be heated red-hot in a strong fire, in which it lies
meridionally (that is, along the path of a meridian circle), and let be
removed from the fire and cooled, and let it return to its former temperature,
remaining in the same position as before; then from this it will turn out that,
if the same ends have been turned to the same poles of the earth, it will
acquire verticity, and the end which looked toward the North on water with
a cork before the heating, if it have been placed during the heating and
cooling toward the fourth, now turns round to the south. But if perchance
sometimes the rotation have been doubtful and somewhat feeble, let it be
placed again in the fire, and when it is taken out at a red heat, let it be
perfectly cooled toward the pole from which we desire the verticity, and the
verticity
* will be acquired. Let the same rod be heated in the contrary
position, and let it be placed so at a red heat it is cool; for it is from its
position in cooling (by the operation of the verticity of the earth) that
verticity is put into the iron, and it turns round to parts contrary to its former
verticity. So the end which formerly looked toward the north now turns to
the south. In accordance with these reasonings and in these ways the boreal
pole of the earth gives to the end of a piece of iron turned toward it a
southern
* verticity, and that end is attracted by that pole. And here it must be
observed that this happens to iron not only when it is cooled in the plane of
the horizon, but also at any angle to it almost up to the perpendicular toward
the centre of the earth. So the heated iron conceives vigour and verticity
from the earth more quickly in the course of its return to its normal state,

and in its recovery, as it were (in the course of which it is transformed), than
by its* mere position alone. This is effected better and more perfectly in
winter and in colder air, when the metal returns more certainly to its natural
temperature, than in summer and in warm regions. Let us see also what
position alone and a direction toward the poles of the earth can effect by
itself without fire and heat. Iron rods which have been placed and fixed for
a long * time, twenty or more years, from south to north (as they not
infrequently are fixed in buildings and across windows), those rods, I say,
by that long lapse of time acquire verticity and turn round, whether hanging
in the air, or floating (being placed on cork), to the pole toward which they
were pointing, and magnetically attract and repel a balanced iron
magnetick; for the long continued position of the body toward the poles is
of much avail. This fact (although conspicuous by manifest experiments) is
confirmed by an incident related in an Italian letter[213] at the end of a book
of Maestro Filippo Costa, of Mantua, Sopra le Compositioni degli Antidoti
written in Italian, which translated runs thus: "A druggist of Mantua showed
me a piece of iron entirely changed into a magnet, drawing another piece of
iron in such a way that it could be compared with a loadstone. Now this
piece of iron, when it had for a long time held up a brick ornament on the
top of the tower of the church of St. Augustine at Rimini, had been at length
bent by the force of the winds, and remained so for a period of ten years.
When the monks wished to bend it back to its former shape, and had handed
it over to a blacksmith, a surgeon named Maestro Giulio Caesare discovered
that it was like a magnet and attracted iron." This was caused by the turning
of its extremities toward the poles for so long a time. And so what has been
laid down before about change of verticity should be borne in mind; how in
fact the poles of iron spikes are altered, when a loadstone is placed against
them only with its pole and points toward them, even at a rather long
distance. Clearly it is in the same way that that large magnet also (to wit,
the earth itself) affects a piece of iron and changes its verticity. For,
although the iron may not touch the pole of the earth, nor any magnetick
part of the earth, yet verticity is acquired and changed; not because the
poles of the earth and the point itself which is 39° distant from our city of
London, changes the verticity at a distance of so many miles; but because
the whole magnetick earth, that which projects to a considerable height, and
to which the iron is near, and that which is situated between us and the pole,
and the vigour existing within the orbe of its magnetick virtue (the nature of

the whole conspiring thereto), produces the verticity. For the magnetick
effluence of the earth rules everywhere within the orbe of its virtue, and
transforms bodies; but those things which are more similar to it, and
specially connected with it by nature, it rules and controls; as loadstone and
iron. Wherefore in very many matters of business and actions it is clearly
not superstitious and idle to observe the positions and conditions of lands,
the points of the horizon and the places of the stars. For as when a babe is
brought forth into the light from its mother's womb, and acquires respiration
and certain animal activities, then the planets and celestial bodies[214],
according to their position in the universe, and according to that
configuration which they have with regard to the horizon and the earth,
instil peculiar and individual qualities into the newly born; so that piece of
iron, whilst it is being formed and lengthened out, is affected by the
common cause (to wit, the earth); whilst it is returning also from its heated
condition to its former temperature, it is imbued with a special verticity in
accord with its position. Rather long pieces of iron sometimes have the
same *verticity at each end; wherefore they have motions which are less
certain and well ordered on account of their length and of the aforesaid
processes, exactly as when an iron wire four feet long is rubbed at each end
upon the same pole of a loadstone.

CHAP. XIII.

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.

igneous 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 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.

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.

uietly 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.

CHAP. XV.

The Poles, Æquator, Centre in an entire Loadstone
remain and continue steady; by diminution and
separation of some part they vary and
acquire other positions.

uppose
* A B to be a terrella, whose centre is E, and whose diameter (as also
its æquinoctial circle) is D F. If you cut off a portion (through the arctic

circle, for example), G H, it is demonstrable
that the pole which was at A now has a
position at I. But the centre and the
æquinoctial recede toward B merely so that
they are always in the middle of the mass that is left
between the plane of the arctick circle G I H and the
antarctick pole B. Therefore the segment of the
terrella comprised between the plane of the former
æquinoctial (that, of course, which was the æquator
before cutting that part away) D E F and the newly acquired æquator M L N
will always
* be equal to the half of that part which was cut off, G I H A. But
if the portions have been taken away from the side C
D, the poles and axis will not be in the line A B, but in
E F, and the axis would be changed in the same
proportion as the æquator in the former figure. For
those positions of forces and virtues, or rather limits of
the virtues, which are derived from the whole form,
are moved forward by change of quantity and shape;
since all these limits arise from the conspiring together
of the whole and of all the parts united; and the
verticity or the pole is not a virtue innate in one part, or in some definite
limit, or fixed in the substance; but it is an inclination of the virtue to that
part. And just as a terrella separated from the earth has no longer the earth's
poles and æquator, but individual ones of its own; so also if it again be
divided, those limits and distinctions of the qualities and virtues pass on to
other parts. But if a loadstone be divided in any way, either along a parallel,
or meridionally, so that by the change of shape either the poles or the
æquator move to other positions, if the part cut off be merely applied in its
natural position and joined to the whole, even without any agglutination or
cementing together, the determining points of the virtues return again to
their former sites, as if no part of the body had been cut off. When a body is
entire, its form remains entire; but when the body is lessened, a new whole
is made, and there arises a new entirety, determined for every loadstone,
however small, even for magnetick gravel, and for the finest sand.

CHAP. XVI.

If the Southern Portion of a Stone be lessened,
something is also taken away from the power
of the Northern Portion.

ow although the southern end of a magnetick iron is attracted by a
northern end, and repelled by a southern, yet the southern portion
of a stone does not diminish, but increases the potency of the
boreal part. Wherefore if a stone be cut in two and divided through
the arctick circle, or through the tropick of Cancer or the æquator, the
southern portion does not attract magnetick substances so strongly with its
pole as before; because a new whole arises, and the æquator is removed
from its old position and moves forward on account of that cutting of the
stone. In the former condition, since the opposite portion of the stone
increases the mass beyond the plane of the æquator, it strengthens also the
verticity, and the potency, and the motion to unity.

CHAP. XVII.

On the Use and Excellence of Versoria: and how iron
versoria used as pointers in sun-dials, and the fine needles
of the mariners' compass, are to be rubbed, that
they may acquire stronger verticity.

ersoria prepared by the loadstone subserve so many actions in
human life that it will not be out of place to record a better method
of touching them and exciting them magnetically, and a suitable
manner of operating. Rich ores of iron and such as yield a greater
proportion of metal are recognized by means of an iron needle suspended in
æquilibrium and magnetically prepared; and magnetick stones, clays, and
earths are distinguished, whether crude or prepared. An iron needle (the
soul of the mariners' compass), the marvellous director in voyages and

finger of God, one might almost say, indicates the course, and has pointed
out the whole way around the earth (unknown for so many ages). The
Spaniards (as also the English) have frequently circumnavigated (by an
immense circuit) the whole globe by aid of the mariners' compass. Those
who travel about through the world or who sit at home have sun-dials. A
magnetick pointer follows and searches out the veins of ore in mines. By its
aid mines are driven in taking cities; catapults and engines of war are aimed
by night; it has been of service for the topography of places, for marking off
the areas and position of buildings, and for excavating aqueducts for water
under ground. On it depend instruments designed to investigate its own dip
and variation.
When iron is to be quickened by the stone, let it be clean and bright,
disfigured by no rust or dirt, and of the best steel[216]. Let the stone itself be
wiped dry, and let it not be damp with any moisture, but let it be filed gently
with some smooth piece of iron. But the hitting of the stone with a hammer
is of no advantage. By these means let their bare surfaces be joined, and let
them be rubbed, so that they may come together more firmly; not so that the
material substance of the stone being joined to the iron may cleave to it, but
they are rubbed gently together with friction, and (useless parts being
rubbed off) they are intimately united; whence a more notable virtue arises
in the iron that is excited. A is the best way of
touching a versorium when the cusp touches the pole
and faces it; B is a moderately good way, when,
though facing it, it is a little way distant from the
pole; also in like manner C is only moderately good
on account of the cusp being turned away from the
pole; D, which is farther distant, is hardly so good; F,
which is prepared crosswise along a parallel, is bad;
of no virtue and entirely irresponsive and feeble is
the magnetick index L, which is rubbed along the æquator; oblique and not
pointing towards the pole as G, and oblique, not pointing toward but turned
away from the pole as H, are bad. These have been placed so that they
might indicate the distinct forces of a round stone. But mechanicians very
often have a stone tending more to a cone shape, and more powerful on
account of that shape since the pole, on which they rub their wires, is at the
apex of the projecting part. Sometimes the stone has on the top and above

its own pole an artificial acorn or snout made of steel for the sake of its
power. Iron needles are rubbed on the top of this; wherefore they turn
toward the same pole as if they had been prepared on that part of the stone
with the acorn removed. Let the stone be large enough and strong; the
needle, even if it be rather long, should be sufficiently thick, not very
slender; with a moderate cusp, not too sharp, although the virtue is not in
the cusp itself only, but in the whole piece of iron. A strong large stone is
not unfit for rubbing all needles on, excepting that sometimes by its strength
it occasions some dip and disturbance in the iron in the case of longer
needles; so that one which, having been touched before, rested in
equilibrium in the plane of the horizon, now when touched and excited dips
at one end, as far as the upright pin on which it turns permits it. Wherefore
in the case of longer versoria, the end which is going to be the Boreal,
before it is rubbed, should be a little lighter, so that it may remain exactly in
æquilibrio
* after it is touched. But a needle in this way prepared does its
work worse the farther it is beyond the æquinoctial circle. Let the prepared
needle be placed in its capsule, and let it not be touched by any other
magneticks, nor remain in the near vicinity of them, lest by their opposing
forces, whether powerful or sluggish, it should become uncertain and dull.
If you also rub the other end of the needle on the other pole of the stone, the
needle will perform its functions more steadily, especially if it be rather
long. A piece of iron touched by a loadstone retains the magnetick virtue,
excited in it even for ages[217], firm and strong, if it is placed according to
nature meridionally and not along a parallel, and is not injured by rust or
any external injury from the surrounding medium. Porta wrongly seeks for
a proportion between the loadstone and the iron: because, he says, a little
piece of iron will not be capable of holding much virtue; for it is consumed
by the great force of the loadstone. A piece of iron receives its own virtue
fully, even if it be only of the weight of one scruple, whilst the mass of the
loadstone is a thousand pounds. It is also useless to make the needle rather
flat at the end that is touched, so that it may be better and more perfectly
magnetick, and that it may best receive and hold certain magnetick
particles; since hardly any part will stick on a sharp point; because he
thought that it was by the adhesion of parts of the loadstone (as it were,
hairs) that the influence is imparted and conserved, though those particles
are merely rubbed off by the rubbing of the iron over the softer stone, and
the iron none the less points toward the North and South, if after it is

