_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_.
_Should 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 [Greek: boreodeixis] 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 {iiij} 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 [Greek: orthoboreodeixis] 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 {v} 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 _[Greek: limeneuretikê]_, 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._
{vj}
* * * * *
_Interpretation of certain words.[1]_
Terrella, a globular loadstone.
Verticity, polar vigour, not [Greek: peridinêsis] but [Greek: peridineisios
dunamis]: not a vertex or [Greek: polos] 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 [Greek: helktikê dunamis] of one only, but a [Greek:
sundromê] 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.
* * * * *