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Full text of "William Gilbert of Colchester, physician of London, On the load stone and magnetic bodies, .."

OF C/LIFCIUI1 



.'lSL.Ei.'j? OP CIVI 



Gift of Lirs, Edv;in H. Warner 
from her husband's library, 

January 1928 




Library 




or CAT IFORNIA 



'ARTMENT OF CIVIL. 
BERKELEY, 




;Aft ****** *^ittt AM 'GILBERT, M.D. ELECTRICIAN 



UNIVERSITY OF 
'ASTTMENT OF C!VIl- 

BERKELEY. CALIFORNIA 



WILLIAM GILBERT 

OF COLCHESTER, 



PHYSICIAN OF LONDON, 



ON THE 



LOADSTONE AND MAGNETIC BODIES, 

AND ON 

THE GREAT MAGNET THE EARTH. 

A NEW PHYSIOLOGY, 

DEMONSTRATED WITH MANY ARGUMENTS AND EXPERIMENTS. 

'* Jtttrua t quae attrahunt eadem ratione ut electricum." 

A TRANSLATION BY 

P. FLEURY MOTTELAY, 

AUTHOR OF "THE CHRONOLOGICAL HISTORY OF ELECTRICITY, MAGNETISM, ETC." 



NEW YORK : 
JOHN WILEY & SONS, 

53 EAST TENTH STREET. 
1893 



.: -: -':: : -\ * : 
* -.* * .".., 

'. : : - :--' * 



COPYRIGHT, 1893, 

BY 
P. F. MOTTELAY. 



ROBERT DKUMMOJTD, FERRIS BROS., 

Electrotyper, Printers, 

t & 44 Pearl Street, 326 Pea rl Street, 
New York. New York. 



Jv: 

G VI LI-ELM I GIL- 

BERT I COLCESTRBN- 

SIS, MEDICI LONDI- 
NENSIS, 



E MA G N^E'TE, U A G N E T I) 

.VE CORPORIBVS,ET DE 
no magnete tellure j,Phyfiologt'a 
jp/ttrimis & argumentis* 

rimentis demonflrata, 




LOHDINI 



EXCVDEBAT PETRVS^SHORT ANNO 
MDC.. 



Engineering 
Library 




TRANSLATOR'S PREFACE. 



I FIRST entered upon the translation of this, the earliest 
known published work treating of both magnetism and elec- 
tricity, in the beginning of 1889. It was then my intention to 
place it before the public during the year following, appreciat- 
ing as I did the demand for an English version which had been 
frequently reiterated by scientists generally in this country, in 
England, and upon the Continent of Europe. But the atten- 
tion I was compelled to give, both here and abroad, to the 
preparation of my " Chronological History of Electricity and 
Magnetism" has unavoidably delayed the publication of the 
present volume. 

The translation of De Magnete has been a task of no or- 
dinary difficulty ; it has brought up problems innumerable, the 
solution of which has involved much laborious research as the 
result was meant to be a clear and competent presentation of 
the author in idiomatic English and not simply a substitution of 
English words for Latin. Nor would I have ventured to appear 
as the English interpreter of the great Gilbert, " father of the 
magnetic philosophy," but for the hearty encouragement and 
very material aid, in translating and otherwise, extended by 
many literary and scientific friends, amongst whom must be 
especially mentioned Mr. Joseph Fitzgerald, Mr. E. McMillan, 



793941 



VI TRANSLATOR'S PREFACE. 

Mr. Joseph Wetzler, Dr. Joseph V. Livingston, Hon. Park Ben- 
jamin, and Prof. Alfred M. Mayer. I am likewise indebted to 
Prof. Charles Sanders Peirce, to Mr. Latimer Clark, F.R.S., to 
Dr. Isaac H. Hall, and to Dr. Charlton T. Lewis for valuable 
suggestions as to the general treatment of the work, and, in 
the words of the celebrated English mathematician, Edward 
Wright, I doubt not that our united efforts " will find the 
heartiest approval among all intelligent men and children of 
magnetic science." 

Not only does Gilbert frequently make use of what he 
terms " words new and unheard-of," besides attaching to many 
others a signification far different from that generally recog- 
nized at this day, but, what is worse, he retains to a great 
extent the terminology of the mediaeval scholastic philoso- 
phers. That terminology the translator must perforce retain ; 
no substitute is possible. Hence is found a multitude of un- 
couth words which, for the modern reader, require explanation. 
Of such it is unnecessary here to make any especial mention, 
since the copious general index to the present work will indicate 
very readily where they are to be found. It is known that in 
the philosophy of the schoolmen (as in that of Aristotle) form 
forma means that which added to matter materia con- 
stitutes the true nature of the thing. Matter per se is indiffer- 
ent, indefinite; form gives it definiteness. The earth is 
informed vttih. verticity that is its prime distinction. When 
any portion of the earth loses verticity it loses its forma is 
deformate. To restore to it verticity, is to reformate* it, or to 
informate it. Portions of the earth that are deformate are, as 
it were, effete, excrementitious, waste matter. Gilbert states 
(Book II, Chapters II and IV) that the natural magnetic 
force (movement) comes from the prime forma of the earth, or 
rather the primary native strength (vigor). Elsewhere he tells 



TRANSLATOR'S PREFACE. Vll 

us that the earth and the loadstone conform conformant 
magnetic movements (Book II, Chapter VI); and he speaks 
of substances conformated conformatum by the earth (Book 
III, Chapter IV), and of the globe of earth as of small account 
and deformate deformatum (Book V, Chapter XII). He 
speaks besides of the formate soul formata anima (Book V, 
Chapter XII) ; of air or water being informated informaren- 
tur by magnetic forms or spheres (Book V, Chapter XI); of 
iron being transformated transformatur (Book III, Chapter 
XII); and he adds that iron will attract more properly if it is 
aftormedaffbrmatum (Book II, Chapter IV); also, that if 
will be better if the iron's " acquired verticity be, by some 
process, rather weakened or deformated" deformata (Book 
III, Chapter XI). 

England's great poet, John Dryden, tells us : " It is almost 
impossible to translate verbally and well at the same time ; for 
the Latin (a most severe and compendious language) often 
expresses that in one word which either the barbarity or the 
narrowness of modern tongues cannot supply in more. . . . 
But since every language is so full of its own proprieties that 
what is beautiful in one is often barbarous, nay, sometimes 
nonsense, in another, it would be unreasonable to limit a 
translator to the narrow compass of his author's words ; it is 
enough if he choose out some expression which does not 
vitiate the sense." While, in order to do this acceptably in 
the present instance, it has often been found necessary to 
adhere very closely (even literally) to the original lines, the 
"candid reader " will naturally observe that greater satisfaction 
has been vouchsafed where paraphrasing has been resorted to 
for the better comprehension, more particularly, of words of 
Gilbert's own coinage. 

Following Dryden, I have translated with latitude, keeping 



Vlll TRANSLATOR'S PREFACE. 

in view the author's sense more particularly than his words, 
and amplifying without altering the former. Nor have I, in 
so doing, attempted, any more than did Gilbert, to impart 
" into the work any graces of rhetoric, any verbal ornateness." 
Like him, I have simply endeavored to treat " knotty ques- 
tions about which little is known in such style and in such 
terms as are needed to make what is said clearly intelligible." 

Such few passages of De Magnete as I have seen inde- 
pendently translated elsewhere will be found reproduced in 
their proper places, and wherever practicable I have followed 
the approved plan adopted in my "Chronological History," of 
quoting numerous authorities and inserting many extracts 
from the writings of different authors in support of the original 
matter. The extent to which this has been done is shown in 
the general index accompanying the present work. 

I may add that I shall be under obligations to those calling 
attention to any errors, typographical or otherwise, that may 
be found herein, as well as to those whose helpful advice may 
make improvement possible in future editions. 

P. FLEURY MOTTELAY. 

NEW YORK, March 10, 1892. 



BIOGRAPHICAL MEMOIR. 



WILLIAM GILBERT or Gilberd, 1 as he wrote it was born in 
1540 at Colchester, County Essex, England, 2 of which borough 
his father, Jerome (Hieron) Gilberd, was recorder " a coun- 
cillor of great esteem in his profession." ! Very little that is 
reliable appears concerning his early years, but it is known 
that he passed through the Grammar School of his native 
place and immediately afterward (May 1558) entered St. 
John's College, Cambridge (whence, some say, he went to 
Oxford), 4 proceeding B.A. 1560, Fellow 1560-1561, M.A. 
1564, mathematical examiner 1565-1566, M.D. 1569, and 

1 "Gilbert or Gilberd. . . . The latter is used both in his own epitaph and 
his father's; and in the records of the town of Colchester : and, therefore, 
seems the truest." (Biographia Britannica, London 1757, Vol. IV, page 2202.) 

2 See the Map of Colchester at page 4, Vol. I, Book I, of Philip 
Morant's " Hist, and Antiq. of Essex," London 1768; also, a full description 
of the town at pages 266-361, Vol. I, of Thos. Wright's " Hist, and Top. of the 
County of Essex," London 1836, as well as at pages 286-322, Vol. V, of " The 
Beauties of England and Wales," by E. W. Bray ley and John Britton, London 
1810. 

3 Dr. Thomas Fuller, " Hist, of the Worthies of England," London 1840, 
page 515. 

4 Antony A. Wood, at pages 737-738, Vol. I, Athena Oxonienses, London 
1813, says he was "educated at both the Universities but whether in Oxon. 
first or in Cambridge, I cannot justly tell "; and Thomas Wright (" Hist, and 
Top. of County of Essex," 1836, Vol. I, page 311) states that "he studied some 
time in the Universities of Oxford and Cambridge." 

ix 



X IOGRAPHICAL MEMOIR. 

being elected a Senior Fellow of St. John's during the last- 
named year. 

Immediately upon leaving college he travelled on the Con- 
tinent, " where probably he had the degree of Doctor of 
Physic conferred upon him, for he doth not appear to have 
taken it either at Oxford or Cambridge," l and where, as well 
as in England, he is said to have "practised as a physician 
with great success and applause." In 1573, he was elected a 
Fellow of the Royal College of Physicians, and filled therein 
many important offices, becoming, in turn, Censor (1581-1582, 
1584-1587, I589-I59)> Treasurer (1587-1591, I59/-I599)> Con- 
siliarius (1597-1599), and President (1600). His skill had 
already attracted the attention of Queen Elizabeth, by whom 
he was appointed her physician-in-ordinary, and who showed 
him many marks of her favor, besides settling upon him an 
annual pension (said to be the only legacy left by her to any 
one) for the purpose of aiding him in the prosecution of his 
philosophical studies. 

Gilbert's removal to court led to the dispersion of the 
members of a society or college which, it appears, frequently 
met at his residence at Colchester (see illustration). This 
house, anciently known as " Lanseles," " Timperley's," " Tym- 
pornell's" (Old Taxation), 1 was located "on St. Peter's Hill, 
between Upper Thames Street and Little Knight-Rider 
Street." 

The early investigations of Gilbert were centred almost 
exclusively upon chemistry, he " attaining to great exactness 
therein," but this branch was ere long made to yield to the 
study of the phenomena of electricity and of magnetism, the 



1 Philip Morant, lac. at., Vol. I, Book II, page 117. See, likewise, Ree's 
Cyclopedia, 1819, Vol. XVI, article "Gilbert." 



BIOGRAPHICAL MEMOIR. Xl 

latter of which had practically lain dormant for two thousand 
y ears since the days of Thales and Theophrastus. How well 
he succeeded in generalizing and classifying these phenomena, 
after a patient and exhaustive line of experiments, is best 
evidenced by the great work which he published during 1600 
under the title of De Magnete magneticisque corporibus, et de 




GILBERT'S HOUSE AT COLCHESTER. 

magno magnete tellure ; Physiologia nova, plurimis et argu- 
mentis et experimentis demonstrata. This book, " full of valu- 
able facts and experiments ingeniously reasoned on " (J. F. W. 
Herschel), upon which Gilbert was actively engaged during eigh- 
teen years, is his best claim to recognition as the most distin- 



Xli BIOGRAPHICAL MEMOIR. 

guished man of science in England during the reign of the 
Virgin Queen. 

" The year 1600," observes the English historian Henry 
Hallam, 1 " was the first in which England produced a remark- 
able work in Physical Science ; but this was one sufficient to 
raise a lasting reputation for its author. Gilbert, a physician, 
in his Latin treatise on the Magnet not only collected all the 
knowledge which others had possessed on the subject, but 
became at once the father of experimental philosophy in this 
island, and, by a singular felicity and acuteness of genius, the 
founder of theories which have been revived after a lapse of 
ages, and are almost universally received into the creed of 
science. . . . Gilbert was one of the earliest Copernicans, at 
least as to the rotation of the earth, and, with his usual 
sagacity, inferred, before the invention of the telescope, that 
there are a multitude of fixed stars beyond the reach of our 
vision." 

Gilbert's book created a powerful impression at the time, 
especially among the learned in other parts of Europe. 
Galileo expressed the highest admiration of the work and of 
its author, and, it is said, pronounced Gilbert "great to a 
degree that is enviable." It was, indeed, by the perusal of 
De Magnete that Galileo was induced to turn his mind to 
magnetism. 3 In his own country, Gilbert was scarcely so 
highly appreciated ; even Bacon, though he praises Gilbert as 
a philosopher, speaks with little respect of his theory. After 
awhile his speculations came to be more esteemed, though 
perhaps not fully understood; but the great superiority of 
Gilbert over all who had previously treated of magnetism, and 

1 "Introd. to the Liu. of Europe in the isth, i6th, and I7th Centuries," 
London 1839, Vol. II, page 463. 

8 Dr. Munk, " Roll of the Roy. Col. of Phys.," 1878, page 78. 



BIOGRAPHICAL MEMOIR. Xlll 

"the extent to which he had anticipated by his conjectures 
much of our present knowledge " has only been perceived 
since the study of magnetism has assumed something like its 
present systematic and comprehensive character. 1 

While Dr. Whewell observes 2 that " Gilbert's work contains 
all the fundamental facts of the science, so fully examined, 
indeed, that even at this day we have little to add to them," Dr. 
Thomas Thomson says 3 that De Magnete " is one of the finest 
examples of inductive philosophy that has ever been pre- 
sented to the world. It is the more remarkable because it 
preceded the Novum Organum of Bacon, in which the in- 
ductive method of philosophizing was first explained." How 
far Gilbert was ahead of his time is best proved by the works 
of those who wrote on magnetism during the first few decades 
after his death. They contributed in reality nothing to the 
extension of this branch of physical science. PoggendorfT, 
from whose u Geschichte der Physik" (page 2$6) this is ex- 
tracted, calls Gilbert "the Galileo of Magnetism." By Dr. 
Priestley he was named " the father of modern electricity." 

In an article written not long since, Mr. Conrad W. 
Cooke, of London, notes the high opinion of Gilbert's 
work entertained, more particularly, by Nathaniel Carpenter, 
William Barlowe, Francis Bacon, Galileo, and Humboldt, and 
he adds : " There is abundant testimony extant that this 
* De Magnete' of Gilbert's produced a profound sensation, 
not only in this country but throughout the then civilized 
world, and it is a singularly curious fact that the brilliancy of 
a reputation so great and so original should have been allowed 
in subsequent generations to have been lost sight of in the 

1 Engl. Cycl., Section " Biography," Vol. Ill, page 102. 

2 "Hist, of the Inductive Sciences," 1859, Vol. II, page 217. 

3 " History of the Royal Society," London 1812. 



X1 V BIOGRAPHICAL MEMOIR. 

more blinding light of more recent knowledge and discoveries, 
and it is equally remarkable that a book so classical in its 
nature, so remarkable in its originality and prescience, and 
which was thought so much of during the periods which 
immediately followed its publication, should never have been 
translated into English, or indeed into any other language ; 
and this is rendered still more curious by the fact that such a 
translation was actually called for at the time, and the want of 
it was considered remarkable as far back as the year 1618; 
and here it will be interesting to quote from the preface to a 
scarce old book, ' Magneticall Advertisements] written at that 
date by the Ven. William Barlowe, 1 Archdeacon of Salisbury, 
and a very intimate friend of Dr. Gilbert. * Many of our 
nation/ he says, 'both Gentlemen and others of excellent 
witts and louers of these knowledges, not able to read Doctor 
Gilbert's booke in Latin haue bin (euer since the first publish- 
ing thereof) exceeding desirous to haue it translated into 
English, but hitherto no man hath done it, neither (to my 
knowledge) as yet goeth about any such matter, whereof one 
principall cause is that there are very few that understande his 
booke, because they haue not Load-stones of diuers formes, but 
especially round ones ; ' and the author gives a further supposi- 
tion that ' a second cause may be for that there are diuers 
wordes of art in the whole course of this booke proper to this 
subject and fitt to the explication of his figures and diagrammes 



1 Speaking of Wm. Barlowe, Anthony A. Wood says : " This was the 
person who had knowledge in the magnet 20 years before Dr. Will. Gilbert 
published his book of that subject, and therefore by those that knew him, he 
was accounted superior, or at least equal to that doctor for an industrious and 
happy searcher and finder out of many rare and magnetical secrets." (A thena 
Oxonienses, London 1813, Vol. II, page 375.) Under heading of Gilbert, the 
"British Museum Catalogue of Printed Books," 1888, has it that "Mag. 
Adv." was compiled partly from De Magnete. 



BIOGRAPHICAL MEMOIR. XV 

which cannot be understood but by the helpe of the Mathe- 
maticks, and good trauelling in the Magneticall practice.' " 

Dr. John Davy says 1 Gilbert's "work is worthy being 
studied, and I am surprised that an English edition (transla- 
tion) of it has never been published." He also alludes to the 
well-known reproach thrown upon Gilbert's philosophy by 
Francis Bacon, who, in his De Augmentis Scientiarum, remarks 
that " Gilbert has attempted to raise a general system upon 
the magnet, endeavoring to build a ship out of materials not 
sufficient to make the rowing-pins of a boat." 

On the other hand, Digby and Barlowe place Gilbert upon 
a level with Harvey, Galileo, Gassendi, and Descartes, 2 while 
the celebrated historian of the Council of Trent, Father Paul 
Fra Paolo Sarpi, who will not be thought an incompetent 
judge, names Gilbert, with Francis Vieta (the greatest French 
mathematician of the sixteenth century), as the only original 
writer among his contemporaries. 3 

It is deserving of notice that Gilbert was the first to use 
the terms " electric force," " electric emanations," and "electric 
attraction." He it was, also, who gave the name of "pole" 
to the extremities of the magnetic needle pointing to the 
poles of the earth, calling south pole the extremity that 
pointed toward the north, and north pole the extremity point- 
ing toward the south. In the words of Sir David Brewster, 
Gilbert applies the term magnetic to all bodies which are acted 
upon by loadstones and magnets, in the same manner as they 
act upon each other, and he finds that all such bodies contain 
iron in some state or other. He considers the phenomena of 

1 " Memoirs of the Life of Sir H. Davy," London 1836, Vol. I, page 309. 

2 "Nouvelle Biog. Generate," 1858, Tome VIII, page 494. 

8 Lettere di Fra Paolo, page 31; Hallam, " Introd. to Lit. . . . ", 1839, Vol. 
II, page 464. 



XVI BIOGRAPHICAL MEMOIR. 

electricity as having a considerable resemblance to those of 
magnetism, though he points out the differences by which the 
two classes of phenomena are marked. 

To give here such an analysis as Gilbert's admirable work 
merits would be impracticable, but the short review of it made 
by Dr. John Robison 1 deserves full reproduction as follows : 
" In the introduction, he recounts all the knowledge of the 
ancients on the subject, and their supine inattention to what 
was so entirely in their hands, and the impossibility of ever 
adding to the stock of useful knowledge, so long as men 
imagined themselves to be philos ^phising, while they were only 
repeating a few cant words and the unmeaning phrases of the 
Aristotelian school. It is curious to mark the almost perfect 
sameness of Dr. Gilbert's sentiments and language with those 
of Lord Bacon. They both charge, in a peremptory manner, 
all those who pretend to inform others, to give over their 
dialectic labours, which are nothing but ringing changes on a 
few trite truths, and many unfounded conjectures, and im- 
mediately to betake themselves to experiment. He has 
pursued this method on the subject of magnetism, with 
wonderful ardour, and with equal genius and success ; for Dr. 
Gilbert was possessed both of great ingenuity, and a mind 
fitted for general views of things. The work contains a pro- 
digious number and variety of observations and experiments, 
collected with sagacity from the writings of others, and insti- 
tuted by himself with considerable expense and labour. It 
would indeed be a miracle if all Dr. Gilbert's general infer- 
ences were just, or all his experiments accurate. It was un- 
trodden ground. But, on the whole, this performance con- 
tains more real information than any writing of the age in 

1 " System of Mechanical Philosophy," London 1822, page 209. 



BIOGRAPHICAL MEMOIR. XV11 

which he lived, and is scarcely exceeded by any that has ap- 
peared since. We may hold it with justice as the first-fruits 
of the Baconian or experimental philosophy. 

"This work of Dr. Gilbert's relates chiefly to the load- 
stone, and what v/e call magnets; that is, pieces of steel which 
have acquired properties similar to those of the loadstone. 
But he extends the term magnetism 1 and the epithet 
magnetic, to all bodies which are affected by loadstones and 
magnets, in a manner similar to that in which they affect each 
other. In the course of his investigations, indeed, he finds 
that these bodies are only such as contain iron in some state 
or other ; and in proving this limitation he mentions a great 
variety of phenomena which have a considerable resemblance 
to those which he allows to be magnetical, namely, those 
which he called electrical, because they were produced in the 
same way that amber is made to attract and repel light bodies. 
He marks, with care, the distinctions between these and the 
characteristic phenomena of magnets. He seems to have 
known, that all bodies may be made electrical, while fer- 
ruginous substances alone can be made magnetical. It is not 
saying too much of this work of Dr. Gilbert's to affirm, that it 
contains almost everything that we know about magnetism. 
His unwearied diligence in searching every writing on the 
subject, and in getting information from navigators, and his 
incessant occupation in experiments, have left very few facts 
unknown to him. We meet with many things in the writings 
of posterior enquirers, some of them of high reputation, and 
of the present day, which are published and received as notable 



1 Humboldt states that in Gilbert " we do not find either the abstract ex- 
pression electridtas ', or the barbarous word magnetismus introduced in the 
eighteenth century. "("Cosmos," 1849, Vol. II, page 726, note.) 



XV111 BIOGRAPHICAL MEMOIR. 

discoveries, but are contained in the rich collection of Dr. 
Gilbert. We by no means ascribe all this to mean plagiarism, 
although we know traders in experimental knowledge who are 
not free from this charge. We ascribe it to the general in- 
dolence of mankind, who do not take the trouble of consulting 
originals, where things are mixed with others which they do 
not want, or treated in a way, and with a painful minuteness, 
which are no longer in fashion. We earnestly recommend it to 
the perusal of the curious reader. He will (besides the phi- 
losophy) find more facts in it than in the two large folios of 
Scarella." 

The manner in which " this great man arrived to discover 
so much of magnetical philosophy " and " all the knowledge 
he got on this subject," we are told by Sir Kenelm Digby, 1 
"was by forming a little load-stone into the shape of the earth. 
By which means he compassed a wonderful designe, which was, 
to make the whole globe of the earth maniable ; for he found 
the properties of the whole earth, in that little body ; which 
he therefore called a terrella, or little earth ; a and which he 
could manage and try experiences upon, at his will. And in 
like manner, any man that hath an aim to advance much in 
natural sciences, must endeavour to draw the matter he en- 
quireth of, into some small modell, or into some kinde of 
manageable method ; which he may turn and wind as he 
pleaseth. And then let him be sure, if he hath a competent 
understanding, that he will not misse his mark." 

Amongst the many other ingenious contrivances frequently 
alluded to in his book, Gilbert mentions the versorium, an iron 
needle moving freely upon a point, with which he was enabled 

1 " Treatise of Bodies," 1645, Chap. XX, page 225. 

2 See De Magnete, Book I, Chap. III. 



BIOGRAPHICAL MEMOIR. xix 

to measure excited electricity. He is, besides, the inventor of 
" two most ingenious and necessarie Instruments for Sea men 
to find out thereby the latitude of any place upon sea or land, 
in the darkest night, that is without the helpe of Sunne, Moone 
or Starre." These instruments are described in Thomas Blun- 
derville's quarto work entitled " The Theoriques of the seuen 
Planets, shewing their diuerse motions 1 . . . printed at London 
1602." 

Of the monumental De Magnete, Prof. Robison states 2 that 
he knew of but two British editions and that he had " seen 
five editions published in Germany and Holland before 1628." 
This would make seven editions in all, if the 1600 Amsterdam 
edition which Kuhn alludes to be included. Sir John Leslie, 
however, says' that " Gilbert's original work was republished 
at Ferrara in 1629, with a commentary by Cabaeus." Thus 
are eight distinct editions referred to. Yet, but 

Two editions (1600, 1633) are named by: J. C. Brunet 
(Londini, Sedini) ; J. C. PoggendorfT 5 and "Inter- 
national Encycl." 6 (London, Stettin); "Allgemeine 
Ency." 7 and " Biographic Universelle " 8 (London, 
Sedan) ; 

Three editions (1600, 1628, 1633) are given by W. T. 
Lowndtfs, 9 S. A. Allibone, 10 J. G. T. Graesse," S. P. 

I " Bibliotheca Britannica," Edinburgh 1824, Vol. I, Authors, by R. Watt, 
pages 124 and 414. 

9 "Edinb. Cyclop.," article Gilbert. See J. C. Poggendorff, " Geschichte 
der Physik," Leipsig 1879, page 279. 

3 Fifth Dissert. "Encycl. Brit.", page 741. 
"Manuel du Libraire," Paris 1861, Vol. II, page 1592. 
" Biog. -Liter. Handw.", Leipsig 1863, Vol. I, page 895. 
Vol. VI, page 679, 1892 ed. 7 Leipzig 1858, Sec. I, page 229. 

Bruxelles 1843-1847, Vol. VII, page 253. 
"The Bibliog. Manual," 1859, Part IV, page 890. 

10 "Critical Diet, of Engl. Lit.", 1850, Vol. I, page 668. 

II "Tresor de Livres Rares et Precieux," 1862. 



XX BIOGRAPHICAL MEMOIR. 

Thompson 1 (Londini, Sedini) ; Dr. J. Lament* 
(Londini, Stettin); British Museum Catalogue of 
Printed Books, London 1888 (Londini, Sedani); 
Four editions are alluded to at page 201 of the (1880) 
Catalogue of the Ronalds Library, edited by Alfred 
J. Frost, viz., Londini 1600, Amsterdam 1600, 
Sedini 1628, 1633 ; and 

Five editions appear in Mr. C. W. Cooke's article 3 as fol- 
lows : London 1600, Stettin 1628, 1633, Franckfort 
1629, 1638, the same being specified in the " Ninth 
Britannica," 4 with the difference that Sedan takes 
the place of Stettin. 

The other editions cannot be traced through any of the 

numerous catalogues of public and private libraries, or in the 

records of prominent sales at auction, which have been consulted. 

The above has brought about the question as to the true 

significance of Sedini, with the result following : 

SEDAN, on the Meuse, in France, is given the Latin 
name Sidanum by Mr. Bescherelle, 5 also Sedanum 
in the " Diet. Gog. Port.", 1809, page 617, as well 
as by Em. Bowen, 6 Henry Cotton, 7 and M. Des- 
champs. 8 

STETTIN, on the Oder, in Prussia, is called in Latin 
Stetinum ("Diet. Geog. Port", 1809, page 652; 
Em. Bowen, loc. cit. Vol. I, page 701). See 



" Gilbert of Colchester, an Eliz. Magn.", 1891, pages 43-44. 
"Handb. des Magnetismus," Leipzig 1867, page 434. 
London " Engineering " for the month of December, 1889. 
Volume X, page 592. 

"Grand Diet, de Geog. Univ.", 1857, Tome IV, page 560. 
"Compl. Syst. of Geog.", 1747, Vol. I, page 401. 
" Typog. Gazetteer," 1825, page 146. 
8 "Diet, de Geog.", 1870, page 1158. 



BIOGRAPHICAL MEMOIR. XXI 

Sedinum likewise Sideni, Sidini, Sudeni, in " Lexi- 
con Geog.", 1657, page 361; " Diet. Geog.", Nice 
1791, page 308, "Diet. Geog. Univ.", 1832, pages 
453-454 ; as well as by Larousse, 1 Cotton, 2 Des- 
champs, 3 and W. Smith. 4 Gilbert alludes to the 
Sudini of Prussia, Book 2, Chap. 2. 
SEDINI, Sedinu, Seduni> Sedunum (French Sion, Ger- 
man Sitteri), were names attaching to place and 
people along the banks of the Rhone in Switzer- 
land (Phil. Brietio, " Parallela Geographic," 1648, 
Vol. I, page 347 ; Geo. Long, " Atlas of Class. 
Geog.", 1874, Map VII ; A. G. Findlay, "Classical 
Atlas," 1853, Map XIII ; Alex. Maclean, "Diet, of 
Am. Geog.", 1773 ; Deschamps, loc.cit. page 1161). 

As the French would say, il y en a un peu pour tous les godts, 
but since Wolfgang Lochman(n), the publisher of the editions 
imprinted Sedini 1628 and 1633, was a resident of Stettin 
(J. C. Poggendorff, " Biogr.-Liter. Handw.," 1863, Vol. I, page 
1484), the natural inference to be drawn is that the imprint 
Sedini stands for Stettin, and not for Sedan as many have it. 

In the present volume will be found photo-lithographic 
reproductions of three of the above-named title-pages. That 
of the 1600 Londini is taken from the copy of Mr. Charles 
L. Clarke, whereto allusion is made hereafter, while the 
1628 Sedini is reproduced from the copy in the library 
of the English Institute of Electrical Engineers, and the 
1633 Sedini from the copy belonging to Dr. Park Benja- 
min of New York City. The 1628 is the most elaborate 

1 "Grand Diet. Univ. ",.1875, Tome XIV, pages 477, 1099. 
* H. Cotton, loc. tit. page 152. 

3 Deschamps, he. tit. pages 1161, 1175. 

4 "Diet, of Gr. and Rom. Geog.", 1857, Vol. II, pages 995, 1042. 



XX11 BIOGRAPHICAL MEMOIR. 

of all known Gilbert title-pages. As described by Prof. Sir 
Wm. Thomson (Lord Kelvin), it is " in the form of a monu- 
ment, ornamented with commemorative illustrations of Gil- 
bert's theory and experiments, and a fantastic indication of 
the earliest European mariner's compass, a floated loadstone, 
but floating in a bowl on the sea and left behind by the ship 
sailing away from it ! In the upper left-hand corner is to be 
seen Gilbert's terrella and or bis virtutis. 1 The terrella is a lit- 
tle globe of loadstone, which he made to illustrate his idea that 
the earth is a great globular magnet. . . . The orbis virtutis 
is simply Gilbert's expression for what Faraday called the field 
of force, that is to say, the space round a magnet, in which 
magnetic force is sensibly exerted on another magnet, as, for 
instance, a small needle, properly placed for the test. Gil- 
bert's word virtue expresses even more clearly than Faraday's 
word force the idea urged so finely by Faraday, and proved so 
validly by his magneto-optic experiment, that there is a real 
physical action of a magnet through all the space round it tho' 
no other magnet be there to experience force and show its 
effects." The meaning of the little bars bordering the terrella 
is explained in Gilbert's book (Lib. I, cap. iii, and Lib. V, 
cap. ii), where he alludes to the application of bits of fine iron 
wire as long as a barley-corn, etc., etc. 

After the death of Queen Elizabeth, March 24, 1603, Gil- 
bert was continued in his position as royal physician by King 
James I., but he survived his benefactress only a few months; 
he died, some say at Colchester, others at London, on the 3Oth 
November of the same year. He was buried in the chancel of 
the Church of the Holy Trinity in Colchester, where a monu- 



1 See cuts of Orbis Virtutis in De Magnete, Book II, Chapters VI and 
XXVII, also Book V, Chap. II. 



BIOGRAPHICAL MEMOIR. xxiii 

ment 1 was erected to him by his brothers, who placed upon 
it a Latin inscription 2 which appears at page 79 of Doctor 
Munk's " Roll of the Royal College of Physicians," London 
1878. Dr. B. W. Richardson has translated the inscription as 
follows : 

Ambrose and William Gilberd have placed this tomb In memory of 
brotherly piety, To William Gilberd, Senior, Gentleman, and doctor of 
medicine. This, the eldest son of Jerome Gilberd, Gentleman, was born 
in the town of Colchester, studied the art of medicine at Cambridge, 
practiced the same for more than thirty years at London, with singular 
credit and success. Hence called to Court, he was received with highest 
favor by Queen Elizabeth, to whom, and to her successor James, he 
served as chief physician. He composed a book celebrated among for- 
eigners concerning the magnet for nautical science. He died in the 
year of the Human Redemption 1603, the last day of November, in the 
63d year of his age. 

The inscription is thus rendered by Thos. Wright, at pages 
310-31 1, Vol. I, of his (London 1836) " Hist, and Topog. of the 
County of Essex:" 

Ambrose and William Gilberd erected this monument to William 
Gilberd, senior, esq., and doctor of physic, in memory of his fraternal 
affection. He was the eldest son of Jerom Gilberd, Esq., born in the 
town of Colchester, studied physic at Cambridge, and practised at Lon- 
don more than thirty years with the greatest applause, and equal suc- 
cess. And being sent for to Court, he was received into the highest 
favor by Queen Elizabeth, to whom as also to her successor, James, he 
was principal physician. He wrote a book concerning the magnet, 
much celebrated by those engaged in nautical affairs. He died in the 
year of Human Redemption 1603 on the last day of November, in the 
63d year of his age. 

1 An engraving of this monument is given in Philip Morant's " History 
of Colchester," and it is described (" Diet, of Nat. Biog.", London 1890, Vol. 
XXI, page 338) as being "a. panel surrounded by a frame of Jacobean pattern, 
surmounted by pinnacles bearing globes and 14 shields of armorial achieve- 
ments." 

9 "The epitaph thereon is very unelegant and hardly latin.. . "(Biog. 
Brit., London 1757, Vol. IV, page 2203.) 



XXIV BIOGRAPHICAL MEMOIR. 

Gilbert was never married. He bequeathed to the College 
of Physicians " all the books in his library, his globes, instru- 
ments and cabinets of minerals." These were, unfortunately, 
consumed in the great London fire of 1666. To the University 
of Oxford he left a portrait which he is said to have ordered 
made of himself for the purpose and which was " placed in 
the Gallery over the Schools." ] In this portrait, which is be- 
lieved to have been destroyed, 3 he appears standing in his 
doctor's robes " holding in his hand a globe inscribed terrella, 
whilst over his head is the inscription * 1591, aetatis 48,' and, a 
little below his left shoulder, the words ' Magneticarum virtu- 
tum, primus indagator Gilbertus.' " 3 

The reader is shown in the frontispiece a copy of the only 
portrait of Gilbert known at this day. It was taken from Vol. 
II, page 33, of S. and E. Harding's " Biographical Mirrour," 
and is said to have been engraved by Clamp " from an original 
picture in the Bodleian Library, Oxford." 4 As will be seen, it 
lacks the inscriptions before spoken of and represents Gilbert 
holding his hand upon an ordinary globe. It was the central 
portion of this picture which was utilized by Mr. Arthur Ack- 
land Hunt for his well-known historical painting, representing 
Gilbert making an experimental demonstration in electricity 
before Queen Elizabeth. 

Speaking of Gilbert, Dr. Fuller writes : " One saith of him 
that he was Stoicall, but not Cynicall, which I understand 



1 " The picture of this famous doctor, drawn to the life, is hanging in the 
school-gallery at Oxon" (Athena Oxonienses, by Anthony a Wood [ist edi- 
tion, 1691-2], London 1813, Vol. I, page 738). 

2 Wood says "decayed and removed," at page 96, Vol. II, of the 1796 
" Hist, and Antiq. of the Univ. of Oxford." 

3 Ninth "Encycl. Brit.", article Gilbert. 

4 Dr. Munk's " Roll of the Roy. Col. of Physicians," 1878, page 79; " Diet. 
of Nat. Biog.", London 1890, VoL XXI, page 338. 



BIOGRAPHICAL MEMOIR. XXV 

Reserved, but not Morose, never married, purposely to be more 
beneficial to his brethren. Such his Loyalty to the Queen that, 
as if unwilling to survive, he dyed in the same year with her, 
1603. His Stature was Tall, Complexion Chearful, an Happi- 
ness not ordinary in so hard a student and retired a person." 