touched it be scoured with sand or emery powder, or with any other
material, even if by long rubbing of this kind the external parts of it are
lessened and worn away. When a needle is being rubbed, one should always
leave off at the end; otherwise, if it is rubbed on the loadstone from the
point toward the middle, less verticity is excited in the iron, sometimes
none at all, or very little. For where the last contact is, there is the pole and
goal of verticity. In order that a stronger verticity may be produced in the
iron by
* rubbing on the loadstone, one ought in northern lands to turn the
true northern pole of the loadstone toward the highest part of the sky; on
this pole that end of the needle is going to be rubbed, which shall afterwards
turn toward the north of the earth; whilst it will be an advantage for the
other end of the needle to be rubbed on the southern pole of the terrella
turned toward the earth, and this being so excited will incline toward the
south. In southern regions beyond the æquator the plan is just the contrary.
The reason of this dissimilarity is demonstrated, Book II., chap, xxxiv., in
which it is shown (by a manifest combination of a terrella and the earth)
why the poles of a loadstone, for different reasons, are one stronger than the
other.*If a needle be touched between the mutually accordant poles of two
loadstones, equal in power, shape, and mass, no strength is acquired by the
needle. A and B are two loadstones attracting one
another, according to nature, at their dissimilar
ends; *C, the point of a needle touched by both at
once, is not excited (even if those loadstones be
connected according to nature), if they are equal;
but if they are not equal, virtue is acquired from
the stronger. When a needle is being excited by a loadstone, begin in the
middle, and draw the needle toward its end; at the end let the application be
continued with a very gentle rubbing around the end for some time; that is
to say, for one or two minutes; do not repeat the motion from the middle to
the end (as is frequently done) for in this way the verticity is injured. Some
delay is desirable, for although the power is imparted instantly, and the iron
excited, yet from the vicinity of the loadstone and a suitable delay, a more
steady verticity arises, and one that is more firmly durable in the iron.
Although an armed stone raises a greater weight of iron than an unarmed
one, yet a needle is not more strongly excited by an armed stone than by an
unarmed one. Let there be two iron wires of the same length, wrought from
the same wire; let one be excited by an armed end, the other by an unarmed

end; it is manifest that the same needles have a beginning of motion or a
sensible inclination at equal distances from the same armed and unarmed
loadstone; this is ascertained by measuring with a longish reed. But objects
which are more powerfully excited move more quickly; those which are
less powerfully excited, more feebly, and not unless brought rather close;
the experiment is made on water with equal corks.

BOOK FOURTH.

CHAP. I.

ON VARIATION.

irection has hitherto been spoken of as if in nature there were no
variation; for in the preceding natural history we wished to omit
and neglect this, inasmuch as in a terrestrial globe, perfect and in
every sense complete, there would be none. Since, however, in
fact, the earth's magnetick direction, owing to some fault and slip, deviates
from its right course and from the meridian, we must extract and
demonstrate the obscure and hidden cause of that variance which has
troubled and sore racked in vain the minds of many. Those who before us
have written on the magnetick movements have made no distinction
between direction and variation, but consider the motion of magnetick iron
to be uniform and simple. Now true direction is the motion of the
magnetick body to the true meridian and its continuance therein with its
appropriate ends towards the poles. But it very often happens at sea and on
land that the magnetick iron does not point to the true pole, and that not
only a versorium and magnetick pieces of iron, and the needle of a

compass,
* or a mariners' compass, but also a terrella in its boat, as well as
iron ore, iron stones, and magnetick earths, properly prepared, are drawn
aside and deviate towards some point of the Horizon very near to the
meridian. For they with their poles frequently face termini away from the
meridian. This variation (observed by means of instruments or a nautical
variation compass) is therefore the arc of the horizon between the common
point of intersecion of it with the true meridian, and the terminus of the
deflecion on the horizon or projection of the deviating needle. That arc
varies and differs with change of locality. To the terminus of the variation is
commonly assigned a great circle, called the circle of variation, and also a
magnetick meridian passing through the zenith and the point of variation on
the horizon. In the northern regions of the earth this variation is either from
the north toward the east or from the north toward the west: similarly in the
southern regions it is from the south toward the east or toward the west.
Wherefore
* one should observe in the northern regions of the earth that end
of the versorium or compass which turns toward the North; but in the
southern regions the other end looking to the south—which seamen and
sciolists for the most part do not understand, for in both regions they
observe only the boreal lily of the compass (that which faces North). We
have before said that all the motions of the magnet and iron, all its turning,
its inclination, and its settlement, proceed from bodies themselves
magnetical and from their common mother the earth, which is the source,
the propagatrix, and the origin of all these qualities and properties.
Accordingly the earth is the cause of this variation and inclination toward a
different point of the horizon: but how and by what powers must be more
fully investigated. And here we must at the outset reject that common
opinion of recent writers concerning magnetick mountains, or any
magnetick rock, or any phantasmal pole distant from the pole of the earth,
by which the motion of the compass or versorium is controlled. This
opinion, previously invented by others, Fracastorio himself adopted and
developed; but it is entirely at variance with experience. For in that case in
different places at sea and on land the point of variation would change
toward the east or west in proportion and geometrical symmetry, and the
versorium would always respect the magnetick pole: but experience teaches
that there is no such definite pole or fixed terminus on the earth to account
for the
* variation. For the arcs of variation are changed variously and
erratically, not only on different meridians but on the same meridian; and

when, according to this opinion of the moderns, the deviation should be
more and more toward the east, then suddenly, with a small change of
locality, the deviation is from the north toward the west as in the northern
regions near Nova Zembla. Moreover, in the southern regions, and at sea at
a great distance from the æquator towards the antarctick pole, there are
frequent and great variations, and not only in the northern regions, from the
magnetick mountains. But the cogitations of others are still more vain and
trifling, such as that of Cortes about a moving influence beyond all the
heavens; that of Marsilius Ficinus about a star in the Bear; that of Peter
Peregrinus about the pole of the world; that of Cardan, who derives it from
the rising of a star in the tail of the Bear[218]; of Bessardus, the Frenchman,
from the pole of the Zodiack; that of Livio Sanuto from some magnetick
meridian; that of Franciscus Maurolycus from a magnetical island; that of
Scaliger from the heavens and mountains; that of Robert Norman, the
Englishman, from a point respective. Leaving therefore these opinions,
which are at variance with common experience or by no means proved, let
us seek the true cause of the variation. The great magnet or terrestrial globe
directs iron (as I have said) toward the north and south; and excited iron
quickly settles itself toward those termini. Since, however, the globe of the
earth is defective and uneven on its surface and marred by its diverse
composition, and since it has parts very high and convex (to the height of
some miles), and those uniform neither in composition nor body, but
opposite and dissimilar: it comes to pass that the whole of that force of the
earth diverts magnetical bodies in its periphery toward the stronger and
more prominent connected magnetick parts. Hence on the outermost surface
of the earth magnetical bodies are slightly perverted from the true meridian.
Moreover, since the surface of the globe is divided into high lands and deep
seas, into great continental lands, into ocean and vastest seas, and since the
force of all magnetical motions is derived from the constant and magnetick
terrestrial nature which is more prevalent on the greater continent and not in
the aquæous or fluid or unstable part; [219]it follows that in certain parts
there would be a magnetick inclination from the true pole east or west away
from any meridian (whether passing through seas or islands) toward a great
land or continent rising higher, that is, obviously toward a stronger and
more elevated magnetick part of the terrestrial globe. For since the diameter
of the earth is more than 1,700 German miles, those large lands can rise
from the centre of the earth more than four miles above the depth of the

ocean bottom, and yet the earth will retain the form of a globe although
somewhat uneven at the top. Wherefore a magnetical body is turned aside,
so far as the true verticity, when disturbed, admits, and departs from its
right (the whole earth moving it) toward a vast prominent mass of land as
though toward what is stronger. But the variation does really take place, not
so much because of the more prominent and imperfect terrestrial parts and
continent lands as because of the inæquality of the magnetick globe, and
because of the real earth, which stands out more under the continent lands
than under the depths of the seas. We must see, therefore, how the apodixis
of this theory can be sustained by more definite observations. Since
throughout all the course from the coast of Guinea to Cape Verde, the
Canary Isles, and the border of the kingdom of Morocco, and thence along
the coasts of Spain, France, England, Belgium, Germany, Denmark, and
Norway, there lie on the right hand and toward the east a continent and
extensive connected regions, and on the left extensive seas and a vast ocean
lie open far and wide, it is consonant with the theory (as has been carefully
observed by many) that magnetical bodies should turn slightly to the East
from the true pole toward the stronger and more remarkable elevations of
the earth. But it is far otherwise on the eastern shores of northern America;
for from Florida by Virginia and Norumbega to Cape Race and away to the
north the versorium is turned toward the west. But in the middle spaces, so
to speak, as in the more westerly Azores, it looks toward the true pole. That
any magnetick body turns itself similarly to the same regions of the earth is
not, however, because of that meridian or because of the concordancy of the
meridian with any magnetick pole, as the crowd of philosophizers reckon,
for it is not so throughout the whole of that meridian. For on the same
meridian
* near Brazil something very different occurs, as we will show
further on. The variation (cæteris paribus) is always less near the æquator,
greater in higher latitudes, with the limitation that it be not very near the
pole *itself. Hence the variation is greater on the coast of Norway and
Belgium than on the coast of Morocco or Guinea: greater also near Cape
Race than in the harbours of Norumbega or of Virginia. On the coast of
Guinea magnetick implements deviate by a third part of one rumbe to the
East: in Cape Verde Islands by a half: on the coast of Morocco by two
thirds: in England at the mouth of the Thames by a whole rumbe: and at
London by nearly eleven degrees and one third. For indeed the moving
magnetick virtue is stronger in a higher latitude; and the larger regions

extending toward the poles dominate the more, as is easily apparent
anywhere on a terrella. For as in the case of true Direction magnetick
bodies tend toward the pole (namely, toward the stronger end, the whole
earth causing the motion), so also do they incline a little toward the stronger
and higher parts by the action of the whole along with the conjoint action of
iron bodies.

CHAP. II.

That the variation is caused by the inæquality of the
projecting parts of the earth.

* emonstration of this may manifestly be made by means of a
terrella in the following way: let there
be a round loadstone somewhat
imperfect in some part, and impaired by
decay (such an one we had with a certain part
corroded to resemble the Atlantick or great
Ocean): place upon it some fine iron wire of the
length of two barleycorns, as in the following
figure. A B, a Terrella in certain parts somewhat
imperfect and of unæqual virtue on the
circumference. The versoria E, F, do not vary, but
look directly to the pole A; for they are placed in the middle of the firm and
sound part of the terrella and somewhat distant from the imperfect part: that
part of the surface which is distinguished by dots and transverse lines is the
weaker. The versorium O also does not vary (because it is placed in the
middle of the imperfect part), but is directed toward the pole, just as near
the western Azores on the earth. The versoria H and L do vary, for they
incline toward the sounder parts very near them. As this is manifest in a
terrella whose surface is sensibly rather imperfect, so also is it in others
whole and perfect, when often one part of the stone has stronger external
parts, which nevertheless do not disclose themselves manifestly to the
senses. In such a terrella the demonstration of the variation and the

* discovery of the stronger parts is on this wise. Let A be
the pole, B the place of the variation, C the stronger
regions; then the horizontal versorium at B varies from
the pole A toward C: so that both the variation is shown
and the stronger places of the loadstone recognized. The
stronger surface is also found by a fine iron wire of the
length of two barleycorns: for since at the pole of the
terrella it rears up perpendicularly, but in other places inclines toward the
æquator, if in one and the same parallel circle it should be more erect in one
place than in another; where the wire is raised more upright, there the part
and surface of the terrella is stronger. Also when the iron wire placed over
the pole
* inclines more to one part than to another. Let
the experiment be made by means of a fine iron wire
of three digits length placed over the pole A, so that its
middle lies over the pole. Then one end is turned away
from B toward C, and is not willing to lie quietly
toward B; but on a terrella which is perfect[220] all
round and even it rests on the pole directed toward any
point of the æquator you please. Otherwise, let there
* be two meridians meeting in the poles A
B, let iron wires be reared just at the ends
D and C of the equal arcs D A and C A;
then the wire at D (the stronger region)
will be more raised up than that at C, the
weaker. And thus the sounder and
stronger part of the loadstone is recognized, which otherwise would not be
perceived by the touch. In a terrella which is perfect, and even, and similar
in all its parts, there is, at equal distances from the pole, no variation[221].
Variation is shown by means of a terrella, a considerable part of which,
forming a surface a little higher than the rest, does, although it be not
decayed
* and broken, allure the versorium from the true direction (the whole
terrella co-operating).

A terrella uneven in surface.

It is shown by a small spike placed over a terrella or by a small versorium;
for they are turned by the terrella toward the mass that stands out and
toward the large eminences. In the same way on the earth the verticity is
perturbed by great continents, which are mostly elevated above the depths
of the seas and make the versorium deviate sometimes from the right tracks
(that is, from the true meridians). On a terrella it is thus demonstrated: the
end of the versorium A is not directed straight to the pole P, if there be a
large protuberance B on the terrella; so also the cusp C deviates from the
pole because of the eminence F. In the middle between the two eminences
the versorium G collimates to the true pole because, being at equal
distances from the two eminences B and F, it turns aside to neither, but
observes the true meridian, especially when the protuberances are of equal
vigour. But the versorium N on the other side varies from the pole M
toward the eminences H, and is not held back, stopped, or restrained by the
small eminence O on the terrella (as it were, some island of land in the
ocean). L, however, being unimpeded, is directed to the pole M. The
variation is demonstrated in another way on a terrella, just as on the earth.
Let A be the pole of the earth, B the equator, C the parallel circle of latitude
of 30 degrees, D a great eminence spread out toward the pole, E another
eminence spread out from the pole toward the æquator. It is manifest that in
the middle of D the versorium F does not vary; while G is very greatly
deflected: but H very little, because it is further removed from D. Similarly
also the versorium I placed directly toward E does not deviate from the
pole: but L and M turn themselves away from the pole A toward the
eminence E.

CHAP. III.

The variation in any one place
is constant.

nless there should be a great dissolution
of a continent and a subsidence of the
land such as there was of the region
Atlantis of which Plato and the ancients
tell, the variation will continue perpetually
immutable; the arc of the variation remains the
same in the same place or region, whether it be at
sea or on land, as in times past a magnetick body
has declined toward the East or the West. The constancy of the variation
and the pointing of the versorium to a definite point on the horizon in
individual regions is demonstrated by a small versorium placed over a
terrella the surface of which is uneven: for it always deviates from the
meridian by an equal arc. It is also shown by the inclination of a versorium
toward a second magnet; although in reality it is by the turning power of the
whole, whether in the earth or in a terrella. Place upon a plane a versorium
whose cusp is directed toward the north A: place beside it a loadstone, B, at

such a distance that the versorium may turn aside toward B to the point C,
and not beyond. Then move the needle of the versorium as often as you will
(the box and the loadstone not being moved), and it will certainly always
return to the point C. In the same manner, if you placed the stone so that it
may be truly directed toward E, the cusp always reverts to E, and not to any
other point of the compass. Accordingly, from the position of the land and
from the distinctive nature of the highest parts of the earth (certain terrene
and more magnetick eminences of the regions prevailing), the variation
indeed becomes definite in one and the same place, but diverse and unæqual
from a change of place, since the true and polar direction originating in the
whole terrestrial globe is diverted somewhat toward certain stronger
eminences on the broken surface.

CHAP. IIII.

The arc of variation is not changed equally
in proportion to the distance of places.

n the open sea, when a vessel is borne by a favourable wind along
the same parallel, if the variation be changed by one degree in the
course of one hundred miles, the next hundred miles do not
therefore lessen it by another degree; for the magnetick [needle]
varies erratically as respects position, form, and vigour of the land, and also
because of the distance. As, for example, when a course from the Scilly
Isles to Newfoundland has proceeded so far that the compass is directed to
the true pole, then, as the vessel proceeds, in the first part of the course the
variation increases toward the north-west[222], but rather indistinctly and
with small difference: thence, after an equal distance, the arc is increased in
a greater proportion until the vessel is not far from the continent: for then it
varies most of all. But before it touches actual land or enters port, then at a
certain distance the arc is again slightly diminished. But if the vessel in its
course should decline greatly from that parallel either toward the south or
the north, the magnetick [needle] will vary more or less, according to the

position
* of the land and the latitude of the region. For (cæteris paribus) the
greater the latitude the greater the variation.

CHAP. V.

An island in Ocean does not change the variation[223], as
neither do mines of loadstone.

slands, although they be more magnetick than the sea, yet do not
change the magnetick directions or variations. For since direction is
a motion derived from the power of the whole earth, not from the
attraction of any hill but from the disposing and turning power of
the whole; so variation (which is a perturbation of the direction) is an
aberration of the real turning power arising from the great inequalities of
the earth, in consequence of which it, of itself, slightly diverts movable
magneticks toward those which are the largest and the more powerful. The
cause now shown may suffice to explain that which some so wonder at
about the Island of Elba (and although this is productive of loadstone, yet
the versorium (or mariners' compass) makes no special inclination toward it
whenever vessels approach it in the Tyrrhenian sea); and the following
causes are also to be considered, viz.: that the virtue of smaller magnetick
bodies extends scarcely or not at all of itself beyond their own mines: for
variation does not occur because of attraction, as they would have it who
have imagined magnetick poles. Besides, magnetick mines are only agnate
to the true earth, not innate: hence the whole globe does not regard them,
and magneticks are not borne to them, as is demonstrated by the diagram of
eminences.

CHAP. VI.

That variation and direction arise from the disponent
power of the earth, and from the natural magnetick tendency
to rotation, not from attraction, or from coition,
or from other occult cause.

wing to the loadstone being supposed (amongst the crowd of
philosophizers) to seize and drag, as it were, magnetick bodies; and
since, in truth, sciolists have remarked no other forces than those so
oft besung of attractive ones, they therefore deem every motion
toward the north and south to be caused by some alluring and inviting
quality. But the Englishman, Robert Norman, first strove to show that it is
not caused by attraction: wherefore, as if tending toward hidden principles,
he imagined a point respective[224], toward which the iron touched by a
loadstone would ever turn, not a point attractive; but in this he erred greatly,
although he effaced the former error about attraction. He, however,
demonstrates his opinion in this way:
Let there be a round vessel filled with water: in the
middle of the surface of the water place a slender iron
wire on a perfectly round cork, so that it may just float
in æquilibrium on the water; let the wire be previously
touched by a magnet, so that it may more readily show
the point of variation, the point D as it were: and let it
remain on the surface for some time. It is demonstrable
that the wire together with the cork is not moved to the side D of the vessel:
which it would do if an attraction came to the iron wire by D: and the cork
would be moved out of its place. This assertion of the Englishman, Robert
Norman, is plausible and appears to do away with attraction because the
iron remains on the water not moving about, as well in a direction toward
the pole itself (if the direction be true) as in a variation or altered direction;
and it is moved about its own centre without any transference to the edge of
the vessel. But direction does not arise from attraction, but from the
disposing and turning power which exists in the whole earth, not in the pole
or in some other attracting part of the stone, or in any mass rising above the
periphery of the true circle so that a variation should occur because of the
attraction of that mass. Moreover, it is the directing power of the loadstone
and iron and its natural power of turning around the centre which cause the

motion of direction, and of conformation, in which is
included also the motion of the dip. And the terrestrial pole
does not attract as if the terrene force were implanted only
in the pole, for the magnetick force exists in the whole,
although it predominates and excels at the pole. Wherefore
that the cork should rest quiescent in the middle and that
the iron excited by a loadstone should not be moved toward the side of the
vessel are agreeable to and in conformity with the magnetick nature, as is
demonstrated by a terrella: for an iron spike placed on the stone at C clings
on at *C, and is not pulled further away by the pole A, or by the parts near
the pole: hence it persists at D, and takes a direction toward the pole A;
nevertheless it clings on at D and dips also at D in virtue of that turning
power by which it conforms itself to the terrella: of which we will say more
in the part On Declination.

CHAP. VII.

Why the variation from that lateral cause is not
greater than has hitherto been observed, having been
rarely seen to reach two points of the mariners'
compass, except near the pole.

he earth, by reason of lateral eminences of the stronger globe,
diverts iron and loadstone by some degrees from the true pole, or
true meridian. As, for example, with us English at London it varies
eleven degrees and ⅓: in some other places the variation is a little
greater, but in no other region is the end of the iron ever moved aside very
much more from the meridian. For as the iron is always directed by the true
verticity of the earth, so the polar nature of the continent land (just as of the
whole terrene globe) acts toward the poles: and even if that mass divert
magnetick bodies from the meridian, yet the verticity of those lands (as also
of the whole earth) controls and disposes them so that they do not turn
toward the East by any greater arc. But it is not easy to determine by any
general method how great the arc of variation is in all places, and how

many degrees and minutes it subtends on the horizon, since it becomes
greater or less from diverse causes. For both the strength of true verticity of
the place and of the elevated regions, as well as their distances from the
given place and from the poles of the world, must be considered and
compared; which indeed cannot be done exactly: nevertheless by our
method the variation becomes so known that no grave error will perturb the
course at sea. If the positions of the lands were uniform and straight along
meridians, and not defective and rugged, the variations near lands would be
simple; such as appear in the following figure.

This is demonstrated by a long loadstone the poles of which are in the ends
A B; let C D be the middle line and the æquinoctial, and let G H and E F
(the lines) be for meridians on which versoria are disposed, the variations of
which are greater at a greater distance from the æquator. But the inequalities
of the maritime parts of the habitable earth, the enormous promontories, the
very wide gulfs, the mountainous and more elevated regions, render the
variations more unequal, or sudden, or more obscure; and, moreover, less
certain and more inconstant in the higher latitude.

CHAP. VIII.