Besides Gilbert's folio De Magnete, there appeared at Am- 
sterdam, in 1651, a quarto volume of 316 pages entitled De 
Mundo Nostro Sublunari Philosophia Nova, which was edited, 
some say by his brother William Gilbert Junior according to 
others, by the eminent English scholar and critic John Gruter 
from two MSS. found in the library of Sir Wm. Boswell, 
Knight. According to Dr. John Davy, " this work of Gil- 
bert's, which is so little known, is a very remarkable one, both 
in style and matter ; and there is a vigour and energy of ex- 
pression belonging to it very suitable to its originality. Pos- 
sessed of a more minute and practical knowledge of natural 
philosophy than Bacon, his opposition to the philosophy of the 
schools was more searching and particular, and at the same 
time probably little less efficient." ' In the opinion of Prof. 
John Robison, De Mundo consists of an attempt to establish 
a new system of natural philosophy upon the ruins of the Aris- 
totelian doctrine. We give an extract from the work, in a 
footnote to the present translation of Gilbert's De Magnete, 
Book VI, Chap. VII, and are also enabled to give a reproduc- 
tion of the 1651 title-page made through the courtesy of Dr. 
Park Benjamin. 

The only known writing of Gilbert in English is in the form 
of a letter dated I4th Februrary (? 1602) which appears at the 
end of William Barlowe's " Magneticall Advertisements or 

1 "Memoirs of the Life of Sir Humphry Davy," London 1836, Vol. I, 
page 311. 



xxvi BIOGRAPHICAL MEMOIR. 

divers observations concerning the loadstone," quarto, Lon- 
don 1616, and reads as follows : 

To the Worship/nil my good friend, Mr. William Barlowe at Easton by 

Winchester. 

Recommendations with many thanks for your paines and courtesies, 
for your diligence and enquiring, and finding diuers good secrets, I pray 
proceede with double capping your load-stone you speake of, I shall bee 
glad to see you, as you write, as any man, I will haue any leisure, if it 
were a moneth, to conferre with you, you have shewed mee more and 
brought more light than any man hath done. Sir, I will commend you 
to my L. of Efnngham, there is heere a wise learned man, a Secretary of 
Venice, he came sent by that State, and was honourably received by her 
Majesty, he brought me a lattin letter from a Gentle-man of Venice that 
is very well learned, whose name is Johannes Franciscus Sagredus, he 
is a great Magneticall man, and writeth that hee hath conferred with 
diuers learned men of Venice and with the Readers of Padua, and re- 
porteth wonderfull liking of my booke, you shall haue a coppy of the 
letter: Sir, I propose to adioyne an appendix of six or eight sheets of 
paper to my booke after a while, I am in hand with it of some new in- 
uentions, and I would haue some of your experiments, in your name 
and inuention put into it, if you please, that you may be knowen for an 
augmenter of that art. So for this time in haste I take my leaue the 
xiiyth of February. 

Your very louing friend, 

W. GILBERT. 

His intention to print the short appendix was never car- 
ried into effect. 

Professor Silvanus P. Thompson states (" Gilbert of Col- 
chester . . . ", London 1891, page 40) that "with the exception 
of a single doubtful inscription, * ex dono auctoris] in a single 
copy of De Magnete, not a line of his [Gilbert's] handwrit- 
ing is known to exist, unless his hand wrote the signature 
* Ye President and Societie ' at the end of a Petition, preserved 
amongst the manuscripts in the British Museum, addressed by 
the Royal College of Physicians in 1596 to the Lords of the 
Privy Council, complaining of the exactions of the Lord 
Mayor and Aldermen of London. It is pretty certain that 



BIOGRAPHICAL MEMOIR. XXVli 

the MS. copy of De Mundo in the British Museum is not in 
the author's handwriting ; for in the Elzevir Print there is a 
note stating that the author's original manuscript was partly 
in English." ' It is unfortunate that Prof. Thompson's atten- 
tion should not at the time have been called to the fact that 
Mr. Bernard Quaritch's Rough List No. 99, for September 
1889, offered at page 80 No. 747 a 1600 De Magnete "Pres- 
entation copy from the author, with inscription on title Dedit 
Guil. Gilbertus Jo. Sherwood propriis manibus" This copy, 
which formerly belonged to Mr. Wm. Constable, F.R.S. and 
F.A.S., is now the property of Mr. Chas. L. Clarke, C.E., New 
York City, through whose courtesy the reproduction of the title 
bearing the inscription appears at page iii. A comparison of 
the writing in both inscriptions would prove interesting. 

" Mahomet's Tombe at Mecha is said strangely to hang 
up, attracted by some invisible Load-stone, but the memory of 
the Doctor will never fall to the ground, which his incompar- 
able Book De Magnete will support to Eternity." a 

In his epistle 3 to Dr. Walter Charleton (physician in ordi- 
nary to King Charles L), the celebrated English poet, John 
Dryden, predicts that 

" Gilbert shall live till loadstones cease to draw, 
Or British fleets the boundless ocean awe." 

1 " A copy in MS. among the Royal collection in the British Museum. . . . 
It consists of five books and is written on paper." (Casley's Catalogue, page 212.) 
The work is alluded to at page 283 " Les Elzevier," Alph. Willems, Bruxelles 
1880, also at page 203 of Ann. de Impr. Elsevirienne, Chas. Pieters, Gand 
1851. 

2 Dr. Thomas Fuller, " The History of the Worthies of England," London 
1840, page 515. See references to Mahomet's Shrine: in Gilbert's De Magnete, 
1600, Book I, Chap. I; in Porta's ^Natural Magick," 1658, Book VII, Chap. 
XXVII; in Sir Thomas Brown's Pseudoloxia, Epidemica, 1658, Book II, pages 
78-79; in Cabaeus, Philosophia Magnetica, 1629, Lib. IV, Chap. XVIII, page 335. 

8 Epistle the Third, at page 15, Vol. XI, of the Works of John Dryden, 
London 1803. 



CONTENTS. 



PAGE 

Translator's Preface - v 

Biographical Memoir ix 

Address by Edward Wright xxxviii 

Author's Preface , . . xlvii 

Explanation of some Terms used in this Work liii 

BOOK I. 

Chapter I. Writings of ancient and modern authors concerning the load- 
stone : various opinions and delusions I 

II. The loadstone: what it is: its discovery 15 

III. The loadstone possesses parts differing in their natural powers, 

and has poles conspicuous for their properties 22 

IV. Which pole is the north: how the north pole is distinguished 

from the south pole 26 

V. One loadstone appears to attract another in the natural posi- 
tion; but in the opposite position repels it and brings it to 

rights 28 

VI. The loadstone attracts iron ore as well as the smelted metal. . . 31 

VII. What iron is; what its matter; its use 33 

VIII. In what countries and regions iron is produced 43 

IX. Iron ore attracts iron ore 46 

X. Iron ore has and acquires poles, and arranges itself with refer- 
ence to the earth's poles , 47 

XI. Wrought-iron, not magnetized by the loadstone, attracts iron. 48 
XII. A long piece of iron, even not magnetized, assumes a north 

and south direction 50 

XIII. Smelted iron has in itself fixed north and south parts, magnetic 

activity, verticity, and fixed vertices or poles 51 

XIV. Of other properties of the loadstone and of its medicinal virtue 52 
XV. The medicinal power of the iron 55 

XVI. That loadstone and iron ore are the same, and that iron is ob- 
tained from both, like other metals from their ores; and 
that all magnetic properties exist, though weaker, both in 

smelted iron and in iron ore 59 

xxxi 



XXX11 CONTENTS. 

PAGE 

XVII. That the terrestrial globe is magnetic and is a loadstone; and, 
just as in our hands the loadstone possesses all the prim- 
ary powers (forces) of the earth, so the earth by reason of 
the same potencies lies ever in the same direction in the 
universe 64 

BOOK II. 

Chapter I. Of magnetic movements 72 

II. Of magnetic coition, and, first, of the attraction exerted by 
amber, or, more properly, the attachment of bodies to 
amber 74 

III. Opinions of others concerning magnetic coition, which they call 

attraction 97 

IV. Of the strength of a loadstone and its form: the cause of coition 105 
V. In what manner the energy inheres in the loadstone 11$ 

VI. How magnetized iron and smaller loadstones conform to the 

terrella, and to the earth itself, and are governed thereby. 121 
VII. Of the potency of the magnetic force, and of its spherical ex- 
tension 123 

VIII. Of the geography of the earth and the terrella 124 

IX. Of the equinoctial circle of earth and terrella 126 

X. The earth's magnetic meridians 126 

XL Parallels 127 

XII. The magnetic horizon I2& 

XIII. Of the magnetic axis and poles 128- 

XIV. Why the coition is stronger at the poles than in the parts be- 

tween equator and pole; and the relative power of coition 

in different parts of the earth and the terrella 129 

XV. The magnetic force imparted to iron is more apparent in an 
iron rod, than in an iron sphere, or cube, or iron of any 

other shape 131 

XVI. That motion is produced by the magnetic force through solid 

bodies interposed: of the interposition of a plate of iron. 132 
XVII. Of the iron helmet (cap) of the loadstone, wherewith it is 
armed at the pole to increase its energy; efficiency of the 

same 137 

XVIII. An armed loadstone does not endow with greater force mag- 
netized iron than does an unarmed one 13$ 

XIX. That unition is stronger with an armed loadstone: heavier 
weights are thus lifted : the coition is not stronger, but 

commonly weaker 139 

XX. That an armed magnet lifts another, and that one a third : this 

holds good though there be less energy in the first 139 

XXI. That when paper or other medium is interposed, an armed load- 
stone does not lift more than one unarmed 140 



CONTENTS. XXX111 

PAGE 

XXII. That an armed loadstone does not attract more than an un- 
armed one; and that the armed stone is more strongly 
united to the iron, is shown by means of an armed load- 
stone and a cylinder of polished iron 140 

XXIII. The magnetic force makes motion toward union, and when 

united connects firmly 142 

XXIV. That iron within the field of a loadstone hangs suspended in air, 

if on account of an obstacle it cannot come near 143 

XXV. Intensifying the loadstone's forces 145 

XXVI. Why the love of iron and loadstone appears greater than that of 
loadstone and loadstone, or iron and iron when nigh a 

loadstone and within its field 148 

XXVII. That the centre of the magnetic forces in the earth is the centre 

of the earth; and in the terrella the terrella's centre 150 

XXVIII. That a loadstone does not attract to a fixed point or pole only, 
but to every part of a terrella, except the equinoctial 

circle 151 

XXIX. Of difference of forces dependent on quantity or mass 152 

XXX. The shape and the mass of an iron object are important in 

magnetic coitions 152 

XXXI. Of oblong and round stones 154 

XXXII. Some problems and magnetic experiments on the coition, and 

repulsion, and regular movement of magnetic bodies .... 155 

XXXIII. Of the difference in the ratio of strength and movement of 

coition within the sphere of influence 161 

XXXIV. Why a loadstone is of different power in its poles as well in the 

north as in the south regions 164 

XXXV. Of a perpetual-motion engine actuated by the attraction of a 

loadstone, mentioned by authors 166 

XXXVI. How a strong loadstone may be recognized 167 

XXXVII. Uses of the loadstone as it affects iron 169 

XXXVIII. Of the attractions of other bodies 170 

XXXIX. Of mutually repellent bodies 175 

BOOK III. 

Chapter I. Of direction 177 

II. Directive (or versorial) force, which we call verticity: what it is; 
how it resides in the loadstone; and how it is acquired 
when not naturally produced 183 

III. How iron acquires verticity from the loadstone, and how this 

verticity is lost or altered 189 

IV. Why magnetized iron takes opposite verticity: and why iron 
touched by the true north side of the stone moves to the 
earth's north, and when touched by the true south side to 



XXXIV CONTENTS. 

PAGE 

the earth's south: iron rubbed with the north point of the 
stone does not turn to the south, nor vice versa, as all 

writers on the loadstone have erroneously thought 192 

V. Of magnetizing stones of different shapes 197 

VI. What seems to be a contrary movement of magnetic bodies is 

the regular tendence to union 198 

VII. A determinate verticity and a directive power make magnetic 
bodies accord, and not an attractional or a repulsive force, 

nor strong coition alone, or unition 200 

VIII. Of disagreements between pieces of iron on the same pole of 
a loadstone; how they may come together and be con- 
joined 201 

IX. Directional figures showing the varieties of rotation 204 

X. Of the mutation of verticity and magnetic properties, or of the 

alteration of the force awakened by the loadstone 208 

XI. Of friction of iron with the mid parts of a loadstone between 

the poles, and at the equinoctial circle of a terrella 210 

XII. How verticity exists in all smelted iron not excited by the load- 
stone 211 

XIII. Why no other bodies save the magnetic are imbued with ver- 

ticity by friction with a loadstone; and why no body 
not magnetic can impart and awaken that force 217 

XIV. The position of a loadstone, now above, anon beneath, a mag- 

netic body suspended in equilibrium, alters neither the 

force nor the verticity of the magnetic body 219 

XV. The poles, equator, centre, are permanent and stable in the un- 
broken loadstone, when it is reduced in size and a part 

taken away, they vary and occupy other positions 220 

XVI. If the south part of a loadstone have a part broken off, some- 
what of power is taken away from the north part also 222 

XVII. Of the use of rotary needles and their advantages; how the di- 
rective iron rotary needles of sun-dials and the needles of 
the mariner's compass are to be rubbed with loadstone in 
order to acquire stronger verticity 223 

BOOK IV. 

Chapter I. Of variation 229 

II. That variation is due to inequality among the earth's eleva- 
tions 235 

III. Variation is constant at a given place 240 

IV. The arc of variation does not differ according to distance be- 
tween places 242 

V. An island in ocean does not alter in variation; neither do 

mines of loadstone 243 



CONTENTS. XXXV 

PAGE 

VI. That variation and direction are due to the controlling force of 
the earth and the rotatory magnetic nature, not by an at- 
traction or a coition or by other occult cause 244 

VII. Why the variation due to this lateral cause is not greater than 
hitherto it has been observed to be, seldom appearing to 
amount to two points of the compass, except near the 

poles 246 

VIII. Of the construction of the common mariner's compass, and of 

the different compasses of various nations 248 

IX. Whether terrestrial longitude can be found from variation .... 251 
X. Why in various places near the pole the variations are much 

ampler than in lower latitudes 254 

XI. Cardan's error in seeking to determine the distance of the 
earth's centre from the centre of the world by means of the 

loadstone (in his De Proportionibus,V) 255 

XII. Of finding the amount of the variation; what the quantity is of 
the arc of the horizon from its arctic or antarctic intersec- 
tion by a meridian to the point toward which the needle 
turns 256 

XIII. Observations made by seamen commonly vary and are untrust- 

worthy, partly though mistakes and want of knowledge 
and the imperfectness of the instruments, and partly be- 
cause the sea is seldom so calm but shadows or lights 
may rest on the instruments 265 

XIV. Of the variation under the equinoctial line and nearby 267 

XV. The variation of the magnetized needle in the great sea, 

Ethiopic and American, below the equator 267 

XVI. Of the variation in Nova Zembla 269 

XVII. Variation in the South Sea 270 

XVIII. Of the variation in the Mediterranean Sea 270 

XIX. The variation in the interior of the great continents 271 

n XX. The variation in the Eastern Ocean 272 

XXI. How the deviation of the needle is greater or less according to 

the distance of places 273 

BOOK V. 

Chapter I. Of the dip of the magnetic needle . , 275 

II. Diagram showing dip of the magnetic needle in different posi- 
tions of a sphere and horizons of the earth in which 

there is a variation of dip 282 

III. An instrument for showing by the action of a loadstone the 
degree of dip below the horizon in any latitude. Descrip- 
tion of the instrument; its uses 285 

IV. Of a suitable length of needle on the terrella for showing the 

dip 288 



XXXVI CONTENTS. 

PAGE 

V. That dip is not caused by the attraction of a loadstone but by 

its power of giving direction and rotation 289 

VI. Of the ratio of the dip to latitude and the causes thereof 292 

VII. Explanation of the diagram of the rotation of magnetized iron. 295 
VIII. Diagram of the rotation of magnetized iron showing the mag- 
netic dip in all latitudes, and showing the latitude from 

the rotation and dip 297 

IX. Demonstration of direction, or of variation from the true di- 
rection, together with dip, simply by the movement in 

water, due to the power of controlling and rotating 301 

X. Of variation of dip 303 

XL Of the formal magnetic act spherically effused 304 

XII. The magnetic force is animate, or imitates a soul; in many re- 
spects it surpasses the human soul while that is united to 
an organic body 308 

BOOK VI. 

Chapter I. Of the globe of earth as a great loadstone 313 

II. The magnetic axis of the earth remains invariable 315 

III. Of the daily magnetic revolution of the globes, as against the 
time-honored opinion of a primum mobile: a probable 

hypothesis 317 

IV. That the earth hath a circular motion 327 

V. Arguments of those who deny the earth's motion, and refuta- 
tion thereof 335 

VI. Of the cause of the definite time of the total revolution of the 

earth 343 

VII. Of the earth's primary magnetic nature whereby her poles are 

made different from the poles of the ecliptic 347 

VIII. Of the precession of the equiuoxes by reason of the magnetic 
movement of the earth's poles in the arctic and antarctic 

circle of the zodiac 348 

IX. Of the anomaly of the precession of the equinoxes and of the 

obliquity of the zodiac 352 



To the most learned Mr. William Gilbert, the distinguished Lon- 
don physician and father of the magnetic philosophy : a 
laudatory address concerning these books on magnetism, by 
Edward Wright. 

Should there be any one, most worthy sir, who shall dis- 
parage these books and researches of yours, and who shall 
deem these studies trifling and in no wise sufficiently worthy 
of a man consecrated to the graver study of medicine, of a 
surety he will be esteemed no common simpleton. For that 
the uses of the loadstone are very considerable, yea admirable, 
is too well known even among men of the lowest class to call 
for many words from me at this time or for any commenda- 
tion. In truth, in my opinion, there is no subject-matter of 
higher importance or of greater utility to the human race 
upon which you could have brought your philosophical talents 
to^bear. For by the God-given favor of this stone has it come 
about that the things which for so many centuries lay hid 
such vast continents of the globe, so infinite a number of 
countries, islands, nations and peoples have been, almost 
within our own memory, easily discovered and oft explored, 
and that the whole circle of the globe has been circumnavi- 
gated more than once by our own Drake and Cavendish : 
which fact I wish to record for the undying remembrance of 
those men. For, by the showing of the magnetized needle, 
the points North, South, East and West and the other points 

of the compass are known to navigators, even while the sky is 

xxx vii 



XXXV111 ADDRESS BY EDWARD WRIGHT. 

murky and in the deepest night ; by this means seamen have 
understood toward what point they must steer their course, a 
thing that was quite impossible before the wondrous discovery 
of the north-pointing power of the loadstone. Hence sailors 
of old were often beset, as we learn from the histories, by an 
incredible anxiety and by great peril, for, when storms raged 
and the sight of sun and stars was cut off, they knew not 
whither they were sailing, neither could they by any means 
or by any device find out. Hence what must have been the 
gladness, what the joy of all mariners when first this magnetic 
pointer offered itself as a most sure guide on the route and as 
a God Mercury ! But it was not enough for this magnetic 
Mercury simply to point out the way and, as it were, to show 
by the extended finger whither the course must be : it soon 
began even to indicate the distance of the place whither the 
voyage is made. For, since the magnetic pointer does not 
always regard the same northern spot in every locality, but 
usually varies therefrom, either to the east or to the west, tho' 
it nevertheless hath and holds ever the same variation in the 
same place, wherever that may be ; it has come about that by 
means of this variation (as it is called) closely observed and 
noted in certain maritime regions, together with an observa- 
tion of the latitude, the same places can afterward be found 
by navigators when they approach and come near to the same 
variation. Herein the Portuguese in their voyages to the 
East Indies have the surest tokens of their approaching the 
Cape of Good Hope, as is shown in the narrations of Hugo 
Lynschetensis 1 and our very learned fellow-countryman Richard 
Hakluyt; hereby, too, many of our skilled British navi- 
gators when voyaging from the Gulf of Mexico to the Azores, 

1 Jan Hugo van Linscho(o)ten, Dutch voyager, 1563-1633. 



ADDRESS BY EDWARD WRIGHT. XXXIX 

can tell when they are come near to these islands, though, 
according to their marine charts, they may appear to be 600 Eng- 
lish miles away. And thus, thanks to this magnetic indication, 
that ancient geographical problem, how to discover the longi- 
tude, would seem to be on the way to a solution ; for, the 
variation of a seaboard place being known, that place can there- 
after be very easily found as often as occasion may require, 
provided its latitude is not unknown. 

Yet somewhat of inconvenience and difficulty seems to at- 
tach to this observation of the variation, for it cannot be made 
except when the sun or the stars are shining. Accordingly 
this magnetic Mercury of the sea, better far than Neptune 
himself or any of the sea gods or goddesses, proceeds still 
further to bestow blessings on all mariners ; and not alone in 
the darkness of night and when the sky is murky does he show 
the true direction, but he seems even to give the surest indica- 
tions of the latitude. For the iron pointer suspended freely 
and with the utmost precision in equilibrium on its axis, and 
then touched and excited with a loadstone, dips down to a 
fixed and definite point below the horizon (e.g. in the latitude 
of London it dips nearly 72 degrees) and there stands. But 
because of the wonderful agreement and congruency mani- 
fested in nearly all and singular magnetic experiments, equally 
in the earth itself and in a terrella (i.e. a spherical loadstone), it 
seems (to say the least) highly probable and more than prob- 
able that the same pointer (similarly stroked with a loadstone) 
will, at the equator, stand in equilibrium on the plane of the 
horizon. Hence, too, it is highly probable that in proceeding a 
very short distance from south to north (or vice versa) there 
will be a pretty sensible change in the dip ; and thus the dip 
being carefully noted once and the latitude observed, the same 
place and the same latitude may thereafter be very readily 



xl ADDRESS BY EDWARD WRIGHT. 

found by means of a dip instrument even in the darkest night 
and in the thickest weather. 

Thus then, to bring our discourse back again to you, most 
worthy and learned Mr. Gilbert (whom I gladly acknowledge as 
my master in this magnetical philosophy), if these books of 
yours on the Loadstone contained nought save this one method 
of finding the latitude from the magnetic dip, now first pub- 
lished by you, even so our British mariners as well as the 
French, the Dutch, the Danes, whenever they have to enter the 
British sea or the strait of Gibraltar from the. Atlantic Ocean, 
will justly hold them worth no small sum of gold. 1 And that 
discovery of yours, that the entire globe is magnetical, albeit 
to many it will seem to the last degree paradoxical, never- 
theless is buttressed and confirmed by so many and so apposite 
experiments in Book II, Chapter XXXIV ; Book III, Chap- 
ters IV and XII ; and throughout nearly the whole of Book 
V, that no room is left for doubt or contradiction. I come 
therefore to the cause of magnetic variation a problem that 
till now has perplexed the minds of the learned ; but no one 
ever set forth a cause more probable than the one proposed 
now for the first time in these your books on the Loadstone. 
The fact that the magnetic needle points due north in the 
middle of the ocean and in the heart of continents or at least 

1 Hardly twenty years after the English artificer, Robert Norman, had, 
in 1576, devised the indinatorium, which enabled him to determine the dip or 
inclination of the magnetic needle, Gilbert boasted that, by means of this in- 
strument, he could ascertain a ship's place in dark starless nights. Gilbert 
commends the method as applicable aere caliginoso; and Edward Knight, the 
English mathematician, in the introduction which he added to his master's 
great work, describes this proposal as "worth much gold." Having fallen into 
the same error with Gilbert! of presuming that the isoclinal lines coincided with 
the geographical parallel circles, and that the magnetic and geographical equa- 
tors were identical, he did not perceive that the proposed method had only a 
local and very limited application (Humboldt, Cosmos, 1849, Vol. I, page 172, 
and Vol. II, page 658). 



ADDRESS BY EDWARD WRIGHT. xll 

in the heart of their more massive and more elevated parts 
while near the coasts there is, afloat and ashore, an inclination 
of the needle toward those more massive parts, just as happens 
in a terrella that is made to resemble the earth globe in its 
greater elevation at some parts and shows that it is weak or 
decayed or otherwise imperfect elsewhere : all this makes ex- 
ceedingly probable the theory that the variation is nothing 
but a deviation of the magnetic needle to those more powerful 
and more elevated regions of the globe. Hence the reason of 
the irregularity that is seen in the variations of the compass 
is easily found in the inequality and anomaly of those more 
elevated parts. Nor do I doubt that all those who have 
imagined or accepted certain " respective points " as well as 
they who speak of magnetic mountains or rocks or poles, will 
begin to waver as soon as they read these your books on the 
Loadstone and will of their own accord come over to your 
opinion. 

As for what you have finally to say of the circular motion 
of the earth and the terrestrial poles, though many will deem 
it the merest theorizing, still I do not see why it should not 
meet with indulgence even among those who do not acknowl- 
edge the earth's motion to be spherical, seeing that even they 
cannot readily extricate themselves from the many difficulties 
that result from a diurnal motion of the whole heavens. For, 
first, it is not reasonable to have that done by many agents 
which can be done by fewer, or to have the whole heavens 
and all the spheres (if spheres there be) of the planets and fixed 
stars made to revolve for the sake of the diurnal motion, which 
may be accounted for by a daily rotation of the earth. Then, 
which theory is the more probable, that the equinoctial circle 
of the earth may make a rotatary movement of one quarter of 
an English mile (60 miles being equal to one degree on the 



xlii ADDRESS BY EDWARD WRIGHT. 

earth's equator) in one second of time, i.e., in about as much 
time as it takes to make only one step when one is walking 
rapidly; or that the equator of the primum mobile in the same 
time, with inexpressible celerity, makes 5000 miles and that in 
the twinkling of an eye it makes about 50 English miles, sur- 
passing the velocity of a flash of lightning, if they are in the 
right who most strenuously deny the earth's motion ? Finally, 
which is the more probable, to suppose that this little globe 
of the earth has some motion, or with mad license of conjec- 
ture to superpose three mighty starless spheres, a ninth, a 
tenth, and an eleventh, 1 upon the eighth sphere of the fixed 
stars, particularly when from these books on the Loadstone and 
the comparison of the earth with the terrella it is plain that 
spherical motion is not so contrary to the nature of the earth 
as it is commonly supposed to be ? 

Nor do the passages quoted from Holy Writ appear to con- 
tradict very strongly the doctrine of the earth's mobility. It 
does not seem to have been the intention of Moses or the 
prophets to promulgate nice mathematical or physical distinc- 
tions : they rather adapt themselves to the understanding of 
the common people and to the current fashion of speech, as 
nurses do in dealing with babes ; they do not attend to unessen- 
tial minutiae. Thus, Genesis i. 16 and Psalm cxxxvi. 7, 9, the 
moon is called a great luminary, because it so appears to us, 
though, to those versed in astronomy, it is known that very 
many stars, fixed and planetary, are far larger. So, too, from 
Ps. civ. 5, 3 no argument of any weight can, I think, be drawn 
to contradict the earth's mobility, albeit it is said that God es- 
tablished the earth on her foundations to the end it should never 

1 See note, Book VI, Chap. III. 

2 Psalm civ. 5, " Who laid the foundations of the earth, that it should not 
be removed forever." 



ADDRESS BY EDWARD WRIGHT. xliii 

be moved ; for the earth may remain forevermore in its own 
place and in the selfsame place, in such manner that it shall not 
be moved away by any stray force of transference, nor carried 
beyond its abiding place wherein it was established in the 
beginning by the divine architect. We, therefore, while we 
devoutly acknowledge and adore the inscrutable wisdom of the 
triune Godhead, having with all diligence investigated and dis- 
cerned the wondrous work of his hands in the magnetic move- 
ments, do hold it to be entirely probable, on the ground of 
experiments and philosophical reasons not few, that the earth 
while it rests on its centre as its basis and foundation, hath a 
spherical motion nevertheless. 

But, apart from these matters (touching which no one, I do 
believe, ever gave more certain demonstrations), no doubt your 
discussion if the causes of variation and of the dip of the needle 
beneath the horizon (to say nothing of sundry other points 
which 'twould take too long to mention) will find the heartiest 
approval among all intelligent men and " children of magnetic 
science " (to use the language of the chemists). Nor have I any 
doubt that, by publishing these your books on the Loadstone, 
you will stimulate all wide-awake navigators to give not less 
study to observation of dip than of variation. For it is highly 
probable, if not certain, that latitude, or rather the effect of lati- 
tude, can be determined much more accurately (even when the 
sky is darkest) from the dip alone, than longitude or the effect 
of longitude can be found from the variation even in the full 
light of day or while all the stars are shining, and with the help 
of the most skilfully and ingeniously contrived instrument. 
Nor is there any doubt that those most learned men, Petrus 
Plantius 1 (a most diligent student not so much of geography as 

1 Peter Plancius, Dutch theologian and astronomer, 1552-1622. 



xliv ADDRESS BY EDWARD WRIGHT. 

of magnetic observations) and Simon Stevinius, 2 a most eminent 
mathematician, will be not a little rejoiced when first they set 
eyes on these your books and therein see their own \i}Jivev- 
periKrjv or method of finding ports so greatly and unexpect- 
edly enlarged and developed ; and of course they will, as far as 
they may be able, induce all navigators among their own coun- 
trymen to note the dip no less than the variation of the 
needle. 

Let your magnetic Philosophy, most learned Mr. Gilbert, go 
forth then under the best auspices that work held back not 
for nine years only, according to Horace's Counsel, but for 
almost other nine ; that Philosophy which by your multitudi- 
nous labors, studies, vigils, and by your skill and at your no 
inconsiderable expense has been after long years at last, by 
means of countless ingenious experiments, taken bodily out of 
the darkness and dense murkiness with which it was surrounded 
by the speculations of incompetent and shallow philosophizers ; 
nor did you in the mean time overlook, but did diligently read 
and digest whatever had been published in the writings whether 
of the ancients or the moderns. Let it not be afraid to face 
the prejudiced censure of any supercilious and dastardly phi- 
losophaster who, by enviously faulting another's work or by 
fraudulently taking the credit to himself, strives to win a most 
unsubstantial renown ; for 

Ingenium magni livor detrectat ffomeri, 

(Envy detracts from the genius of mighty Homer; 

2 Simon Stevin Stevinus celebrated Flemish mathematician (1548-1628), 
published in 1586 his well-known work on statics and hydrostatics, in the pref- 
ace of which he endeavors to prove that the Dutch language is more ancient 
than any other. This work was soon followed by others, including his De Motu 
Cceli, and, in 1599, by his Dutch treatise on navigation, translated in Latin by 
Grotius and published in Leyden. See references made at page 486 of the 
Ronalds Library Catalogue, likewise note Book Iv, Chap. IX, of the present 
work. 



ADDRESS BY EDWARD WRIGHT. xlv 

but 

Quisquis es, ex illo, Zoile, nomen habes. 
whoever thou art, from him, Zoilus, dost thou derive thy fame.) 1 

Your work, I say, that has been kept back for so many 
years, your New Physiology of the Loadstone and of the Great 
Magnet (i.e. the Earth) a philosophy never to be sufficiently 
admired ; let it go forth into the light of publicity ; for, believe 
me, 

Siquid habent veri vatum pr&sagia, 

(If the presages of poets have aught of truth) 1 

these your books on the Loadstone (De Magnete) will do more 
to perpetuate your memory than would the monument of any 
Magnate (Magnatis cujusvis) erected over your grave. 

1 Ovid's Remedia Amoris, Bohn, London 1852, page 475, tr. of Mr. Henry 
T. Riley, who adds: It was unknown of what parentage and country Zoilus 
was. He compiled a work in dispraise of Homer, and was called by the 
ancients ' Homeromastix,' 'the scourge of Homer. 

2 "The Metamorphoses of Ovid," XV, 878 (tr. by Mr. Henry T. Riley), 
Bohn, London 1851, page 553. 




AUTHOR'S PREFACE. 



TO THE CANDID READER, STUDIOUS OF THE 
MAGNETIC PHILOSOPHY. 

SINCE in the discovery of secret things and in the investi- 
gation of hidden causes, stronger reasons are obtained from sure 
experiments and demonstrated arguments than from probable 
conjectures and the opinions of philosophical speculators of 
the common sort ; therefore to the end that the noble sub- 
stance of that great loadstone, our common mother (the earth), 
still quite unknown, and also the forces extraordinary and ex- 
alted of this globe may the better be understood, we have 
decided first to begin with the common stony and ferruginous 
matter, and magnetic bodies, and the parts of the earth that 
we may handle and may perceive with the senses ; then to pro- 
ceed with plain magnetic experiments, and to penetrate to 
the inner parts of the earth. For after we had, in order to dis- 
cover the true substance of the earth, seen and examined very 
many matters taken out of lofty mountains, or the depths of 
seas, or deepest caverns, or hidden mines, we gave much atten- 

xlvii 



xlviil AUTHOR'S PREFACE. 

tion for a long time to the study of magnetic forces won- 
drous forces they, surpassing the powers of all other bodies 
around us, though the virtues of all things dug out of the 
earth were to be brought together. Nor did we find this our 
labor vain or fruitless, for every day, in our experiments, novel, 
unheard-of properties came to light : and our Philosophy be- 
came so widened, as a result of diligent research, that we have 
attempted to set forth, according to magnetic principles, the 
inner constitution of the globe and its genuine substance, and 
in true demonstrations and in experiments that appeal plainly 
to the senses, as though we were pointing with the finger, to 
exhibit to mankind Earth, mother of all. 

And even as geometry rises from certain slight and readily 
understood foundations to the highest and most difficult 
demonstrations, whereby the ingenious mind ascends above 
the aether : so does our magnetic doctrine and science in due 
order first show forth certain facts of less rare occurrence ; 
from these proceed facts of a more extraordinary kind ; at 
length, in a sort of series, are revealed things most secret and 
privy in the earth, and the causes are recognized of things that, 
in the ignorance of those of old or through the heedlessness of 
the moderns, were unnoticed or disregarded. But why should I, 
in so vast an ocean of books whereby the minds of the studious 
are bemuddled and vexed ; of books of the more stupid sort 
whereby the common herd and fellows without a spark of 
talent are made intoxicated, crazy, puffed up ; are led to write 
numerous books and to profess themselves philosophers, phy- 
sicians, mathematicians, and astrologers, the while ignoring and 
contemning men of learning : why, I say, should I add aught 
further to this confused world of writings, or why should I sub- 
mit this noble and (as comprising many things before unheard 
of) this new and inadmissible philosophy to the judgment of 



AUTHOR'S PREFACE. xlix 

men who have taken oath to follow the opinions of others, to 
the most senseless corrupters of the arts, to lettered clowns, 
grammatists, sophists, spouters, and the wrong-headed rabble, 
to be denounced, torn to tatters and heaped with contumely. 
To you alone, true philosophers, ingenuous minds, who not 
only in books but in things themselves look for knowledge, 
have I dedicated these foundations of magnetic science a new 
style of philosophizing. But if any see fit not to agree with 
the opinions here expressed and not to accept certain of my 
paradoxes ; still let them note the great multitude of experi- 
ments and discoveries these it is chiefly that cause all philoso- 
phy to flourish ; and we have dug them up and demonstrated 
them with much pains and sleepless nights and great money ex- 
pense. Enjoy them you, and, if ye can, employ them for better 
purposes. I know how hard it is to impart the air of newness to 
what is old, trimness to what is gone out of fashion ; to lighten 
what is dark ; to make that grateful which excites disgust ; to 
win belief for things doubtful ; but far more difficult is it to 
win any standing for or to establish doctrines that are novel, 
unheard-of, and opposed to everybody's opinions. We care 
naught, for that, as we have held that philosophy is for 
the few. 

We have set over against our discoveries and experiments 
larger and smaller asterisks according to their importance and 
their subtility. Let whosoever would make the same experi- 
ments, handle the bodies carefully, skilfully and deftly, not 
heedlessly and bunglingly ; when an experiment fails, let him 
not in his ignorance condemn our discoveries, for there is naught 
in these Books that has not been investigated and again and 
again done and repeated under our eyes. Many things in our 
reasonings and our hypotheses will perhaps seem hard to 
accept, being at variance with the general opinion ; but I have 



1 AUTHOR'S PREFACE. 

no doubt that hereafter they will win authoritativeness from 
the demonstrations themselves. Hence the more advanced 
one is in the science of the loadstone, the more trust he has in 
the hypotheses, and the greater the progress he makes ; nor 
will one reach anything like certitude in the magnetic philoso- 
phy, unless all or at all events most of its principles are known 
to him. 