On the construction of the common mariners'
compass[225], and on the diversity of the compasses
of different nations.

n a round[226] hollow wooden bowl, all the upper part of which is closed
with glass, a versorium is placed upon a rather long pin which is fixed in

the middle. The covering prevents the wind, and the motion of air
from any external cause. Through the glass everything within can
be discerned. The versorium is circular, consisting of some light
material (as card), to the under part of which the magnetick pieces
of iron are attached. On the upper part 32 spaces (which are commonly
called points) are assigned to the same number of mathematical intervals in
the horizon or winds which are distinguished by certain marks and by a lily
indicating the north. The bowl is suspended in the plane of the horizon in
æquilibrium in a brass ring which also is itself suspended transversely in
another ring within a box sufficiently wide with a leaden weight attached;
hence it conforms to the plane of the horizon even though the ship be tossed
to and fro by the waves. The iron works are either a pair with their ends
united, or else a single one of a nearly oval shape with projecting ends,
which does its work more certainly and more quickly. This is to be fitted to
the cardboard circle so that the centre of the circle may be in the middle of
the magnetick iron. But inasmuch as variation arises horizontally from the
point of the meridian which cuts the horizon at right angles, therefore on
account of the variation the makers in different regions and cities mark out
the mariners' compass in different ways, and also attach in different ways
the magnetick needles to the cardboard circle on which are placed the 32
divisions or points. Hence there are commonly in Europe 4 different
constructions and forms. First that of the States on the Mediterranean Sea,
Sicily, Genoa, and the Republick of Venice. In all these the needles are
attached under the rose or lily on the cardboard versorium, so that (where
there is no variation) they are directed to the true north and south points.
Wherefore the north part marked with the lily always shows exactly the
point of variation when the apex itself of the lily on the movable circle,
together with the ends of the magnetick wires attached below, rests at the
point of variation. Yet another is that of Dantzig, and throughout the Baltic
Sea, and the Belgian provinces; in which the iron works fixed below the
circle diverge from the lily ¼ of a rumbe to the east. For navigation to
Russia the divergency is ⅔. But the compasses which are made at Seville,
Lisbon, Rochelle, Bordeaux, Rouen, and throughout all England have an
interval of ½ a rumbe. From those differences most serious errors have
arisen in navigation, and in the marine science. For as soon as the bearings
of maritime places (such as promontories, havens, islands) have been first
found by the aid of the mariners' compass, and the times of sea-tide or high

water determined from the position of the moon over this or that point (as
they say) of the compass, it must be further inquired in what region or
according to the custom of what region that compass was made by which
the bearings of those places and the times of the sea-tides were first
observed and discovered. For one who should use the British compass and
should follow the directions of the marine charts of the Mediterranean Sea
would necessarily wander very much out of the straight course. So also he
that should use the Italian compass in the British, German, or Baltic Sea,
together with marine charts that are made use of in those parts, will often
stray from the right way. These different constructions have been made on
account of the dissimilar variations, so that they might avoid somewhat
serious errors in those parts of the world. But Pedro Nuñez seeks the
meridian by the mariners' compass, or versorium (which the Spanish call
the needle), without taking account of the variation: and he adduces many
geometrical demonstrations which (because of his slight use and experience
in matters magnetical) rest on utterly vicious foundations. In the same
manner Pedro de Medina, since he did not admit variation, has disfigured
his Arte de Navegar with many errors.

CHAP. IX.

Whether the terrestrial longitude can be found from
the variation.

rateful would be this work to seamen, and would bring the greatest
advance to Geography. But B. Porta in chap. 38 of book 7 is
mocked by a vain hope and fruitless opinion. For when he supposes
that the magnetick needle would follow order and proportion in
moving along meridians, so that "the neerer it is to the east, the more it will
decline from the Meridian line, toward the east; and the neerer it comes to
the west, the point of the needle will decline the more to the west" (which is
totally untrue), he thinks that he has discovered a true index of longitude.
But he is mistaken. Nevertheless, admitting and assuming these things (as
though they were perfectly true), he makes a large compass indicating

degrees and minutes, by which these proportional changes of the versorium
might be observed. But those very principles are false, and ill conceived,
and very ill considered; for the versorium does not turn more to the east
because a journey is made toward the east: and although the variation in the
more westerly parts of Europe and the adjoining ocean is to the east and
beyond the Azores is changed a little to the west, yet the variation is, in
various ways, always uncertain, both on account of longitude and of
latitude, and because of the approach toward extensive tracts of land, and
also because of the form of the dominant terrestrial eminences; nor does it,
as we have before demonstrated, follow the rule of any particular meridian.
It is with the same vanity also that Livio Sanuto so greatly torments himself
and his readers. As for the fact that the crowd of philosophizers and sailors
suppose that the meridian passing through the Azores marks the limits of
variation, so that on the other and opposite side of that meridian a
magnetick body necessarily respects the poles exactly, which is also the
opinion of Joannes Baptista Benedictus and of many other writers on
navigation, it is by no means true. Stevinus (on the authority of Hugo
Grotius) in his Havenfinding Art distinguishes the variation according to the
meridians: "It may be seene in the Table of variations, that in Coruo the
Magneticall needle pointeth due North: but after that, the more a man shal
goe towards the East, so much the more also shall he see the needle varie
towards the East [ἀνατολίζειν], till he come one mile to the Eastward from
Plimouth, where the variation comming to the greatest is 13 degr. 24 min.
From hence the Northeasting [Anatolismus] beginneth to decrease, til you
come to Helmshude (which place is Westward from the North Cape of
Finmark) where againe the needle pointeth due North. Now the longitude
from Coruo to Helmshude is 60 degr. Which things being well weighed, it
appeareth that the greatest variation [Chalyboclysis] 13 degr. 24 minutes at
Plimmouth (the longitude whereof is 30 degr.) is in the midst betweene the
places where the needle pointeth due North." But although this is in some
part true in these places, yet it is by no means true that along the whole of
the meridian of the island of Corvo the versorium looks truly to the north;
nor on the meridian of Plymouth is the variation in other places 13 deg. 24
min.—nor again in other parts of the meridian of Helmshuda does it point
to the true pole. For on the meridian passing through Plymouth in Latitude
60 degrees the North-easterly variation is greater: in Latitude 40 deg. much
less; in Latitude 20 deg. very small indeed. On the meridian of Corvo,

although there is no variation near the island, yet in Latitude 55 degrees the
variation is about ½ a rumbe to the North-west; in Latitude 20 deg. the
versorium inclines ¼ of a rumbe toward the East. Consequently the limits
of variation are not conveniently determined by means of great circles and
meridians, and much less are the ratios of the increment or decrement
toward any part of the heavens properly investigated by them. Wherefore
the rules of the abatement or augmentation of Northeasting or
Northwesting, or of increasing or decreasing the magnetick deviation, can
by no means be discovered by such an artifice. The rules which follow later
for variation in southern parts of the earth investigated by the same method
are altogether vain and absurd. They were put forth by certain Portuguese
mariners, but they do not agree with the observations, and the observations
themselves are admitted to be bad. But the method of haven-finding in long
and distant voyages by carefully observed variation (such as was invented
by Stevinus, and mentioned by Grotius) is of great moment, if only proper
instruments are in readiness, by which the magnetick deviation can be
ascertained with certainty at sea.

CHAP. X.

Why in various places near the pole the variations
are much more ample than in a
lower latitude.

ariations are often slight, and generally null, when the versorium is
at or near the earth's æquator. In a higher Latitude of 60, 70 or 80
deg. there are not seldom very wide variations. The cause of this is
to be sought partly from the nature of the earth and partly from the
disposition of the versorium. The earth turns magnetick bodies and at the
æquator directs them strongly toward the pole: [227]at the poles there is no
direction, but only a strong coition through the congruent poles. Direction is
therefore weaker near the poles, because by reason of its own natural
tendency to turn, the versorium dips very much, and is not strongly
directed. But since the force of those elevated lands is more vigorous, for

the virtue flows from the whole globe, and since also the causes of variation
are nearer, therefore the versorium deflects the more from its true direction
toward those eminences. It must also be known that the direction of the
versorium on its pin along the plane of the Horizon is much stronger at the
æquator than anywhere else by reason of the disposition of the versorium;
and this direction falls off with an increase of latitude. For on the æquator
the versorium is, following its natural property, directed along the plane of
the horizon; but in other places it is, contrary to its natural property,
compelled into æquilibrium, and remains there, compelled by some external
force: because it would, according to its natural property, dip below the
horizon in proportion to the latitude, as we shall demonstrate in the book
On Declination. Hence the direction falls off and at the pole is itself
nothing: and for that reason a feebler direction is easily vanquished by the
stronger causes of variation, and near the pole the versorium deflects the
more from the meridian. It is demonstrated by means of a terrella: if an iron
wire of two digits length be placed on its æquator, it will be strongly and
rapidly directed toward the poles along the meridian, but more weakly so in
the mid-intervals; while near the poles one may discern a precipitate
variation.

CHAP. XI.

Cardan's error when he seeks the distance of the
centre of the earth from the centre of the cosmos by the
motion of the stone of Hercules; in his
book 5, On Proportions.

ne may very easily fall into mistakes and errors when one is
searching into the hidden causes of things, in the absence of real
experiments, and this is easily apparent from the crass error of
Cardan; who deems himself to have discovered the distances of the
centres of the cosmos and of the earth through a variation of the magnetick
iron of 9 degrees. For he reckoned that everywhere on the earth the point of
variation on the Horizon is always distant nine degrees from the true north,

toward the east: and from thence he forms, by a most foolish error, his
demonstrative ratio of the separate centres.

CHAP. XII.

On the finding of the amount of variation: how great
is the arc of the Horizon from its arctick or antarctick
intersection of the meridian, to the point
respective of the magnetick needle.

irtually the true meridian is the chief foundation of the whole
matter: when that is accurately known, it will be easy by a
mariners' compass (if its construction and the mode of attachment
of the magnetick iron works are known) or by some other larger
horizontal versorium to exhibit the arc of variation on the Horizon. By
means of a sufficiently large nautical variation compass (two equal altitudes
of the sun being observed before and after midday), the variation becomes
known from the shadow; the altitude of the sun is observed either by a staff
or by a rather large quadrant.
On land the variation is found in another way which is easier, and because
of the larger size of the instrument, more accurate. Let a thick squared
board be made of some suitable wood, the surface of which is two feet in
length and sixteen inches in width: describe upon it some semicircles as in
the following figure, only more in number. In the centre let a brass style be
reared perpendicularly: let there be also a movable pointer reaching from
the centre to the outmost semicircle, and a magnetick versorium in a cavity
covered over with glass: then let the board be exactly adjusted to the level
of the Horizon by the plane instrument with its perpendicular; and turn the
lily of the instrument toward the north, so that the versorium may rest truly
over the middle line of the cavity, which looks toward the point of variation
on on the Horizon. Then at some convenient hour in the morning (eight or
nine for instance) observe the apex of the shadow thrown by the style when
it reaches the nearest semicircle and mark the place of the apex of this

shadow with chalk or ink: then bring round the movable index to that mark,
and observe the degree on the Horizon numbered from the lily, which the
index shows. In the afternoon see when the end of the shadow shall again
reach the periphery of the same semicircle, and, bringing the index to the
apex of the shadow, seek for the degree on the other side of the lily. From
the difference of the degrees becomes known the variation; the less being
taken from the
greater, half
the remainder
is the arc of
variation. The
variation is
sought by
many other
instruments
and methods in
conjunction
with a
convenient
mariners'
compass; also by a globe, by numbers, and by the ratios of triangles and
sines, when the latitude is known and one observation is made of the sun's
altitude: but those ways and methods are of less use, for it is superfluous to
try to find in winding and roundabout ways what can be more readily and as
accurately found in a shorter one. For the whole art is in the proper use of
the instruments by which the sun's place is expeditiously and quickly taken
(since it does not remain stationary, but moves on): for either the hand
trembles or the sight is dim, or the instrument makes an error. Besides, to
observe the altitude on both sides of the meridian is just as expeditious as to
observe on one side only and at the same time to find the elevation of the
pole. And he who can take one altitude by the instrument can also take
another; but if the one altitude be uncertain, then all the labour with the
globe, numbers, sines and triangles is lost; nevertheless those exercises of
ingenious mathematicians are to be commended. It is easy for anyone, if he
stand on land, to learn the variation by accurate observations and suitable
instruments, especially in a nearly upright sphere; but on the sea, on
account of the motion and the restlessness of the waters, exact experiments