This natural philosophy (physiologia) is almost a new thing, 
unheard-of before ; a very few writers have simply published 
some meagre accounts of certain magnetic forces. Therefore 
we do not at all quote the ancients and the Greeks as our 
supporters, for neither can paltry Greek argumentation demon- 
strate the truth more subtilly nor Greek terms more effectively, 
nor can both elucidate it better. Our doctrine of the loadstone 
is contradictory of most of the principles and axioms of the 
Greeks. Nor have we brought into this work any graces of 
rhetoric, any verbal ornateness, but have aimed simply at 
treating knotty questions about which little is known in such a 
style and in such terms as are needed to make what is said 
clearly intelligible. Therefore we sometimes employ words 
new and unheard-of, not (as alchemists are wont to do) in 
order to veil things with a pedantic terminology and to make 
them dark and obscure, but in order that hidden things which 
have no name and that have never come into notice, may be 
plainly and fully published. 

After the magnetic experiments and the account of the 
homogenic parts of the earth, we proceed to a consideration of 
the general nature of the whole earth ; and here we decided to 
philosophize freely, as freely, as in the past, the Egyptians, 
Greeks, and Latins published their dogmas ; for very many of 
their errors have been handed down from author to author 
till our own time ; and as our sciolists still take their stand on 



AUTHOR'S PREFACE. H 

these foundations, they continue to stray about, so to speak, 
in perpetual darkness. To those men of early times and, as it 
were, first parents of philosophy, to Aristotle, Theophrastus, 
Ptolemaeus, Hippocrates, Galen, be due honor rendered ever, 
for from them has knowledge descended to those that have 
come after them : but our age has discovered and brought to 
light very many things which they too, were they among the 
living, would cheerfully adopt. Wherefore we have had no 
hesitation in setting forth in hypotheses that are provable, the 
things that we have through a long experience discovered. 
Farewell. 1 



1 See the rendering of this Preface by Dr. B. W. Richardson and Mr. 
James Menzies, which appeared in "The Asclepiad " under the title of "The 
first electrician, William Gilbert, M.D." 



EXPLANATION OF SOME TERMS USED IN THIS 

WORK. 

Terrella. A spherical loadstone or natural magnet. 1 

Veracity* Polar strength activity (or what in Gilbert's day was under- 
stood as energy) ; not gyrating, vertiginous, but turning power : nor 
is it polar revolution, but a directing virtue, an innate turning vigor 
(virtus convert ens). 3> 4 

Electrics. Bodies that attract in the same way as amber. 

Excited magnetic body. One (such as iron or steel) that acquires mag- 
netism from a loadstone or natural magnet. 

Magnetized versorium. An iron bar or needle resting on a point 
(electroscope 6 ) and put in motion excited by the loadstone or 
natural magnet. 

Non-magnetized versorium (the electroscope itself). Made of any 
metal, for use in electrical experiments. 

Armed loadstone. One that is furnished with an iron helmet or cap. 6 

Meridionally. In the direction of a meridian. 

Paralleletically. In the direction of a parallel of latitude. 

Cuspis (point). The end of a magnetized versorium. 

1 See Kenelm Digby's allusion to terrella in the Biographical Memoir, also 
De Magnete, Book I, Chap. III. 

2 See De Magnete, Book I, Chap. X. 

3 See De Magnete, Book II, Chap. VI, also Prof. Sir Wm. Thomson's allu- 
sion to the orbis virtutis in the Biographical Memoir. 

4 "Therefore true it is, and conformable by every experiment, that Steel 
and good Iron never excited by the Load-stone, discover in themselves a ver- 
ticity; that is, a directive or polary facultie whereby, conveniently placed, they 
do septentrionate at one extream, and Australize at another " (Thomas Brown, 
Pseudoloxia Epidemica, 1658, Book II, Chapter II, page 63). 

5 Humboldt says ("Cosmos," 1849, Vol. II, page 726) that Gilbert meas- 
ured the strength of excited electricity by means of a small needle "not made 
of iron . . . ." De Magnete states that the versorium was made of any metal 
(ex quouis metallo) (Verborum, eighth line, and Book II, Chap. II, page 48), 
and alludes (Book III, Chap. I, page 115) to the construction of a versorium 
of two pieces of curved iron (ex duobus curvis ferramentis). 

6 See De Magnete, Book II, Chap. XVII. 

liii 



liv EXPLANATION OF SOME OF THE TERMS USED. 

Crotch. Name sometimes given to the end not touched and excited, 
although in some instruments both ends are commonly so desig- 
nated, according as they are most convenient for excitation by the 
loadstone. 1 

Cork. Bark of the cork-tree. 

Radius (of a loadstone's sphere). A right line drawn in the shortest 
way from the surface of a spherical loadstone to the surface of a 
body, and which when produced passes through the centre of the 
loadstone. 

Sphere of influence. The entire space over which the force of a load- 
stone extends. 2 

Sphere of coition. The entire space over which the smallest magnetic 
body moves toward a loadstone. 

Ostensio. Physical demonstration (opposed to theory). 

Magnetic coition* This phrase is used rather than attraction because 
magnetic movements do not result from attraction of one body 
alone but from the coming together of two bodies harmoniously 
(not the drawing of one by the other) 'Ojuodpourf, the coition is 
always vigorous, even though heavy substances make opposition. 

Declinator ium. A bar or needle movable vertically on its axis and 
that is excited with a loadstone ; used in the dip instrument. 

1 See De Magnete, Book II, Chap. XXXII. 

2 See note 3, page xxxi. 

8 See De Magnete, Book II, Chap. I, et seq. 




WILLIAM GILBERT. 



BOOK FIRST. 



CHAPTER I. 

WRITINGS OF ANCIENT AND MODERN AUTHORS CONCERNING 
THE LOADSTONE : VARIOUS OPINIONS AND DELUSIONS. 

IN former times when philosophy, still rude and uncul- 
tured, was involved in the murkiness of errors and ignorances, 
a few of the virtues and properties of things were, it is true, 
known and understood : in the world of plants and herbs all was 
confusion, mining was undeveloped, and mineralogy neglected. 
But when, by the genius and labors of many workers, certain 
things needful for man's use and welfare were brought to light 
and made known to others (reason and experience meanwhile 
adding a larger hope), then did mankind begin to search the 
forests, the plains, the mountains and precipices, the seas and 
the depths of the waters, and the inmost bowels of earth, and to 
investigate all things. And by good luck at last the loadstone 
was found, as seems probable, by iron-smelters or by miners in 
veins of iron ore. On being treated by the metallurgists, it 



2 WILLIAM GILBERT. 

quickly exhibited that strong powerful attraction of iron no la- 
tent nor obscure property, but one easily seen of all; one observed 
and commended with many praises. And after it had come forth 
as it were out of darkness and out of deep dungeons and been 
honored of men on account of its strong and marvellous attrac- 
tion .of i.-o'-i! then many ancient philosophers and physicians 
, discoursed, of it, "and briefly (but briefly only) made it matter 
J <6f record": ' as, for instance, Plato in the /<?, Aristotle only in 
his first book De Anima; likewise Theophrastus the Lesbian, 
Dioscorides, Caius Plinius secundus, Julius Solinus. These 
record only that the loadstone attracts iron : its other proper- 
ties were all hid. But lest the story of the loadstone should 
be jejune and too brief, to this one sole property then known 
were app'ended certain figments and falsehoods which in the 
early time no less than nowadays were by precocious sciolists 
and copyists dealt out to mankind to be swallowed. For ex- 
ample, they asserted that a loadstone rubbed with garlic does 
not attract iron ; nor when it is in presence of a diamond. 1 
The like of this is found in Pliny and in Ptolemy's Quadripar- 
titum ; and errors have steadily been spread abroad and been 

1 " As to what some writers have related, that a load-stone will not attract 
iron if there be a diamond near (Pliny, Book XXXVII,Chap. IV) and that onions 
and garlic will make it lose its vertue; these are contradicted by a thousand ex- 
periments which I have tried. For I have shown that this stone will attract iron 
through the very thickest diamonds and through a great many thick skins which 
an onion is made up of (Rohault's ' Syst. Nat. Phil./ 1728, Vol. II, page 186). 
That garlic does not hinder the action of the load-stone is likewise shown by 
Porta, ' Nat. Magick,' 1658, Book VII, Chap. XLVIII, and by Sir Thos. Brown, 
at page 74 of his Pseudoloxia Epidemica published in the same year, but the 
contrary is shown by Sir Hugh Plat in The Jewell House of Arte and Nature, 
originally published in 1594." Consult, also, Plutarch, Quast. Conviv. Lib. II, 
Quaest 7) ; Barthol. de Glanvil, Lib. de Prop., Lyons 1480, folio, Lib. XVI; 
Pietro d'Abano (Conciliator Differentiarum, LI, Venice ed. 1526); Ibn Roschd's 
Comment, on Aristotle, 1550, T. 4, p. 143 t.; Nic. de Cusa, Opera, Basilae 1565, 
p. 175 ; Cardan, De Subtil., Lib. VII, Op. T. Ill, Basilae ed. 1582 ; Porta, 
" Nat. Magick," 1658, Book VII, Chap. LV, page 215. 



ANCIENT AND MODERN AUTHORS ON THE LOADSTONE. 3 

accepted even as evil and noxious plants ever have the most 
luxuriant growth down to our day, being propagated in the 
writings of many authors who, to the end that their volumes 
might grow to the desired bulk, do write and copy all sorts 
about ever so many things of which they know naught for cer- 
tain in the light of experience. Such fables about the loadstone 
even Georgius Agricola, a man that has deserved well indeed 
of letters, has inserted as truthful history in his books De 
Natura Fossilium, putting his trust in others' writings. 1 Ga- 
len, in the ninth book of his De Simplicium Medicamentorum 
Facultatibus, recognizes its medicinal virtue, and its natural 
power of attracting iron, in the first book of his De Naturalibus 
Facultatibus ; but he knew not the cause, any more than 
Dioscorides before him, nor did he seek further. But his 
translator Matthiolus furbishes again the garlic and diamond 
story, and further brings in the fable of Mahomet's shrine hav- 
ing an arched roof of magnets so that the people might be 
fooled by the trick of the coffin suspended in air, as though 
'twere some divine miracle. But this is shown to be, false by 
the reports of travellers. Pliny, however, records that the 
architect Chinocrates began to put an arched roof of load- 
stone on the temple of Arsinoe at Alexandria, so that her 
effigy in iron might seem to be suspended in air: in the 
meantime the architect died, as also Ptolemy, who had or- 
dered the work to be done in honor of his sister. 3 But little 

1 See account of the life and writings of George Agricola in the sixth 
chapter of "The History of Chemistry," by Dr. Thomas Thomson, who calls 
him one of the most extraordinary men as well as one of the greatest promoters 
of chemistry that have ever existed, and who pronounces Agricola's De Re 
Metallica as, beyond comparison, the most valuable chemical work which the 
sixteenth century produced. 

s "So it is reported by Ruffinus, that in the Temple of Serapis there was an 
iron chariot suspended by Loadstones in the ayr; which stones removed, the 
chariot fell and dashed into pieces. The like doth Beda report of Bellerophon's 



4 WILLIAM GILBERT. 

has been written by the ancients about the causes of the 
attraction of iron : some trifling remarks of Lucretius and 
others are extant ; other authors barely make slight mention 
of the attraction of iron : all these are berated by Cardan for 
being so heedless and indifferent about so notable a matter, 
60 broad a field of philosophizing, and for not giving a fuller 
account or a more developed philosophy ; yet Cardan himself 
in his ponderous volumes has handed down to posterity, be- 
yond a few commonplaces and quotations from other writers 
and false discoveries, naught that is worthy of a philosopher. 1 
Of later authors, some tell only of its efficacy in medicine, as 
Antonius Musa Brasevolus, Baptista Montanus, Amatus Lu- 
sitanus, as did before them Oribasius in book I3th of the De 
Facultate Metallicorum, Avicenna, Serapio Mauritanus, Abo- 
hali (Hali Abbas), Santes de Ardoniis, Petrus Apponensis, 
Marcellus, Arnaldus. Only a few points touching the load- 
stone are very briefly mentioned by Marbodeus Gallus, 
Albertus, Matthaeus Silvaticus, Hermolaus Barbatus, Camillus 
Leonhardus, Cornelius Agrippa, Fallopius, Joannes Langius, 
Cardinal de Cusa, Hannibal Roserius Calaber : by all these 
the subject is handled in the most careless way, while they 
repeat only the figments and ravings of others. Matthiolus 
compares the attractive virtues of the loadstone, which pass 
through iron, to the mischief of the torpedo, whose poison 



horse, which, framed of iron, was placed between two Loadstones, with wings 
expansed, pendulous in the ayr " (Thom. Brown, Pseudoloxia Epidemica, 1658, 
Book II, page 79). Consult : Ath. Kircheri, Magnes; Sive dearie magnetica, 1643, 
Lib. II, Pars IV, Problema VI; Vincentii Burgundi Spec. Mai., T. I, L. VIII, 
C. 34, Douai ed. 1624 ; Alb. Magnus, De Mineralibus, LI I, Tr. Ill, c. vi, p. 
243, Lione 1651 ; Ausonio L. Ampelius, Lib. Memorialis, c. viii, Paris 1827 ; 
J. H. Martin, " Observ. et Theories . . .," Rome, 1865, pp. 5, 6, 7. 

1 For a better list than Cardan's, of authors who have written on the load- 
stone, consult "Petri Peregrini . . . Achillem T. Gasserum . . . Augs- 
burgi . . . 1558." 



ANCIENT AND MODERN A UTHORS ON THE LOADSTONE. 5 

passes through bodies and spreads in an occult way. Guliel- 
mus Puteanus in his Ratio Purgantium Medicamentorum dis- 
cusses the loadstone briefly and crudely. Thomas Erastus, 
knowing naught of the nature of the loadstone, draws from 
it weak arguments against Paracelsus. Georgius Agricola, 
like Encelius and other writers on metals, simply describes it. 
Alexander Aphrodiseus, in his Problemata, judges the question 
of the loadstone to be incapable of explication. Lucretius 
Carus, the Epicurean poet, deems the attraction to be due to 
this, that as there is from all things an efflux of minutest 
bodies, so there is from iron efflux of atoms into the space 
betwixt the iron and the loadstone a space emptied of air 
by the loadstone's atoms (seeds) ; and when these begin to 
return to the loadstone, the iron follows, the corpuscles being 
entangled with each other. Something similar is said by 
Joannes Costaeus, following Plutarch. Thomas Aquinas, in his 
Physica, Bk. 7, treating briefly of the loadstone, gets at the na- 
ture of it fairly well : with his godlike and perspicacious mind 
he would have developed many a point had he been acquainted 
with magnetic experiments. Plato holds the magnetic virtue 
to be divine. But when, some three or four hundred years ago, 
the magnetic movement to the north and the south was discov- 
ered or recognized anew, many learned men, each according 
to his own gifts, strove to honor with admiration and praise or 
to explain with feeble reasonings a property so curious and so 
necessary for the use of mankind. Of more recent authors, 
very many have striven to discover the cause of this direction 
and movement to north and south, and to understand this so 
great miracle of nature and lay it open to others : but they 
wasted oil and labor, because, not being practical in the re- 
search of objects in nature, being acquaint only with books, 
being led astray by certain erroneous physical systems, and 



UNIVERSITY OF 
'ARTMBNT OF CIVIL ENGINEERING 
BERKELEY, CALIFORNIA 



O WILLIAM GILBERT. 

having made no magnetical experiments, they constructed 
certain raciocinations on a basis of mere opinions, and old- 
womanishly dreamt the things that were not. Marcilius 
Ficinus chews the cud of ancient opinions, and to give the 
reason of the magnetic direction seeks its cause in the constel- 
lation Ursa : in the loadstone, says he, the potency of Ursa 
prevails and hence it is transferred into the iron. Paracelsus 
declares that there are stars which, gifted with the loadstone's 
power, do attract to themselves iron. Levinus Lemnius de- 
scribes and praises the mariner's compass, and on certain 
grounds infers its antiquity ; he does not divulge the hidden 
miracle which he makes profession to know. The people of 
Melfi, in the kingdom of Naples, first, 'tis said, constructed a 
mariner's compass ; and, as Flavius Blondus says, the towns- 
men do not without reason boast, they were so taught by one 
Joannes Goia, a fellow-citizen, in the year I3OO. 1 This town 
is in the Kingdom of Naples, not far from Salerno, and near 
the promontory of Minerva. The sovereignty of the place 
was conferred by Charles V. on Andrea Doria, the great naval 
commander, in recognition of his splendid achievements. 
And that nothing ever has been contrived by the art of man 
nor anything been of greater advantage to the human race 
than the mariner's compass is certain : but many infer from 
ancient writings and from certain arguments and conjectures, 
that the compass was discovered earlier and received among 
the arts of navigation. Knowledge of the mariner's compass 



1 In his "Essay on Several Important Subjects," London 1676, Joseph 
Glanvill remarks (page 33): " I think there is more acknowledgement due to the 
name of this obscure fellow, that hath scarce any left, than to a thousand Alex- 
anders and Caesars, or to ten times the number of Aristotles and Aquinas. 
And he really did more for the increase of knowledge, and advantage of the 
world, by this one experiment, than the numerous subtile disputers that have 
lived ever since the Erection of the School of Wrangling." 



ANCIENT AND MODERN A UTHORS ON THE LOADSTONE. ? 

appears to have been brought into Italy by the Venetian 
Paolo [Paulum Venetum Marco Polo] who about the year 
1260 learned the art of the compass in China, 1 still I do not 
want to strip the Melfitani of so great an honor, seeing that by 
them compasses were first commonly made in Mediterranean 
lands. Goropius ascribes the invention to the Cimbri or Teu- 
tons, on the ground that the thirty-two names of the winds 
inscribed on the compass are pronounced in German by all 
mariners, whether they be British or Spaniards, or French- 
men. But the Italians give them names in their own ver- 
nacular. Some think that Solomon, King of Judea, was 
acquaint with the compass and taught the use of it to his 
pilots for their long voyages when they brought from the 
Western Indies such a quantity of gold : hence Arias Monta- 
nus holds that the regions in Peru that abound in gold got 
their name from the Hebrew word Paruaim. But it is more 
probable that the gold came from the coast of lower Ethiopia, 
or, as others declare, from the region called Cephala. The 
story seems less true for the reason that the Phoenicians, next 
neighbors of Judea, most skilful navigators in early times 

1 It appears to be a remarkable fact that Gilbert, the earliest classical 
writer on terrestrial magnetism, who cannot be supposed to have had the 
slightest knowledge of Chinese literature, should regard the mariner's compass 
as a Chinese invention, which had been brought to Europe by Marco Polo. 
The idea of the introduction of the compass by the last named, whose travels 
occurred in the interval between 1271 and 1295, and who, therefore, returned 
to Italy after the mariner's compass had been mentioned as a long-known in- 
strument by Guyot de Provins in his politico-satirical poem (" La Bible," 1190), 
as well as by Jacques de Vitry (" Historiae Hierosolimitanae," Cap. 89), and 
Dante (" Paradise," Cant. XII), is not supported by any evidence. Before 
Marco Polo set out on his travels in the middle of the thirteenth century, 
Catalans and Basques already made use of the compass (Humboldt, "Cosmos," 
Vol. II, pages 625, 656; Raymond Lully, in his " De Contemplatione," 
" Fenix de las maravillas del orbe," and " Arte de Naveguar;" Azuni, "Bous 
sole," page 69; Miller, " History Philos. 111.", London 1849, Vol. I, pages 179- 
180). 



8 WILLIAM GILBERT. 

(whose talents, labor, and counsels Solomon employed in 
building ships and in his expeditions as well as in other ways), 
were ignorant of magnetic aids, of the use of the mariner's 
compass: for were it used by them, doubtless the Greeks, the 
Italians, and all the Barbarians would have known of a thing 
so necessary and so celebrated through common use ; nor 
would things famous, most easily known, and of the highest 
necessity, ever perish in oblivion ; on the contrary, the knowl- 
edge would have been handed on to posterity, or some memo- 
rial in writing would survive. 

Sebastian Cabot first discovered that the magnetized iron 
(needle) varied. 1 Gonzales Oviedo first made mention in his 
history that in the meridian of the Azores there is no varia- 
tion. [Jean Francois] Fernel, in his book De Abditis Rerum 
CausiSj says that in the loadstone is a hidden and abstruse 
cause : elsewhere he says this cause is celestial ; and he does 
but explain the unknown by the more unknown. This search 
after hidden causes is something ignorant, beggarly, and re- 
sultless. The ingenious Fracastorio, a philosopher of no com- 
mon stamp, 8 asks what gives direction to the loadstone 



1 At page 150 of the 1869 London edition of Mr. J. F. Nicholls' Life of 
Seb. Cabot, it is said the latter represented 1 to the King of England that the 
variation of the compass was different in many places, and was not absolutely 
regulated by distance from any particular meridian; also, that he could point to 
a spot of no variation, and that those whom he trained as seamen, as Chancel- 
lor and Stephen Burrough were particularly attentive to this problem, noting it 
at one time thrice within a short space (" Biddle," Memoir of Sebastian Cabot, 
1831; Humboldt, in both his " Examen Critique " and his "Cosmos," treating 
of " Oceanic Discoveries "). 

2 Hieronymus Fracastorio, the great cotemporary of Columbus, to whom 
Gilbert alludes so frequently, was one of the most learned men of his time 
(1483-1553). From his early youth, he devoted himself to the study of the 
sciences, medicine especially, and he is said to have been made professor of 
logic at the University of Padua when only nineteen years of age. The first 
edition of his complete works appeared at Venice in 1555. Edward Biot tells us 
that it was Fracastorio and Peter Appian, who first made generally known in 



ANCIENT AND MODERN A UTHORS ON THE LOADSTONE. Q 

[needle], and imagines the existence of hyperborean magnetic 
mountains, attracting objects of magnetic iron. This opinion, 
in some degree accepted by others also, many authors follow 
in their writings, their geographical maps, their marine charts, 
and their descriptions of the globe : dreaming [imagining to 
themselves the existence of] magnetic poles and mighty cliffs, 
apart from the earth's poles. Of date two hundred years or 
more earlier than Fracastorio, is a small work attributed to one 
Petrus Peregrinus, a pretty erudite book considering the time : 
many believe it owes its origin to the opinions of Roger 
Bacon, Englishman of Oxford. 1 In this work the arguments 
touching the magnetic direction are drawn from the celestial 
poles and from the heaven itself. From this book of Petrus 
Peregrinus, Joannes Taisner Hannonius 3 extracted the matter 

Europe the peculiar fact, noticed by the Chinese astronomers as early as 837, 
that the tails of comets are always turned away from the sun, so that their line 
of prolongation passes through its centre (Humboldt, "Cosmos," 1849, Vol. I, 
page 86, and Vol. II, page 697). 

1 Roger Bacon, sometimes called Friar Bacon, flourished after the dis- 
tinguished Albertus Magnus (who, strangely enough, is omitted by Olaus Bor- 
richius in his list of alchymistical writers), and was by far the most illustrious 
and best informed of all the alchymists. In one of his numerous works he 
dwells upon the mariner's compass as a miraculum in parte notum. Alexander 
von Humboldt remarked that Roger Bacon, Albertus Magnus, as well as the 
Arabian philosophers Avicenna and Averroes, passed for the representatives of 
all the knowledge of their time. 

2 Joannes Taisner of Ath in Hainault (hence Hannonius) is mentioned 
(Ronald's Catalogue, page 493) as the author of "...Z>e Natura Magnetis et 
ejus effectibus . . . /'Colonise 1562, an English translation of which, by Richarde 
Eden, was published in London about 1579. Tne first Gasser's printed edition 
of Petrus Peregrinus is dated Augsburg 1558. To Peregrinus is ascribed the first 
mention of the double polarity of the magnet (Nicolas Cabeo, PhiL Magnetica, 
Ferrara 1629, Lib. II, C. 3, 8), as well as the designation of the word poles for 
points of greatest energy in the magnet (Bertelli Barnabita, " Sopra P. Pere- 
grino . . . ," Roma 1868, pp. 34, 62, 63, 70, 71). As is already known, the last 
claim has by others been made for Gilbert. Taisner's De Natura, again alluded 
to by Gilbert (Book II, Chap. XXXV), is said by Bertelli and others to be a more 
manifest plagiarism upon Peregrinus than even that of Antonius Fantis of 
Treviso. (Nic. Cabeo, Phil, Magn., 1629, page 23.) 



IO WILLIAM GILBERT. 

of a little volume, which he published for new. Cardan makes 
much of the star in the tail of Ursa Major ; the cause of varia- 
tion he assigns to its rising, thinking that variation is always 
certain at the rising of the star. But the difference of varia- 
tion for change of locality, and the mutations in many places 
mutations that even in the southern regions are irregular 
preclude this exclusive dominance of one star at its northern 
rising. The College of Coimbra seeks the cause in some 
region of the heavens nigh to the pole; Scaliger, in the I3ist 
of his Exercitationes on Cardan's work De Subtilitate, brings in 
a celestial cause to himself unknown, and terrestrial loadstones 
that have nowhere been discovered ; and seeks the cause not 
in the " siderite mountains " but in that force which formed 
them, to wit, in the part of the heavens which overhangs that 
northern point. This opinion the learned author dresses in 
abundant verbiage and crowns with many subtile observations 
in the margin : but his reasons are not so subtile. Martinus 
Cortesius holds that the seat of the attraction is beyond the 
poles, and that it is the heavens in motion. One Bessard, a 
Frenchman, studies the pole of the Zodiac, but to as little pur- 
pose. Jacobus Severtius, of Paris, after quoting a few obser- 
vations of others, fashions new errors about loadstones of dif- 
ferent regions being different in direction, as also about the 
eastern and western parts of a loadstone. Robert Norman, an 
Englishman, posits a point and place toward which the 
magnet looks (but whereto it is) not drawn : toward which 
magnetized iron, according to him, is collimated, but which 
does not attract it. Franciscus Maurolycus 1 discusses a few 
problems regarding the loadstone, adopting the current 
opinions of others ; he believes that the variation is caused by 

1 An account of Francis Maurolycus appears in a note, Book I, Chap. XVII, 
of present work. 



ANCIENT AND MODERN AUTHORS ON THE LOADSTONE, II 

a certain magnetic island mentioned by Olaus Magnus. 
Josephus Costa, knowing nothing whatever of the subject, 
nevertheless pours out empty words about the loadstone. 
Livio Sanuto in his Geography (written in Italian) discourses 
at length of the prime magnetic meridian, of the magnetic 
poles, whether they are terrestrial or celestial ; treats also of 
an instrument for finding the longitude ; but as he does not 
understand the nature of the loadstone, he does but add 
errors and obscurities to his otherwise excellent treatise. 
Fortunius Affaitatus has some rather silly philosophizing 
about attraction of iron and the turning toward the poles. 
Very recently Baptista Porta, a philosopher of no ordinary 
note, makes the 7th book of his Magia Naturalis a very 
storehouse and repertory of magnetic wonders ; but he knows 
little about the movements of the loadstone, and never has 
seen much of them ; much of what he has learned about its 
obvious properties, either from Messer Paolo, the Venetian, or 
through his own studies, is not very accurately noted and ob- 
served ; the book is full of most erroneous experiments, as will 
appear in fitting place; still I hold him worthy of praise for 
that he essayed so great a task (even as he has essayed many 
another task, and successfully too, and with no inconsiderable 
results), and that he has given occasion for further researches. 
All these philosophers, our predecessors, discoursing of 
attraction on the basis of a few vague and indecisive experi- 
ments and of reasonings from the recondite causes of things ; 
and reckoning among the causes of the direction of the magnet, 
a region of the sky, celestial poles, stars, asterisms ; or moun- 
tains, cliffs, vacant space, atoms, attractional or collimational 
regions beyond the heavens, and other like unproved para- 
doxes, are world-wide astray from the truth and are blindly 
wandering. But we do not propose just now to overturn with 



12 WILLIAM GILBERT. 

arguments either these their errors and impotent reasonings, 
or the other many fables about the loadstone, or the fairy-tales 
of mountebanks and story-tellers; as, for example, the ques- 
tions raised by Franciscus Rueus about the loadstone, whether 
it is an imposture of cacodaemons ; or the assertion that a 
loadstone placed unawares under the head of a sleeping woman 
drives her out of the bed if she be an adulteress ; or that by its 
fume and vapor the loadstone is of use to thieves, as though 
the stone were by nature given to promote thefts ; or that it 
withdraws bolts and opens locks, as Serapio insanely imagines ; 
or that iron held by a loadstone's attraction, being placed in 
a balance, adds nought to the weight of the loadstone, as 
though the weight of the iron were absorbed by the virtue of 
the loadstone ; or that, as Serapio and the Moors report, there 
are in Indian seas certain sharp-pointed rocks abounding in 
loadstone, the which draw every nail out of ships that land 
alongside them and hold the vessels : this story, Olaus Magnus 
does not fail to recite : he tells of mountains in the North 
possessing such power of attraction, that ships have to be con- 
structed with wooden pegs, so that as they sail by the 
magnetic cliffs there be no iron nails to draw out. 1 Nor will 



1 Olaus Magnus, Historia de Gentibus Septentrionalibus , Romae 1555, Book 
II, Chap. XXVI, page 89. This is likewise alluded to by Porta in his Magia 
Naturalis, 1658 ed., Book VII, Chap. I, page 191, and 1664 ed., Book VII, 
Chap. I, page 288. 

"Of Rocks Magnetical there are likewise two relations; for some are 
delivered to be in the Indies and some in the extremity of the North and about 
the very Pole. The Northern account is commonly ascribed unto Olaus 
Magnus, Arch-Bishop of Upsale, who out of his Predecessor, Joannes, Saxo, 
and others compiled a history of some Northern Nations; but this assertion we 
have not discovered in that work of his which commonly passeth among us; 
and should believe his Geography herein no more then that in the first line of 
his book; when he affirmeth that Biarmia (which is not 70 degrees in latitude) 
hath the Pole for its Zenith, and Equinoctial for the Horizon" (Thomas Brown, 
Pseudoloxia Epidemica, 1658, Book II, page 78). Consult, also, Claudius Ptolo- 



ANCIENT AND MODERN A UTHORS ON THE IOADSTONE- 1 3 

we take the trouble to refute such stories as that a white load- 
stone may be used as a philter ; or that, as Abohali (Hali 
Abbas) rashly asserts, when held in the hand it cures pains of 
the feet and cramps ; or that, as Pictorius sings, it gives one 
favor and acceptance with princes or makes one eloquent ; 
that, as Albertus Magnus says, there are two species of load- 
stones, one pointing north, the other south ; or that iron is 
directed toward the northern stars by a force communicated 
from the polar stars, even as plants, like the sunflower, 
follow the sun ; or, as the astrologer Lucas Gauricus held, that 
beneath the tail of Ursa Major is a loadstone ; Lucas further 
assigns the loadstone (as the sardonyx and the onyx) to the 
planet Saturn, but also to Mars (with the diamond, jasper, and 
ruby), so that the loadstone, according to him, is ruled by two 
planets ; further, Lucas says that the loadstone belongs to the 
sign Virgo ; and with a veil of mathematical erudition does he 
cover many similar disgraceful stupidities. Gaudentius Merula 
advises that on a loadstone be graven the image of a bear, 
when the moon looks to the north, so that being suspended by 
an iron thread it may win the virtue of the celestial Bear ; 
Ficinus writes, and Merula copies, that the loadstone draws 
iron and makes it point north, because it is of higher order 
than iron in the Bear. Others tell that in daytime the load- 
stone possesses the power of attracting iron, but that at night 
this power is feeble or rather null ; Ruellius writes that the 
loadstone's force, when failing or dulled, is restored by the 
blood of a buck ; it has been said that a buck's blood frees the 
magnet from the diamond's sorcery, giving back its lost power 



maeus. Geographia, Lib. vii, c. 2; Klaproth Boussole, Paris 1834, p. 116, etc.; 
Taisnier's De Natura, 1562, Eden tr. p. 12; "Bead Alb. Magni, Ratisbonien- 
sis . . . ," Lib. viii, Lugduni 1651 ; J. H. Martin, " Observ. et Theories," 
Rome 1865, p. 304. 



14 WILLIAM GILBERT. 

when the magnet is bathed in the blood this, because of the 
variance between that blood and the diamond ; * Arnoldus de 
Villanova fancies that the loadstone frees women from witch- 
craft and puts demons to flight ; Marbodaeus, a Frenchman, 
fugleman of vain imaginings, says that it can make husbands 
agreeable to wives and may restore wives to their husbands ; 
Caelius Calcagninius in his Relationes says that a magnet 
pickled with salt of the sucking-fish has the power of picking 
up a piece of gold from the bottom of the deepest well. In 
such-like follies and fables do philosophers of the vulgar sort 
take delight ; with such-like do they cram readers a-hungered 
for things abstruse, and every ignorant gaper for nonsense. 
But when the nature of the loadstone shall have been in the 
discourse following disclosed, and shall have been by our 
labors and experiments tested, then will the hidden and recon- 
dite but real causes of this great effect be brought forward, 
proven, shown, demonstrated; then, too, will all darkness 
vanish ; every smallest root of error, being plucked up, will be 
cast away and will be neglected; and the foundations of a 
grand magnetic science being laid will appear anew, so that 
high intellects may no more be deluded by vain opinions. 

There are other learned men who on long sea voyages 
have observed the differences of magnetic variation ; as that 
most accomplished scholar Thomas Hariot, Robert Hues, 
Edward Wright, Abraham Kendall, all Englishmen ; others 
have invented and published magnetic instruments and ready 
methods of observing, necessary for mariners and those who 
make long voyages : as William Borough in his little work the 
Variation of the Compass, William Barlo (Barlowe) in his 

1 Consult: Simon, Clavis Sanationis, Padua 1474; C. G. Solino, Polyhistor> 
p. 154, Lyons ed. 1538; Vincentii Burgundi, Spec. Mai. T. I, Lib. 8, c. 40, 
Douai ed. 1624. 



THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. 1 5 

Supplement, Robert Norman in his New Attractive the same 
Robert Norman, skilled navigator and ingenious artificer, who 
first discovered the dip of the magnetic needle. 1 Many others 
I pass by of purpose : Frenchmen, Germans, and Spaniards of 
recent time who in their writings, mostly composed in their 
vernacular languages, either misuse the teachings of others, 
and like furbishers send forth ancient things dressed with new 
names and tricked in an apparel of new words as in prosti- 
tutes' finery ; or who publish things not even worthy of record; 
who, pilfering some book, grasp for themselves from other 
authors, and go a-begging for some patron, or go a-fishing 
among the inexperienced and the young for a reputation ; who 
seem to transmit from hand to hand, as it were, erroneous 
teachings in every science and out of their own store now and 
again to add somewhat of error. 



CHAPTER II. 
THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. 

THIS stone is commonly called magnet, either after its 
finder (not Pliny's mythical herdsman copied from Nicander 
the hobnails of whose brogues and the point of whose staff 

1 Whewell thus renders the passage (" Hist. Ind. Sc.", 1859, Vol. II, page 
218): " Other learned men have, in long navigations, observed the differences 
of magnetic variations, as Thomas Hariot, Robert Hues, Edward Wright, 
Abraham Kendall, all Englishmen: others have invented magnetic instruments 
and convenient modes of observation, such as are requisite for those who take 
long voyages, as William Borough in his Book concerning the variation of the 
compass, William Barlo in his Supplement, Robert Norman in his 'New At- 
tractive.' This is that Robert Norman (a good seaman and an ingenious 
artificer) who first discovered the dip of magnetic iron." This important dis- 
covery was made in 1576 (" Enc. Met.", page 738). Read paragraph 366 of J. 
F. W. Herschel's "Prelim. Disc.", 1855. 



10 WILLIAM GILBERT. 

were held fast in a magnetic region while he was pasturing his 
cattle), or after the district Magnesia in Macedonia, 1 abound- 
ing in loadstones ; or after the City of Magnesia in Ionia of 
Asia Minor, on the river Maender ; hence Lucretius writes, 
Quern Magneto, vacant patrio de nomine Graii, Magnetum quia 
sit patriis in montibus ortus? It is called Heracleus from the 
City Heraclea, 3 or after that unconquerable hero Hercules, 
because of its great strength and its power and dominion over 
iron which is thesubduer of all things; it is also called Sideritis, 
as though one should say Ferrarius (Ferrarius lapis iron- 
stone). It was not unknown to the earliest writers, whether 
among the Greeks, as Hippocrates and others, or (as I believe) 
among the Jews and the Egyptians ; for in the most ancient 
iron mines, in particular the most famous mines of Asia, the 
loadstone, brother uterine of iron, was oft dug out in company 
with that ore. And if those things be true which are told 

1 Magnesia. Many authors erroneously allude to a city or town called 
Magnesia in the country of Magnesia in Thessaly, one of the number being 
the learned Dr. W. Smith, who further states (" Diet, of Greek and Roman 
Geogr.", 1857, Vol. II, page 1170) that the Thessalian Magnetes Magnesians 
are said to have founded both the Ionian and the Lydian Magnesias. The 
celebrated historian Barthold George Niebuhr, in his " Lectures on Ancient 
Ethnography and Geography," states (transl. of Dr. L. Schmitz, London 1853, 
Vol. I, page 168) that the "town of Magnesia never existed, it is a mere blun- 
der, . . . not mentioned by either Scylax, Herodotus, or Demosthenes," and, 
furthermore, that the province of Magnesia was governed by the Macedonians, 
and that it is not probable it was ever incorporated by the Romans with 
either Thessaly or Macedonia. 

2 Transl. Which the Greeks call magnetes, from the name of its country, 
for it had its origin in the native hills of the Magnesians. 

3 Heraclea, a town of uncertain site in Lydia, perhaps not far from (the 
Lydian) Magnesia at the foot of Mount Sipylus (ad Sipylurn) (Dr. W. Smith, 
"Diet, of Greek and Roman Geogr.", 1857, Vol. I, page 1049). Gilbert has 
alluded to the celebrated Magnesia in Ionia (ad Maendrum\ but it is uncertain 
which of the two Magnesias is really meant (Ninth "Encycl. Brit.", Vol. XV, 
page 219, note). At page 470, Vol. VI, of the " Diet. Geogr. Univ.", Paris 1829, 
it is said that it was the Magnesia ad Sipylum Manika-Mansa which gave its 
name to the Magnes, and this view is taken by many authors. 



THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. I/ 

about the people of China, neither were they in primitive 
times ignorant of magnetic experiments, for even in their 
country are seen the most excellent magnets in the world. 
The Egyptians, as Manetho relates, give it the name of l the 
bone of Horus,' calling the potency that presides over the 
revolution of the sun Horus, as the Greeks called it Apollo. 
But later, as Plato declares, Euripides gave to it the name 
magnet. It is mentioned and praised by Plato in the 70, by 
Nicander of Colophon, Theophrastus, Dioscorides, Pliny, Soli- 
nus, Ptolemy, Galen, and other investigators of nature. But 
considering the great differences of loadstones, their dissim- 
ilitude in hardness, softness, heaviness, lightness, density, 
firmness, friableness : in color and in all other qualities ; these 
writers have not handed down any sufficient account of it. 
The history of the magnet was overlooked by them, or, if 
written, was incompletely given, because in olden time objects 
of many kinds and foreign products never before seen were 
not brought in by traders and mariners as they are wont to 
be brought in now, when all manner of commodities stones, 
woods, spices, herbs, metals, and metallic wares are eagerly 
sought for all over the earth; neither was mining carried on 
everywhere in early times as it is now. 

The difference between loadstones rests on their respective 
power : hence one loadstone is male, another female : so the 
ancients were wont to distinguish many objects of the same 
species. Pliny quotes from Sotacus five kinds, viz. : the load- 
stones of Ethiopia, Macedonia, Boeotia, Troas, and Asia, re- 
spectively, which were the chief sorts known to the ancients. 1 

1 Porta has it: "The Ethiopian, the Magnesian from Magnesia near 
Macedonia, as the way lies to the Lake Bcebis, on the right hand; the third in 
Echium of Boetia, the fourth about Alexandria at Troaderum; the fifth in 
Magnesia of Asia" ("Nat. Mag.," Book VII, Chap. I). 



1 8 WILLIAM GILBERT. 

But we recognize as many kinds as there are in the whole world 
regions differing in soil ; for in every clime, in every province, 
in all kinds of land, either the loadstone is found or lies un- 
known because of its deep site or its inaccessible situation ; or, 
because of its weaker and less potent virtues, it is not recog- 
nized by us the while we see it and touch it. 1 

For the ancients, the differences were based on the color : 
The magnets from Magnesia in Macedonia were red and black, 
those from Bceotia red rather than black, those from the Troad 
black without strength, those from Asian Magnesia white, 
without power of attracting iron, and resembling pumice. A 
strong loadstone and one that under experiment demonstrates 
its power, nowadays generally resembles unpolished iron and 
usually is found in iron mines : sometimes it is found also form- 
ing a continuous vein by itself : such loadstones are imported 
from the East Indies, China, and Bengal, and they are of the 
color of iron, or of a dark blood-red or liver color. These are 
the most excellent and often are of great size and weight, as if 
broken off a great rock ; or again they are as if complete in 
themselves. Some of these, though they may weigh but one 
pound, will lift 4 ounces, or half a pound, or even an entire 
pound of iron. In Arabia are found red loadstones shaped 
like tiles, not as heavy as those imported from China, yet strong 
and good. Rather black loadstones are found in Ilva, an island 
of the Etrurian sea ; with these occur also white loadstones 
like those from the mines of Caravaca in Spain : but they are 
of inferior strength. Black loadstones also are found, and 
these, too, are rather inferior in strength, for example, those 
met with in the iron mines of Norway and in the coast region 



1 Consult Johann S. T. Gehler's " Physikalisches Worterbuch," article 
" Magnetismus." 



THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. 19 

along the Cattegat. Blue-black and dusky-blue loadstones are 
likewise powerful and highly prized. 1 But there are others of a 
lead color, fissile or not fissile, that can be split up like slate ; 
I have also loadstones resembling an ashy-gray marble, mottled 
like gray marble : these take a high polish. In Germany, are 
loadstones perforated like the honeycomb : these are lighter 
than the other sorts, yet they are powerful. The metallic load- 
stones are those which are smelted into the best of iron ; the 
rest are not easily smelted, but are burnt. 

There are loadstones that are very heavy, as there are others 
very light ; some are very powerful and carry masses of iron ; 
others are weaker and less powerful ; some so faint and void of 
strength that they can hardly attract ever so small a piece of 
iron, nor do they repel an opposite magnetized body. Others 
are firm and tough, nor are they easy to work ; others are fri- 
able. Again, some are dense and hard like corundum, or light 
or soft like pumice; porous or solid ; smooth and uniform, or 
irregular and corroded. Now hard as iron, nay sometimes 
harder to cut or to file than iron ; again as soft as clay. Not 
all magnets can properly be called stones : some there are that 
represent rather rocks ; others are rather metallic ores ; others 
are like clods of earth. So do they vary and differ from one 
another, and some possess more, others less, of the peculiar 
magnetic virtue. For they differ according to the nature of 
the soil, and the different mixtures of clays and humors ; ac- 
cording to the lie of the land and the decay of this highest 
substance born to Earth : decay due to the concurrence of many 



1 "They are proved to be the best which are most of blewe or heavenly 
colour" (Taisnier, De Natura, 1562, Eden tr. p. n). "It is certain, that the 
bluer they are, the better they are " (Porta, "Natural Magick," 1658, Chap. 
VII, page 191). Consult Epistola P. Peregrini De Magnete, Cap. Ill, and 
Barthol. de Glanvil, L,ib. de Prop., Lyons 1480, fol., Lib. XVI, Cap. LXII. 



20 WILLIAM GILBERT. 

causes and the never-ceasing vicissitude of rise and decline and 
the mutations of bodies. Nor is this stone, endowed as it is 
with such power, a rarity : there is no country wherein it may 
not be found in one form or other. But were men to seek it 
more diligently and at greater expense, and could they in the 
face of difficulties mine it, it might be obtained everywhere, 
as later we will prove. In many regions are found and are now 
opened mines of powerful loadstones unknown to ancient 
authors, in Germany, for example, where none of them ever 
said that loadstones were mined ; and yet since the time within 
the memory of our fathers when the business of mining began 
there to be developed, in many parts of Germany powerful 
loadstones of great virtues have been taken out of the earth, as 
in the Black Forest near Helceburg : in Mt. Misena not far 
from Schwarzberg ; some of considerable strength from the 
region betwixt Schneeberg and Annaberg in the Joachimsthal, 
as was observed by Cordus ; also near Pela in Franconia ; in 
Bohemia from the iron mines near Lesse ; and in other places, 
as we are informed by Georgius Agricola and other men learned 
in the art of mining. The like is to be said of other countries 
in our time ; for this stone, famous for its virtues, as to-day it 
is well known throughout the world, so is produced in every 
land ; it is, so to speak, a native of all countries. In East India, 
in China, in Bengal, along the banks of the Indus, it is plenti- 
ful, also in certain marine rocks ; in Persia, too, in Arabia and 
the isles of the Red Sea ; in many parts of Ethiopia, as was 
anciently Zimiri, mentioned by Pliny ; in Asia Minor around 
Alexandria, Boeotia, Italy, the island Elba, Barbary ; in Spain, 
still in many localities as of old ; in England quite recently a 
vast quantity was found in a mine owned by a gentleman, named 
Adrian Gilbert, as also in Devonshire and in the Forest of 
Dean ; in Ireland too, in Norway, Denmark, Sweden, Lapland, 



THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. 21 

Livonia, Prussia, Poland, Hungary. 1 For albeit the terrestrial 
globe, various humors and diversities of soils being produced 
by the perpetual vicissitude of generation and decay, is ever to 
a greater and greater depth beneath the surface in the lapse of 
ages efflorescing, and is being clothed as it were with a diversi- 
fied and perishable covering and wrappage ; still from its in- 
terior arises in many places a progeny nigher to the more per- 
fect body, and makes its way into the sunlit air. But the weak 
loadstones and those of less strength, which thus have been 
deprived of their virtue by being soaked with humors, are 
visible everywhere, in every country-side ; great masses of these 
are to be found in every quarter, without tunnelling mountains 
or sinking mines, and without any of the toils and difficulties 
of mining, as we will show in the sequel. These we will so 
manipulate according to a simple process, that their languid 
and dormant properties shall be made manifest. 

The magnet is called by the Greeks 'HpaxXeioS, as by Theo- 
phrastus, and MayvfjTiS and Matyv^s, as by Euripides, quoted 
by Plato in the lo ; by Orpheus it is called also M.ayvfjoo'a and 
2siSrjpiTrjs (quasi ironstone) ; by the Latins it is called Magnes 
Herculeus ; by the French Aimant, a corruption of adamas ; 
by the Spaniards Piedramant ; by the Italians Calamita ; by 
the English Xoa&StOUC attfc Hfcatttant StOUe; by the Germans 
Magness and Siegelstein. Among the English, French, and 
Spaniards, it has its common name from adamas, and this is 
probably because at some time those people were led astray 
by the term siderites, which was applied both to the diamond 
and the magnet. 8 The magnet is called ^idrfpirrfS because 



1 "The most powerful native magnets are found in Siberia, and in the 
Hartz; they are also obtainable on the Island of Elba " (Dana). See Gilbert, 
Book IV, Chap. V. 

8 Consult Vincentii Burgundi, Spec. Mai., Douai ed. 1624, T. I, LVIII, 
C. 34, 39-4i; Alb. Magnus, De Mineral., Op. T. II, Lione 1651, Tr. II, C. I. 



22 WILLIAM GILBERT. 

of its property of attracting iron ; and the diamond is called 
^idrjpiTijs from the glistening of polished iron. Aristotle 
merely names the loadstone in his work De Anima, I. : "EoiKe 
de KOLI &a\r(S eg cor dTtojjivejA.ovevovcri, KIVTJTIKOV ti rrjv 
ipvxrfv iTtohajApdveiv, einep rov XiBov ipvxrfy e<prf ex^iv 9 on 
TOY (Tidrjpov Kivei. (Thales, too, seems, from what they relate, 
to regard the soul as somewhat producing motion, for he said 
that this stone has a soul, since it moves iron.) The name 
magnet is also given to another stone differing widely from 
the siderites, and having the look of silver: in its nature 
this stone resembles amianth (asbestus), and in form differs 
from that inasmuch as it consists, like mica, of laminae ; the 
Germans call it Katzensilber and Talk. 



CHAPTER III. 

THE LOADSTONE POSSESSES PARTS DIFFERING IN THEIR NAT- 
URAL POWERS, AND HAS POLES CONSPICUOUS FOR THEIR 
PROPERTIES. 

THE many qualities exhibited by the loadstone itself, 
qualities hitherto recognized yet not well investigated, are to 
be pointed out in the first place, to the end the student may 
understand the powers of the loadstone and of iron, and not 
be contused through want of knowledge at the threshold of 
the arguments and demonstrations. In the heavens, astrono- 
mers give to each moving sphere two poles ; thus do we find 

page 227, and C. XI, page 233; C. G. Solino, Exerdtationes Plin., Rhenuni 
1689, page 109. The Macedonian diamond, as well as the adamas cyprius and 
siderites, wete obviously not diamonds, but soft stones (Thomson, " Hist, of 
Chem.", 1830, Vol. I, page 98). 



QUALITIES OF THE LOADSTONE. 2$ 

two natural poles of excelling importance even in our terres- 
trial globe, constant points related to the movement of its 
daily revolution, to wit, one pole pointing to Arctos (Ursa) and 
the north ; the other looking toward the opposite part of the 
heavens. In like manner the loadstone has from nature its 
two poles, a northern and a southern ; fixed, definite points in 
the stone, which are the primary te-rmini of the movements 
and effects, and the limits and regulators of the several actions 
and properties. It is to be understood, however, that not from 
a mathematical point does the force of the stone emanate, but 
from the parts themselves ; and all these parts in the whole 
while they belong to the whole the nearer they are to the 
poles of the stone the stronger virtues do they acquire and 
pour out on other bodies. These poles look toward the poles 
of the earth, and move toward them, and are subject to them. 
The magnetic poles may be found in every loadstone, whether 
strong and powerful (male, as the term was in antiquity) or 
faint, weak, and female ; whether its shape is due to design or 
to chance, and whether it be long, or flat, or four-square, or 
three-cornered, or polished ; whether it be rough, broken-off, 
or unpolished : the loadstone ever has and ever shows its poles. 
But inasmuch as the spherical form, which, too, is the most 
perfect, agrees best with the earth, which is a globe, and also 
is the form best suited for experimental uses, therefore we pur- 
pose to give our principal demonstrations with the aid of a 
globe-shaped loadstone, as being the best and the most fitting. 
Take then a strong loadstone, solid, of convenient size, uni- 
form, hard, without flaw ; on a lathe, such as is used in turning 
crystals and some precious stones, or on any like instrument 
(as the nature and toughness of the stone may require, for often 
it is worked only with difficulty), give the loadstone the form 
of a ball. The stone thus prepared is a true homogeneous off- 



24 WILLIAM GILBERT. 

spring of the earth and is of the same shape, having got from 
art the orbicular form that nature in the beginning gave to the 
earth, the common mother ; and it is a natural little body en- 
dowed with a multitude of properties whereby many abstruse 
and unheeded truths of philosophy, hid in deplorable dark- 
ness, may be more readily brought to the knowledge of man- 
kind. To this round stone we give the name MiKfjoyrj (microge) 
or Terrella (earthkin, little earth). 1 

To find, then, poles answering to the earth's poles, take in 
your hand the round stone, and lay on it a needle or a piece of 
iron wire : the ends of the wire move round their middle point, 
and suddenly come to a standstill. Now, with ochre or with 
chalk, mark where the wire lies still and sticks. Then move 
the middle or centre of the wire to another spot, and so to a 
third and a fourth, always marking the stone along the length 
of the wire where it stands still : the lines so marked will ex- 
hibit meridian circles, or circles like meridians on the stone or 
terrella ; and manifestly they will all come together at the poles 
of the stone. The circles being continued in this way, the 
poles appear, both the north and the south, and betwixt these, 
midway, we may draw a large circle for an equator, as is done by 
the astronomer in the heavens and on his spheres and by the 
geographer on the terrestrial globe ; for the line so drawn on 
this our terrella is also of much utility in our demonstrations 
and our magnetic experiments. Poles are also found in the 
round stone, in a versorium, in a piece of iron touched with a 
loadstone and resting on a needle or point (attached at its 
base to the terrella), so that it can freely revolve, as in the 
figure. 

1 Sir Kenelm Digby, "A Treatise of Bodies," London 1645, Chap. XX, 
page 225. 



QUALITIES OF THE LOADSTONE. 2$ 

On top of the stone AB is set the versorium in such a 
way that its pointer may remain in equilibrium : mark with 
chalk the direction of the pointer when at rest. Then move 
the instrument to another spot and again mark the direction 
in which the pointer looks ; repeat this many times at many 
different points and you will, from the convergence of the 
lines of direction, find one pole at the point A, the other at 
B. A pointer also indicates the true pole if brought near to 




the stone, for it eagerly faces the stone at right angles, and 
seeks the pole itself direct and turns on its axis in a right 
line toward the centre of the stone. Thus the pointer D* 
regards A and F, the pole and the centre, but the pointer E 
looks not straight either toward the pole A or the centre F. 
A bit of fine iron wire as long as a barley-corn is laid on the 
stone and is moved over the zones and the surface of the 
stone till it stands perpendicularly erect ; for at the poles, 
whether N. or S., it stands erect ; but the farther it is from the 
poles (towards the equator) the more it inclines. The poles 
thus found, you are to mark with a sharp file or a gimlet. 



26 WILLIAM GILBERT. 



CHAPTER IV. 

WHICH POLE IS THE NORTH : HOW THE NORTH POLE IS 
DISTINGUISHED FROM THE SOUTH POLE. 

ONE of the earth's poles is turned toward Cynosura and 
steadily regards a fixed point in the heavens (save that it is 
unmoved by the precession of the fixed stars in longitude, 
which movement we recognize in the earth, as we shall later 
show) ; the other pole is turned toward the opposite aspect of 
the heavens, an aspect unknown to the ancients, but which is 
adorned with a multitude of stars, and is itself a striking spec- 
tacle for those who make long voyages. So, too, the loadstone 
possesses the virtue and power of directing itself toward the 
north and the south (the earth itself co-operating and giving 
to it that power) according to the conformation of nature, 
which adjusts the movements of the stone to its true locations. 
In this manner it is demonstrated : Put the magnetic stone 
(after you have found the poles) in a round wooden vessel a 
bowl or a dish ; then put the vessel holding the magnet (like a 
boat with a sailor in it) in a tub of water or a cistern where it 
may float freely in the middle without touching the rim, and 
where the air is not stirred by winds (currents) which might 
interfere with the natural movement of the stone : there the 
stone, as if in a boat floating in the middle of an unruffled 
surface of still water, will straightway set itself, and the vessel 
containing it in motion, and will turn in a circle till its south 
pole shall face north and its north pole, south. For, from a 
contrary position, it returns to the poles ; and though with its 



WHICH POLE IS THE NORTH. 2J 

first too strong impetus it passes beyond, still, as it comes 
back again and again, at last it rests at the poles or in the 
meridian (save that, according to the place, it diverges a very 
little from those points, or from the meridional line, the cause 
of which we will define later). As often as you move it out of 
its place, so often, by reason of the extraordinary power with 
which nature has endowed it, does it seek again its fixed and 
determinate points. Nor does this occur only when the poles 
of the loadstone in the float are made to lie evenly in the 
plane of the horizon ; it takes place also even though one pole, 
whether north or south, be raised or depressed 10, 20, 30, 40, 
or 80 degrees from the plane of the horizon ; you shall see the 
north part of the stone seek the south, and the south part the 
north ; so that if the pole of the stone be but one degree from 
the zenith and the centre of the heavens, the whole stone re- 
volves until the pole finds its own place ; and though the pole 
does not point exactly to its seat, yet it will incline toward it, 
and will come to rest in the meridian of its true direction. 
And it moves with the same impetus whether the north pole 
be directed toward the upper heavens, or whether the south 
pole be raised above the horizon. Yet it must always be 
borne in mind that though there are manifold differences be- 
tween stones, and one far surpasses another in virtue and effi- 
ciency, still all loadstones have the same limits and turn to the 
same points. Further, it is to be remembered that all who 
hitherto have written about the poles of the loadstone, all in-* 
strument-makers, and navigators, are egregiously mistaken in 
taking for the north pole of the loadstone the part of the 
stone that inclines to the north, and for the south pole the 
part that looks to the south : this we will hereafter prove to 
be an error. So ill-cultivated is the whole philosophy of the 
magnet still, even as regards its elementary principles. 



28 WILLIAM GILBERT. 



CHAPTER V. 

ONE LOADSTONE APPEARS TO ATTRACT ANOTHER IN THE 
NATURAL POSITION ; BUT IN THE OPPOSITE POSITION 
REPELS IT AND BRINGS IT TO RIGHTS. 

FIRST we have to describe in popular language the potent 
and familiar properties of the stone ; afterward, very many 
subtile properties, as yet recondite and unknown, being in- 
volved in obscurities, are to be unfolded ; and the causes of all 
these (nature's secrets being unlocked) are in their place to be 
demonstrated in fitting words and with the aid of apparatus. 
The fact is trite and familiar, that the loadstone attracts iron ; 
in the same way, too, one loadstone attracts another. Take 
the stone on which you have designated the poles, N. and S., 
and put it in its vessel so that it may float ; let the poles lie 
just in the plane of the horizon, or at least in a plane not very 
oblique to it ; take in your hand another stone the poles of 
which are also known, and hold it so that its south pole shall 
lie toward the north pole of the floating stone, and near it 
alongside ; the floating loadstone will straightway follow the 
other (provided it be within the range and dominion of its 
powers), nor does it cease to move nor does it quit the other 
till it clings to it, unless, by moving your hand away, you man- 
age skilfully to prevent the conjunction. In like manner, if 
you oppose the north pole of the stone in your hand to the 
south pole of the floating one, they come together and follow 
each other. For opposite poles attract opposite poles. But, 
now, if in the same way you present N. to N. or S. to S., one 



ONE LOADSTONE APPEARS TO ATTRACT ANOTHER. 29 

stone repels the other ; and as though a helmsman were hear- 
ing on the rudder it is off like a vessel making all sail, nor 
stands nor stays as long as the other stone pursues. One 
stone also will range the other, turn the other around, bring it 
to right about and make it come to agreement with itself. 
But when the two come together and are conjoined in nature's 
order, they cohere firmly. For example, if you present the 
north pole of the stone in your hand to the Tropic of Capri- 





corn (for so we may distinguish with mathematical circles the 
round stone or terrella, just as we do the globe itself) or to 
any point between the equator and the south pole : immedi- 
ately the floating stone turns round and so places itself that 
its south pole touches the north pole of the other and is most 
closely joined to it. In the same way you will get like effect 
at the other side of the equator by presenting pole to pole ; 
and thus by art and contrivance we exhibit attraction and re- 
pulsion, and motion in a circle toward the concordant position, 
and the same movements to avoid hostile meetings. Further- 
more, in one same stone we are thus able to demonstrate all 



3O WILLIAM GILBERT. 

this: but also we are able to show how the self-same part of 
one stone may by division become either north or south. 
Take the oblong stone ad in which a is the north pole and 
d the south. Cut the stone in two equal parts, and put part 
a in a vessel and let it float in water. 

You will find that a, the north point, will turn to the south 
as before ; and in like manner the point d will move to the 
north, in the divided stone, as before division. But b and c, 
before connected, now separated from each other, are not 
what they were before, b is now south while c is north. 
b attracts c, longing for union and for restoration of the 
original continuity. They are two stones made out of one, 
and on that account the c of one turning toward the b of the 
other, they are mutually attracted, and, being freed from all 
impediments and from their own weight, borne as they are on 
the surface of the water, they come together and into con- 
junction. But if you bring the part or point a up to c of the 
other, they repel one another and turn away ; for by such a 
position of the parts nature is crossed and the form of the 
stone is perverted : but nature observes strictly the laws it 
has imposed upon bodies: hence the flight of one part from 
the undue position of the other, and hence the discord un- 
less everything is arranged exactly according to nature. And 
nature will not suffer an unjust and inequitable peace, or an 
unjust and inequitable peace and agreement, but makes war 
and employs force to make bodies acquiesce fairly and justly. 
Hence, when rightly arranged, the parts attract each other, 
i.e., both stones, the weaker and the stronger, come together 
and with all their might tend to union : a fact manifest in all 
loadstones, and not, as Pliny supposed, only in those from 
Ethiopia. The Ethiopic stones if strong, and those brought 
from China, which are all powerful stones, show the effect 



THE LOADSTONE ATTRACTS IRON ORE. 3! 

most quickly and most plainly, attract with most force in the 
parts nighest the pole, and keep turning till pole looks 
straight on pole. The pole of a stone has strongest attraction 
for that part of another stone which answers to it (the adverse 
as it is called) ; e.g., the north pole of one has strongest attrac- 
tion for, has the most vigorous pull on, the south part of 
another: so too it attracts iron more powerfully, and iron 
clings to it more firmly, whether previously magnetized or 
not. Thus it has been settled by nature, not without rea- 
son, that the parts nigher the pole shall have the greatest 
attractive force ; and that in the pole itself shall be the seat, 
the throne as it were, of a high and splendid power ; and that 
magnetic bodies brought near thereto shall be attracted most 
powerfully and relinquished with most reluctance. So, too, 
the poles are readiest to spurn and drive away what is pre- 
sented to them amiss, and what is inconformable and 
foreign. 1 



CHAPTER VI. 

THE LOADSTONE ATTRACTS IRON ORE AS WELL AS THE 
SMELTED METAL. 

THE most potent virtue of the loadstone and the one 
valued by the ancients is the attraction for iron; for Plato 
mentions that the magnet, so called by Euripides, draws to 
itself iron, and not only attracts iron rings but also endows 
them with the power of doing as the stone itself, to wit, of 
attracting other rings, and that thus sometimes a long chain of 
iron objects, as nails, or rings, is made, the several parts hang- 

1 Dr. J. Lament's " Handbuch des Magnetismus," Leipzig 1867, page 15. 



32 WILLIAM GILBERT. 

ing from one another. The best iron (such as that which 
from its uses is called acies, and from the country of the 
Chalybes, chalybs) is most readily and strongly attracted by a 
good magnet ; ' but inferior iron, iron that is impure, rusty, 
not well purged of dross, and not worked over in the second, 
furnace is attracted more weakly ; and any iron is more faintly 
attracted if covered and smeared with thick, greasy, tenacious 
fluids. The loadstone also attracts iron ores rich ores and 
those of the color of iron ; poor ores and those without much 
pure metal it does not attract unless they receive special 
treatment. The loadstone loses some part of its attractive 
power, and, as it were, enters on the decline of old age, if it 
be too long exposed in open air and not kept in a case, with a 
covering of iron filings or iron scales : hence it must be packed 
in such material. Nothing withstands this unimpairable 
virtue, except what destroys the form of the body or corrodes 
it ; no, not a thousand adamants made into one. Nor do I 
believe in the theamedes, or that it has a power the opposite of 
the loadstone's, 2 albeit Pliny, that eminent author and best of 
compilers (for he has handed down to posterity the observa- 
tions and discoveries of others and not always or mainly his 

1 See Aristotle's reference to the iron of the Chalybes at page 20. Dr. 
Thomson informs us the general opinion of the ancients was that the method 
of smelting iron ore had been brought to perfection by the Chalybes, a small 
nation located near the Black Sea (Xenophon's Anabasis, V. 5), and that the 
name chalybs, occasionally used for steel, was derived from that people. Porta, 
at Book XIII, Chap. I, of his " Natural Magick," says: " Justine, the historian, 
reports that in Gallicia of Spain, the chiefest matter for iron is found, .... and 
there is no weapon approved amongst them that is not made of the River Bib- 
ilis, or tempered with the water of Chalybes. And hence are those people that 
live neer this River called Chalybes; and they are held to have the best iron. 
Yet Strabo saith that the Chalybes were people in Pontus near the River Ther- 
modon." See Gilbert, Book I, Chap. VIII. 

* " Iron is attracted by the magnet and repelled by another stone, the the- 
amedes" (Pliny, Hist. Nat., XX, i). See, likewise, Cardan, De Subtil, 
Norimb. 1600, folio, Lib. VII, page 386. 



WHAT IRON IS; WHAT ITS MATTER; ITS USE. 33 

own), copies out of other writers the theamedes fable, now 
from repetition become a familiar story among the moderns, 
The story is that in India are two mountains near the river 
Indus, and that one of them consisting of loadstone pos- 
sesses the power of holding everything containing iron ; while 
the other, consisting of theamedes, repels the same. Hence if 
you should have iron nails in the soles of your shoes, it would 
be impossible to lift your foot if you were standing on one of 
the mountains, and impossible to stand on the other at all. 
Albertus Magnus writes that in his time a loadstone was found 
that on one side drew iron to itself and on the other side 
repelled it. 1 But Albertus's observation was faulty, for every 
loadstone attracts on one side magnetized iron, on the other 
repels, and attracts magnetized iron more powerfully than 
non-magnetized. 



CHAPTER VII. 

WHAT IRON IS ; WHAT ITS MATTER ; ITS USE. 

HAVING declared the origin and nature of the loadstone, 
we hold it needful first to give the history of iron also, and to 
point out properties of iron as yet not known, before we come 
to the explication of difficulties connected with the loadstone, 

1 Somewhat in this connection, Gilbert has already (Book I, Chap. I) 
alluded to Albertus Magnus, of whom mention was made in note I, page 9. 
In his De Mineralibus Lyons ed. 1651, Treat. Ill, Lib. II, Cap. VI, p. 243 
Albertus says, " One angle ... is to the zoron (north), . . . but another angle of 
the magnet opposite to it attracts to the aphron (south)." Consult Cardan, De 
Subtil., Lugduni 1663; Salmanasar, Book II ("Of the Egyptian Hermitus, 19 
stars, and 15 stones, and 15 herbs, and 15 figures"), " On one side (the magnet) 
attracts iron, on the other repels it;" Pietro d'Abano, Conciliator Differentia- 
rum Mantuse, 1472, Diff. 51, page 104, "Know that a magnet is discovered 
which attracts iron on one side and repels it on the other." 



34 WILLIAM GILBERT. 

and to the demonstrations; before we come to the consider- 
ation of its uniting and according with iron. Iron is, by all, 
classed among metals ; it is of bluish color, very hard, grows 
red hot before fusion, is very hard to fuse, spreads under the 
hammer, and is resonant. Chemists say that, if fixed earthy 
sulphur be combined with fixed earthy mercury and these two 
bodies present not a pure white but a bluish-white color, if the 
sulphur prevail, iron results. For those hard masters of the 
metals, who in many various processes put them to the tor- 
ture, by crushing, calcining, smelting, subliming, precipitating, 
distinguish this, on account both of the earthy sulphur and the 
earthy mercury, as more truly the child of earth than any 
other metal ; for neither gold, nor silver, nor lead, nor tin, nor 
even copper do they hold to be so earthy ; and therefore it is 
treated only in the hottest furnaces with the help of bellows J 
and when thus smelted if it becomes hard again it cannot be 
smelted once more without great labor ; and its slag can be 
fused only with the utmost difficulty. It is the hardest of 
metals, subduing and breaking them all, because of the strong 
concretion of the more earthy substance. Hence we shall 
better understand what iron is when we shall have developed, 
in a way different from that of those who have gone before us, 
what are the causes and the matter of metals. Aristotle sup- 
poses their matter to be an exhalation. The chemists in 
chorus (unison) declare that sulphur and quicksilver are the 
prime elements. Gilgil, the Mauretanian, holds the prime ele- 
ment to be ash moistened with water ; Georgius Agricola, a 
mixture of water with earth ; and his opinion differs nought 
from Gilgil's thesis. But our opinion is that metals have their 
origin and do effloresce in the uppermost parts of the globe, 
each distinct by its form, as do many other minerals and all 
the bodies around us. The globe of the earth is not made of 



WHAT IRON IS; WHAT ITS MATTER; ITS USE. 35 

ash or of inert dust. Nor is fresh water an element, but only 
a less complex consistence of the earth's evaporated fluids. 
Unctuous bodies (pinguia corpora), fresh water void of proper- 
ties, quicksilver, sulphur : these are not the principles of the 
metals : they are results of another natural process ; nor have 
they a place now or have they had ever, in the process of 
producing metals. The earth gives forth sundry humors, not 
produced from water nor from dry earth, nor from mixtures of 
these, but from the matter of the earth itself : these are not 
distinguished by opposite qualities or substances. Nor is the 
earth a simple substance, as the Peripatetics imagine. The 
humors come from sublimed vapors that have their origin in 
the bowels of the earth. And all waters are extractions from 
the earth and exudations, as it were. Therefore Aristotle is 
partly in the right when he says that the exhalation which 
condenses in the earth's veins is the prime matter of metals : 
for exhalations are condensed in situations less warm than the 
place of their origin, and owing to the structure of lands and 
mountains, they are in due time condensed, as it were, in 
wombs, and changed into metals. But they do not of them- 
selves alone constitute the veins of ore ; only they flow into 
and coalesce with solider matter and form metals. When, 
therefore, this concreted matter has settled in more temperate 
cavities, in these moderately warm spaces it takes shape, just 
as in the warm uterus the seed or the embryo grows. Some- 
times the exhalation coalesces only with matter homogene- 
ous throughout, and hence some metals are now and then 
but not often obtained pure and not needing to be smelted. 
But other exhalations, being mixed with foreign earths, must 
be smelted ; and thus are treated the ores of all metals, which 
are freed from all their dross by the action of fire ; when smelted 
into the metallic state they are fluid and then are freed from 



$6 WILLIAM GILBERT. 

earthly impurities but not from the true substance of the earth. 
But that there is gold, or silver, or copper, or that any other 
metals exist, does not happen from any quantitas or propor- 
tion of matter nor by any specific virtues of matter, as the 
chemists fondly imagine ; but it happens when, earth cavities 
and the conformation of the ground concurring with the fit 
matter, those metals take from universal nature the forms by 
which they are perfected, just as in the case of all other min- 
erals, all plants and all animals : else the kinds of metals would 
be vague and undefined : in fact the varieties are very few, 
hardly ten in number. But why nature should be so grudging 
in the number of metals, or why there should be even so many 
metals as are recognized by man, were not easy to explain, 
though simpletons and raving astrologers refer to the several 
planets their respective metals. 1 But neither do the planets 
agree with the metals nor the metals with the planets, either 
in number or in properties. For what is common be- 
tween Mars and iron, save that, like many other implements, 
swords and artillery are made of iron ? What has copper to 
do with Venus? Or how does tin, or zinc, relate to Jupiter? 
These were better dedicated to Venus. But a truce to old 
wives' talk. Thus exhalations are the remote cause of the 
generation of metals ; the proximate cause is the fluid from the 
exhalations : like the blood and the semen in the generation of 
animals. But these exhalations and the fluids produced from 

1 In his account of Geber (Abou-Moussah-Dschafar-Al-Soli), " the patri- 
arch of chemistry," Dr. Thos. Thomson says this Arabian philosopher was 
acquainted with the metals gold, silver, copper, iron, tin, and lead, and that they 
are usually distinguished by him under the respective names of Sol, Luna, 
Venus, Mars, Jupiter, and Saturn. He adds : "Whether these names of the 
planets were applied to the metals by Geber, or only by his translators, I can- 
not say; but they were always employed by the Alchy mists, who never desig- 
nated the metals by any other appellations" (" Hist, of Chem.", 1830, Vol. I, 
pages 117, 1 1 8). 



WHAT IRON IS; WHAT ITS MATTER; ITS USE. 3/ 

them enter bodies often and change them into marchasites 1 
and they pass into veins (we find many instances of timber so 
transformed), into appropriate matrices within bodies, and these 
metals are formed ; oftenest they enter the more interior and 
more homogeneous matter of the globe, and in time there re- 
sults a vein of iron, or loadstone is produced, which is nothing 
but a noble iron ore ; and for this reason and also on account 
of its matter being quite peculiar and distinct from that of all 
other metals, nature very seldom or never mingles with iron any 
other metal, though the other metals are very often commin- 
gled in some small proportion and are produced together. 
Now, when these exhalations or fluids happen to meet efflo- 
rescences altered from the homogeneous matter of the globe 
sundry precipitates, and salts, in suitable matrices (operant 
forms) the other metals are produced (a specificating nature 
operating in that place). For within the globe are hidden the 
principles of metals and stones, as at the earth's surface are 
hidden the principles of herbs and plants. And earth dug from 
the bottom of a deep pit, where there appears to be no chance 
of any seed being formed, produces, if strewn on the top of a 
very high tower, green herbage and unbidden grasses, the sun 
and. the sky brooding over earth ; the earth regions produce 
those things which in each are spontaneous ; each region pro- 
duces its own peculiar herbs and plants, its own metals. 