in degrees and minutes cannot be made: and with the usual instruments
scarcely within the third or even the halt of a rumbe, especially in a higher
latitude; hence so many false and bad records of the observations of
navigators. We have, however, taken care for the finding of the deviation by
a sufficiently convenient and ready instrument, by means of the rising of
certain stars, by the rising or setting of the sun, and in northern regions by
the Pole Star: for the variation is learned with greater certainty even by the
skilful with an instrument which is at once simple and less sensitive to the
waves of the sea. Its construction is as follows.
[228]Let an instrument be made of the form of a true and meridional
mariners' compass of at least one foot in diameter (with a versorium which
is either nude or provided with a cardboard circle): let the limb be divided
into four quadrants, and each quadrant into 90 degrees. The movable
compass-box (as is usual in the nautical instrument) is to be balanced below
by a heavy weight of sixteen pounds. On the margin of the suspended
compass-box, where opposite quadrants begin, let a half-ring rising in an
angular frame in the middle be raised (with the feet of the half-ring fixed on
either side in holes in the margin) so that the top of the frame may be
perpendicular to the plane of the compass; on its top let a rule sixteen digits
in length be fastened at its middle on a joint like a balance beam, so that it
may move, as it were, about a central axis. At the ends of the rule there are
small plates with holes, through which we can observe the sun or stars. The
variation is best observed and expeditiously by this instrument at the
equinoxes by the rising or setting sun. But even when the sun is in other
parts of the zodiack, the deviation becomes known when we have the
altitude of the pole: that being known, one can learn the amplitude on the
Horizon and the distance from the true east both of the sun and of the
following fixed stars by means of a globe, or tables, or an instrument. Then
the variation readily becomes known by counting from the true east the
degrees and minutes of the amplitude at rising. Observe the preceding star
of the three in the Belt of Orion as soon as it appears on the horizon; direct
the instrument toward it and observe the versorium, for since the star has its
rising in the true east about one degree toward the south, it can be seen how
much the versorium is distant from the meridian, account being taken of
that one degree. You will also be able to observe the arctick pole star when
it is on the meridian, or at its greatest distance from the meridian of about

three degrees (the pole star is distant 2
deg. 55 min. from the pole, according to
the observations of Tycho Brahe), and by
the instrument you will learn the
variation (if the star be not on the
meridian) by adding or subtracting,
secundum artem, the proper reduction
[prostaphæresis][229] of the star's
distance from the meridian. You will find
when the pole star is on the meridian by
knowing the sun's place and the hour of
the night: for this a practised observer
will easily perceive without great error
by the visible inclination of the
constellation: for we do not take notice
of a few minutes, as do some who, when
they toil to track the minutes of degrees
at sea, are in error by a nearly whole
rumbe. A practised observer will, in the
rising of sun or stars, allow something
for refraction, so that he may be able to
use a more exact calculation.

Bright and conspicuous stars[230] which are
not far distant from the equator which it
will be useful to observe at their rising and
setting: the amplitude at the Horizon on
rising being known from the altitude of the
pole and from the declination of the stars, by
means of a globe, or tables, or an instrument
whence the variation is perceived by
technical calculation.

Right Ascension Declination
Oculus Tauri 62° 55' 15° 53' N

Sinister humerus Orionis 72° 24' 4° 5' N
Dexter humerus Orionis 83° 30' 6° 19' N
Præcedens in cingulo Orionis 77° 46' 1° 16' S
Canis major 97° 10' 15° 55' S
Canis minor 109° 41' 5° 55' N
Lucida Hydræ 137° 10' 5° 3' S
Caput Geminorum australe 110° 21' 28° 30' N
Caput boreale 107° 4' 32° 10' N
Cor Leonis 146° 8' 13° 47' N
Cauda Leonis 171° 38' 16° 30' N
Spica Virginis 195° 44' 8° 34' S
Arcturus 29° 13' 21° 54' N
Cor Aquilæ 291° 56' 7° 35' N

An instrument for finding the amplitude at rising on the horizon.
Describe the circumference of a circle and let it be divided into quadrants
by two diameters intersecting each other at right angles at its centre. One of
these will represent the æquinoctial circle, the other the axis of the world.
Let each of these quadrants be divided (in the accustomed way) into 90
degrees; on every fifth or tenth of which at each end of each diameter and
on each side let marks (showing the numbers) be inscribed on the two limbs
or margins made for that purpose outside the circumference. Then from
each degree straight lines are drawn parallel to the æquator. You will then
prepare a rule or alhidade equal to the diameter of that circle and divided
throughout into the same parts into which the diameter of the circle
representing the axis of the world is divided. Let there be left a small
appendage attached to the middle of the rule, by which the middle of the
fiducial line itself of the rule may be connected with the centre of the circle:
but to every fifth or tenth part of that rule let numbers be attached
proceeding from the centre toward each side. This circle represents the
plane of the meridian; its centre the actual point of east or west, i.e., the
common intersection of the horizon and æquator; all those lines æquidistant
from the æquator denote the parallels of the sun and stars; the fiducial line
of the rule or alhidade represents the horizon; and its parts signify the
degrees of the horizon, beginning from the point of setting or of rising.

Therefore if the fiducial line of the rule be applied to the given latitude of
the place reckoned from either end of that diameter which represents the
axis of the world; and if further the given declination of the sun or of some
star from the æquator (less than the complement of the latitude of the place)
be found on the limb of the instrument; then the intersection of the parallel
drawn from that point of the declination with the horizon, or with the
fiducial line of the rule or alhidade, will indicate for the given latitude of the
place the amplitude at rising of the given star or the sun.

CHAP. XIII.

The observations of variation by seamen vary, for the
most part, and are uncertain: partly from error and inexperience,
and the imperfections of the instruments; and partly
from the sea being seldom so calm that the

shadows or lights can remain quite
steady on the instruments.

fter the variation of the compass had first been noticed, some more
diligent navigators took pains to investigate in various ways the
difference of aspect of the mariners' compass. Yet, to the great
detriment of the nautical art, this has not been done so exactly as it
ought to have been. For either being somewhat ignorant they have not
understood any accurate method or they have used bad and absurd
instruments, or else they merely follow some conjecture arising from an ill-
formed opinion as to some prime meridian or magnetick pole; whilst others
again transcribe from others, and parade these observations as their own;
and they who, very unskilful themselves, first of all committed their
observations to writing are, as by the prerogative of time, held in esteem by
others, and their posterity does not think it safe to differ from them. Hence
in long navigations, especially to the East Indies, the records by the
Portuguese of the deviating compass are seen to be unskilful: for whoever
reads their writings will easily understand that they are in error in very
many things, and do not rightly understand the construction of the
Portuguese compass (the lily of which diverges by half a rumbe from the
needles toward the west), nor its use in taking the variation. Hence, while
they show the variation of the compass in different places, it is uncertain
whether they measure the deviation by a true meridional compass or by
some other whose needles are displaced from the lily. The Portuguese (as is
patent in their writings) make use of the Portuguese compass, whose
magnetick needles are fixed aside from the lily by half of one rumbe toward
the east. Moreover on the sea the observation of the variation is a matter of
great difficulty, on account of the motion of the ship and the uncertainty of
the deviation, even with the more skilful observers, if they use the best
made instruments hitherto known and used. Hence there arise different
opinions concerning the magnetick deviation: as, for instance, near the
Island of St. Helena the Portuguese Rodriguez de Lagos measures half a
rumbe. The Dutch in their nautical log fix it at a whole rumbe. Kendall, the
expert Englishman, with a true meridional compass admits only a sixth part
of a rumbe. A little to the East of Cape Agullias Diego Alfonso makes no
variation, and shows by an Astrolabe that the compass remains in the true
meridian. Rodriguez shows that the compass at Cape Agulhas has no

variation if it is of Portuguese construction, in which the needles are
inclined half a rumbe to the East. And there is the same confusion,
negligence, and vanity in very many other instances.

CHAP. XIIII.

On the variation under the æquinoctial line,
and near it.

n the North the magnetick needle varies because of the Boreal
eminences of the continent; in the South because of the Austral; at
the æquator, if the regions on both sides were equal, there would be
no variation. But because this rarely happens some variation is
often observed under the æquator; and even at some distance from the
æquator of three or 4 degrees toward the North, there may be a variation
arising from the south, if those very wide and influential southern
continents be somewhat near on one side.

CHAP. XV.

The variation of the magnetick needle in the great
Æthiopick and American sea, beyond
the æquator.

iscourse hath already been had of the mode and reason of the
variation in the great Atlantick Ocean: but when one has advanced
beyond the æquator off the east coast of Brazil the magnetick
needle turns aside toward the mainland, namely, with that end of it
which points to the south; so that with that end of the versorium it deviates
from the true meridian toward the west; which navigators observe at the
other end and suppose a variation to occur toward the east. But throughout

the whole way from the first promontory on the east of Brazil, by Cape St.
Augustine and thence to Cape Frio, and further still to the mouth of the
Strait of Magellan, the variation is always from the south toward the west
with that end of the versorium which tends toward the antarctick pole. For it
is always with the accordant end that it turns toward a continent. The
variation, however, occurs not only on the coast itself, but at some distance
from land, such as a space of fifty or sixty German miles or even more. But
when at length one has progressed far from land, then the arc begins to
diminish: for the magnetick needle turns aside the less toward what is too
far off, and is turned aside the less from what is present and at hand, since it
enjoys what is present. In the Island of St. Helena (the longitude of which is
less than is commonly marked on charts and globes) the versorium varies
by one degree or nearly two. The Portuguese and others taught by them,
who navigate beyond the Cape of Good Hope to the Indies, set a course
toward the Islands of Tristan d'Acunha, in order that they may enjoy more
favourable winds; in the former part of their course the change of variation
is not great; but after they have approached the islands the variation
increases; and close to the islands it is greater than anywhere else in the
whole course. For the end of the versorium tending to the south (in which
lies the greatest source of the variation) is caught and allured toward the
south-west by the great promontory of the southern land. But when they
proceed onward toward the Cape of Good Hope the variation diminishes the
more they approach it. But on the prime meridian in the latitude of 45
degrees, the versorium tends to the south-east: and one who navigates near
the coast from Manicongo to the tropick, and a little beyond, will perceive
that the versorium tends from the south to the east, although not much. At
the promontory of Agulhas it preserves slightly the variation which it
showed near the islands of d'Acunha, which nevertheless is very much
diminished because of the greater remoteness from the cause of variation,
and consequently there the southern end of the versorium does not yet face
exactly to the pole.

CHAP. XVI.

On the variation in Nova Zembla.

ariations in parts near the pole are greater (as has been shown
before) and also have sudden changes, as in former years the Dutch
explorers observed not badly, even if those observations were not
exact—which indeed is pardonable in them; for with the usual
instruments it is with difficulty that the truth becomes known in such a high
latitude (of about 80 degrees). Now, however, from the deviation of the
compass the reason for there being an open course to the east by the Arctick
Ocean appears manifest; for since the versorium has so ample a variation
toward the north-west, it is demonstrable that a continent does not extend
any great distance in the whole of that course toward the east. Therefore
with the greater hope can the sea be attempted and explored toward the east
for a passage to the Moluccas by the north-east than by the north-west.

CHAP. XVII.

Variation in the Pacifick Ocean.

assing the Strait of Magellan the deviation on the shore of Peru is
toward the south-east, i.e., from the south toward the east. And a
similar deflection would be continued along the whole coast of
Peru as far as the æquator. In a higher latitude up to 45 deg. the
variation is greater than near the æquator; and the deflection toward the
south-east is in nearly the same proportion as was the deviation from the
south toward the west on the eastern shore of South America. From the
æquator toward the North there is little or no variation until one comes to
New Galicia; and thence along the whole shore as far as Quivira the
inclination is from the north toward the east.

CHAP. XVIII.

On the variation in the Mediterranean Sea.

icilian and Italian sailors think that in the Sicilian Sea and toward
the east up to the meridian of the Peloponnesus (as Franciscus
Maurolycus relates) the magnetick needle "græcizes," that is, turns
from the pole toward what is called the greek wind or Boreas; that
on the shore of the Peloponnesus it looks toward the true pole; but that
when they have proceeded further east, then it "mistralizes," because it
tends from the pole toward the mistral or north-west wind: which agrees
with our rule for the variation. For as the Mediterranean Sea is extended
toward the west from that meridian, so on the side toward the east the
Mediterranean Sea lies open as far as Palestine; as toward North and East
lie open the whole Archipelago and the neighbouring Black Sea. From the
Peloponnesus toward the north pole the meridian passes through the largest
and most elevated regions of all Europe; through Achaia, Macedonia,
Hungary, Transylvania, Lithuania, Novogardia, Corelia and Biarmia.

CHAP. XIX.

The variation in the interior of large
Continents.

ost of the great seas have great variations; in some parts, however,
they have none, but the true directions are toward the pole. On
continents, also, the magnetick needle often deviates from the
meridian, as on the edge of the land and near the borders; but it is
generally accustomed to deviate by a somewhat small arc. In the middle,
however, of great regions there are no variations. Hence in the middle lands
of Upper Europe, in the interior of Asia, and in the heart of Africa, of Peru,
and in the regions of North or Mexican America, the versorium rests in the
meridian.

CHAP. XX.

Variation in the Eastern Ocean.

ariation in the Eastern Ocean throughout the whole voyage to Goa
and the Moluccas is observed by the Portuguese; but they err
greatly in many things, following, as they do, the first observers
who note down variations in certain places with ill-adapted
instruments, and by no means accurate observations, or by some
conjectures. As, for instance, in Brandöe Island, they make the versorium
deviate by 22 degrees to the north-west. For in no region or place in the
whole world, of not greater latitude, is there so great a deviation; and, in
reality, there the deviation is slight. Also when they make out that at
Mosambique the compass deviates by one rumbe to the north-west, it is
false; even though they use (as they are accustomed to do) the Portuguese
compass: for beyond all doubt on the shore of Mosambique the versorium
inclines ¼ rumbe or even more to the south-west. Very wrongly also beyond
the æquator in the course to Goa they make the little compass incline by 1½
rumbe to the west: whereas they should rather have said that in the first part
of the course the Portuguese compass inclines by 1 rumbe: but that the true
meridional compass inclines by ½ rumbe only. In order that the amount of
variation in the Eastern Ocean may be accurately settled in most places by
our rules, there is needed a more exact and truer survey of the southern
land, which spreads out from the south to the æquinoctial more than is
commonly described on maps and globes.

CHAP. XXI.

How the deviation of the versorium is augmented and
diminished by reason of the distance of places.

n the middle of great and continent lands there is no variation. Nor,
generally, in the middle of very great seas. On the margin of those
lands and seas the variation is often ample, yet not so great as at a

little further distance on the sea. As, for example, near Cape St. Augustine
the compass varies; but at 50 miles from land toward the East it varies
more; and 80 miles off it varies still more; and yet still more at a distance of
100 miles. But from a distance of 100 miles the diminutions of deviation
are slower, when they are navigating toward the mainland, than at a
distance of 80 miles, and at a distance of 80 miles than at 50: for the
deviations change and are diminished rather more swiftly the more they
approach and draw near land than when at a great distance off. As, for
instance, navigating toward Newfoundland the change of variation is more
rapid (that is, it decreases a degree in a smaller arc of the course on the
parallel) when they are not far from land than when they are a hundred
miles distant: but when travelling on land toward the interiors of regions the
changes are slower in the first parts of the journey than when they come
more into the interior.
The ratio of the arcs on a parallel circle, when a versorium is moved toward
continents which extend to the pole, corresponds with the degrees of
variation. Let A be the pole; B the eminences of the dominant lands; at C
there is no variation caused by B, for it is too far away; at D the variation is
very great because the versorium is allured or turned by the whole earth
toward the eminent land B; and moreover it is not hindered, or restrained or
brought back to the pole by the verticity of the earth; but, tending of its own
nature to the pole, it is nevertheless deflected from it by reason of the site,
or position, and convenient distance of the dominant and high lands.

Now from C toward D the variation increases; the versorium, however, does
not deviate so rapidly in the first spaces as near D: for more miles are traversed
on the parallel circle C D, near C, in order that the versorium may deviate by
one degree from the pole A, than near D. So also in order that the variation
may be diminished from D toward E more miles are required near D than near
E. Thus the deviations become equal in unequal courses, whether the variation
be increasing or decreasing; and yet the variation decreases by lesser intervals
than it increases. There intervene, however, many other causes which perturb
this proportion.

BOOK FIFTH.

CHAP. I.

ON DECLINATION.

n due course we have now come to that notable experiment, and remarkable
motion of magnetick bodies dipping below the horizon by their own rotatory

nature; by the knowledge of which is revealed a unity, a concordancy,
and a mutual agreement between the terrestrial globe and the
loadstone (or the magnetick iron), which is wonderful in itself, and is
made manifest by our teaching. This motion we have made known in
many striking experiments, and have established its rules; and in the following
pages we shall demonstrate the causes of it, in such a way that no sound,
logical mind can ever rightly set at nought or disprove our chief magnetick
principles. Direction, as also variation, is demonstrated in a horizontal plane,
when a balanced magnetick needle comes to rest at some definite point; but
declination is seen to be the motion of a needle, starting from that point of the
horizon, first balanced on its own axis, then excited by a loadstone, one end or
pole of it tending toward the centre of the earth. And we have found that it
takes place in proportion to the latitude of each region. But that motion arises
in truth, not from any motion from the horizon toward the centre of the earth,
but from the turning of the whole magnetick body toward the whole of the
earth, as we shall show hereafter. Nor does the iron dip from the horizontal in
some oblique sphere, according to the number of degrees of elevation of the
pole in the given region, or by an equal arc in the quadrant, as will appear
hereafter.

Instrument of the Declination

Now how much it dips at every horizon may be ascertained in the first place
by a contrivance, which, however, is not so easily made as is that in dials for
measuring time, in which the needle turns to the points of the horizon, or in the
mariners' compass. From a plank of wood let a smooth and circular instrument
be prepared, at least six digits in diameter, and affix this to the side of a square
pillar, which stands upright on a wooden base. Divide the periphery of this
instrument into 4 quadrants: then each quadrant into 90 degrees. At the centre
of the instrument let there be placed a brass peg, at the centre of the end of
which let there be a small hollow, well polished. To this wooden instrument let
a brass circle or ring be fixed, about two digits in width, with a thin plate or
flat rod of the same metal, representing the horizon, fixed across it, through the
middle of the circle. In the middle of the horizontal rod let there be another
hollow, which shall be exactly opposite the centre of the instrument, where the
former hollow was made. Afterward let a needle be fashioned out of steel, as
versoria are accustomed to be made. Divide this at right angles by a thin iron
axis (like a cross) through the very middle and centre of the wire and the cross-
piece. Let this dipping-needle be hung (with the ends of the cross resting in the

aforesaid holes) so that it can move freely and evenly on its axis in the most
perfect æquilibrium, so accurately that it turns away from no one point or
degree marked on the circumference more than from another, but that it can
rest quite easily at any. Let it be fixed upright to the front part of the pillar,
whilst at the edge of the base is a small versorium to show direction. Afterward
touch the iron, suspended by this ingenious method, on both ends with the
opposite ends of a loadstone, according to the scientifick method, but rather
carefully, lest the needle be twisted in any way; for unless you prepare
everything very skilfully and cleverly, you will secure no result. Then let
another brass ring be prepared, a little larger, so as to contain the former one;
and let a glass or a very thin plate of mica be fitted to one side of it. When this
is put over the former ring, the whole space within remains inclosed, and the
versorium is not interfered with by dust or winds. Dispose the instrument, thus
completed, perpendicularly on its base, and with the small versorium
horizontal, in such a way that, while standing perpendicularly, it may be
directed toward the exact magnetical point respective. Then the end of the
needle which looks toward the north dips below the horizon in northern
regions, whilst in southern regions the end of the needle which looks toward
the south tends toward the centre of the earth, in a certain proportion (to be
explained afterward) to the latitude of the district in question, from the æquator
on either side. The needle, however, must be rubbed on a powerful loadstone;
otherwise it does not dip to the true point, or else it goes past it, and does not
always rest in it. A larger instrument may also be used, whose diameter may be
10 or 12 digits; but in such an instrument more care is needed to balance the
versorium truly. Care must be taken that the needle be of steel; also that it be
straight; likewise that both ends of the cross-piece be sharp and fixed at right
angles to the needle, and that the cross-piece pass through the centre of the
needle. As in other magnetical motions there is an exact agreement between
the earth and the stone, and a correspondence manifestly apparent to our
senses by means of our experiments; so in this declination there is a clear and
evident concordance of the terrestrial globe with the loadstone. Of this motion,
so important and so long unknown to all men, the following is the sure and
true cause. A magnet-stone is moved and turned round until one of its poles
being impelled toward the north comes to rest toward a definite point of the
horizon. [231]This pole, which settles toward the north (as appears from the
preceding rules and demonstrations), is the southern, not the boreal; though all
before us deemed it to be the boreal, on account of its turning to that point of
the horizon. A wire or versorium touched on this pole of the stone turns to the

south, and is made into a boreal pole, because it was touched by the southern
terminal of the stone. So if the cusp of a versorium be excited in a similar
manner, it will be directed toward the southern pole of the earth, and will
adjust itself also to it; but the cross (the other end) will be southern, and will
turn to the north of the earth (the earth itself being the cause of its motion); for
so direction is produced from the disposition of the stone or of the excited iron,
and from the verticity of the earth. But declination takes place when a
magnetick is turned round toward the body of the earth, with its southern end
toward the north, at some latitude away from the æquator. For this is certain
and constant, that exactly under the cœlestial æquator, or rather over the
æquator of the terrestrial globe, there is no declination of a loadstone or of
iron; but in whatever way the iron has been excited or rubbed, it settles in the
declination instrument precisely along the plane of the horizon, if it were
properly balanced before. Now this occurs thus because, when the magnetick
body is at an equal distance from either pole, it dips toward neither by its own
versatory nature, but remains evenly directed to the level of the horizon, as if it
were resting on a pin or floating free and unhindered on water. But when the
magnetick substance is at some latitude away from the æquator, or when either
pole of the earth is raised (I do not say raised above the visible horizon, as the
commonly imagined pole of the revolving universe in the sky, but above the
horizon or its centre, or its proper diameter, æquidistant from the plane of the
visible horizon, which is the true elevation of the terrestrial pole), then
declination is apparent, and the iron inclines toward the
body of the earth in its own meridian. Let A B, for
example, be the visible horizon of a place; C D the
horizontal through the earth, dividing it into equal
parts; E F the axis of the earth; G the position of the
place. It is manifest that the boreal pole E is elevated
above the point C by as much as G is distant from the
æquator. Wherefore, since at E the magnetick needle
stands perpendicularly in its proper turning (as we have often shown before),
so now at G there is a certain tendency to turn in proportion to the latitude (the
magnetick dipping below the plane of the horizon), and the magnetick body
intersects the horizon at unequal angles, and exhibits a declination below the
horizon. For the same reason, if the declinatory needle be placed at G, its
southern end, the one namely which is directed toward the North, dips below
the plane of the visible horizon A B. And so there is the greatest difference
between a right sphere[232] and a polar or parallel sphere, in which the pole is

at the very Zenith. For in a right sphere the needle is parallel to the plane of the
horizon; but when the cœlestial pole is vertically overhead, or when the pole of
the earth is itself the place of the region, then the needle is perpendicular to the
horizon. This is shown by a round stone. Let a small dipping-needle, of two
digits length (rubbed with a magnet), be hung in the air like a balance, and let
the stone be carefully placed under it; and first let the terrella be at right
angles, as in a right sphere, and as in the first figure; for so the magnetick
needle will remain in equilibrium. But in an oblique position of the terrella, as
in an oblique sphere, and in the second figure, the needle dips obliquely at one
end toward the near pole, but does not rest on the pole, nor is its dip ruled by
the pole, but by the body and mass of the whole; for the dip in higher latitudes
passes beyond the pole. But in the third position of the terrella the needle is
perpendicular; because the pole of the stone is placed at the top, and the needle
tending straight toward the body reaches to the pole. The cross in the
preceding figures always turns toward the boreal pole of the terrella, having
been touched by the boreal pole of the terrella; the cusp of the needle, having
been touched by the southern pole of the stone, turns to the south. Thus one
may see on a terrella the level, oblique, and perpendicular positions of a
magnetick
* needle.