Do you not see how Tmolus sends fragrant saffron, India its ivory, 
the Sabaens their frankincense, the naked Chalybes iron, Pontus the 
malodorous castor, Epirus the mares that have won at Olympia? 
(Virgilius, Georgica, Book I, pages 56-59.) 

1 Marchasites, marcasites the crystallized form of iron pyrites. What 
substance Geber designated by the name cf marchasite (fire-stone, as Porta 
calls it " Nat. Magick," Book V, Chap. IV) is not known to Dr. Thomson, who 
suspects it to have been a sulphide of antimony long in common use through- 
out Asia. 



3 WILLIAM GILBERT. 

What the chemists (as Geber and others) call the fixed 
earthy sulphur in iron, is nothing else but the homogenic mat- 
ter of the globe held together by its own humor, hardened by 
a second humor : with a minute quantity of earth-substance not 
lacking humor is introduced the metallic humor. Hence it is 
said very incorrectly by many authors that in gold is pure 
earth, in iron impure ; as though natural earth and the globe 
itself were become in some incomprehensible sense impure. In 
iron, especially in best iron, is earth in its true and genuine 
nature. In the other metals is not so much earth as, instead 
of earth and precipitate, condensed and (so to speak) fixed 
salts, which are efflorescences of the Earth, and which also dif- 
fer in firmness and consistence. In mines they ascend in great 
volume, with double humor from the exhalations ; in the sub- 
terranean spaces they are consolidated into metallic ores ; so 
too they are produced together, and in virtue of their place 
and of the surrounding bodies, they acquire, in natural matrices, 
their specific forms. Of the various bodily constitutions of 
loadstones, their different substances, colors, and properties, 
we have spoken before : but now after having declared the 
cause and origin of metals, the matter of iron, not in the smelted 
metal but in the ore from which that is obtained by smelting, 
has to be examined. Iron, that from its color appears pure, is 
found in the earth ; yet it is not exactly metallic iron, not 
quite suitable for the different uses of iron. Sometimes it is 
found covered with a white moss-like substance, or with a coat- 
ing of other stones. Such ore is often seen in the sands of 
rivers : such is the ore from Noricum (the region south of 
the Danube, watered by the Inn [CEnus] and the Drave \_Drau~\ ; 
mostly comprised in the modern Austria). Iron ore, nearly 
pure, is often mined in Ireland : from this the smith, without 
the labor of the furnace, forges in his shop iron implements. 



WHAT IRON IS; WHAT ITS MATTER; ITS USE. 39 

From an ore of liver color is very often obtained in France an 
iron with bright scales (bractece) 1 ; such iron is made in England 
without the scales ; carpenters use it instead of chalk. In Sus- 
sex, in England, is a rich ore of dark, and one of pale ashy 
color ; both of these ores when made red hot for some time, 
or when kept in a moderate fire, take the color of liver : in 
Sussex also is a dark-colored ore in square masses, with a black 
rind of harder material. The liver-like ore is often mixed with 
other stones in various ways, as also with perfect loadstone, 
which yields the best iron. There is likewise rust-colored ore, 
ore of a lead color mixed with black, simply black, or black 
mixed with cobalt ; there is also an ore with admixture of 
pyrites or sterile plumbago. One kind of ore resembles jet, 
another the precious stone hcematites. The stone smiris 
(emery ; corundum) used by workers in glass for glass-cutting 
and called by the English emerelstone and by the Germans 
smear ^el (sc/unergel), is of iron, albeit iron is smelted from it 
with difficulty ; it attracts an unmagnetized needle. It is often 
found in deep silver and iron mines. Thomas Erastus tells of 
having been informed by a certain learned man, of iron ores, 
in color resembling metallic iron, but quite soft and greasy, 
capable of being moulded with the fingers like butter ; we have 
seen ores of about the same kind that were found in England : 
they resemble Spanish soap. Besides the numberless forms of 
stony ores, there is a substance like iron rust deposited from 
ferriferous water : it is got from mud, loam, and from ochre. 
In England, a good deal of iron is obtained in the furnace from 



1 At page 280, Vol. I, of Thomson's " Hist, of Chem.", London 1830, 
will be found an account of the difficulty experienced by Reaumur in removing 
the scales from the iron imported from Germany into France. Elsewhere, he 
tells us that the rust of iron and the scales of iron were used by the ancients as 
astringent medicines. See note at Book II, Chap. XXIII, of the present work. 



40 WILLIAM GILBERT. 

sand stones and clayey stones that appear to contain not so 
much iron as sand, marl, or other mud. In Aristotle's book 
De Admirandis Narrationibus we read : 

'Tis said the iron of the Chalybes and the Myseni has 
quite a peculiar origin, being carried in the gravel of the 
streams. Some say that, after being merely washed, it is 
smelted in the furnace ; others that is washed repeatedly, and 
as often the residue treated with fire in the furnace, together 
with the stone pyrimachus (a stone refractory to the action of 
fire), which occurs there in great abundance. Thus do many 
sorts of substances contain in themselves strikingly and most 
plentifully this ferric and telluric element. Many, too, and 
most plentiful in every soil are the stones and earths and the 
various bodies and compounds, which contain iron (though not 
in such abundance) and yield it in the furnace fire, but which 
are rejected by the metallurgist as not workable with profit ; 
and there are other earths that give evidence of the presence 
of iron in them ; these, being very poor in the metal, are not 
smelted at all, and not being esteemed they are not known. 

The kinds of manufactured iron differ very much from one 
another. For one kind has great tenacity ; and that is the 
best. There is a medium kind. Another kind is brittle ; 
that is the worst. Sometimes the iron, on account of the ex- 
cellence of the ore, is made into steel ; as in Noricum at present. 
From the best iron also, worked over and over again, and purged 
of all impurities, or plunged red-hot into water, is produced 
what the Greeks call O-TOJLK&JMX l and the Latins acies and 
aciarium (steel), and which is variously called Syrian, Parthian, 



1 Stomoma was also the name given to an oxide of copper, which was 
gradually formed upon the surface of metal, when it was kept in a state of 
fusion. Such oxides of copper were used as external applications, seemingly 
as escharotics (Dr. Thomson's Chemistry, 1830, Vol. I, page 60). 



WHAT IRON IS; WHAT ITS MATTER; ITS USE. 41 

Norican, Comese and Spanish ; in other places it takes its name 
from the water in which it is repeatedly immersed, as at Como 
in Italy, and Bilbao and Tariassone in Spain. Steel sells at a 
far higher price than iron. And, on account of its superiority, 
it is in better accord with the magnet. It is often made from 
powerful loadstone, and it acquires the magnetic virtue readily, 
retains it a long time unimpaired and fit for all magnetic ex- 
periments. 

The iron, after it has been smelted in the first furnace, is 
then treated with various processes in great forges or mills, the 
metal under mighty blows acquiring toughness, and dropping 
its impurities. When first smelted it is brittle and by no means 
perfect. Therefore, here in England, when great cannons are 
cast, in order that they may be able to withstand the explo- 
sive force of the ignited gunpowder, the metal is specially 
purged of impurities : while fluid it is made to pass a second 
time through a narrow opening, and thus is freed of recre- 
mental substances. Smiths, with the use of certain liquids and 
hammer-strokes, toughen the iron laminae from which are made 
shields and coats of mail not penetrable by any musket-ball. 
Iron is made harder by skill and tempering; but skill also 
makes it softer and as pliant as lead. It is made hard by cer- 
tain waters into which it is plunged at white heat, as in Spain. 
It is made soft again either by fire alone when, without ham- 
mering and without the use of water, it is allowed to grow 
cool ; or by being dipped in grease ; or it is variously tempered, 
to serve the purposes of the different arts, by being smeared 
with special preparations. This art is described by Baptista 
Porta in book 13 of the Magia Naturalis. 

Thus is this ferric and telluric substance contained in and 
extracted from various kinds of stones, ores, and earths; 
thus too does it differ in appearance, form, and efficiency ; and 



42 WILLIAM GILBERT. 

by various processes of art it is smelted and purified and made 
to serve man's uses in all sorts of trades and in all sorts of tools, 
as no other body can serve. One kind of iron is suitable for 
breastplates, another withstands cannon balls, another pro- 
tects against swords or the curved blades called cimetars ; one 
kind is used in making swords, another in forging horseshoes. 
Of iron are made nails, hinges, bolts, saws, keys, bars, doors, 
folding-doors, spades, rods, pitchforks, heckles, hooks, fish- 
spears, pots, tripods, anvils, hammers, wedges, chains, manacles 
fetters, hoes, mattocks, sickles, hooks for pruning vines and, 
for cutting rushes (scirpiculce), shovels, hoes, weeding-hooks, 
ploughshares, forks, pans, ladles, spoons, roasting-spits, knives, 
daggers, swords, axes, Celtic and Gallic darts (gesstz), Mace- 
donian pikes (saris$&), lances, spears, anchors and many nauti- 
cal implements ; furthermore, bullets, javelins, pikes, corselets, 
helmets, breastplates, horseshoes, greaves, wire, strings of mu- 
sical instruments, armchairs, portcullises, bows, catapults, and 
those pests of humanity, bombs, muskets, cannon-balls, and 
no end of implements unknown to the Latins. I have re- 
counted so many uses in order that the reader may know in 
how many ways this metal is employed. Its use exceeds that 
of all other metals a hundredfold ; it is smelted daily ; and 
there are in every village iron forges. For iron is foremost 
among metals and supplies many human needs, and they the 
most pressing : it is also far more abundant in the earth than 
the other metals, and it is predominant. Therefore it is a vain 
imagination of chemists to deem that nature's purpose is to 
change all metals to gold, that being brightest, heaviest, strong- 
est, as though she were invulnerable, would change all stones 
into diamonds because the diamond surpasses them all in 
brilliancy and in hardness. Iron ore, therefore, as also manu- 
factured iron, is a metal slightly different from the primordial 



IN WHAT COUNTRIES IRON IS PRODUCED. 43 

homogenic telluric body because of the metallic humor it has 
imbibed ; yet not so different but that in proportion as it is 
purified it takes in more and more of the magnetic virtues, and 
associates itself with that prepotent form and duly obeys the 
same. 



CHAPTER VIII. 
IN WHAT COUNTRIES AND REGIONS IRON IS PRODUCED. 

IRON mines are very numerous everywhere both the 
ancient mines mentioned by the earliest writers and the new 
and modern ones. The first and greatest were, I think, in 
Asia, for in the countries of Asia, which naturally abound in 
iron, government and the arts did most flourish ; and there 
were the things needful for man's use first discovered and 
sought for. It is related that iron existed in the neighborhood 
of Andria ; in the land of the Chalybes, on the banks of the 
river Thermodon in Pontus ; in the mountains of Palestine 
on the side toward Arabia ; in Carmania. In Africa, there 
was an iron mine in the island of Meroe. In Europe, iron was 
found in the hills of Britain, as Strabo writes ; in hither Spain, 
in Cantabria ; among the Petrocorii and the Cabi Bituriges in 
Gaul, were smithies in which iron was made. In Germany was 
a mine near Luna, mentioned by Ptolemy ; the Gothinian iron 
is spoken of by Cornelius Tacitus ; and the iron of Noricum is 
famed in poesy ; there was also iron in Crete and in Euboea. 
Many other mines, neither meagre nor scant, but of vast ex- 
tent, were overlooked by writers or were unknown to them. 
Pliny calls hither Spain and the whole region of the Pyrenees 



44 WILLIAM GILBERT. 

an iron country; and he says that, in the part of Cantabria 
washed by the ocean, there is a mountain steep and high which 
(wonderful to tell) is all iron. The earliest mines were iron 
mines, not mines of gold, silver, copper or lead : for iron is 
more sought after for the needs of man ; besides, iron mines 
are plainly visible in every country, in every soil, and they are 
less deep and less encompassed with difficulties than other 
mines. But were I simply to enumerate modern iron mines 
and those worked in our own time, a very large book would 
have to be written, and paper would fail me before iron : yet 
each one of these mines could supply 1000 forges. For among 
minerals there is no other substance so plentiful : all metals 
and all stones distinct from iron ore are surpassed by ferric and 
ferruginous substances. For you cannot easily find a district, 
hardly a township, throughout all Europe, if you search 
thoroughly, that has not a rich and plentiful vein of iron, or 
that does not yield an earth either saturated with iron-rust or 
at least slightly tinctured with it. That this is so, is easily shown 
by any one versed in metallurgy and chemistry. 

Besides iron and its ore, there is another ferric substance, 
which, however, does not yield the metal, because the thin 
humor is burnt up by the fierce fires and is converted into dross 
like that separated from the metal when first smelted. Such 
is the white clay and argillaceous earth which is seen to make 
up great part of our British island ; this, if treated with strong 
heat, either exhibits a ferric and metallic body, or is trans- 
formed into a ferric vitrification : this fact can be verified in 
houses built of brick, for the bricks that in the kiln are laid 
nearest to the fires, and are there burnt, show ferric vitrifica- 
tion at their other end, which grows black. Furthermore, all 
those earths when prepared, are attracted by the magnet like 
iron. Lasting and plentiful is the earth's product of iron. 



IN WHAT COUNTRIES IRON IS PRODUCED. 45 

Georgius Agricola says that nearly all mountainous regions are 
full of its ores ; and we, ourselves, do know that a rich iron ore 
is often dug in the lowlands and plains throughout England 
and Ireland, as Agricola tells of iron being dug in the meadows 
near the town of Saga 1 out of ditches not more than two feet 
deep. Nor is iron lacking, as some say, in the West Indies ; 
but, there, the Spaniards, intent on gold, avoid the toilsome 
manufacture of iron and do not search for rich iron ores and 
mines. It is probable that nature and the terrestrial globe 
cannot repress, but is ever sending forth into the light a great 
quantity of its own native substance, and that this action is not 
entirely impeded by the pressure of the mingled substances 
and efflorescences at the circumference. But iron is produced 
not only in the common mother (the globe of Earth), but 
sometimes is also in the air, in the uppermost clouds from the 
earth's vapors. It rained iron in Lucania the year that Marcus 
Crassus met his death. They tell, too, of a mass of iron, re- 
sembling slag, having fallen out of the air in the Nethorian 
forest near Grina, which is said to have weighed several 
pounds ; and that it could not be carried to that village it was 
so heavy, and could not be taken on a wagon because there 
were no roads. This happened before the Civil War of the 
Saxons, waged by the Dukes. A similar occurrence is men- 
tioned by Avicenna. In the Torinese, it once rained iron at 
several points, some three years before that province was con- 
quered by the King. In the year 1510, as Cardan relates in 

1 "The like wee reade of at Saga in Ligys, where they digge over their 
iron mines every tenth yeare. . . . But whosoever readeth that which Francis 
Leandro hath written touching the iron mineralls in the He of Elba, will cleave 
perhaps to a third conceit, for he avoucheth that the trenches out of which the 
oare there is digged, within twenty or thirty yeares, become alike full againe 
of the same mettall as at first " (Geo. Hakewill's " Apologie," 1635, Lib. II, 
Sec. 7, pages 164-165). 



46 WILLIAM GILBERT. 

his book De Rerum Varietate, there fell from the sky, upon a 
field near the river Abdua, 1200 stones, one of which weighed 
1 20, another 30 or 40, pounds, all of them the color of iron and 
exceedingly hard. These occurrences, because they happen 
seldom, seem to be portents, like the earth-rains and stone- 
showers mentioned in the annals of the Romans. But that it 
ever rained other metals is not mentioned ; for it does not ap- 
pear that gold, silver, lead, tin, or zinc ever fell from heaven. 
But copper has sometimes been observed to fall from the 
clouds a metal differing not much from iron : and this cloud- 
gendered iron and copper are seen to be imperfect metals, ab- 
solutely infusible and unforgeable. For the earth, in its emi- 
nences, abounds in store of iron, and the globe contains great 
plenty of ferric and magnetic matter. Exhalations of such 
matter sent forth with some violence may, with the concur- 
rence of powerful agencies, become condensed in the upper 
regions, and so may be evolved a certain monstrous progeny 
of iron. 



CHAPTER IX. 

IRON ORE ATTRACTS IRON ORE. 

LIKE the other metals, iron is obtained from various sub- 
stances stones, earths, and such-like concretions, called by 
miners ores, or veins, because they are produced in fissures 
of the earth. Of the diversity of ores we have already spoken. 
A piece of crude iron ore of the color of iron and rich, as 
miners say, when floated in a bowl or other vessel in water (as 
in the case of the loadstone supra) is usually attracted by a 



IRON ORE HAS AND ACQUIRES POLES. 47 

like piece of ore held in the hand and brought near to it, but 
it is not attracted strongly and with rapidity as a loadstone is 
drawn by a loadstone, but slowly and weakly. Stony ores, 
and those of an ashy, brown, ruddy, etc., color, neither attract 
one another nor are attracted even by a powerful loadstone, 
any more than so much wood or lead or silver or gold would be. 
Take some pieces of such ores and roast or rather heat them 
in a moderate fire so that they may not suddenly split or fly to 
pieces, and retain them ten or twelve hours in the fire, which 
is to be kept up and moderately increased ; then suffer them 
to cool, according to the method given in Book III, Of Direc- 
tion : these stones so manipulated, the loadstone now attracts ; 
they show mutual sympathy, and, when arranged according to 
artificial conditions, they come together through the action of 
their own forces. 



CHAPTER X. 

IRON ORE HAS AND ACQUIRES POLES, AND ARRANGES ITSELF 
WITH REFERENCE TO THE EARTH'S POLES. 

MEN are deplorably ignorant with respect to natural things,* 
and modern philosophers, as though dreaming in the darkness, 
must be aroused and taught the uses of things, the dealing 
with things ; they must be made to quit the sort of learning 
that comes only from books, and that rests only on vain argu- 
ments from probability and upon conjectures. For the science 
of iron (than which nought is more in use among us), as of 
many other bodies, remains unknown iron, I say, whose rich 
ore, by an inborn force, when floated in a vessel on water, as- 



48 WILL1A2I GILBERT. 

sumes, like the loadstone, a north and south direction, coming 
to a standstill at those points, whence if it be turned away, it 
goes back to them again in virtue of its inborn activity. But 
of less perfect ores which, however, under the guise of stone 
or earth contain a good deal of iron, few possess the power of 
movement ; yet when treated artificially with fire, as told in the 
foregoing chapter, these acquire polar activity,strength (verticity, 
as we call it) ; and not only such ores as miners seek, but even 
earths simply impregnated with ferruginous matter, and many 
kinds of rock, do in like manner (provided they be skilfully 
placed), tend and glide toward those positions of the heavens, 
or rather of the earth, until they reach the point they are 
seeking : there they eagerly rest. 



CHAPTER XI. 

WROUGHT-IRON, NOT MAGNETIZED BY THE LOADSTONE, 
ATTRACTS IRON. 

IRON is extracted in the first furnace from the ore, which is 
converted or separated partly into metal, partly into dross, by 
the action of very great heat continued for eight, ten, or twelve 
hours. The metal flows out, leaving behind the dross and use- 
less substances, and forms a great long mass, which under the 
blows of a large hammer is cut into pieces : from these, after 
being reduced in another furnace and again put on the anvil, 
the workmen form cubical masses, or more usually bars, which 
are sold to merchants and blacksmiths : from these blocks or 
bars are everywhere made in smiths' shops various implements. 



WROUGHT-IRON, NOT MAGNETIZED, ATTRACTS IRON. 49 

This we call wrought-iron, and, as every one knows, it is at- 
tracted by the loadstone. But we, steadily trying all sorts of 
experiments, have discovered that mere iron itself, magnetized 
by no loadstone, nor impregnated with any extraneous force, 
attracts other iron, though it does not seize the other iron as 
eagerly nor as suddenly pulls it to itself as would a strong 
loadstone. That this is so you may learn from the following 
experiment : A small piece of cork, round, and the size of a 
filbert, has an iron wire passed through it to the middle 
of the wire : float this in still water and approach (without 
contact) to one end of that wire, the end of another wire : 
wire attracts wire, and when the one is withdrawn slowly the 
other follows, yet this action takes place only within fit limits. 
In the figure, A is the cork holding the wire, B one end of the 




wire rising a little out of the water, C the end of the second 
wire, which pulls B. You may demonstrate the same thing 
with a larger mass of iron. Suspend in equilibrium with a 
slender silken cord a long rod of polished iron, such as are used 
to support hangings and curtains ; bring within the distance of 
half a finger's length of one end of this as it rests still in the 
air, some oblong mass of polished iron with suitable end : the 
balanced rod returns to the mass : then quickly withdraw 
your hand with the mass in a circular track around the point 
of equilibrium of the suspended rod, and the cord holding the 
rod will travel in a circle. 



50 WILLIAM GILBERT. 



CHAPTER XII. 

A LONG PIECE OF IRON, EVEN NOT MAGNETIZED, ASSUMES A 
NORTH AND SOUTH DIRECTION. 

ALL good and perfect iron, if it be drawn out long, acts 
like a loadstone or like iron rubbed with loadstone : it takes the 
direction north and south a thing not at all understood by 
our great philosophers who have labored in vain to demon- 
strate the properties of the loadstone and the causes of the 
friendship of iron for the loadstone. Experiment can be made 
either with large or small objects of iron, either in air or in 
water. A straight rod of iron six feet in length and as thick 
as one's finger is (as described in the foregoing chapter) sus- 
pended in exact equilibrium with a fine but strong silk thread. 
The thread, however, should be composed of several silk fila- 
ments, twisted differently and not all in one direction. Let the 
experiment be made in a small room with doors and windows all 
closed, to prevent currents of air in the room : hence it is not 
well to experiment on windy days or when a storm is brewing. 
The rod of iron freely acts according to its property and moves 
slowly until at last coming to a stop at its goals it points north 
and south, like magnetized iron in a sun-dial, a common mag- 
netic compass, and the mariner's compass. You may, if you 
are curious of such experiments, suspend at once from slender 
threads, iron rods, or wires, or knitting-needles : you shall find 
them all in accord unless there is some flaw in the conduct of 
this interesting experiment ; for unless you make all the 
preparations precisely and exactly, your labor will be vain. 



FIXED NORTH AND SOUTH PARTS OF IRON. 51 

Test the thing in water also : here the result is more sure and 
more easily obtained. Pass through a round cork an iron wire 
two or three fingers long, more or less, so that it may just float 
in water: the moment you put it in the water it turns round 
on its centre, and one end of the wire travels to the north, the 
other to the south : the cause of this, you will find later, when 
we treat of the reasons of the loadstone's directions. And* 
it is well to know and to hold fast in memory, that as a strong 
loadstone and iron magnetized by the same, point not always 
toward the true pole, but exactly to the point of variation ; 
likewise will a weaker loadstone and iron that directs itself by 
its own force, and not by force derived from the impress of 
any magnet ; so, too, all iron ores, and all substances imbued 
with any ferric matter and duly prepared, turn to the same 
point in the horizon to the place of variation of the locality 
concerned (if variation exist there), and there they remain and 
rest. 



CHAPTER XIII. 

SMELTED IRON HAS IN ITSELF FIXED NORTH AND SOUTH 
PARTS, MAGNETIC ACTIVITY, VERTICITY, AND FIXED 
VERTICES OR POLES. 

IRON takes a direction toward north and south, but not* 
with the same point directed toward either pole ; for one end 
of a piece of iron ore or of an iron wire steadily and constantly 
points to the north and the other to the south, whether it be 
suspended in air, or floating in water, and whether the speci- 
mens be iron bars or thin wires. Even an iron rod or wire ten, 



5 2 WILLIAM GILBERT. 

twenty, or more ells in length will point with one extremity to 
the north, with the other to the south. And if you cut off a 
part, if the farther end of that piece is boreal (northern), the 
farther end of the other piece, with which it was before joined, 
will be austral (southern). And so, if you divide the rod or 
wire into several pieces, you shall know the poles even before 
you make an experiment by floating the pieces in water. In 
all these fragments a boreal end attracts an austral, and repels 
a boreal, and vice versa, according to magnetic law. But, herein, 
manufactured iron so differs from loadstone and iron ore, that 
in a ball of iron of whatever size e.g., bombs, cannon-balls, 
culverin balls, falcon balls polarity (verticity) is less easily 
acquired and less readily manifested than in the loadstone 
itself, in ore, and in a round loadstone ; but in iron instruments 
of any length the force is at once seen : the cause of which, as 
also the modes of acquiring polarity and poles without a load- 
stone, together with the account of all other recondite facts 
touching verticity, we will set forth when we come to treat of 
the movement of direction. 



CHAPTER XIV. 

OF OTHER PROPERTIES OF THE LOADSTONE AND OF ITS 
MEDICINAL VIRTUE. 

DlOSCORlDES tells that loadstone blended in water is ad- 
ministered in a dose of three oboli 1 to expel gross humors. 
Galen writes that it has virtues like those of bloodstone. 

1 Obolus, the sixth part of a drachm. 



OTHER PROPERTIES OF THE LOADSTONE. 53 

Others say that loadstone causes mental disturbance and 
makes people melancholic, and often is fatal. Gartias ab 
Horto does not think it injurious or unwholesome. The people 
of East India, he says, declare that loadstone taken in small 
quantity preserves youthfulness: for this reason the elder King 
Zeilam (Zeilan) is said to have ordered made of loadstone some 
pans for cooking his food (victus). " The man who was ordered 
to do this thing told me," says Gartias. 1 Many are the varie- 
ties of loadstone, produced by different mixtures of earths, 
metals, and humors; therefore are they totally different in 
their virtues and effects, according to the neighborhoods of 
places and the nearness of adhering bodies, and the pits them- 
selves unclean matrices, as it were. Hence one loadstone is 
able to purge the bowels, and another loadstone to stay the 
purging ; with a sort of fumes, it can gravely affect the mind ; 
it may corrode the stomach and produce in it serious disease : 
for such disorders, quacks prescribe gold and emerald, prac- 
tising the vilest imposture for lucre's sake. Pure loadstone 
also may be harmless ; and not only that, but many correct ex- 
cessive humors of the bowels and putrescence of the same, and 
may bring about a better temperature : such loadstones are 
the Oriental ones from China, the more compact loadstones of 



1 GARCIA D'ORTA, "Coloquios dos simples .... pello doutor GARCIA 
DORTA" {sic} Goa 1563. The name of the Portuguese author of this rare work 
who was physician to the Spanish Viceroy (Brown's "Vulgar Errors," Book 
II, page 81) appears as GARCIA AB HORTO in the abridged Latin translation 
made by Charles de 1'Ecluse, Antwerp 1567, 1574, 1579, 1593, under title 
" Aromatum et Simplicium . . . ," and it is rendered in French GARCIE DU 
JARDIN, by Antoine Colin in his " Histoire des Drogues," Lyon 1619, whilst 
in other versions it is given as GARCIA DEL HUERTO. For the passage above 
alluded to by Gilbert, see, more particularly, the last (1593) edition, article De 
Magnete, Lib. I, Cap. LVI, pages 178, 179. Hakewill observes (" Apologie," 
1635, Lib. II, page 165), " Remarkable indeed that is which GARZIAS AB HORTO 
writes concerning the load-stone in Simp I Indite, Lib. I, Cap. XLVII." 



54 WILLIAM GILBERT. 

Bengal : these kinds of loadstone are not distasteful nor un- 
grateful to the senses. Plutarch and Caius Ptolemy, and all 
the copyists that came after them, believe that loadstone 
rubbed with garlic does not attract iron. Hence some writers 
conjecture that garlic is of service against the harmful action 
of loadstone : in this way does many an untrue and vain opinion 
in philosophy take its rise in fables and falsehoods. 1 Not a 
few physicians have thought that loadstone has power to ex- 
tract an iron arrow-head from a human body : but a loadstone 
attracts when it is whole, not when reduced to powder, de- 
formed, buried in a plaster ; for it does not with its matter at- 
tract in such case, but serves rather to heal the ruptured tissues 
by exsiccation, so causing the wound to close and dry up, 
whereby the arrow-head becomes fixed in the wound. Thus 
do pretenders to science vainly and preposterously seek for 
remedies, ignorant of the true causes of things. Headaches, 
despite the opinion of many, are no more cured by application 
of a loadstone, than by putting on the head an iron helmet or 
a steel hat. Administration of loadstone to dropsical persons 
is either an error of the ancients or a blundering quotation of 
their transcribers, albeit a loadstone may be found capable of 
purging the bowels, after the manner of sundry metallic sub- 
stances : but the effect would be due to some vice of the stone, 
not to its magnetic force. Nicolaus puts into his " divine 
plaster" a good deal of loadstone, as do the Augsburg doctors 
in their " black plaster" for fresh wounds and stabs ; because 
of the exsiccating effect of the loadstone without corrosion, it 
becomes an efficacious and useful remedy, Paracelsus, in like 
manner and for the same end, makes loadstone an ingredient 
of his plaster for stab-wounds. 

1 See note, Book I, Chap. I, of present work. 



THE MEDICINAL POWER OF THE IRON. 55 



CHAPTER XV. 

THE MEDICINAL POWER OF THE IRON. 

IT will not be alien to our purpose to treat briefly of the 
medicinal power of iron ; for it is beneficial in many diseases 
of the human system, and by its virtues, both natural and 
acquired through fit and skilful preparation, it brings about won- 
derful changes in the human body ; so that we may more clearly 
describe its nature through its medicinal power and by means 
of a few well-known experiments ; to the end that even those 
prentices of medicine who abuse this most excellent medicinal 
agent may learn to prescribe it more judiciously, for the curing 
of patients, not as is too often the case, to their destruction. 
The best iron, i.e., stomoma, chalybs, acies, or aciarium (steel), 
is reduced by filing to a fine powder ; this powder has strongest 
vinegar poured on it, is dried in the sun, again treated with 
vinegar, and once more dried. Then it is washed in spring 
water or other water at hand, and dried. It is again pulverized 
and pounded fine on porphyry, sifted through a fine sieve, and 
kept for use. It is given chiefly in cases of lax and over- 
humid liver, and in cases of tumid spleen after suitable evacua- 
tions ; hence young women of pale, muddy, blotchy complexion 
are by it restored to soundness and comeliness, for it is highly 
exsiccative and harmlessly astringent. But some, who in every 
internal disorder always recognize obstructions of liver and 
spleen, think it beneficial in such cases, as removing obstruc- 
tions ; and herein they accept the opinions chiefly of certain 
Arabic writers. Hence in cases of dropsy, schirrus of the 



5 6 WILLIAM GILBERT. 

liver, of chronic jaundice, and hypochondriac melancholia, or 
complaints of the oesophagus, they prescribe it, or add it to 
electuaries, often to the sure destruction of many a patient. 1 
Fallopius recommends a preparation of iron of his own for 
schirrus of the spleen ; but he is much mistaken, for though 
loadstone is exceedingly beneficial where the spleen is lax and 
tumid on account of humors, so far is it from curing a spleen 
thickened to a schirrus, that it makes the mischief far worse ; 
for agents that are greatly siccative and that absorb humors, 
transform viscera that have been thickened by schirrus, into 
the hardness almost of a stone. Some there are who dry it 
at a high temperature in an oven, burning it till its color is 
changed to red : it is then called " saffron of Mars," 2 and is a 
very powerful exsiccant and quickly penetrates the intestines. 
Further, they prescribe violent exercise so that the remedy 
may enter the heated intestines and reach the part affected. 
Hence it is reduced to a very fine powder ; else it would re- 
main in the oesophagus and in the chyle and would not pene- 
trate to the intestines. Therefore this dry, earthly medicament 
is proved by the most conclusive tests to be, after due evacua- 
tions, a remedy in diseases arising from humor (when the intes- 
tines are running and overflowing with morbid fluids). A 
preparation of steel is indicated for tumid spleen ; chalybeate 
waters also reduce the spleen, albeit, as a rule, iron is of frigid 
efficiency and a constringent rather than a resolvent ; but it 
does this neither by heat nor by cold, but by its own dryness 

1 " The magnet .... gives comfort and grace, and is a cure for many com- 
plaints, it is of great value in disputes. When pulverized, it cures many burns. 
It is a remedy for dropsy " (J. Sermone di F. Sacchetti , 18). Ac- 
cording to Dias, "the magnet reconciles husbands to their wives," and Platea 
remarks that "it is principally of use to the wounded," while Avicenna says 
it " is a remedy against spleen, the dropsy, and alopecian." 

3 See Book II, Chap. XXIII. 



THE MEDICINAL POWER OF THE IRON. $? 

when mixed with a penetrant fluid ; in this way it dissipates 
humors, thickens the villi ; strengthens the fibres and when 
they are lax makes them contract ; then the natural warmth in 
the organs thus strengthened becoming stronger does the rest ; 
but should the liver be indurated and impaired through age or 
chronic obstruction, or should the spleen be dried up and 
thickened into a schirrhus, under which complaints the flesh 
parts of the members become atrophied, and water collects all 
over the body under the skin in such cases the preparation 
of steel does but hasten a fatal result and makes the mischief 
worse. Some recent authorities prescribe, as a* highly com- 
mended and celebrated remedy for dried-up liver, an electuary 
of iron slag described by Razes (Rhazes Abu Bekr Arrasi) in 
book ninth Ad Almansorem, or of prepared steel filings: bad 
and pernicious counsel. But now if they never will learn from 
our philosophy, at least daily experience and the decline and 
death of their patients will convince them, slow and sluggish 
as they are. Whether iron be warm or cold is a question over 
which many contend. Manardus, Curtius, Fallopius, and others 
bring many arguments for both sides : every one judges accord- 
ing to his own way of looking at it. Some will have it cold, 
saying that iron has the power of refrigeration, since Aristotle 
in the Meteorologica declares it to belong to the class of bodies 
that become concreted through cold by emission of all their 
warmth. Galen, too, says that iron gets its consistency from 
cold ; further, that it is an earthy body and dense. It is de- 
clared to be cold also because it is astringent, and because 
chalybeate water stills thirst ; they mention also the sensation 
of coolness produced by thermic chalybeate waters. But others 
hold it to be warm, since Hippocrates says that chalybeate 
waters issuing from places where iron exists are warm. Galen 
says that in all metals there is much substance or essence of 



5 WILLIAM GILBERT. 

fire. Razes will have it that iron is warm and dry in the third 
degree. The Arabs hold that iron opens the spleen and the 
liver : hence it is warm. Montagnana recommends it for frigid 
complaints of uterus and oesophagus. And thus do sciolists 
wrangle with one another, and confuse the minds of learners 
with their questionable cogitations, and debate over the ques- 
tion of goat's wool, philosophizing about properties illogically 
inferred and accepted : but these things will appear more 
plainly when we come to treat of causes, the murky cloud being 
dispersed that has so long involved all philosophy. Iron filings, 
iron scales, iron dross, do not, says Avicenna, lack harmful 
quality (perhaps when they are not properly prepared, or are 
taken in too large doses), hence they produce violent intes- 
tinal pains, roughness in the mouth and on the tongue, 
marasmus, and drying up of the members. But mistakenly 
and old womanishly does Avicenna declare that the true anti- 
dote of this ferric poison is a drachm of loadstone taken in a 
draught of the juice of dog's mercury or of beet-root ; for load- 
stone too is of a twofold nature, and often is injurious and 
fatal in its effects ; neither does it withstand iron, for it attracts 
it ; nor is it able to attract when drunk as a powder in liquid ; 
rather does it cause the self-same mischiefs. 



IDENTITY OF LOADSTONE AND IRON ORE. 59 



CHAPTER XVI. 

THAT LOADSTONE AND IRON ORE ARE THE SAME, AND THAT 
IRON IS OBTAINED FROM BOTH, LIKE OTHER METALS FROM 
THEIR ORES ; AND THAT ALL MAGNETIC PROPERTIES EX- 
IST, THOUGH WEAKER, BOTH IN SMELTED IRON AND IN 
IRON ORE. * 

So far we have been telling of the nature and properties of 
loadstone, as also of the properties and nature of iron ; it now 
remains that we point out their mutual affinities their consan- 
guinity, so to speak and that we show the two substances to 
be very nearly allied. In the uppermost part of the terrestrial 
globe or its superficies of detritus its rind as it were these 
two bodies come into being and are generated in the same 
matrix, in one bed, like twins. Strong loadstones are mined 
from separate deposits, and weaker loadstones also have 
their own beds. Both occur in iron mines. Iron ore occurs 
usually by itself, unaccompanied by strong loadstone (for the 
more perfect loadstones occur more rarely). A strong load- 
stone looks like iron : from it is often made the best iron, which 
the Greeks call stomoma, the Latins odes, and the Barbarians, 
not inappropriately, aciare or aciarium. This stone attracts and 
repels other loadstones, and governs their directions ; points to 
the earth's poles, attracts molten iron, and does many other 
wonderful things, some of which we have already mentioned, 
but many more remain yet to be pointed out. A weak load- 
stone will do the same, but less forcefully : and iron ore, and 
also smelted iron (if they be prepared), show their virtues 



60 WILLIAM GILBERT. 

* in all magnetic experiments, no less than do weak magnets ; 
and the inert iron ore, endowed with no magnetic powers, 
that is taken out of the mine, becomes awake when treated 
in the furnace and fittingly prepared, and then is a loadstone 

*in power and properties. Sometimes ironstone or iron 
ore exerts attractive action the moment it comes from the 
mine, and without being prepared in any way ; native iron, 
also, or ore of iron color, attracts iron and makes it point 
to the poles. Thus the form, appearance, and essence are one. 
For to me there seems to be greater difference and unlikeness 
between a very strong loadstone and a weak one that is hardly 
able to attract a single particle of iron filings ; between a hard, 
firm, and metallic loadstone and one that is soft, friable, clayey, 
with so great a difference between them in color, substance, 
qualities and weight ; than between the best ore, rich in iron, 
or iron that from the first is metallic, on the one hand, and the 
best loadstone on the other. Nay, the two are usually not to 
be distinguished by any signs, nor can miners tell one from the 
other, for they agree in all respects. Further, we see both 
the finest magnet and iron ore visited as it were by the same 
ills and diseases, aging in the same way and with the same in- 
dications, preserved by the same remedies and protective meas- 
ures, and so retaining their properties : so, too, the one adds 
to the other's power and intensifies and increases it, when the 
two are artificially connected. For they are both impaired by 
the action of acrid liquids as though by poisons ; the aqua 
fortis of the chemists does equal injury to both; exposed for a 
long time to the action of the atmosphere they both, in equal de- 
gree, age as it were and decline ; each is saved from impairment 
by being kept in the debris and scrapings of the other, and a suit- 
able piece of steel or iron being applied to its pole, the mag- 
netic power is intensified by the steadfast union. A loadstone 



IDENTITY OF LOADSTONE AND IRON ORE. 6 1 

is kept in iron filings not as though it fed on iron, or as though 
it were a living thing needing victual, as Cardan philosophizes ; 
neither because thus it is protected from the injurious action of 
the atmosphere (wherefore both the loadstone and iron are 
kept in bran by Scaliger; though Scaliger is mistaken here, for 
they are not best preserved so, and loadstone and iron in some 
of their forms last a long time) ; but because each is kept unim- 
paired in filings of the other and their extremities do not be- 
come weak, but are cherished and preserved. For as in their 
native sites and mines, similar bodies surrounded by other 
bodies of the same kind, e.g., the minor interior parts of some 
great mass, endure for ages whole and undecayed ; so load- 
stone, and iron ore, when buried in a like material, do not part 
with their native humor, and do not become weak, but retain 
their original properties. A loadstone packed in iron filings, 
as also iron ore in scrapings of loadstone, and manufactured 
iron in the same or in iron filings, lasts longer. Thus these 
two associated bodies possess the true, strict form of one species, 
though, because of their outwardly different aspect and the in- 
equality of the self-same innate potency, they have hitherto 
been by all held to be different, and by sciolists to be specifi- 
cally different, for sciolists have not understood that in both 
substances reside exactly the same potencies, differing however 
in strength. They are in fact true parts and intimate parts of 
the globe, retaining nature's primal powers of mutual attrac- 
tion, of mobility, and of ordering themselves according to the 
position of the globe itself : these powers they impart to each 
other, enhancing each other's powers, confirming them, taking 
them from each other, and holding them. The stronger invig- 
orates the weaker, not as if it imparted of its own substance or 
parted with aught of its own strength, neither by injecting into 
that other any physical substance ; but the dormant power of 



62 WILLIAM GILBERT. 

one is awakened by the other's without expenditure. For if 
with one loadstone you magnetize one thousand compass 
needles for mariners' use that loadstone not less powerfully 
attracts iron than it did before ; with one stone weighing a 
pound any one can suspend in air 1000 pounds of iron. For 
if one were to drive into a wall a number of iron nails weighing 
all together 1000 pounds, and were to apply to them an equal 
number of other nails properly magnetized by contact with a 
loadstone, the nails would plainly hang suspended in air through 
the power of one single stone. Hence this is not the action, 
work, or outlay of the loadstone solely, for the iron, which is 
something extracted from loadstone, a transformation of load- 
stone into metal, and which gains force from the loadstone and 
(whatever ore it may have been derived from) by its proximity 
strengthens the loadstone's magnetic power, at the same time 
enhances its own native force by the proximity of the load- 
stone and by contact therewith, even though solid bodies inter- 
vene between them. Iron touched by loadstone renovates 
other iron by contact and gives it magnetic direction ; and 
that does the same for a third piece of iron. But if you rub 
with loadstone any other metal, or wood, or bone, or glass, as 
they will not move toward a fixed and determinate quarter of 
the heavens, nor will be attracted by a magnetized body ; so 
they cannot impart by attrition or by infection any magnetic 
property either to other bodies or to iron itself. Loadstone 
differs from iron ore, as also from some weak loadstones, in that 
when reduced in the furnace to a ferric and metallic molten 
mass, it does not always assume readily the fluid condition and 
become changed to metal, but sometimes is burnt into ash in 
the large furnaces ; this, either because of a certain admixture 
of sulphurous matter, or because of its own excellence and 
more simple nature ; or because of the resemblance it bears 



IDENTITY OF LOADSTONE AND IRON ORE. 63 

to nature, and the form it has in common with that mother 
of all ; for earths, ferruginous stones, and loadstones rich in 
metal, are much loaded and disfigured with drossy metallic 
humors and with foreign earthy admixtures in their substance, 
like most weak magnets from the mines ; hence they are farther 
removed from the common mother and are degenerate, and in 
the furnace they are more easily melted and give a softer sort 
of iron and no good steel. Most loadstones, if they be not un- 
duly burnt, yield in the furnace the best of iron. But in all 
these prime qualities iron ore agrees with loadstone, for both, 
being more akin to the earth and more nearly associated to it 
than any other bodies around us, possess within themselves the 
magnetic, genuine, homogenic and true substance of the terres- 
trial globe, less tainted and impaired by foreign impurities, and 
less mixed with the efflorescences on the earth's surface and 
the debris of generations of organisms. And on this ground 
does Aristotle seem, in book fourth of his Meteora, to distinguish 
iron from all other metals. Gold, says he, silver, copper, tin, 
lead, pertain to water ; but iron is earthy. Galen, in the fourth 
book De Facultatibus Simplicium Medicament or um, says that 
iron is an earthy and dense body. So, according to our rea- 
soning, loadstone is chiefly earthy ; next after it comes iron ore 
or weak loadstone ; and thus loadstone is by origin and nature 
ferruginous, and iron magnetic, and the two are one in species. 
Iron ore in the furnace yields iron ; loadstone in the furnace 
yields iron also, but of far finer quality, which is called steel ; 
and the better sort of iron ore is weak loadstone, just as the 
best loadstone is the most excellent iron ore in which we will 
show that grand and noble primary properties inhere. It 
is only in weaker loadstone, or iron ore, that these properties 
are obscure, or faint, or scarcely perceptible to the senses. 



64 WILLIAM GILBERT. 



CHAPTER XVII. 

THAT THE TERRESTRIAL GLOBE IS MAGNETIC AND IS A LOAD- 
STONE ; AND JUST AS IN OUR HANDS THE LOADSTONE 
POSSESSES ALL THE PRIMARY POWERS (FORCES) OF THE 
EARTH, SO THE EARTH BY REASON OF THE SAME POTEN- 
CIES LIES EVER IN THE SAME DIRECTION IN THE UNI- 
VERSE. 

BEFORE we expound the causes of the magnetic movements 
and bring forward our demonstrations and experiments touch- 
ing matters that for so many ages have lain hid the real 
foundations of terrestrial philosophy we must formulate our 
new and till now unheard-of view of the earth, and submit it 
to the judgment of scholars. When it shall have been sup- 
ported with a few arguments of prima facie cogency, and these 
shall have been confirmed by subsequent experiments and 
demonstrations, it will stand as firm as aught that ever was pro- 
posed in philosophy, backed by ingenious argumentation, or but- 
tressed by mathematical demonstrations. The terrestrial mass 
which together with the world of waters produces the spherical 
figure and our globe, inasmuch as it consists of firm durable 
matter, is not easily altered, does not wander nor fluctuate with 
indeterminate movements like the seas and the flowing streams ; 
but in certain hollows, within certain bounds, and in many 
veins and arteries, as it were, holds the entire volume of liquid 
matter, nor suffers it to spread abroad and be dissipated. But 
the solid mass of the earth has the greater volume and holds 
preeminence in the constitution of our globe. Yet the water is 



THE TERRESTRIAL GLOBE A LOADSTONE. 65 

associated with it, though only as something supplementary 
and as a flux emanating from it ; and from the beginning it is 
intimately mixed with the smallest particles of earth and is 
innate in its substance. The earth growing hot emits it as 
vapor, which is of the greatest service to the generation of 
things. But the strong foundation of the globe, its great mass, 
is that terrene body, far surpassing in quantity the whole 
aggregate of fluids and waters whether in combination with 
earth or free (whatever vulgar philosophers may dream about 
the magnitudes and proportions of their elements) ; and this 
mass makes up most of the globe, constituting nearly its whole 
interior framework, and of itself taking on the spherical form. 
For the seas do but fill certain not very deep hollows, having 
very rarely a depth of a mile, and often not exceeding 100 or 
50 fathoms. This appears from the observations of navigators 
who have with line and sinker explored their bottoms. In view 
of the earth's dimension, such depressions cannot much impair 
the spheroidal shape of the globe. Still the portion of the 
earth that ever comes into view for man or that is brought to 
the surface seems small indeed, for we cannot penetrate deep 
into its bowels, beyond the debris of its outermost efflorescence, 
hindered either by the waters that flow as through veins into 
great mines ; or by the lack of wholesome air necessary to sup- 
port the life of the miners ; or by the enormous cost of exe- 
cuting such vast undertakings, and the many difficulties attend- 
ing the work. Thus we cannot reach the inner parts of the 
globe, and if one goes down, as in a few mines, 400 fathoms, or 
(a very rare thing) 500 fathoms, it is something to make every 
one wonder. But how small, how almost null, is the proportion 
of 500 fathoms to the earth's diameter, 6,872 miles, can be easily 
understood. So we do only see portions of the earth's circum- 
ference, of its prominences ; and everywhere these are either 



65 



IV ILL I A M GILBER T. 



loamy, or argillaceous, or sandy ; or consist of organic soils or 
marls ; or it is all stones and gravel ; or we find rock-salt, or 
ores, or sundry other metallic substances. In the depths of 
the ocean and other waters are found by mariners, when they 
take soundings, ledges and great reefs, or bowlders, or sands, 
or ooze. The Aristotelian element, earth, nowhere is seen, 
and the Peripatetics are misled by their vain dreams about 
elements. But the great bulk of the globe beneath the sur- 
face and its inmost parts do not consist of such matters ; for 
these things had not been were it not that the surface was in 
contact with and exposed to the atmosphere, the waters, and 
the radiations and influences of the heavenly bodies ; for by 
the action of these are they generated and made to assume 
many different forms of things, and to change perpetually. 
Still do they imitate the inner parts and resemble their source, 
because their matter is of the earth, albeit they have lost the 
prime qualities and the true nature of terrene matter; and they 
bear toward the earth's centre and cohere to the globe and can- 
not be parted from it save by force. Yet the loadstone and all 
magnetic bodies not only the stone but all magnetic, homo- 
genie matter seem to contain within themselves the potency 
of the earth's core and of its inmost viscera, and to have and 
comprise whatever in the earth's substance is privy and inward : 
the loadstone possesses the actions peculiar to the globe, of at- 
traction, polarity, revolution, of taking position in the universe 
according to the law of the whole ; it contains the supreme 
excellencies of the globe and orders them : all this is token and 
proof of a certain eminent combination and of a most accord- 
ant nature. For, if among bodies one sees aught that moves 
and breathes and has senses and is governed and impelled by 
reason, will he not, knowing and seeing this, say that here is a 
man or something more like man than a stone or a stalk ? The 



THE TERRESTRIAL GLOBE A LOADSTONE. 6? 

loadstone far surpasses all other bodies around us in the 
virtues and properties that pertain to the common mother of 
all ; but those properties have been very little understood and 
noted by philosophers. Toward it, as we see in the case of the 
earth, magnetic bodies tend from all sides, and adhere to it ; 
it has poles not mathematical points, but natural points of 
force that through the co-operation of all its parts excel in 
prime efficiency; such poles exist also in the same way in the 
globe, and our forefathers always sought them in the heavens. 
Like the earth, it has an equator, a natural line of demarkation 
between the two poles ; for of all the lines drawn by mathe- 
maticians on the terrestrial globe, the equator (as later will 
appear) is a natural boundary, and not merely a mathematical 
circle. Like the earth, the loadstone has the power of direction 
and of standing still at north and south ; it has also a circular 
motion to the earth's position, whereby it adjusts itself to the 
earth's law. It follows the elevations and depressions of the 
earth's poles, and conforms precisely to them : according to the 
position of the earth and of the locality, it naturally and of 
itself elevates its poles above the horizon, or depresses them. 
The loadstone derives properties from the earth ex tempore, 
and acquires verticity ; and iron is affected by the verticity of 
the globe as it is affected by a loadstone. Magnetic bodies 
are governed and regulated by the earth, and they are subject 
to the earth in all their movements. All the movements of the 
loadstone are in accord with the geometry and form of the 
earth and are strictly controlled thereby, as will later be proved 
by conclusive experiments and diagrams ; and the greater part 
of the visible earth is also magnetic, and has magnetic move- 
ments, though it is defaced by all sorts of waste matter and 
by no end of transformations. Why, then, do we not recog- 



68 WILLIAM GILBERT. 

nize this primary and homogeneous earth-substance, likest of 
all substances to the inmost nature, to the very marrow, of the 
earth itself, and nearest to it ? For not any of the other mixed 
eaiths those suitable for agriculture, not any of the metal- 
liferous veins, no stones, no sands, no other fragments of the 
globe that come under our notice, possess such stable, such 
distinctive virtues. Yet we do not hold the whole interior of 
this our globe to be of rock or of iron, albeit the learned 
Franciscus Maurolycus l deems the earth in its interior to con- 
sist throughout of rigid rock. For not every loadstone that 
we find is a stone, being sometimes like a clod of earth, or like 
clay, or like iron ; consisting of various materials compacted 
into hardness, or soft, or by heat reduced to the metallic state ; 
and in the earth's surface formations, according to circum- 
stances of place, of the bodies around it, and of its matrix in 
the mine, a magnetic substance is distinguished by divers 
qualities and by adventitious accretions, as we see in marl, 
in some stones, and in iron ores. But the true earth-matter 
we hold to be a solid body homogeneous with the globe, 
firmly coherent, endowed with a primordial and (as in the 
other globes of the universe) an energic form. By being so 
fashioned,, the earth has a fixed verticity, and necessarily re- 
volves with an innate whirling motion : this motion the load- 
stone alone of all the bodies around us possesses genuine and 



1 Francis Maurolico Maurolycus, Marullo (1494-1575) was abbot of 
Messina, where he publicly taught mathematics, and was quite a voluminous 
writer upon different scientific subjects, his works including very able treatises, 
more particularly on the sphere, on astronomical instruments, etc. A full 
account of his life and writings was issued at Messina (Messanae) in 1613, the 
date and place likewise of his very interesting magnetical book entitled " Prob- 
lemata mechanica, cum appendice et ad magnetem, et ad pixidem nauticam 
pertinentia." 



THE TERRESTRIAL GLOBE A LOADSTONE. 69 

true, less spoilt by outside interferences, less marred than in 
other bodies, as though the motion were an homogeneous 
part taken from the very essence of our globe. This pure 
native iron is produced when homogenic portions of the 
earth's substance coalesce to form a metallic vein ; loadstone 
is produced when they are transformed into metallic stone or 
a vein of the finest iron or steel ; so, too, rather imperfect 
homogenic material collects to form other iron ores just as 
many parts of the earth, even parts that rise above the general 
circumference, are of homogenic matter, only still more de- 
based. Native iron is iron fused and reduced from homogenic 
matters, and coheres to earth more tenaciously than the ores 
themselves. Such, then, we consider the earth to be in its in- 
terior parts ; it possesses a magnetic homogenic nature. On 
this more perfect material (foundation) the whole world of 
things terrestrial, which, when we search diligently, manifests 
itself to us everywhere, in all the magnetic metals and iron ores 
and marls, and multitudinous earths and stones ; but Aristotle's 
" simple element," and that most vain terrestrial phantasm of 
the Peripatetics, formless, inert, cold, dry, simple matter, the 
substratum of all things, having no activity, never appeared 
to any one even in dreams, and if it did appear would be of 
no effect in nature. Our philosophers dreamt only of an inert 
and simple matter. Cardan thinks the loadstone is not a stone 
of any species, but that it is, as it were, a perfect portion of a 
certain kind of earth that is absolute, whereof a proof is its 
abundance, for there is no place where it is not found. He 
says that this kind of conceptive, generative earth, possessed 
of an affinity like that of the marriage tie, is perfected when 
it has been placed in contact with, or received the fecundating 
influence of, the masculine or Herculean stone, it having been, 



7O V/ILLIAM GILBERT. 

moreover, shown in a previous proposition (Libra de Propor- 
tionibus] that the loadstone is true earth. 1 

A strong loads.tone shows itself to be of the inmost earth, 
and in innumerable experiments proves its claim to the honor 
of possessing the primal form of things terrestrial, in virtue of 
which the earth itself remains in its position and is directed in 
its movements. So a weak loadstone, and all iron ore, all 
marls and argillaceous and other earths (some more, some less, 
according to the difference of their humors and the varying 
degrees in which they have been spoilt by decay), retain, de- 
formed, in a state of degeneration from the primordial form, 
magnetic properties, powers, that are conspicuous and in the 
true sense telluric. For not only does metallic iron turn to the 
poles, not only is one loadstone attracted by another and made 
to revolve magnetically, but so do (if prepared) all iron ores 
and even other stones, as slates from the Rhineland, the black 
slates (ardoises, as the French call them) from Anjou, which 
are used for shingles, and other sorts of fissile stone of different 
colors ; also clays, gravel, and several sorts of rock ; and, in 
short, all of the harder earths found everywhere, provided 
only they be not fouled by oozy and dank defilements like 
mud, mire, heaps of putrid matter, or by the decaying remains 
of a mixture of organic matters, so that a greasy slime oozes 
from them, as from marl, they are all attracted by the load- 
stone, after being prepared simply by the action of fire and 
freed from their excrementitious humor ; and as by the load- 
stone, so, too, are they magnetically attracted and made to 
point to the poles by the earth itself, therein differing from all 

1 Consult Cardan's Works, Lugduni (Lyons), 1663 e d., Vol. II, De Ex- 
tniplo. . . ., pages 539, 546, Vol. Ill, Lib. V, Cap. XVII-XIX, Vol. X, Cap. VI, 
page 12. 



THE TERRESTRIAL GLOBE A LOADSTONE. Jl 

other bodies ; and by this innate force they are made to con- 
form to the ordering and planning of the universe and the 
earth, as later will appear. Thus every separate fragment of 
the earth exhibits in indubitable experiments the whole im- 
petus of magnetic matter; in its various movements it follows 
the terrestrial globe and the common principle of motion. 





BOOK SECOND. 



CHAPTER I. 

OF MAGNETIC MOVEMENTS. 

OF opinions touching the loadstone and its varieties ; of its 
poles and its recognized faculties (facultatibus) ; of iron and its 
properties ; of the magnetic substance common to loadstone 
and iron and the earth itself, we have treated briefly in the 
foregoing book. Now remain the magnetic movements and 
their broader philosophy as developed by experiments and 
demonstrations. These movements are impulsions of homo- 
geneous parts toward one another or toward the primary con- 
formation of the whole earth. Aristotle admits only two 
simple movements of his elements from the centre and 
toward the centre ; light objects upward, heavy objects down- 
ward : so that in the earth there is but one motion of all its 
parts toward the centre of the world, a wild headlong falling. 
We, however, will elsewhere consider what this ' light ' may 

be, and will show how erroneously it is inferred by the Peri- 

72 



OF MAGNETIC MOVEMENTS. 73 

patetics from the simple motion of the elements ; we shall 
also inquire what 'heavy' means. 1 But now we have to in- 
quire into the causes of the other movements depending on 
its true form : these we see clearly in all magnetic bodies ; these 
also we find existing in the earth and all its homogenic parts ; 
further, we find that they are in accord with the earth, and are 
bound up in its forces. Now five movements or differences of 
movement are perceived by us : COITION 2 (commonly called 
attraction), an impulsion to magnetic union ; DIRECTION 3 
toward the earth's poles, and verticity of the earth toward 
determinate points in the universe, and the standstill there ; 
VARIATION, 4 deflection from the meridian, this we call a per- 
verted motion ; DECLINATION 6 (inclination or dip), a descent 
of the magnetic pole beneath the horizon ; and circular move- 
ment, or REVOLUTION. 6 Of each of these we will treat sepa- 
rately, and will show how they all proceed from a congregant 
nature, or from verticity or from volubility. Jofrancus Offusius 
distinguishes several magnetic movements, the first to the 
centre, the second to the pole, traversing 77 degrees, the third 
to iron, the fourth to a loadstone. The first is not always to 
the centre, for only at the poles is it in a right line to the 
centre, if the motion is magnetic, otherwise it is only the 
movement of matter toward its mass and toward the earth. 
The second, of 77 degrees to the pole, is no movement, but a 
direction or a variation to the earth's pole. The third and 
the fourth are magnetic, and are but one movement. Thus 
this author recognizes no true magnetic movement but coition 



1 See Plato's Timceus (tr. of Mr. Henry Davis), London 1849, Vol. II, 
pages 372-374- 

2 See Book II, Chap. II, et seq. 3 See Book III. 
4 See Book IV. 6 See Book V. 

6 See Book VI, Chap. Ill, et seq. 



74 WILLIAM GILBERT. 

toward iron or loadstone, commonly known as attraction. 
There is another movement in the earth as a whole, which 
does not take place toward the terrella or the parts, i.e., the 
movement of coacervation and that movement of matter 
called by philosophers a " right movement:" of that elsewhere. 



CHAPTER II. 

OF MAGNETIC COITION ; AND, FIRST, OF THE ATTRACTION EX- 
ERTED BY AMBER, OR MORE PROPERLY THE ATTACHMENT 
OF BODIES TO AMBER. 

GREAT has ever been the fame of the loadstone and of 
amber in the writings of the learned : many philosophers cite 
the loadstone and also amber whenever, in explaining mysteries, 
their minds become obfuscated and reason can no farther go. 1 
Over-inquisitive theologians, too, seek to light up God's mys- 
teries and things beyond man's understanding by means of 
the loadstone and amber : just as light-headed metaphysicians, 
when they utter and teach their vain imaginings, employ the 
loadstone as a sort of Delphic sword and as an illustration of 
all sorts of things. Medical men also (at the bidding of Galen), 
in proving that purgative medicines exercise attraction through 
likeness of substance and kinships of juices (a silly error and 
gratuitous !), bring in as a witness the loadstone, a substance 

1 Dr. Wm. Whewell remarks that the manner in which Gilbert expresses 
himself shows us how mysterious the fact of attraction then appeared, so that, 
as he says, " the magnet and amber were called in aid by philosophers as 
illustrations, when our sense is in the dark in abstruse inquiries; and when our 
reason can go no further" (" Hist, of Ind. Sc.", 1859, Vol. II, page 192). 



MAGNETIC COITION. ?$ 

of great authority and of noteworthy efficiency, and a body of 
no common order. Thus in very many affairs persons who 
plead for a cause the merits of which they cannot set forth, 
bring in as masked advocates the loadstone and amber. But 
all these, besides sharing the general misapprehension, are 
ignorant that the causes of the loadstone's movements are 
very different from those which give to amber its properties ; 
hence they easily fall into errors, and by their own imaginings 
are led farther and farther astray. For in other bodies is seen 
a considerable power of attraction, differing from that of the 
loadstone, in amber, for example. Of this substance a few 
words must be said, to show the nature of the attachment of 
bodies to it, and to point out the vast difference between this 
and the magnetic actions; for men still continue in ignorance, 
and deem that inclination of bodies to amber to be an attrac- 
tion, and comparable to the magnetic coition. The Greeks call 
this substance //Ae/crpor, because, when heated by rubbing, it 
attracts to itself chaff ; whence it is also called apnag, and 
from its golden color, jpvcro0opor. 1 But the Moors call it 
carabe, because they used to offer it in sacrifices and in the 



1 The ancients were acquainted with but two electrical bodies amber, 
(electron), which has given the denomination of the science; and lyncurium, 
which is either the tourmaline or the topaz (Dr. Davy, " Mem. Sir Hum. 
Davy," 1836, Vol. I, page 309). From a recent article treating of gems, the 
following is extracted: The name of the precious stone inserted in the ring of 
Gyges has not been handed down to us, but it is probable that it was the topaz, 
whose wonders Philostrates recounts in the life of Apollonius. An attribute of 
the sun and of fire, the ancients called it the gold magnet, as it was credited 
with the power of attracting that metal, indicating its veins, and discovering 
treasures. Heliodorus, in his story of Theagenes and Caricles, says that the 
topaz saves from fire all those who wear it, and that Caricles was preserved by 
a topaz from the fiery vengeance of Arsaces, Queen of Ethiopia. This stone 
was one of the irst talismans that Theagenes possessed in Egypt. The topaz 
at present symbolizes Christian virtues, faith, justice, temperance, gentleness, 
clemency. 



76 WILLIAM GILBERT. 

worship of the gods; for in Arabic carab means oblation, not 
rapiens paleas (snatching chaff), as Scaliger would have it, 
quoting from the Arabic or Persian of Abohali (Hali Abbas). 1 
Many call this substance ambra (amber) f especially that which 
is brought from India and Ethiopia. 2 The Latin name succi- 
num appears to be formed from succus, juice. 3 The Suda- 
vienses or Sudini call the substance geniter, as though genitum 
terra (produced by the earth). The erroneous opinion of the 
ancients as to its nature and source being exploded, it is 
certain that amber comes for the most part from the sea : it is 
gathered on the coast after heavy storms, in nets and through 
other means, by peasants, as by the Sudini of Prussia ; it is 
also sometimes found on the coast of our own Britain. But it 
seems to be produced in the earth and at considerable depth 
below its surface, like the rest of the bitumens ; then to be 
washed out by the sea-waves, and to gain consistency under 
the action of the sea and the saltness of its waters. For at 
first it was a soft and viscous matter, and hence contains, 
buried in its mass forevermore (czternis sepulchris relucentes], 
but still (shining) visible, flies, grubs, midges, and ants. The 
ancients as well as moderns tell (and their report is confined 
by experience) that amber attracts straws and chaff. The 
same is done by jet, a stone taken out of the earth in Britain, 
Germany, and many other regions : it is a hard concretion of 
black bitumen, a sort of transformation of bitumen to stone. 



1 Salmasius says that the word karabe, the Arabian word for amber, 
signifies the power of attracting straws. (Note, first page article " Electricity " 
in the Encyclopaedia Britannica.) 

2 Consult the very interesting tables given by Joannes Zahn, at page 51, 
Chap. VII, Vol. II, of his "Specula physico-mathematico-historica notabi- 
lium. . . .", Norimbergae 1696. 

8 Pliny considers amber as the juice of a tree concreted into a solid form 
(Dr. Thos. Thomson, "Hist, of Chem.", 1830, Vol. I, page 101). 



MAGNETIC COITION. 77 

Many modern authors have written about amber and jet as 
attracting chaff and about other facts unknown to the gen- 
erality, or have copied from other writers : with the results of 
their labors booksellers' shops are crammed full. Our gen- 
eration has produced many volumes about recondite, abstruse, 
and occult causes and wonders, and in all of them amber and 
jet are represented as attracting chaff ; but never a proof from 
experiments, never a demonstration do you find in them. 1 
The writers deal only in words that involve in thicker dark- 
ness subject-matter ; they treat the subject esoterically, mir- 
acle-mongeringly, abstrusely, reconditely, mystically. Hence 
such philosophy bears no fruit ; for it rests simply on a few 
Greek or unusual terms just as our barbers toss off a few 
Latin words in the hearing of the ignorant rabble in token of 
their learning, and thus win reputation bears no fruit, be- 
cause few of the philosophers themselves are investigators, or 
have any first-hand acquaintance with things ; most of them 
are indolent and untrained, add nothing to knowledge by their 
writings, and are blind to the things that might throw a light 
upon their reasonings. For not only do amber and (gagates 
or) jet, 2 as they suppose, attract light corpuscles (substances) : 
the same is done by diamond, sapphire, carbuncle, iris stone,* 
opal, amethyst, vincentina, English gem (Bristol stone, bris- 
tola), beryl, rock crystal. 3 Like powers of attracting are 

1 " Stuffed the booksellers' shops by copying from one another extrava- 
gant stories concerning the attraction of magnets and amber without giving any 
reason from experiment " (Dr. Wm. Whewell, " Hist, of Ind. Sciences," 1859, 
Vol. II, page 192). 

* The gagates, from the account given of it by Pliny, was obviously pit- 
coal or jet (Thomson's Chemistry, Vol. I, page 101). Cardan states, Gagates non 
lapis est (Lugduni ed. 1663, Vol. X, page 528). 

8 Sir David Brewster was the discoverer of the pyro-electrical condition 
of the diamond, the garnet, the amethyst, etc. See Mottelay's " Chronological 
History" at A.D. 1717 and 1820, and the references to rock-crystal, etc., 
throughout the remainder of present chapter. 



? WILLIAM GILBERT. 

possessed by glass, especially clear, brilliant glass ; by artificial 
gems made of (paste) glass or rock crystal, antimony glass, 
many fluor-spars, and belemnites. Sulphur also attracts, and 
likewise mastich, and sealing-wax [of lac], hard resin, orpiment 
(weakly).' Feeble power of attraction is also possessed in 
favoring dry atmosphere by sal gemma [native chloride of 
sodium], mica, rock alum. 2 This we may observe when in 
mid-winter the atmosphere is very cold, clear, and thin ; when 
the electrical effluvia of the earth offer less impediment, and 
* electric bodies are harder: of all this later. These several 
bodies (electrics) not only draw to themselves straws and chaff, 
but all metals, wood, leaves, stones, earths, even water and oil ; 
in short, whatever things appeal to our senses or are solid : 
yet we are told that it attracts nothing but chaff and twigs. 
Hence Alexander Aphrodiseus incorrectly declares the ques- 
tion of amber to be unsolvable, because that amber does 
attract chaff, yet not the leaves of basil ; but such stories are 



1 Whewell quotes: "Not only amber and agate attract small bodies, as 
some think, but diamond, sapphire, carbuncle, opal, amethyst, Bristol gem, 
beryl, crystal, glass, glass of antimony, spar of various kinds, sulphur, mastic, 
sealing-wax ;" and adds that Gilbert mentioned other substances (" Hist. Ind. 

Sc.", 1859, Vo1 - Ir P a e T 9 2 )- 

9 The passage is thus rendered by Humboldt : "The force of attraction 
belongs to a whole class of very different substances, as glass, sulphur, sealing- 
wax, and all resinous substances, rock crystal, and all precious stones, alum, 
and rock salt" (" Cosmos," 1849, Vol. II, page 726). 

Dr. Thos. Brown says (Pseudoloxia Epidemica, 1658, page 87): "Unto these 
Cabeus addeth white Wax, Gum Elimi, Gum Guaici, Pix Hispanica and 
Gipsum. And unto these we add Gum Anine, Benjamin, Talcum, Chyna- 
dishes, Sandaraca, Turpentine, Styrax Liquida, and Caranna dried into a hard 
consistence. . . ." (Dantzick Memoirs, Vol. I, page 180). To Dr. Gilbert's list 
of electrics Robert Boyle added the resinous cake which remained after evapo- 
rating one-fourth part of good oil of turpentine; the dry mass which remains 
after distilling a mixture of petroleum and strong spirits of nitre, glass of anti- 
mony, glass of lead, caput mortuum of amber, white sapphire, white amethyst, 
diaphanous ore of lead, carnelian, and a green stone supposed to be a sapphire 
(art. " Electricity," Ency. Brit.). 



MAGNETIC COITION. 79 

false, disgracefully inaccurate. 1 Now in order clearly to 
understand by experience how such attraction takes place, and 
what those substances may be that so attract other bodies 
(and in the case of many of these electrical substances, though 
the bodies influenced by them lean toward them, yet because 
of the feebleness of the attraction they are not drawn clean up 
to them, but are easily made to rise), make yourself a rotating- 
needle (electroscope versorium) of any sort of metal, 2 three 
or four fingers long, pretty light, and poised on a sharp point 
after the manner of a magnetic pointer. Bring near to 




one end of it a piece of amber or a gem, lightly rubbed, 
polished and shining: at once the instrument revolves. Several 
objects are seen to attract not only natural objects, but things 
artificially prepared, or manufactured, or formed by mixture. 
Nor is this a rare property possessed by one object or two (as 
is commonly supposed), but evidently belongs to a multitude 
of objects, both simple and compound, e.g., sealing-wax and 
other unctuous mixtures. But why this inclination and what 



1 When amber has been rubbed, many "particles of matter, like so many 
fine threads, too small to be seen, come out of it, and dart themselves into the 
air, where meeting with small bodies, they get into the pores of them, and 
then return back into the amber; at the same time the air continually repelling 
these small threads, and forcing them to contract themselves into less and less 
compass, presses likewise in the same manner upon the light bodies into the 
pores of which these small threads have thrust themselves; so that in returning 
back to the amber they carry small straws, in whose pores they are engaged 
along with them " (Rohault's "System of Nat. Phil.", London 1728, page 187; 
Rohmilti Physica, London 1718, Par. Ill, Cap. VIII, page 408). 