CHAP. II.

Diagram of declinations of the magnetick needle, when
excited, in the various portions of the sphere, and horizons
of the earth, in which there is no variation
of the declination.

s æquator let A B be taken, C the north pole, D the south, E G
dipping-needles in the northern, H F in the southern part of the earth
or of a terrella. In the diagram before us all the cusps have been
touched by the true Arctick pole of the terrella.
Here we have the level position of the magnetick needle on the æquator of the
earth and the stone, at A and B, and its perpendicular position at C, D, the
poles; whilst at the places midway between, at a distance of 45 degrees, the
crosses of the needle dip toward the south, but the cusps just as much toward
the north. Of which thing the reason will become clear from the
demonstrations that follow.

* Diagram of the rotation and declination of a terrella
conforming to the globe of the earth, for a
latitude of 50 degrees north.

A is the boreal pole of the earth or of a rather large terrella, B the southern, C a
smaller terrella, E the southern pole of the smaller terrella, dipping in the

northern regions[233]. The centre C is placed on the surface of the larger
terrella, because the smaller terrella shows some variation on account of the
length of the axis; inappreciable, however, on the earth. Just as a magnetick
needle dips in a regional latitude of 50 degrees, so also the axis of a stone (of a
spherical stone, of course) is depressed below the horizon, and its natural
austral pole falls, and its boreal pole is raised on the south toward the Zenith.
In the same way also a circular disc of iron behaves, which has been carefully
touched at opposite parts on its circumference; but the magnetical experiments
are less clear on account of the feebler forces in round pieces of iron.

Variety in the declinations of iron spikes at various latitudes of a terrella.

The declination of a magnetick needle above a terrella is shown by means of
several equal iron wires, of the length of a barleycorn, arranged along a
meridian. The wires on the æquator are directed by the virtue of the stone
toward the poles, and lie down upon its body along the plane of its horizon.
The nearer they are brought to the poles, the more they are raised up by their
versatory nature. At the poles themselves they point perpendicularly toward
the very centre. But iron spikes, if they are of more than a due length, are not
raised straight up except on a vigorous stone.

CHAP. III.

* An indicatory instrument, showing by the virtue of a
stone the degrees of declination from the horizon

of each several latitude.

Description of the Instrument, and its use.
ake a terrella of the best strong loadstone, and homogeneous
throughout, not weakened by decay or by a flaw in any parts; let it be
of a fair size, so that its diameter is six or seven digits; and let it be
made exactly spherical. Having found its poles according to the
method already shown, mark them with an iron tool; then mark also the
æquinoctial circle. Afterwards in a thick squared block of wood, one foot in
size, make a hemispherical hollow, which shall hold half of the terrella, and
such that exactly one half of the stone shall project above the face of the block.
Divide the limb close to this cavity (a circle having been drawn round it for a
meridian) into 4 quadrants, and each of these into 90 degrees. Let the terminus
of the quadrants on the limb be near the centre of a quadrant described on the

block, also divided into 90 degrees. At that centre let a short, slender versorium
(its other end being rather sharp and elongated like a pointer) be placed in
æquilibrio on a suitable pin. It is manifest that when the poles of the stone are
at the starting points of the quadrants, then the versorium lies straight, as if in
æquilibrio, over the terrella. But if you move the terrella, so that the pole on
the left hand rises, then the versorium rises on the meridian in proportion to the
latitude, and turns itself as a magnetick body; and on the quadrant described on
the flat surface of the wood, the degree of its turning or of the declination is
shown by the versorium. The rim of the cavity represents a meridional circle,
to which corresponds some meridian circle of the terrella, since the poles on
both sides are within the circumference of the rim itself. These things clearly
always happen on the same plan on the earth itself when there is no variation;
but when there is variation, either in the direction or in the declination (a
disturbance, as it were, in the true turning, on account of causes to be
explained later), then there is some difference. Let the quadrant be near the
limb, or have its centre on the limb itself, and let the versorium be very short,
so as not to touch the terrella, because with a versorium that is longer or more
remote, there is some error; for it has a motion truly proportionate to the
terrella only on the surface of the terrella. But if the quadrant, being far distant
from the terrella, were moved within the orbe of virtue of the terrella toward
the pole on some circle concentrick with the terrella, then the versorium would
indicate the degrees of declination on the quadrant, in proportion to and
symmetrically with that circle, not with the terrella.

CHAP. IIII.

Concerning the length of a versorium convenient
for declination on a terrella.

eclination being investigated on the earth itself by means of a
declination instrument, we may use either a short or a very long
versorium, if only the magnetick virtue of the stone that touches it is
able to permeate through the whole of its middle and through all its
length. For the greatest length of a versorium has no moment or perceptible
proportion to the earth's semi-diameter. On a terrella, however, or in a plane
near a meridian of a terrella, a short versorium is desirable, of the length, say,

of a barleycorn; for longer ones (because they reach further) dip and turn
toward the body of the terrella suddenly and irregularly in the first degrees of
declination. For example, as soon as the long versorium is
moved forward from the aequator A to C, it catches on the
stone with its cusp (as if with a long extended wing), when the
cusp reaches to the parts about B, which produce a greater
rotation than at C. And the extremities of longer wires also and
rods turn irregularly, just as iron wires and balls of iron and
other orbicular loadstones are likewise turned about irregularly
by a long non-orbicular loadstone. Just so magneticks or iron bodies on the
surface of a terrella ought not to have too long an axis, but a very short one; so
that they may make a declination on the terrella truly and naturally
proportionate to that on the earth. A long versorium also close to a terrella with
difficulty stands steady in a horizontal direction on a right sphere, and,
beginning to waver, it dips immediately to one side, especially the end that was
touched, or (if both were touched) the one which felt the stone last.

CHAP. V.

That declination does not arise from the attraction
of the loadstone, but from a disposing and
rotating influence.

n the universe of nature that marvellous provision of its Maker should
be noticed, whereby the principal bodies are restrained within certain
habitations and fenced in, as it were (nature controlling them). For
this reason the stars, though they move and advance, are not thrown
into confusion. Magnetical rotations also arise from a disposing influence,
whether in greater and dominating quantity, or in a smaller, and compliant
quantity, even though it be very small. For the work is not accomplished by
attraction, but by an incitation of each substance, by a motion of agreement
toward fixed bounds, beyond which no advance is made. For if the versorium
dipped by reason of an attractive force, then a terrella made from a very strong
magnetick stone would cause the versorium to turn toward itself more than one
made out of an average stone, and a piece of iron touched with a vigorous

loadstone would dip more. This, however, never happens. Moreover, an iron
snout placed on a meridian in any latitude does not raise a spike more toward
the perpendicular than the stone itself, alone and unarmed; although when thus
equipped, it plucks up and raises many greater weights[234]. But if a loadstone
be sharper toward one pole, toward the other blunter, the sharp end or pole
allures a magnetick needle more strongly, the blunt, thick end makes it rotate
more *strongly; but an orbicular stone makes it rotate strongly and truly, in
accordance with magnetick rules and its globular form. A long stone, on the
other hand, extended from pole to pole, moves a versorium toward it
irregularly; for in this case the pole of the versorium always looks down on the
pole itself. Similarly also, if the loadstone have been made in the shape of a
circle, and its poles are on the circumference, whilst the body of it is plane, not
globular, if the plane be brought near a versorium, the versorium does not
move with the regular magnetick rotation, as on a terrella; but it turns looking
always toward the pole of the loadstone, which has its seat on the
circumference of the plane. Moreover, if the stone caused the versorium to
rotate by attracting it, then in the first degrees of latitude, it would attract the
end of a short versorium toward the body itself of the terrella; yet it does not so
attract it that they are brought into contact and unite; but the versorium rotates
just so* far as nature demands, as is clear from this example. For
the cusp of a versorium placed in a low latitude does not touch
the stone or unite with it, but only inclines toward it. Moreover,
when a magnetick body rotates in dipping, the pole of the
versorium is not stayed or detained by the pole of the earth or
terrella; but it rotates regularly, and does not stop at any point
or bound, nor point straight to the pole toward which the centre of the
versorium is advancing, unless on the pole itself, and once only between the
pole and the æquator; but it dips as it advances, according as the change of
position of its centre gives a reason for its inclination in accordance with rules
magnetical. The declination of a magnetick needle in water also, as
demonstrated in the following pages, is a fixed quantity[235]; the magnetick
needle does not descend to the bottom of the vessel, but remains steady in the
middle, rotated on its centre according to its due amount of declination. This
would not happen, if the earth or its poles by their attraction drew down the
end of the magnetick needle, so that it dipped in this way.

CHAP. VI.

On the proportion of declination to latitude[236], and
the cause of it.

oncerning the making of an instrument for finding declination, the
causes and manner of declination, and the different degrees of
rotation in different places, the inclination of the stone, and
concerning an instrument indicating by the influence of a stone the
degree of declination from any horizon we have already spoken. Then we
spoke about needles on the meridian of a stone, and their rotation shown for
various latitudes by their rise toward the perpendicular. We must now,
however, treat more fully of the causes of the degree of that inclination. Whilst
a loadstone and a magnetick iron wire are moved along a meridian from the
aequator toward the pole, they rotate toward a round loadstone, as also toward
the earth with a circular movement. On a right horizon (just as also on the
æquinoctial of the stone) the axis of the iron, which is its centre line, is a line
parallel to the axis of the earth. When that axis reaches the pole, which is the
centre of the axis, it stands in the same straight line with the axis of the earth.
The same end of the iron which at the æquator looks south turns to the north.
For it is not a motion of centre to centre, but a natural turning of a magnetick
body to a magnetick body, and of the axis of the body to the axis; it is not in
consequence of the attraction of the pole itself that the iron points to the earth's
polar point. Under the æquator the magnetick needle remains in æquilibrio
horizontally; but toward the pole on either side, in every latitude from the
beginning of the first degree right up to the ninetieth, it dips. The magnetick
needle does not, however, in proportion to any number of degrees or any arc of
latitude fall below the horizon just that number of degrees or a similar arc, but
a very different one: because this motion is not really a motion of declination,
but is in reality a motion of rotation, and it observes an
arc of rotation according to the arc of latitude. Therefore
a magnetick body A, while it is advancing over the earth
itself, or a little earth or terrella, from the æquinoctial G
toward the pole B, rotates on its own centre, and
halfway on the progress of its centre[237] from the
æquator to the pole B it is pointing toward the æquator
at F, midway between the two poles. Much more
quickly, therefore, must the versorium rotate than its centre advances, in order

that by rotating it may face straight toward the point F. Wherefore the motion
of this rotation is rapid in the first degrees from the æquator, namely, from A to
L; but more tardy in the later degrees from L to B, when facing from the
æquator at F to C. But if the declination were equal to the latitude (i.e., always
just as many degrees from the horizon, as the centre of the versorium has
receded from the æquator), then the magnetick needle would be following
some potency and peculiar virtue of the centre, as if it were a point operating
by itself. But it pays regard to the whole, both its mass, and its outer limits; the
forces*of both uniting, as well of the magnetick versorium as of the earth.

CHAP. VII.