9 See note 5, page xxxi. 



8O WILLIAM GILBERT. 

these forces, on which points a few writers have given a very 
small amount of information, while the common run of phi- 
losophers give us nothing, these questions must be considered 
fully. Galen recognizes in all three kinds of attractions in 
nature : first, the attraction exercised by those bodies which 
attract by an elemental quality heat, to wit ; secondly, by 
those which attract by the in-rush into a vacuum ; thirdly, by 
those which attract through a property pertaining to their 
entire mass: and these three kinds are enumerated by Avi- 
cenna and others. This division cannot by any means content 
us, nor does it define the causes (causas) of amber, jet, diamond, 
and other like substances, which owe to the same virtue the 
forces they possess ; nor of loadstone or of other magnetic 
bodies, which possess a force altogether different from that of 
those other bodies, both in its efficiency and in the sources 
whence it is derived. We must, therefore, find other causes 
of movements, or must with these stray about as it were in 
darkness, never at all reaching our goal. Now amber does not 
* attract by heat, for when heated at a fire and brought near to 
straws, whether it is merely warm, or whether it is hot, even 
burning hot, or even brought to the flaming point, it has no 
attraction. Cardan (and Pictorius too) is of opinion that the 
attraction of amber is much like that seen in the cupping-glass : 
yet the attractional force of the cupping-glass does not really 
come from igneous force ; but he had already said that a dry 
body is eager to drink up one that is moist and juicy, and 
therefore such bodies are drawn to it. These two explications 
are inconsistent, and they are without ground in reason also. 
For were amber to move toward its sustenance, or other bodies 
to turn to amber, as to their food, the one, being swallowed up, 
would disappear, while the other would increase in size. And 
then why seek in amber the attractive force of fire? If fire 



MAGNETIC COITION. 8 1 

attracts, why do not many other bodies heated by the fire, 
the sun, or by friction attract also? Nor can attraction, be- 
cause of air displaced, occur in open air, though this is the 
cause Lucretius assigns for magnetic movements ; nor in the 
cupping-glass can heat or fire feeding on the air attract : the 
air in the cupping-glass rarefied to flame, when again it be- 
comes dense and is compressed into small space, causes the 
skin and flesh to rise, because nature avoids a vacuum. In 
open air, heated objects cannot attract, not even metals or 
stones brought to a very high temperature by fire. For an 
iron rod at white heat, a flame, a candle, a flaming torch, or a* 
red-hot coal when brought near to straws or to a revolving 
pointer (versoriuwi) does not attract ; and yet plainly all these 
cause the air to come to them in a current, for they consume 
air as a lamp consumes oil. But of heat, and how very different 
is the view held by the whole crowd of the philosophers, as to 
its attractive power in natural bodies and materia rnedica, from 
the fact as seen in nature, we will treat elsewhere when we 
come to explain what heat and cold really are. They are 
very general properties or close appurtenances of substances, 
but are not called true causes ; and if I may use the expres- 
sion, they utter certain words, but in fact they show nothing 
specifically. Nor does the supposed attractive force of amber 
arise from any peculiar property of its substance or from any 
special relation between it and other bodies; for in many oiher 
substances, if we but search with any diligence, we see the 
same effect, and, by them, all other bodies, of whatever proper- 
ties possessed, are attracted. And likeness is not the cause of 
amber's attracting, for all things that we see on the globe, 
whether similar or dissimilar, are attracted by amber and such 
like ; hence no strong analogy is to be drawn either from like- 
ness or from identity of substance. Besides, like docs not 



82 WILLIAM GILBERT. 

attract like a stone does not attract a stone, flesh flesh : there 
is no attraction outside of the class of magnetic and electric 
bodies. Fracastorio thinks that all bodies that mutually at- 
tract are alike, or of the same species, and that, either in their 
action or in their proper subjectum : " now the proper sub- 
jectum" says he, " is that from which is emitted that emana- 
tional something which attracts, and, in mixed substances, this 
is not perceptible on account of deformation, whereby they 
are one thing actu, another potentid. Hence, perhaps, hairs 
and twigs are drawn to amber and diamond not because they 
are hairs, but because there is imprisoned within them either 
air or some other principle that is first attracted and that has 
reference and analogy to that which of itself attracts ; and 
herein amber and diamond are as one, in virtue of a principle 
common to both." So much for Fracastorio. But had he in 
experiment noted that all bodies are attracted by electrics save 
those which are afire or flaming, or extremely rarefied, he 
never would have entertained such views. Men of acute in- 
telligence, without actual knowledge of facts, and in the 
absence of experiment, easily slip and err. In greater error 
are they who hold amber, diamond, etc., and the objects 
attracted by them, to be like one another, but not the same, 
near to one another in kind, and that therefore like moves 
toward like, and is by it perfected. But that is reckless specu- 
lation; for all bodies are drawn to all electrics, save bodies 
aflame or too rarefied, as the air which is the universal effluvium 
of the globe. Plants draw moisture, and thus our crops thrive 
and grow ; but from this analogy Hippocrates in his book De 
Natura Hominis, I., illogically infers that morbid humor is 
purged by the specific virtue of a drug. Of the action of 
purges we will treat elsewhere. Wrongly, too, attraction is 
postulated to exist in other effects ; e.g., when a stoppered 



MAGNETIC COITION. 83 

bottle of water being covered with a heap of wheat, its liquid 
is drawn out ; for in fact the liquid is reduced to vapor by the 
spirit of the fermenting wheat, and "the wheat takes in that 
vapor. Nor do elephants' tusks suck up moisture, but trans- 
form it into vapor and absorb it. And thus very many bodies 
are said to attract, whereas the ground of their action is to be 
sought elsewhere. A large polished lump of amber attracts;' 
a smaller piece, or a piece of impure amber, seems not to 
attract without friction. But very many electric bodies (as 
precious stones, etc.) do not attract at all unless they are first 
rubbed; while sundry other bodies, and among them some 
gems, have no power of attraction, and cannot be made to 
attract, even by friction ; such bodies [anelectrics non-elec- 
trics] are emerald, agate, carnelian, 1 pearls, jasper, chalcedony, 
alabaster, porphyry, coral, the marbles, lapis lydius (touch- 
stone, basanite), flint, bloodstone, emery or corundum (mugris\ 
bone, ivory ; the hardest woods, as ebony ; some other woods, 
as cedar, juniper, cypress; metals, as silver, gold, copper, iron. 
The loadstone, though it is susceptible of a very high polish, 
has not the electric attraction. On the other hand, many 
bodies (already mentioned) that can be polished attract when 
rubbed. All this we shall understand when we have more 
closely studied the prime origin of bodies. As is plain to all, 
the earth's mass or rather the earth's framework and its crust 
consist of a twofold matter, a matter, to wit, that is fluid and 
humid, and a matter that is firm and dry. From this two- 
fold matter, or from the simple concretion of one of these 
matters, come all the bodies around us, which consist in major 
proportion now of terrene matter, anon of watery. Those 

1 Sarda was the name of carnelian, so called because it was first found 
near Sardis. The sardonyx was also another name for carnelian (Dr. Th. 
Thomson's "Chemistry," 1830, Vol. I, page 100). 



84 WILLIAM GILBERT. 

that derive their growth mainly from humors, whether watery 
humor or one more dense ; or that are fashioned from these 
humors by simple concretion, or that were concreted out of 
them long ages ago ; if they possess sufficient firmness, and 
after being polished are rubbed, and shine after friction, such 
substances attract all bodies presented to them in the air, 
unless the said bodies be too heavy. For amber and jet are 
concretions of water; so too are all shining gems, as rock- 
crystal, which is a product of limpid water, not always of such 
water at an extremely low temperature, as some have thought, 
but sometimes at a more moderate degree of cold, the nature 
of the ground fashioning them, and the humor or juices being 
prisoned in definite cavities, just as fluorites are generated in 
mines. So clear glass is reduced from sand and other sub- 
stances that have their origin in humid juices. But these 
* substances contain a quantity of impurities of metals, or 
metals themselves, stones, rocks, wood, earth, or are largely 
mixed with earth ; therefore they do not attract. Rock crys- 
tal, mica, glass, and other electric bodies do not attract if they 
be burned or highly heated, for their primordial humor is de- 
stroyed by the heat, is altered, and discharged as vapor. Hence 
all bodies that derive their origin principally from humors, and 
that are firmly concreted, and that retain the appearance and 
property of fluid in a firm, solid mass, attract all substances, 
whether humid or dry. Such as are parts of the true sub- 
stance of the earth or differ but little from that, appear to 
attract also, but in a very different way, and, so to speak, mag- 
netically : of them we are to treat later. But those that con- 
sist of mixed water and earth, and that result from equal deg- 
radation of both elements in which the magnetic force of 
the earth is degraded and lies in abeyance, while the aqueous 
humor, spoilt by combination with a quantity of earth, does not 



MAGNETIC COITION. 8$ 

form a concretion by itself, but mingles with the earthy matter 
such bodies are powerless to attract to themselves aught 
that they are not in actual contact with, or to repel the same. 
For this reason it is that neither metals, marbles, flints, woods, 
grasses, flesh, nor various other substances can attract or 
solicit a body, whether magnetically or electrically (for it 
pleases us to call electric force that force which has its origin* 
in humors). But bodies consisting mostly of humor and not 
firmly compacted by nature wherefore they do not stand fric- 
tion, but either fall to pieces or grow soft, or are sticky, as 
pitch, soft rosin, camphor, galbanum, ammoniacum, storax, 
asa, gum benjamin, asphaltum (especially in a warm atmos- 
phere), do not attract corpuscles. For without friction few 
bodies give out their true natural electric emanation and 
effluvium. Turpentine resin in the liquid state does not at-* 
tract, because it cannot be rubbed ; but when it hardens to a 
mastic it does attract. 

And now, at last, we have to see why corpuscles are 
drawn toward substances that derive their origin from water, 
and by what manner of force, by what hands, so to speak, 
such substances lay hold of matters nigh them. 

In all bodies everywhere are presented two causes or prin- 
ciples whereby the bodies are produced, to wit, matter (mate- 
ria) and form (forma). Electrical movements come from the 
materia, but magnetic from the prime forma ; and these two 
differ widely from each other and become unlike, the one 
ennobled by many virtues, and prepotent ; the other lowly, of 
less potency, and confined in certain prisons, as it were ; 
wherefore its force has to be awakened by friction till the sub- 
stance attains a moderate heat, and gives out an effluvium, 
and its surface is made to shine. Moist air blown upon it from * 
the mouth or a current of humid air from the atmosphere 



86 WILLIAM GILBERT. 

chokes its powers ; and if a sheet of paper or a linen cloth be 
interposed there is no movement. But loadstone, neither 
rubbed nor heated, and even though it be drenched with 
liquid, and whether in air or water, attracts magnetic bodies, 
and that, though solidest bodies or boards, or thick slabs of 
stone or plates of metal, stand between. A loadstone at- 
tracts only magnetic bodies ; electrics attract everything. A 
loadstone lifts great weights ; a strong one weighing two 
ounces lifts half an ounce or one ounce. Electrics attract 
only light weights; e.g., a piece of amber three ounces in 
weight lifts only one-fourth of a barleycorn's weight. 

But this attraction of amber and of electric bodies must be 
investigated further ; and since it is an acquired state (affectio), 
the question arises why amber is rubbed, and what state is 
brought about by rubbing ; also, what causes are evoked that 
seize all sorts of substances. By friction it is made moder- 
ately hot and also smooth ; and these conditions must in most 
cases concur ; but a large polished piece of amber or of jet 
attracts even without friction, though not strongly ; yet if it 
1 be carefully brought nigh to a flame or a red coal and warmed 
to the same degree as by friction, it does not attract corpus- 
cles, because it becomes involved in dark fumes from the body 
of the hot or flaming mass, which emits a hot exhalation ; and 
the vapor from that other body is driven upon it something 
quite alien to the nature of the amber. Besides, the exhalation 
produced in the amber by an alien heat is feeble, for the amber 
must not have any heat save that produced by friction : its 
own heat, so to speak, not heat contributed by other bodies. 
For as the igneous heat emitted by any flaming matter is use- 
less to procure for electrics their virtue, so, too, heat from the 
sun's rays does not excite an electric by the right dissolution 
of its matter, rather dissipates and consumes it (albeit a body 



MAGNETIC COITION. 8/ 

that undergoes friction and then is exposed to the solar rays 
retains its powers longer than it does in shade, because that in 
shade effluvia are condensed more and more quickly) ; further, * 
the sun's heat, heightened by means of a burning-glass, im- 
parts no power to amber, for it dissipates and spoils all the 
electric effluvia. Again, flaming sulphur and burning sealing- 
wax do not attract, for heat produced by friction dissolves* 
bodies into effluvia, and these are consumed by flame. It is 
impossible for solid electrics to be resolved into their effluvia 
otherwise than by attrition, save a few that, because of their 
native strength, emit effluvia continually. They are to be 
rubbed with bodies that do not foul the surface, and that 
cause them to shine, e.g., strong silk, and coarse woollen cloth, 
scrupulously clean, and the dry palm of the hand. Amber 
may be rubbed with amber, with diamond, with glass, etc. 
Thus are electrics made ready for action. 

And now what is it that produces the movement? The 
body itself circumscribed by its contour ? Or is it something 
imperceptible for us flowing out of the substance into the 
ambient air? (This appears to have been in some sense the 
opinion of Plutarch, who, in the Qucestiones Platonica, says 
that there is in amber something flame-like, or having the 
nature of the breath, and that this, when the paths are cleared 
by friction of the surface, is emitted and attracts bodies.) 
And if it is an effluvium, does the effluvium set the air in cur- 
rent, and is the current then followed by the bodies ? or is it 
the bodies themselves directly that are drawn up ? But if the 
amber attracts the body itself, then supposing its surface is 
clean and free from adhesions, what need is there of friction ? 
Nor does the force come from the lustre proceeding from the 
rubbed and polished electric ; for the vincentina, the diamond, 
and pure glass attract when they are rough, but not so strongly 



88 WILLIAM GILBERT. 

nor so readily ; because then they are not so easily cleansed 
of extraneous moisture settled on the surface, nor are they sub- 
jected all over to such an equal degree of friction as to be 
resolved into effluvia. Nor does the sun, with its shining and 
its rays, which are of vast importance in nature, attract bodies 
thus ; and yet the common run of philosophizers think that 
liquids are attracted by the sun, whereas only the denser 
humors are resolved into rarer, (and) into vapor and air ; and 
thus, through the motion given to them by diffusion, they 
ascend to the upper regions, or, being attenuated exhalations, 
are lifted by the heavier air. Neither does it seem that the 
electric attraction is produced by the effluvia rarefying the air 
so that bodies, impelled by the denser air, are made to move 
toward the source of the rarefaction : if that were so, then hot 
bodies and flaming bodies would also attract other bodies ; 
but no lightest straw, no rotating pointer is drawn toward a 
flame. If there is afflux and appulsion of air, how can a mi- 
nute diamond of the size of a chick-pea pull to itself so much 
air as to sweep in a corpuscle of relatively considerable 
length, the air being pulled toward the diamond only from 
around a small part of one or other end ? Besides, the at- 
tracted body must stand still or move more slowly before 
coming into contact, especially if the attracting body be a 
broad flat piece of amber, on account of the heaping up of air 
on the surface, and its rebounding after collision. And if the 
effluvia go out rare and return dense (as with vapors), then the 
body would begin to move toward the electric a little after 
the beginning of its application ; yet, when rubbed electrics 
*are suddenly applied to a versorium, instantly the pointer 
turns, and the nearer it is to the electric the quicker is the 
attraction. But if rare effluvia rarefy the medium, and there- 
fore the bodies pass from a denser into a rarer medium, then 



MAGNETIC COITION. 89 

the bodies might be attracted sideways or downward, but not 
upward, or the attraction and holding of the bodies would be 
only for a moment. But jet and amber after one friction 
strongly and for a length of time solicit and attract bodies, 
sometimes for as long as five minutes, especially if the weather 
is fair. But if the mass of amber be large, and its surface 
polished, it attracts without friction. Flint, on being struck, 
gives off inflammable matter that turns to sparks and heat. 
Hence the denser fire-containing effluvia of flint are very 
different indeed from the electrical effluvia, which, by reason 
of their extreme tenuity, cannot take fire, nor are they fit 
matter of flame. They are not a breath, for, when given forth, 
they do not exert propelling force ; they flow forth without 
any perceptible resistance, and reach bodies. They are ex- 
ceedingly attenuated humors, much more rarefied than the 
ambient air ; to produce them requires bodies generated of 
humor and consolidated to considerable hardness. Non-elec- 
tric bodies are not resolvable into humid effluvia ; and such 
effluvia mingle with the common and general effluvia of the 
earth, and are not peculiar. In addition to the attracting of 
bodies, electrics hold them for a considerable time. Hence it* 
is probable that amber exhales something peculiar that attracts 
the bodies themselves, and not the air. It plainly attracts the 
body itself in the case of a spherical drop of water standing 
on a dry surface ; for a piece of amber held at suitable dis- 
tance pulls toward itself the nearest particles and draws them* 
up into a cone ; were they drawn by the air the whole drop 
would come toward the amber. And that amber does not 
attract the air is thus proved : take a very slender wax candle 
giving a very small clear flame ; bring a broad flat piece of * 
amber or jet, carefully prepared and rubbed thoroughly, with- 
in a couple of fingers' distance from it ; now an amber that 



90 WILLIAM GILBERT. 

will attract bodies from a considerable radius will cause no 
motion in the flame, though such motion would be inevitable 
if the air were moving, for the flame would follow the current 
of air. The amber attracts from as far as the effluvia are sent 
out; but as the body comes nearer the amber its motion is 
quickened, the forces pulling it being stronger, as is the case 
also in magnetic bodies, and in all natural motion ; and the 
motion is not due to rarefaction of the air or to an action of 
the air impelling the body to take the vacated place ; for in 
that case the body would be pulled but not held, since, at first, 
approaching bodies would even be repelled just as the air itself 
would be : yet in fact the air is not in the least repelled even 
at the instant that the rubbed amber is brought near after 
very rapid friction. An effluvium is exhaled by the amber 
and is sent forth by friction ; pearls, carnelian, agate, jasper, 
chalcedony, coral, metals, and the like, when rubbed are inac- 
tive ; but is there nought that is emitted from them also by 
heat and friction ? There is indeed ; but what is emitted 

. from the denser bodies, and those with considerable admix- 
ture of earth matter, is thick and vaporous ; and in fact in the 

*case of very many of the electric bodies, if they be violently 
rubbed, there is but a faint attraction of bodies to them, or 
none at all ; the best method is to use gentle but very rapid 
friction, for so the finest effluvia are elicited. The effluvia 
arise from a subtle solution of moisture, not from force ap- 
plied violently and recklessly; this is true especially of bodies 
that are of oily substance consolidated, which, when the at- 
mosphere is thin and the wind is from the north, or here in 

* England from the east, produce their effects best and with 
most certainty ; but in a south wind and a humid atmosphere 
the effect is very slight : so that effluvia that attract but feebly 
when the weather is clear, produce no motion at all when it is 



MAGNETIC COITION. 9! 

cloudy. And this as well because in thick weather light 
objects are harder to move, as also (and rather) because the 
effluvia are stifled, and the surface of the rubbed body is 
affected by the vaporous air, and the effluvia are stopped at 
their very origin ; hence it is that in amber, jet, and sulphur, 
because these bodies do not so readily collect the humid air on 
their surface, and are much more thoroughly resolved, this 
force is not so easily suppressed as in gems, rock-crystal, glass, 
and the like, which collect the condensed moist air on their 
surface. But the question may arise, why amber attracts 
water, though water existing on a surface annuls its action. 
That is because it is one thing to suppress the effluvium at its 
rise, another to destroy it after it is emitted. Thus a certain* 
gauzy texture of silk, commonly called sarsnet, when quickly 
laid over amber immediately after friction, hinders the body's* 
attraction ; but if it be interposed midway between the two 
bodies, it does not altogether annul the attraction. Moisture 
from steam, a breath from the mouth, water thrown on the 
amber, instantly check the effluvium. But olive-oil that is* 
light and pure does not prevent it, and even rubbing amber* 
with a warm finger dipped in the oil does not prevent attraction. 
But if after that friction the amber be drenched with alcohol, 
or brandy, it does not attract, as the spirit is heavier, denser, 
than the oil, and when added to the oil sinks below it. For 
olive-oil is light and rare, and does not oppose the passage of 
the lightest effluvia. A breath, then, proceeding from a body 
that is a concretion of moisture or aqueous fluid, reaches the 
body that is to be attracted, and as soon as it is reached it is 
united to the attracting electric ; and a body in touch with 
another body by the peculiar radiation of effluvia makes of the 
two one : united, the two come into most intimate harmony, 
and that is what is meant by attraction. This unity is, ac- 



92 WILLIAM GILBERT. 

cording to Pythagoras, the principle, through participation, in 
which a thing is said to be one. For as no action can be per- 
formed by matter save by contact, these electric bodies do 
not appear to touch, but of necessity something is given out 
from the one to the other to come into close contact there- 
with, and be a cause of incitation to it. 

All bodies are united and, as it were, cemented together by 
moisture, and hence a wet body on touching another body 
attracts it if the other body be small ; and wet bodies on the 
surface of water attract wet bodies. But the peculiar effluvia 
of electrics, being the subtilest matter of solute moisture, 
attract corpuscles. 1 Air, too (the earth's universal effluvium), 
unites parts that are separated, and the earth, by means of 
the air, brings back bodies to itself ; else bodies would not so 
eagerly seek the earth from heights. The electric effluvia 
differ much from air, and as air is the earth's effluvium, so elec- 
tric bodies have their own distinctive effluvia ; and each pecu- 
liar effluvium has its own individual power of leading to union, 
its own movement to its origin, to its fount, and to the body 
that emits the effluvium. But bodies that give out a thick or 
a vaporous or an aerial effluvium when rubbed have no effect ; 
for either such effluvia are diverse from humor (unifier of all 
things), or, being very like the common air, they become 
blended with the air and one with it : wherefore they have 
no effect in the air, and do not produce any movements dif- 
ferent from those of that universal and common element. 
* Bodies tend to come together and move about on the surface 
of water like the rod C, which dips a little into the water. 



1 Consult Robert Boyle's "Of the Strange Subtilty of Effluviums," 1673, 
pages 38-42, 52, 53; "Of the Great Efficacy of Effluviums," 1673, pages 
18, 19, 32, 33; "Of the Determinate Nature of Effluviums," 1673, pages 21, 57; 
"An Essay about. . . . Gems," 1672, pages 108-112. 



MAGNETIC COITION. 



93 



Evidently the rod EF, floated by the cork H and having only 
the wetted end F above the water's surface, will be attracted 
by the rod C, if C be wetted a little above the water's surface. 




As a drop brought into contact with another drop is attracted, 
and the two forthwith unite, in the same way a wet object on 
the surface of water seeks union with another wet object when 
the surface of the water rises in both : at once, like drops or 
bubbles of water, they ccme together; but they are in much 
nigher neighborhood than in the case of electrics, and they 
unite by their wetted surfaces. But if the whole rod C be 
dry above the water, it no longer attracts but repels the rod 
EF. The same is seen in the case of bubbles on water : one 
is seen to approach another, all the more rapidly the nearer 
they are. Solids draw to solids through the medium of liquid ; 
e.g., touch the end of a versorium with the end of a rod on 
which a drop of water stands : the instant the rotating pointer 
comes in contact with the circumference of the drop it ad- 
heres to it with a sudden motion. So do bodies concreted 
from liquids when melted a little in the air exercise attraction, 
their effluvia being the means of unition ; for the water in 
humid bodies or in bodies drenched with superficial moisture 
on the top of water has the force of an effluvium. A clear 
atmosphere is a good medium for the electric effluvium devel- 
oped from concreted humor. Wet bodies projecting out of 
the surface of water come together, if they be near, and unite. 



94 WILLIAM GILBERT. 

for the water's surface rises around wet surfaces. A dry body 
does not move toward a wet, nor a wet toward a dry, but 
rather they seem to go away from each other ; for if all of the 
body that is above the water is dry, the nearest water surface 
does not rise but falls away with subsidence of the surface 
around the dry object. So, too, a dry body does not run to 
the dry rim of a vessel containing water ; but, on the contrary, 
a wet object does. In the figure, AB is the water surface ; 




C, D, two rods with their projecting ends wet. Evidently the 
surface of the water at C and D rises simultaneously with the 
rods ; hence the rod C, because its water, standing above the 
general level, seeks equilibrium and union, moves with the 
water toward D. On the wet rod E the water rises also, but 
by the dry rod F the water is depressed, and as it strives to 
depress also the water rising on , the higher water at E 
turns away from F, for it refuses to be depressed. All elec- 
tric attractions are effected by means of moisture, and thus 
all things come together because of humor : fluid bodies and 
aqueous bodies come together on the surface of water, and 
concreted bodies, if reduced to vapor, come together in the 
air. And in the air the effluvium of electrics is very rare, that 
so it may more thoroughly permeate the atmosphere, and yet 
not give it impulsion by its own motion. For were this efflu- 
vium as dense as air, or the winds, or the fumes of burning 



MAGNETIC COITION. 95 

saltpetre, or as the thick, foul effluvia emitted with much force 
from other bodies, or as the air from vaporized water rushing 
forth from a pipe (as in the instrument described by Hero of 
Alexandria in his book Spiritualid) : in such case it would 
repel everything, and not attract. But those thinner effluvia 
lay hold of the bodies with which they unite, enfold them, as it 
were, in their arms, and bring them into union with the elec- 
trics ; and the bodies are led to the electric source, the effluvia 
having greater force the nearer they are to that. But what is 
the effluvium from rock-crystal, glass, diamond substances 
very hard and very highly compressed ? For such effluvium 
there is no need of any notable or sensible outflow of sub- 
stance : no need of abrading, or rubbing, or otherwise dis- 
figuring the electric body: odoriferous substances give forth 
fragrance for many years, exhale continually, yet are not soon 
consumed. Cypress wood, as long as it remains sound and 
it lasts a very long time is fragrant, as many learned men 
testify from experience. Such an electric, after only a mo- 
ment's friction, emits powers subtile and fine, far beyond all 
odors ; but sometimes an odor also is emitted by amber, jet, 
sulphur, these bodies being more readily resolved. Hence it 
is that usually they attract after the gentlest friction, or even 
without friction ; and they attract more powerfully and keep 
hold longer because their effluvia are stronger and more last- 
ing. But diamond, glass, rock-crystal, and very many of the 
harder and more compacted gems are heated, and then rubbed 
for a good while at first, after which they, too, attract strongly : 
they cannot be resolved in any other way. Electrics attract 
all things save flame and objects aflame, and thinnest air. 
And as they do not draw to themselves flame, so they have 
no effect on a versorium if it have very near it on any side the 
flame of a lamp or of any burning substance ; for it is plain 



96 WILLIAM GILBERT. 

*that the effluvia are consumed by flame and igneous heat. 
Therefore electrics do not attract either flame or bodies near 
flame ; for such effluvia have the virtue and analogy of rarefied 
humor, and they will produce their effect, bringing about 
unition and continuity, not through the external action of 
humors, or through heat, or through attenuation of heated 
bodies, but through the attenuation of the humid substance 

*into its own specific effluvia. 1 Yet they draw to themselves 
the smoke from an extinguished candle ; and the lighter the 
smoke becomes as it ascends, the less strongly is it attracted, 
for substances that are too rare do not suffer attraction. At 

*last, when the smoke has nearly vanished, it is not attracted 
at all, as is plainly seen when the fact is observed toward the 
light. But when it has passed quite into the air it is not 
stirred by electrics, as has already been shown. For thin air 
itself is in no wise attracted, save by reason of its coming into 
a vacuum, as is seen in furnaces in which air is supplied by 
means of appliances for drawing it in. Therefore the efflu- 
vium called forth by a friction that does not clog the surface 
an effluvium not altered by heat, but which is the natural 
product of the electric body causes unition and cohesion, 
seizure of the other body, and its confluence to the electrical 
source, provided the body to be drawn is not unsuitable by 
reason either of the circumstances of the bodies or of its own 
weight. Hence corpuscles are carried to the electrical bodies 
themselves. The effluvia spread in all directions : they are 
specific and peculiar, and sui generis, different from the com- 
mon air ; generated from humor ; called forth by calorific 
motion and rubbing, and attenuation ; they are as it were 



1 Nicolao Cabeo, Philosophia Magnetica, 1629, Lib. II, Cap. XXI, page 
194. 



CONCERNING MAGNETIC COITION. 97 

material rods hold and take up straws, chaff, twigs, till their 
force is spent or vanishes ; and then these small bodies, being 
set free again, are attracted by the earth itself and fall to the 
ground. The difference (distinction) between electric and 
magnetic bodies is this : all magnetic bodies come together by 
their joint forces (mutual strength) ; electric bodies attract the 
electric only, and the body attracted undergoes no modifica- 
tion through its own native force, but is drawn freely under 
impulsion in the ratio of its matter (composition). Bodies are* 
attracted to electrics in a right line toward the centre of elec- 
tricity : a loadstone approaches another loadstone on a line 
perpendicular to the circumference only at the poles, else- 
where obliquely and transversely, and adheres at the same 
angles. The electric motion is the motion of coacervation of 
matter ; the magnetic is that of arrangement and order. The 
matter of the earth's globe is brought together and held to- 
gether by itself electrically. The earth's globe is directed and 
revolves magnetically ; it both coheres and, to the end it may 
be solid, is in its interior fast joined. 5 



CHAPTER III. 

OPINIONS OF OTHERS CONCERNING MAGNETIC COITION, 
WHICH THEY CALL ATTRACTION. 

HAVING treated of electrics, we have now to set forth 
the causes of magnetic coition. Coition, we say, not attraction, 
for the term attraction has wrongfully crept into magnetic 

1 "In these obscure axioms we trace the recognition of terrestrial electric- 
iiy, the expression of a force, which, like magnetism, appertains as such to 
matter. As yet we meet with no allusions to repulsion, or the difference 
between insulators and conductors " (Humboldt, " Cosmos," 1849, Vol. II, page 
727). 



9 WILLIAM GILBERT. 

philosophy, through the ignorance of the Ancients ; for where 
attraction exists, there, force seems to be brought in and a 
tyrannical violence rules. Hence, if we have at any time 
spoken of magnetic attraction, what we meant was magnetic 
coition and primary confluence. 1 But here it will be not 
unprofitable first to set forth briefly the views of others, both 
among the ancients and the moderns. Orpheus, in his hymns, 
tells that iron is drawn by the loadstone as the bride to the 
embraces of her spouse. Epicurus holds that iron is drawn 
by the loadstone as straws by amber ; and adds a reason : 
" Atoms," he says, " and indivisible bodies that flow from 
stone and from iron, agree together in their figures, so that 
they readily embrace mutually ; hence, when they impinge on 
concretions both of iron and stone, they rebound into the 
middle space, connected together on the way, and carry the 
iron with them." This, surely, cannot be, for though solid and 
very dense bodies, or blocks of marble, stand between, they 
do not hinder the passage of this potency, though they can 
separate atoms from atoms ; besides, on the hypothesis, the 
stone and iron would quickly be resolved into atoms, so pro- 
fuse and incessant would be the atomic outflow. And as the 
mode of attraction is quite different in amber, there the Epicu- 
rean atoms cannot agree in their figures. Thales, as we are 
told by Aristotle, in Book I, De Anima, deemed the loadstone 
endowed with a sort of life, because it possesses the power of 
moving and attracting iron. Anaxagoras was of the same 
opinion. The opinion of Plato in the Timceus, about the 
effect of the Herculean stone, is baseless. He says : " With 
respect to all the motions of water, the fallings of thunder, and 

1 " Coition, says Gilbert, is not made by any attractive faculty, either of 
the load-stone or of the iron, but by a Syndrome, or concordance of both of 
them " (Creech's translation of Lucretius, London 1714, Vol. II, page 720). 



CONCERNING MAGNETIC COITION. 99 

the wonderful circumstances observed in the attraction of 
amber, and the Herculean stone, in all these, no real attrac- 
tion takes place at all, but, as a vacuum can nowhere be found, 
the particles are mutually impelled by each other; hence, as 
they all individually, both in a separate and mingled state, 
have an attraction for their own proper seats, it is by the 
mutual intermingling of these affections, that such admirable 
effects present themselves to the view of the accurate inves- 
tigator." x Galen knows not why Plato should have chosen 
rather the theory of circumpulsion than of attraction (on this 
point alone differing from Hippocrates), seeing that circumpul- 
sion harmonizes in fact neither with reason nor with experi- 
ment. For neither is air nor anything else circumpelled, and 
even the bodies that are attracted are not borne to the attract- 
ing bo^ in confused fashion or in a circle. The Epicurean 
poet Lucretius thus presents his master's theory : 

Principle, fluere lapide hoc permulta necesse est 

Semina sive aestum, qui discutit aera plagis; 

Inter qui lapidem, ferrumque est, cunque locatus, 

Hoc ubi inanitur spatium, multisque vacefit 

In medio locus : extemplo primordia ferri 

In vacuum prolapsa cadunt coniuncta ; fit utque 

Annulus ipse sequatur, eatque ita corpore toto, etc. 2 

1 In his note to the translation of the J^imaus (Bohn, London 1849, 
Vol. II, page 394), Mr. Henry Davis adds: This is a very memorable 
passage, and clearly shows that Plato was not only well acquainted with the 
doctrine of attraction and repulsion, but was of opinion also that the law of 
repulsion depended on the congregation of similar elements throughout all na- 
ture. The whole matter, however, is largely treated by Plutarch in his Sixth 
Platonic Dissertation, Vol. II, page 1004, ed. Par. 

8 Mr C. F. Johnson renders the passage as follows (" Nature of Things," 
1872, page 291): 

First, from the stone innumerous atoms flow, 

In streams that form an atmosphere around, 

Displacing air between it and the stone. 

Thus rarefied, the space, the particles 

Of metal press, vacated place to fill, 

And drag with them the mass to which they're joined ; 

For nothing is than steel more closely knit. 



IOO WILLIAM GILBERT. 

A similar explication is offered by Plutarch in the Quces- 
tiones Platonicce. He says that the loadstone emits heavy 
exhalations, whereby the contiguous air, being impelled, makes 
dense the air in front of it, and that air, driven round in a 
circle and returning to the part whence the air was displaced, 
forcibly carries the iron with it. The following theory of the 
powers of loadstone and amber is propounded by Joannes 
Costaeus of Lodi : Costaeus holds that " there is work on both 
sides, result on both sides, and therefore the motion is pro- 
duced in part by the loadstone's attraction, in part by the 
iron's spontaneous movement ; for, as we say that the vapors 
given out by the loadstone do by their own nature haste to 
attract the iron, so, too, do we say that the air impelled by 
the vapors, while seeking a place for itself, is turned back, and 
when turned back impels and transfers the iron, which is 
picked up, as it were, by it, and which, besides, is exerted on 
its own account. In this way there is found a certain compos- 
ite movement, resulting from the attraction, the spontaneous 
motion, and the impulsion ; which composite motion, how- 
ever, is rightly to be referred to attraction, because the begin- 
ning of this motion is invariably from one term , and its end is 
there too ; and that is precisely the distinguishing character 
of attraction." There is, it is true, mutual action, not mutual 
work ; the loadstone does not thus attract, and there is no im- 
pulsion ; neither is the principle of the motion found in vapors 

Nor more compacted in its elements : 

Hence, little wonder, if, as said before, 

The particles thus streaming to the void 

Should drag with them along the chain entire ! 

And this they do ; drag it to magnet stone, 

Whereto it close adheres by secret bond. 

T. LUCRETTT CARI, De Rerum Natura, London 1824, Book VI, v. 1000-1006. 
See Thomas Creech's translation, London 1714, Vol. II, pages 726, 727; 
likewise Mr. H. A. J. Monro's Explanatory Notes, II, Cambridge and London, 
1886, pages 386, 387. 



CONCERNING MAGNETIC COITION. IOI 

and their return movements : that is Epicurus's theory, so oft 
repeated by others. Galen errs in his first book, De Naturali- 
bus Facultatibus, cap. 14, when he expresses the opinion that 
whatever agents draw out the venom of serpents; 02;; narrows 
possess the same powers as the loadstone. As, 1 for -this attrac-, 
tion (if attraction it may be called) of medicaments, 'we will 
treat of it in another place. Drugs against poisons and arrow- 
wounds have no relation, no resemblance, to the actions of 
magnetic bodies. Galen's followers, who teach that purgative 
medicines attract because of likeness of substance, say that 
bodies are attracted on account of resemblance, not of iden- 
tity ; therefore, say they, loadstone draws iron, but iron does 
not draw loadstone. But we say and prove that this takes 
place in all prime bodies, and in bodies that are allied and 
especially that are near akin to these, and this on account 
of identity: wherefore loadstone draws loadstone, and iron 
draws iron ; all true earth substance draws its kind ; and iron 
invigorated by the action of a loadstone within whose sphere 
of influence it is, draws iron more powerfully than it does 
loadstone. Cardan asks why no other metal is drawn by any 
stone ; and his answer is, because no other metal is so cold as 
iron : as if, forsooth, cold were cause of attraction, or iron were 
much colder than lead, which neither follows the loadstone 
nor leans toward it. But this is sorry trifling, no better than 
old wives' gossip. Of the same sort is the belief that the 
loadstone is a living thing, and that iron is its victual. But 
how does loadstone feed on iron if the iron filings it is kept in 
neither are consumed nor become lighter in weight ? Corne- 
lius Gemma (Cosmocrit, X), declares that loadstone draws iron 
to itself by means of invisible rods ; and to this opinion he 
tacks on a story of the sucking-fish and the catablepas. Guil- 
elmus Puteanus deduces the power of the loadstone, not from 



102 WILLIAM GILBERT 

a property of its whole substance unknown to any one and in- 
capable of demonstration (as Galen held, and after him nearly 
all physicians), but from " its substantial form as from a prime 
motor "arid self-motor, and as from its own most potent nature 
and 1 'its natural* temperament, as the instrument which the 
efficient form of its substance, or the second cause, which is 
without a medium, employs in its operations. So the load- 
stone attracts iron not without a physical cause, and for the 
sake of some good." But nothing like this is done in other 
bodies by any substantial form unless it be the primary one, 
and this Puteanus does not recognize. Naught but good is 
assuredly held out (sed bonum sane) to the loadstone, to be got 
from the appulsion of the iron (a sort of friendly association), 
yet the temperament of which he speaks is not to be found, 
cannot even be imagined as something that is to be the instru- 
ment of the form. For of what use can temperament be in 
magnetic movements that are calculable, definite, constant, 
comparable to the movements of the stars ; at great distance, 
with thick, dense bodies interposed. In Baptista Porta's 
opinion, the loadstone seems to be a mixture of stone and 
iron, i.e., ferruginous stone, or stony iron. " The stone," he 
says, 1 " is not changed into iron so as to lose its own nature, 
nor is the iron so merged in the stone but that it retains its 
own essence ; and while each strives to overcome each, from 
the struggle results attraction of the iron. In the mass (of the 
loadstone) there is more stone than iron ; therefore the iron, 
lest it should be dependent on (subdued by) the stone, craves 
the strength and company of iron, to the end that what it 
cannot procure of itself it may obtain by the help of the 
other. . . . The loadstone does not attract stones because it 

> "Natural Magick," 1658, Book VII, Chap. II. 