Explanation of the diagram of the rotation of
a magnetick needle.

uppose A C D L to be the
body of the earth or of a
terrella, its centre M,
Æquator A D, Axis C L, A B
the Horizon, which changes
according to the place. From the
point F on a Horizon distant from the
æquator A by the length of C M, the
semi-diameter of the earth or terrella,
an arc is described to H as the limit
of the quadrants of declination; for
all the quadrants of declination
serving the parts from A to C begin
from that arc, and terminate at M, the
centre of the earth. The semi-
diameter of this arc is a chord drawn from the æquator A to the pole C; and a
line produced along the horizon from A to B, equal to that chord, gives the
beginning of the arc of the limits of arcs of rotation and revolution, which is
continued as far as G. For just as a quadrant of a circle about the centre of the
earth (whose beginning is on the horizon, at a distance from the æquator equal
to the earth's semi-diameter) is the limit of all quadrants of declination drawn

from each several horizon to the centre; so a circle about the centre from B, the
beginning of the first arc of rotation, to G is the limit of the arcs of rotation.
The arcs of rotation and revolution of the magnetick needle are intermediate
between the arcs of rotation B L and G L. The centre of the arc is the region
itself or place in which the observation is being made; the beginning of the arc
is taken from the circle which is the limit of rotations, and it stops at the
opposite pole; as, for example, from O to L, in a latitude of 45 degrees. Let any
arc of rotation be divided into 90 equal parts from the limit of the arcs of
rotation toward the pole; for whatever is the degree of latitude of the place, the
part of the arc of rotation which the magnetick pole on or near the terrella or
the earth faces in its rotation is to be numbered similarly to this. The straight
lines in the following larger diagram show this. The magnetick rotation at the
middle point in a latitude of 45 degrees is directed toward the æquator, in
which case also that arc is a quadrant of a circle from the limit to the pole; but
previous to this all the arcs of rotation are greater than a quadrant, whilst after
it they are smaller; in the former the needle rotates more quickly, but in the
succeeding positions gradually more slowly. For each several region there is a
special arc of rotation, in which the limit to which the needle rotates is
according to the number of degrees of latitude of the place in question; so that
a straight line drawn from the place to the point on that arc marked with the
number of degrees of latitude shows the magnetick direction, and indicates the
degree of declination at the intersection of the quadrant of declination which
serves the given place. Take away the arc of the quadrant of declination drawn
from the centre to the line of direction; that which is left is the arc of
declination below the horizon. As, for example, in the rotation of the
versorium N, whose line respective proceeds to D, from the quadrant of
declination, S M, take away its arc R M; that which is left is the arc of
declination: how much, that is, the needle dips in the latitude of 45 degrees.

CHAP. VIII.

Diagram of the rotation of a magnetick needle,
indicating magnetical declination in all latitudes, and
from the rotation and declination, the
latitude itself.

n the more elaborate diagram a circle of rotations and a circle of
declinations are adjusted to the body of the earth or terrella, with a
first, a last, and a middle arc of rotation and declination. Now from
each fifth division of the arc which limits all the arcs of rotation (and
which are understood[238] as divided into 90 equal parts) arcs are drawn to the
pole, and from every fifth degree of the arc limiting the quadrants of
declination, quadrants are drawn to the centre; and at the same time a spiral
line is drawn, indicating (by the help of a movable quadrant) the declination in
every latitude. Straight lines showing the direction of the needle are drawn
from those degrees which are marked on the meridian of the earth or a terrella
to their proper arcs and the corresponding points on those arcs.

To ascertain the elevation of the pole or the latitude of a place anywhere
in the world, by means of the following diagram, turned into
a magnetick instrument, without the help of the cœlestial
bodies, sun, planets, or fixed stars, in fog
and darkness.

We may see how far from unproductive magnetick philosophy is, how
agreeable, how helpful, how divine! Sailors when tossed about on the waves
with continuous cloudy weather, and unable by means of the cœlestial
luminaries to learn anything about the place or the region in which they are,
with a very slight effort and with a small instrument are comforted, and learn
the latitude of the place. With a declination instrument the degree of
declination of the magnetick needle below the horizon is observed; that degree
is noted on the inner arc of the quadrant, and the quadrant is turned round

about the centre of the instrument until that degree on the quadrant touches the
spiral line; then in the open space B at the centre of the quadrant the latitude of
the region on the circumference of the globe is discerned by means of the
fiducial line A B. Let the diagram be fixed on a suitable flat board, and let the
centre of the corner A of the quadrant be fastened to the centre of it, so that the
quadrant may rotate on that centre. But it must be understood that there is also
in certain places a variation in the declination on account of causes already
mentioned (though not a large one), which it will be an assistance also to allow
for on a likely estimate; and it will be especially helpful to observe this
variation in various places, as it seems to present greater difficulty than the
variation in direction; but it is easily learnt with a declination instrument, when
it dips more or less than the line in the diagram.

To observe magnetick declination at sea.
Set upon our variation instrument a declination instrument; a wooden disc
being placed between the round movable compass and the declination
instrument: but first remove the versorium, lest the versorium should interfere
with the dipping needle. In this way (though the sea be rough) the compass
box will remain upright at the level of the horizon. The stand of the declination
instrument must be directed by means of the small versorium at its base, which
is set to the point respective of the variation, on the great circle of which

(commonly called the magnetick meridian), the plane of the upright box is
arranged; thus the declinatorium (by its versatory nature) indicates the degree
of declination.

In a declination instrument the magnetick needle, which
in a meridional position dips, if turned
along a parallel hangs perpendicularly.
In a proper position a magnetick needle, while by its rotatory nature
conformed to the earth, dips to some certain degree below the horizon on an
oblique sphere. But when the plane of the instrument is moved out of the plane
of the meridian, the magnetick needle (which tends toward the pole) no longer
remains at the degree of its own declination, but inclines more toward the
centre; for the force of direction is stronger than that of declination, and all
power of declination is taken away, if the plane of the instrument is on a
parallel. For then the magnetick needle, because it cannot maintain its due
position on account of the axis being placed transversely, faces down
perpendicularly to the earth; and it remains only on its own meridian, or on
that which is commonly called the magnetick meridian.

CHAP. IX.

Demonstration of direction, or of variation from the
true direction, at the same time with declination, by
means of only a single motion in water, due
to the disposing and rotating virtue.

ix a slender
* iron wire of three digits length through a round cork, so that the
cork may support the iron in water. Let this water be in a good-sized glass vase
or bowl. Pare the round cork little by little with a very sharp knife (so that it
may remain round), until it will stay motionless one or two digits below the
face of the water; and let the wire be evenly balanced. [239]Rub one end of the
wire thus prepared on the boreal end of a loadstone and the other on the
southern part of the stone (very skilfully, so that the cork may not be moved
ever so little from its place) and again place it in the water; then the wire will
dip with a circular motion on its own centre below the plane of the horizon, in

proportion to the latitude of the region;
and, even while dipping, will also show
the point of variation (the true direction
being perturbed). Let the loadstone
(that with which the iron is rubbed) be a strong
one, such as is needed in all experiments on
magnetick declination. When the iron, thus put
into the water and prepared by means of the
loadstone, has settled in the dip, the lower end
remains at the point of variation on the arc of a
great circle or magnetick meridian passing
through the Zenith or vertex, and the point of
variation on the horizon, and the lowest point of
the heavens, which they call the Nadir. This fact
is shown by placing a rather long magnetick versorium on one side a little way
from the vase. This is a demonstration of a more absolute conformity of a
magnetick body with the earth's body as regards unity; in it is made apparent,
in a natural manner, the direction, with its variation, and the declination. But it
must be understood that as it is a curious and difficult experiment, so it does
not remain long in the middle of the water, but sinks at length to the bottom,
when the cork has imbibed too much moisture.

CHAP. X.

On the variation of the declination.

* irection has been spoken of previously, and also variation, which is
like a kind of dragging aside of the direction. Now in declination
such irregular motion is also noticed, when the needle dips beyond
the proper point or when sometimes it does not reach its mark. There
is therefore a variation of declination, being the arc of a magnetick meridian
between the true and apparent declination. For as, on account of terrestrial
elevations, magnetick bodies are drawn away from the true meridian, so also
the needle dips (its rotation being increased a little) beyond its genuine
position. For as variation is a deviation of the direction, so also, owing to the
same cause, there is some error of declination, though often very slight.

Sometimes, also, when there is no variation of direction in the horizontal, there
may nevertheless be variation of the declination; namely, either when more
vigorous parts of the earth crop out exactly meridionally, i.e. under the very
meridian; or when those parts are less powerful than nature in general requires;
or when the virtue is too much intensified in one part, or weakened in another,
just as one may observe in the vast ocean. And this discrepant nature and
varying effect may be easily seen in certain parts of almost any round
loadstone. Inæquality of power is recognized in any part of a terrella by trial of
the demonstration in chap. 2 of this book. But the effect is clearly
demonstrated by the instrument for showing declination in chap. 3 of this
book.

CHAP. XI.

On the essential magnetick activity sphærically
effused.

* iscourse hath often been held concerning the poles of the earth and of
the stone, and concerning the æquinoctial zone; whilst lately we have
been speaking about the declining of magneticks toward the earth
and toward the terrella, and the causes of it. But while by various and
complicated devices we have laboured long and hard to arrive at the cause of
this declination, we have by good fortune found out a new and admirable
(beyond the marvels of all virtues magnetical) science of the orbes themselves.
For such is the power of magnetick globes, that it is diffused and extended into
orbes outside the body itself, the form being carried beyond the limits of the
corporeal substance; and a mind diligently versed in this study of nature will
find the definite causes of the motions and revolutions. The same powers of a
terrella exist also within the whole orbe of its power; and these orbes at any
distance from the body of the terrella have in themselves, in proportion to their
diameter and the magnitude of their circumference, their own limits of
influences, or points wherein magnetick bodies rotate; but they do not look
toward the same part of the terrella or the same point at any distance from the
same (unless they be on the axis of the orbes and of the terrella); but they
always tend to those points of their own orbes, which are distant by similar
arcs from the common axis of the orbes. As, for example, in the following

diagram, we show the body of a terrella, with its poles and æquator; and also a
versorium on three other concentrick orbes around the terrella at some distance
from it. In these orbes (as in all those which we may imagine without end) the
magnetick body or versorium conforms to its own orbe in which it is located,
and to its diameter and poles and æquator, not to those of the terrella; and it is
by them and according to the magnitude of their orbes that the magnetick body
is governed, rotated, and directed, in any arc of that orbe, both while the centre
of the magnetick body stands still, and also while it moves along. And yet we
do not mean that the magnetick forms and orbes exist in air or water or in any
medium that is not magnetical; as if the air or the water were susceptible of
them, or were induced by them; for the forms are only effused and really
subsist when magnetick substances are there; whence a magnetick body is laid
hold of within the forces and limits of the orbes; and within the orbes
magneticks dispose magneticks and incite them, as if the orbes of virtue were
solid and material loadstones. For the magnetick force does not pass through
the whole medium or really exist as in a continuous body; so the orbes are
magnetick, and yet not real orbes nor existent by themselves.

Diagram of motions in magnetick orbes.
A B is the axis of the terrella and
of the orbes, C D the æquator.
On all the orbes, as on the
terrella, at the equator the
versorium arranges itself along
the plane of the horizon; on the
axis it everywhere looks
perpendicularly toward the
centre; in the intermediate spaces
E looks toward D; and G looks
toward H, not toward F, as the
versorium L does on the surface
of the terrella. But as is the
relation of L to F on the surface
of the terella, so is that of G to H
on its orbe and of E to D on its orbe; also all the rotations on the orbes toward
the termini of the orbes are such as they are on the surface of the terrella, or
toward the termini of its surface. But if in the more remote orbes this fails
somewhat at times, it happens on account of the sluggishness of the stone, or