CONCERNING MAGNETIC COITION. IO3 

has no need of them, there being stone enough in its mass ; 
and if one loadstone attracts another that is not for the sake 
of the stone, but of the iron shut up in the stone." As though 
the iron in a loadstone were a distinct body and not one 
blended with another, like all other metals in their ores. And 
it is height of absurdity to speak of these substances, thus 
confounded together, as warring with each other and quarrel- 
ing, and calling out from the battle for forces to come to their 
aid. Now, iron itself when touched with loadstone seizes iron 
with not less force than loadstone itself. These rights, sedi- 
tions, conspiracies, in a stone, as though it were nursing quar- 
rels as an occasion for calling in auxiliary forces, are the 
maunderings of a babbling hag, rather than the devices of an 
accomplished prestigiator. Others have thought that the 
cause is a sympathy. But even were fellow-feeling there, even 
so, fellow-feeling is not a cause ; for no passion can rightly be 
said to be an efficient cause. Others again assign as the cause 
likeness of substance, and still others postulate rods (radii) 
imperceptible to the senses. These, in very many ways, make 
a sad misuse of a term first employed by mathematicians. In 
more scholarly fashion, Scaliger declares that iron moves to the 
loadstone as to its mother's womb, there to be perfected with 
recondite principles, as the earth tends to the centre. The 
godlike Thomas, 1 in Book 7 of his Physica, treating of the 



1 Thomas Aquinas, famous schoolman of the middle ages, also called the 
Angelic Doctor, and considered by many the greatest of Christian philosophers, 
was well worthy the profound respect and high admiration in which he was 
held by our author. His chief work, the Summa Theologies, to which he de- 
voted the last nine years of his life, has been called the supreme monument of 
the thirteenth century. One of his biographers remarks that those wishing to 
thoroughly comprehend the peculiar character of metaphysical thought in the 
middle ages should study Aquinas, in whose writings it is seen with the 
greatest consistency. Aquinas died in 1274, and was canonized forty-nine 
years later by Pope John XXII. 



IO4 WILLIAM GILBERT. 

causes of motion, says : " A thing can in another sense be said 
to pull, in that it moves (an object) toward itself, by altering 
it in any way, by which alteration it comes about that the 
body altered moves with respect to place ; and in this way is 
the loadstone said to draw iron : for as a generant moves 
heavy things and light in so far as it gives them the form 
whereby they are moved to a place ; so does the loadstone 
give to iron some quality through which it is moved to the 
loadstone." This view, one by no means ill-conceived, this 
most learned man, proceeds later briefly to corroborate, citing 
incredible accounts of the loadstone and of the power of garlic 
over the loadstone. Nor is what Cardinal de Cusa states to be 
disregarded. Says he : " Iron hath in the loadstone a certain 
principle of its efflux, and while the loadstone by its presence 
excites the heavy and ponderous iron, the iron is, by a won- 
derful longing, raised above the natural motion (whereby it 
ought to tend downward according to its weight), and moves 
upward, uniting in its principle. For w r ere there not in iron 
some natural foretaste of the loadstone, it would no more 
move toward that than toward any other stone ; and were 
there not in the loadstone a stronger inclination toward iron 
than toward copper, that attraction would not exist." Such, 
as propounded by different writers, are current opinions about 
the attraction of the loadstone, all of them full of doubt and 
uncertainty. As for the causes of magnetic movements, re- 
ferred to in the schools of philosophers to the four elements 
and to prime qualities, these we leave for roaches and moths 
to prey upon. 



STRENGTH OF A LOADSTONE. IO5 



CHAPTER IV. 

OF THE STRENGTH OF A LOADSTONE AND ITS FORM : THE 
CAUSE OF COITION. 

QUITTING the opinions of others about the attraction of 
the loadstone, we will now show the reason of its coition and 
the nature of its motion. There are two kinds of bodies that 
are seen to attract bodies by motions perceptible to our senses 
electric bodies, and magnetic. Electrical bodies do this 
by means of natural effluvia from humor ; magnetic bodies by 
formal efficiencies or rather by primary native strength (vigor). 
This form is unique and peculiar : it is not what the Peri- 
patetics call causa formalis and causa specifica in mixtis and 
secunda forma ; nor is it causa propagatrix generantium corpo- 
rum ; but it is the form of the prime and principal globes ; and 
it is of the homogeneous and not altered parts thereof, the 
proper entity and existence which we may call the primary, 
radical, and astral form ; x not Aristotle's prime form, but 
that unique form which keeps and orders its own globe. Such 
form is in each globe the sun, the moon, the stars one ; in 
earth also 'tis one, and it is that true magnetic potency which 
we call the primary energy. Hence the magnetic nature is 
proper to the earth and is implanted in all its real parts 
according to a primal and admirable proportion. It is not 
derived from the heavens as a whole, neither is it generated 
thereby through sympathy, or influence, or other occult quali- 
ties : neither is it derived from any special star ; for there is 
in the earth a magnetic strength or energy (vigor) of its own, 

1 Whewell, " Hist, of Ind. Sciences," 1859, Vol. II, Chap. II, page 220. 



IO6 WILLIAM GILBERT. 

as sun and moon have each its own forma ; and a little frag- 
ment of the moon arranges itself, in accordance with lunar 
laws (lunatice\ so as to conform to the moon's contour and 
form, or a fragment of the sun to the contour and form of the 
sun, just as a loadstone does to the earth or to another load- 
stone, tending naturally toward it and soliciting it. Thus we 
have to treat of the earth, which is a magnetic body, a load- 
stone ; then, too, of its true, native parts, which are magnetic, 
and of how they are affected by coition. 

A body that is attracted by a magnetic body is not by it 
altered, but remains unimpaired and unchanged as it was be- 
fore, neither has it now greater virtue. A loadstone draws 
magnetic bodies, and they from its energy eagerly draw 
' forces not in their extremities only, but in their inmost parts. 
For an iron rod held in the hand is magnetized in the end 
where it is grasped, and the magnetic force travels to the 
other extremity, not along the surface only, but through the 
inside, through the middle. Electrical bodies have material, 
corporeal effluvia. Is any magnetic effluvium emitted, corpo- 
real or incorporeal ? Or is nothing at all that subsists emitted ? 
But if the effluvium is a body, it must needs be light and spir- 
itual so as to enter the iron. Is it such as is exhaled from 
lead when quicksilver, which is liquid and fluid, is by the mere 
odor and vapor of lead solidified, and remains as a strongly 
coherent metal ? Gold, too, which is very solid and dense, is 
reduced to a powder by the thin vapor of lead. Can it be 
that as quicksilver can enter gold, so the magnetic odor can 
enter the substance of iron, changing it by its substantial 
property, though in the bodies themselves there is no change 
perceptible by our senses ? For without such entering a body 
is not changed by another body, as the chemists, not without 
reason, do teach. But if these effects were produced by a 



STRENGTH OF A LOADSTONE. IO/ 

material entrance, then were resistant, dense bodies interposed 
between such bodies ; or were the magnetic bodies shut up in 
the middle of very thick, dense bodies, objects of iron would 
not be acted on by the loadstone. Nevertheless, these two 
do strive to come together and are changed. Therefore the 
magnetic forces have no such conception, no such origin, as 
this : nor are they due to those most minute particles of load- 
stone imagined by Baptista Porta concentrated as it were 
into hairs, and springing from friction of the loadstone, which 
parts fastening on to the iron give it the magnetic powers. 
For the electric effluvia, as they are hindered by the interposi- 
tion of any dense body, so too are unable to attract through a 
flame, or if a flame be near by. But iron, which is hindered 
by no obstacle (from) deriving from the loadstone force and 
motion, passes through the midst of a flame to join the load- 
stone. Take a short piece of iron wire, and when you have * 
brought it near to a loadstone it will make its way through 
the flames to the stone ; and a needle turns no less rapidly, no 
less eagerly, to the loadstone though a flame intervenes than 
if only air stands between. Hence a flame interposed does 
not prevent coition. But were the iron itself red-hot, it cer- 
tainly would not be attracted. Apply a red-hot iron rod to a * 
magnetized needle and the needle stands still, not turning to 
the iron ; but as soon as the temperature has fallen somewhat 
it at once turns to it. A piece of iron that has been magnet- 
ized, if placed in a hot fire until it becomes red-hot, and per- * 
mitted to remain for a little while, loses the magnetic power. 1 

1 " For if a Load stone be made red hot, it loseth the magnetical vigour it 
had before in itself, and acquires another from the Earth in its refrigeration; 
for that part which cooleth toward the Earth will acquire the respect of the 
North, and attract the Southern point or cuspis of the Needle" (Thomas 
Brown, Pseudoloxia Epidemica, 1658, page 65). Kenelm Digby, " The Nature of 
Bodies," 1645, Chapter XXI, pages 232-233. 



IO8 WILLIAM GILBERT. 

Even loadstone itself loses its native and inborn powers of at- 
tracting, and all other magnetic properties, if left long in fire. 
And though some magnetic ores when roasted exhale a deep- 
blue or sulphurous and foul-smelling vapor, nevertheless such 
vapor is not the soul of the loadstone ; neither is it the cause 
of the attraction of iron, as Porta supposes. l Nor do all 
loadstones when roasted or burned smell of sulphur or give 
out sulphur fumes : that property is something added, a sort 
of congenital evil which comes from the foul bed or matrix 
in which the loadstone is produced ; nor does the material 
corporeal cause introduce into the iron anything of the same 
sort, for iron derives from loadstone the power of attracting 
and the property of verticity, though glass or gold or another 
sort of stone stand between, as later, when treating of the 
magnetic direction, we shall clearly prove. But fire destroys 
in the loadstone the magnetic qualities, not because it plucks 
out of it any particular attractional particles, but because the 
quick, penetrating force of the flame deforms it by breaking 
its matter up ; just as in the human body the soul's primary 
powers are not burnt, though yet the burnt body remains 
without faculties. But though the iron remains after perfect 
ignition, and is not converted into either ash or slag ; still, as 
Cardan not injudiciously remarks, red-hot iron is not iron, but 
something lying outside its own nature, until it returns to 
itself. For just as, by the cold of the ambient air, water is 
changed from its own nature into ice, so iron made white-hot 
by fire has a confused, disordered form, and therefore is not 
attracted by a loadstone, and even loses its power of attract- 
ing, however acquired ; it also acquires a different verticity 
when, as though born anew, it is impregnated by a loadstone 



1 Porta's " Natural Magick," 1658, Book VII, Chapter II. 



STRENGTH OF A LOADSTONE. IO9 

or the earth ; in other words, when its form, not utterly de- 
stroyed, yet confused, is restored. I shall have more to say 
on this subject when treating of changed verticity (Book III, 
Chap. 10). Hence, Fracastorio finds no confirmation of his 
opinion that the iron is not altered; "for," says he, "if it 
were altered by the loadstone's form, the form of the iron 
would be spoiled." Yet this alteration is not generation, but 
restitution and re-formation of a confused form. 

Hence that is not corporeal which emanates from the load- 
stone, or which enters the iron, or which is given forth again 
by the awakened iron ; but one loadstone gives portion to 
another loadstone by its primary form. And a loadstone re- 
calls the cognate substance, iron, to formate energy and gives 
it position : hence does it leap to the loadstone and eagerly 
conforms thereto (the forces of both harmoniously working to 
bring them together) ; for the coition is not indeterminate and 
confused, it is not a violent inclination of body to body, not a 
mad chance confluence. Here no violence is offered to bodies, 
there are no strifes or discords ; but here we have, as the con- 
dition of the world holding together, a concerted action, to 
wit, an accordance of the perfect, homogeneous parts of the 
world's globes with the whole, a mutual agreement of the chief 
forces therein for soundness, continuity, position, direction, 
and unity. In view of this so wonderful effect, this stupendous 
innate energy, an energy (strength) not existing in other 
elements, the opinion of Thales the Milesian is, in Scaliger's 
judgment, not utterly absurd, not a lunatic's fancy. Thales 
ascribed to the loadstone a soul, for it is incited, directed, and 
moved in a circle by a force that is entire in the whole and 
entire in each part, as later will appear, and because it seems 
most nearly to resemble a soul. For the power of self-move- 
ment seems to betoken a soul, and the supernal bodies, which 



HO WILLIAM GILBERT. 

we call celestial, as it were divine, are by some regarded as 
animated because that they move with wondrous regularity. 
If two loadstones be set over against each other in their floats 
on the surface of water, they do not come together forthwith, 
but first they wheel round, or the smaller obeys the larger and 
takes a sort of circular motion ; at length, when they are in 
their natural position they come together. In iron that has 
not been excited by the loadstone, there is no need of these 
preliminaries ; for iron, though made from the finest loadstone, 
has no verticity save such as it gets by chance and momen- 
tarily ; and this is not stable nor fixed, for while it ran liquid in 
the furnace its parts were thrown into confusion. Such a body 
instantly receives from the presence of the loadstone verticity 
and natural conformity to it, being powerfully altered and 
converted, and absolutely metamorphosed into a perfect mag- 
net : so, like an actual part of the loadstone, it flies to it. For 
there is naught that the best loadstone can do which cannot 
be done by iron excited by a loadstone not magnetized at 
all, but only placed in the neighborhood of a loadstone. For 
as soon as it comes within the loadstone's sphere of influence, 
though it be at some distance from the loadstone itself, the 
iron changes instantly, and has its form renewed, which before 
was dormant and inert, but now is quick and active : all this 
will appear clearly when we come to present the proofs of 
magnetic direction (in Book III). Thus the magnetic coition 
is the act of the loadstone and of the iron, not of one of them 
alone : it is evre\exeia, not epyov$ it is (rvvevrekexeia and 
conactus (mutual action) rather than sympathy. There is, 
properly speaking, no magnetic antipathy ; for the flight and 
turning away of the poles and the wheeling around of the 
whole is the act of each of the two toward unition, resulting 



STRENGTH OF A LOADSTONE. Ill 

from the crvvevreXexeia and conactus 1 of both. Thus the 
iron puts on anew its form ; and because that is awakened, as 
also in order more surely to gain its form, it rushes headlong 
on the loadstone, and not with circlings and wheelings, as in 
the case of two loadstones. For as, long ages ago, nay at the 
very beginning of things, there were gendered in the loadstone 
and therein fixed verticity and the power of coordinating; 
and since the great mastering form of the earthly globe can- 
not be readily changed by another magnet, as iron is changed, 
therefore, the nature of each being constant, neither hath the 
momentary power of altering the verticity of the other, but 
the two do but come to agreement with each other. And 
magnetized iron, in case it is unable for whatever reason to * 
cause the piece of iron in the natural state to turn, as does the 
pointer of a versorium, is itself seized at either end by a load- 
stone brought nigh it. For the loadstone, as it imparts so can it 
alter verticity, and it can in an instant bestow the formal energy 
in either end. Thus iron may be transformed variously, as 
that form is adventitious and has not yet abided long in the 
metal. In iron, because its body is fused when a magnetic or 
a ferruginous ore is smelted, the virtue of the primal form, 
which previously existed distinct, is now confused ; but a 
sound loadstone, when brought near, sets up again the primal 
action : the form, now arranged and ordered again, joins 
forces with the loadstone, and, each with other, the two come 
to agreement, after the manner of the loadstone, in all their 
movements toward union ; they enter into alliance, and whether 
joined by bodily contact or standing within their sphere of 
influence, are one and the same. For when iron is reduced in 
the furnace from its ore, or when steel is got from its ore, 

1 Conactus, i.e., combined or mutual action. See Book V, Chanter XII. 



112 WILLIAM GILBERT. 

which is loadstone, the metallic matter is melted and becomes 
fluid, and the iron and the steel run off, leaving their slag : this 
slag consists of matter spoilt by the intense heat of the fire, 
or of useless matter, or of dross, due to some imperfection or 
to some intermixture in the projecting surface of the earth. 
Thus the iron or steel is a purified material, wherein the metal- 
lic element, all disordered by the smelting (for the forces of 
that primal form are all confused and unsettled), is brought 
back again, as it were, to life, to normal form, and to complete- 
ness. Its matter is thus awakened, and tends to union, which 
is the bond of the universe and the necessary condition of the 
conservation of all things. 

For this reason, and because of the purging of the ore and 
its change into a purer body, the loadstone gives to iron 
greater power of attracting than exists in itself. For if you 
put some iron-filings or a nail on a large magnet, a piece of 
iron joined to the magnet steals the filings and the nail, and 
holds them as long as it remains alongside the magnet : so, 
too, iron attracts iron more powerfully than does a loadstone, 
if the iron be afformed, and remain within the sphere of the 
form given out to it. Again, a piece of iron nicely adjusted 
to the pole of a loadstone holds a greater weight than the 
loadstone does. So, then, iron and steel are the better ele- 
ments of their ores, purified by the action of fire, and the load- 
stone impregnates them again with their forms ; wherefore to 
it do they come by spontaneous approach, so soon as they 
enter the circle of the magnetic forces, for by it are they first 
possessed, and made continuous, and united with perfect union. 
Once within that circle they have absolute continuity, and they 
are joined by reason of their accordance, albeit the bodies 
themselves be separated. For the iron is not, after the man- 
ner of electrics, possessed and pulled by substantial effluvia, 



STRENGTH OF A LOADSTONE. 113 

but only by the immaterial act of the form or by its incorporeal 
going forth, which as in a continuous and homogeneous body 
doth act in the iron subjectum, and is received into it ; nor 
has it need of wider paths. 

Hence it is that, with the densest bodies interposed, the 
iron is put in motion throughout and is attracted, and that the 
iron, in presence of the loadstone thoroughly stirs and attracts 
the loadstone itself, and that with their mutual forces they 
make that rush toward union which commonly is called attrac- 
tion. But these formal forces sally forth and in meeting unite; 
and the force conceived in the iron, that also forthwith has its 
efflux. But Julius Scaliger, who, in his 344th disquisition, 
cites other examples to prove this explanation to be absurd, is 
far astray. For the virtues of prime bodies are not compara- 
ble with those that are derivate and mixed. Were he still 
among the living, he might now, in the chapter on Effused 
Magnetic Spherical Forms, discover what is the nature of 
effused forms. 

But if iron be badly injured by rust it is but little or not at 
all affected by the loadstone, for when the metal is corroded 
and marred by external causes or by decay it is spoilt, as has 
been said of the loadstone, and loses its prime qualities that 
are conjoined to its form, or, the stone being impaired by age, 
these qualities are weak and feeble ; neither can it be duly in- 
formed when once it has suffered decay. But a strong, fresh 
(vegetus) loadstone pulls all sound clean iron, and the iron 
(having conceived force) powerfully attracts other iron as 
pieces of iron wire, iron nails ; and not only these separately 
and directly, but one after another, one at the end of another, 
thus holding three, four, or five : thus forming as it were a 
chain, the successive nails sticking to one another and sus- 
pended from one another. But the loadstone would not 



114 WILLIAM GILBERT. 

attract the last piece in such a line if there were no nails in 
the mid-space. Thus a loadstone placed at A pulls the nail 
or bar B, and, in like manner, after B pulls C, and after C, D ; 
but at the same distance does not pull aloft D : that is so for 

27 C 3 



the reason that when the nails form an unbroken line the 
presence of the loadstone A, because of its proper forces, 
raises the magnetic form of the iron objects B and C, and 
makes them as it were its auxiliary forces, while B and C, like 
a continuous magnetic body, conduct on to D the force where- 
by it is seized or conformed, yet not so powerfully as C is 
seized by B. And these iron nails derive the force from the 
mere contact, and from the presence of the loadstone without 
contact, and they retain it in their bodies, as will be shown 
when we treat of Direction (Book III). For the iron does not 
assume these powers only while in presence of a loadstone, nor 
does it hold them of the stone only momentarily as [the distin- 
guished orator " Euphrades "] Themistius [of Paphlagonia] 
supposes in his Physica, VIII. The best iron (steel) is solicited 
by the loadstone from a greater distance, a greater weight of 
it is lifted, it is more powerfully held, and it acquires greater 
force, than does common, cheaper iron, for it is made of the 
best ore or of loadstone, and is imbued with superior forces ; 
but iron from impure ores is weaker, and is attracted more 
feebly. As for what Fracastorio writes, of having seen a bit 
of loadstone that on one side attracted loadstone but not iron, 
on another side attracted iron but not loadstone, and on 
another attracted both, proof, according to him, that in one 
spot there was more loadstone, in another more iron, in the 
third the two were present equally ; hence the difference in 



IN WHAT MANNER ENERGY INHERES. 

the attraction, all this is utterly erroneous, and the result of 
mal-observation on the part of Fracastorio, who did not know 
how to present one loadstone to another properly. Loadstone 
attracts iron and loadstone if both be properly situated, and 
free to move and unrestrained. A light object is more readily 
moved from its position and place than a heavy one, for heavy 
objects make greater resistance, but a light object bestirs 
itself to meet a heavy one and is pulled by it. 



CHAPTER V. 

IN WHAT MANNER THE ENERGY INHERES IN THE LOADSTONE. 

THAT the loadstone draws loadstone, iron, and other mag- 
netic bodies was shown in Book I, as also by what forces the 
magnetic coition is regulated ; we have now to inquire how 
this energy is ordered in magnetic bodies. Here we must 
bring in the analogy of a large loadstone. A magnetic body 
unites forcibly with a loadstone if the loadstone is powerful, 
feebly if it be defective or if it has from any fault become im 
paired. Loadstone does not attract iron with equal force at 
every point ; in other words, the magnetic body does not tend 
with the same force to every point of the loadstone ; for the 
loadstone has points (i.e., true poles) at which its rare energy 
is most conspicuous. And the regions nearest the poles are 
the stronger, those remotest are the weaker ; yet in all the 
energy is in some sense equal. In the figure of a terrella, 
A, B, are the poles, CD is the equinoctial line; the greatest 
attractive force is seen at A and B. At C and D there is no 
force that attracts to the body the ends of magnetic objects, 



Il6 WILLIAM GILBERT. 

for the forces tend toward each of the poles. But the directive 
force at the equator is strong. C and D are at equal distances 
from both poles ; hence a piece of iron on the line CD, being 




pulled in contrary directions, does not cling steadily, but it 
stays and adheres to the stone only when it falls to either side 
of the line. At E the attractive force is greater that at F, for 
E is nigher the pole. And this is not for the reason that there 
is more energy resident at the pole, but because all the parts, 
being united in the whole, direct their forces to the pole. 

By the confluence of the forces from the plane of the 
equinoctial toward the pole the energy increases poleward, 
* and absolute verticity is seen at the pole so long as the load- 
stone remains whole ; but let it be divided or broken up, and 
in the separate parts the verticity will find other abiding- 
places. For with change of mass always goes change of ver- 
ticity. Hence, if the terrella be severed along the line AB so 
as to make two stones, the poles in the severed parts will not 
be AB, but FG and HI. And though these two stones now 
are so interrelated that F does not tend to H, nevertheless if, 
before division, A was the north pole, F likewise is now north, 
as is H also. For the verticity is not reversed, as Baptista 



IN WHAT MANNER ENERGY INHERES. 



117 



Porta erroneously affirms (Porta, VII, 4);' for though F and 
H are not so related as mutually to attract, yet the two turn 
to the same point of the horizon. If the hemisphere HI be 
cut in two quarter spheres, one pole will be at H and the 
other at /. The integral mass of the stone, as I have said, 



* A 




Gr B I 




gives to the vertex or pole a constant place ; and any part of 
the stone, before it was hewed out of the rock might have 
been the pole or vertex : but of this we shall have more to say 
under Direction. For the present, the thing to be understood 
and to be borne steadily in mind is, that the poles are domi- 
nant in virtue of the force of the whole, for (the magnetic 
empire being divided in two by the equinoctial line) all the 



1 John Baptist Porta, "Natural Magick," 1658, Book VII, Chapter IV, 
page 193: "But the two points we speak of are the end of the right line, run- 
ning through the middle of the stone from North to south; if any man break 
the stone, and break this line, those ends of the division will presently be of 
another property and vertue, and will be enemies one to the other: which is 
great wonder: for these two points, when they were joined together, had the 
same force of turning to the pole, but, now being parted asunder, one will turn 
to the North, the other to the South, keeping the same posture and position 
they had in the Mine where they were bred: and the same happens in the least 
bits that are seen in the greatest load-stone." 



WILLIAM GILBERT. 

forces of the hemisphere tend north, and, conversely, ail those 
of the other hemisphere tend south, so long as the parts are 
united, as appears from the following demonstration. For 




the whole force tends separately to the two poles along an 
infinity of curves starting from every point of the equator that 
divides the sphere into two equal parts: from every point 
of the superficies from the equator to the north on one side, 
and from the equator to the south on the other. Hence the 
verticity is, in each hemisphere, from the equinoctial circle to 
the pole. This force resides in the whole mass. From A the 
energy is transmitted to B, from AB to C, from ABC to D, 
and from them to E, and likewise from G to H] and so on as 
long as the whole mass is one body. But if the piece AB be 



IN WHAT MANNER ENERGY INHERES. 119 

cut out, though it be near the equator, nevertheless the effect 
will be as great on the magnetic action as if CD or DE, equal 
quantities, had been taken away. For no part has any super- 
eminent value in the whole ; whatever it be, that it is because 
of the parts adjoining, whereby an absolute and perfect whole 
is produced. 

DIAGRAM OF THE MAGNETIC ENERGY DIFFUSED FROM THE 
PLANE OF THE EQUATOR TO THE PERIPHERY OF A TER- 
RELLA OR OF THE EARTH. 

Let HEQ be a terrella, E a pole, M the centre, HMQ the 
plane of the equinoctial circle. From every point of the 
equinoctial plane the energy reaches out to the periphery, but 
differently from each : for from A the formal energy goes 
toward CFNE and to every point betwixt C and E (the pole), 
and not toward B ; neither from G toward C. The attractive 
force in the region FGH is not strengthened by the force 
residing in the region GMFE ; but FGH increases the energy 
in the rising curve FE. Thus energy never proceeds from the 
lines parallel to the axis to points above those parallels, but 
always internally from the parallels to the pole. From every 
point of the plane of the equator the energy goes to the 
pole E ; the point F derives its forces only from GH, and the 
point N from OH\ but the pole E is strengthened by the 
whole plane HO. Therefore this mighty power has here its 
chief excellency ; here is its throne, so to speak. But in the 
intervals at F, for example, there resides so much attractional 
energy as can be given by the section HG of the plane. 



120 



WILLIAM GILBERT. 





MAGNETIZED IRON AND SMALLER LOADSTONES. 121 



CHAPTER VI. 

HOW MAGNETIZED IRON AND SMALLER LOADSTONES CON- 
FORM TO THE TERRELLA AND TO THE EARTH ITSELF, 
AND ARE GOVERNED THEREBY. 

COITION of bodies that are separate from one another, and 
that cohere naturally, takes place by another sort of move- 
ment, if they be free to move. The terrella sends its force 
abroad in all directions, according to its energy and its quality. 
But whenever iron or other magnetic body of suitable size 
happens within its sphere of influence it is attracted ; yet the 
nearer it is to the loadstone the greater the force with which 
it is borne toward it. Such bodies tend to the loadstone not * 
as toward a centre nor towards its centre : that they do only 
at its poles, i.e., when that which is attracted and the pole of 
the loadstone, as well as its centre, are in a right line. But in 
the intervals between they tend to it in an oblique line, as 
seen in the figure below, wherein is shown how the force goes 
out to the magnetic associate bodies within the sphere. At 
the poles the line is a right one. The nearer the parts to 
the equinoctial circle the more obliquely do magnetic bodies 
attract, but the parts nearer the poles attract more directly ; 
at the poles themselves attraction is in a right line. All load- 
stones alike, whether spherical or oblong, have the self-same 
mode of turning to the poles of the world ; but it is easiest to 
experiment with oblong ones. For whatever the shape, ver- 
ticity is present, and there are poles ; but owing to imperfect 
and irregular shape, loadstones are often subject to drawbacks, 



122 WILLIAM GILBERT. 

and are interfered with in their movements. If the loadstone 
be oblong, with vertices at the extremities and not at the 




sides, it attracts best at the vertex ; for the parts convey to 
the poles a greater force in right lines than in oblique. Thus 
do the loadstone and the earth conform magnetic movements. 



POTENCY OF THE MAGNETIC FORCE. 12$ 



CHAPTER VII. 

OF THE POTENCY OF THE MAGNETIC FORCE, AND OF ITS 
SPHERICAL EXTENSION. 1 

THE magnetic force is given out in all directions around 
the body ; around the terrella it is given out spherically ; 
around loadstones of other shapes unevenly and less regularly. 
But the sphere of influence does not persist, nor is the force 
that is diffused through the air permanent or essential ; the 
loadstone simply excites magnetic bodies situate at convenient 
distance. And as light so opticians tell us arrives instantly 
in the same way, with far greater instantaneousness, the mag- 
netic energy is present within the limits of its forces ; and 
because its act is far more subtile than light, and it does not 
accord with non-magnetic bodies, it has no relations with air, 
water, or other non-magnetic body ; neither does it act on 
magnetic bodies by means of forces that rush upon them with 
any motion whatever, but being present solicits bodies that 
are in amicable relations to itself. And as a light impinges 
on whatever confronts it, so does the loadstone impinge upon 
a magnetic body and excites it. And as light does not remain 
in the atmosphere above the vapors and effluvia nor is re- 
flected back by those spaces, so the magnetic ray is caught 
neither in air nor in water. The forms of things are in an 
instant taken in by the eye or by glasses ; so does the mag- 
netic force seize magnetic bodies. In the absence of light 



1 Sir Kenelm Digby, " A Treatise of Bodies," London 1645, Chap. XXI, 
pages 238, 239. 



I2 4 



WILLIAM GILBERT. 



bodies and reflecting bodies, the forms of objects are neither 
apprehended nor reflected ; so, too, in the absence of mag- 
netic objects neither is the magnetic force imbibed nor is it 
again given back to the magnetic body. But herein does the 
magnetic energy surpass light, that it is not hindered by any 
dense or opaque body, but goes out freely and diffuses its 
force every whither. In the case of the terrella and in a 
spherical loadstone the magnetic energy extends outside the 
body in a circle ; yet in the case of an oblong loadstone it 
does not extend out in a circle, but into an area of form de- 
termined by the shape of the stone, as in the stone A, in the 
figure, the energy reaches to the limits FCD, everywhere equi- 
distant from the stone A. 




CHAPTER VIII. 

OF THE GEOGRAPHY OF THE EARTH AND THE TERRELLA. 

WE have next to speak of magnetic circles and magnetic 
limits, so that what follows later may be better understood. 
Astronomers, in order to account for and observe the move- 



GEOGRAPHY OF THE EARTH. 12$ 

ments of the planets and the revolution of the heavens, as also 
more accurately to describe the heavenly order of the fixed 
stars, have drawn in the heavens certain circles and bounds, 
which geographers also imitate so as to map out the diversi- 
fied superficies of the globe and to delineate the fairness of 
the several regions. In a different sense we accept those 
bounds and circles, for we have discovered many such, both in 
the terrella and in the earth ; but these are determined by 
nature itself, and are not merely imaginary lines. Geographers 
make a division of the earth chiefly by defining the equator 
and the poles ; and these bounds are set and defined by nature. 
Meridians, too, indicate tracks from pole to pole, passing 
through fixed points in the equator ; along such lines the mag- 
netic force proceeds and gives direction. But the tropics and 
the arctic circles, as also the parallels of latitude, are not nat- 
ural bounds described on the earth ; yet all these parallel cir- 
cles indicate that a certain conformity between themselves 
exists among regions of the earth situate in the same latitude 
or diametrically opposite to them. All these are of service to 
mathematicians in constructing globes and maps. Thus such 
circles are of use in the terrella, but they need not be drawn 
as geographers draw them on the surface, for the loadstone 
may be perfectly even and uniform all over. Nor are there 
any " upper" or " lower" parts, in the terrestrial globe, as there 
are also none in the terrella, save perhaps that one may choose 
to call these parts " upper" which are at the periphery and 
those " lower" which are nigher the centre. 



126 WILLIAM GILBERT. 

CHAPTER IX. 

OF THE EQUINOCTIAL CIRCLE OF EARTH AND TERRELLA. 

THE equinoctial circle imagined by astronomers, which is 
equidistant from both poles and divides the earth in the mid- 
dle, measures the movements of their primum mobile or tenth 
sphere, 1 and is called the zone of the/nr*i mobile ; it is called 
" equinoctial " because when the sun is in this circle which 
must happen twice a year the days are of equal length with 
the nights. This circle is designated also aquidialis ; hence 
the Greeks give it the name ivrjuepivos (which means the 
same, " equal day"). And it is also well called " equator," for 
it divides the whole globe of the earth from pole to pole in 
two equal parts. To the terrella also is justly assigned an 
equator whereby its power is distributed between two parts. 
By the plane of this equator, as it passes through the centre, 
the whole terrella is divided into two parts equal in mass and 
in verticity, and imbued with equal energy, as though a wall 
stood betwixt the two verticities. 



CHAPTER X. 
THE EARTH'S MAGNETIC MERIDIANS. 

GEOGRAPHERS have devised meridians for the purpose of 
distinguishing the longitude and latitude of regions. But the 

1 F or primum mobile, see Book VI, Chapter III. 



PARALLELS. 12? 

magnetic meridians are numberless, and, even as the earth's 
meridians, they pass through fixed and opposite points in the 
equator and through the poles. On them also is magnetic 
latitude measured. By means of them we understand decli- 
nations ; and along them there is a fixed direction toward the 
poles, except when the magnetic body for any cause varies, 
and is jostled out of the right course. The meridian com- 
monly called magnetic is not properly magnetic, neither is it 
a meridian, but is supposed to pass through the limits of 
variation in the horizon. Variation is in fact a faulty devia- 
tion from the meridian in various places it is not fixed or con- 
stant in any meridian. 1 



CHAPTER XL 

PARALLELS. 

IN parallel circles the same energy and equal potency is 
seen throughout, when different magnetic bodies are placed 
on one and the same parallel, either of the earth or of the 
terrella. For the bodies are at equal distances from the poles 
and have equal changes of declination, and are attracted and 
held and come together under the action of like forces ; just 
as regions of the earth on the same parallel, though they may 
differ in longitude, are said to have still the same quantity of 
daylight and the same climate. 

1 Nicolao Cabeo, Philosophia Magnetica, 1629, Lib. Ill, Cap. VI, page 

211. 



128 WILLIAM GILBERT. 

CHAPTER XII. 

THE MAGNETIC HORIZON. 

AN horizon is a great circle separating the things seen 
from those that are out of sight, as one half of the heavens is 
always plainly visible while another half is always hid. So it 
seems to us by reason of the great distance of the starry 
sphere ; yet the difference is in the ratio of the earth's semi- 
diameter to the semi-diameter of the starry heavens a differ- 
ence not perceived by the senses. But we take the magnetic 
horizon to be a plane perfectly level throughout, tangent to 
the earth or to the terrella at the place of the region, with 
which plane the semi-diameter, whether of the earth or of the 
terrella, being extended, makes right angles on all sides. Such 
a plane is to be imagined for the earth, and for the terrella 
likewise, for the sake of magnetic proofs and demonstrations. 
For we are considering the bodies themselves, and not the 
general aspects of the world. Therefore, not with reference to 
sight for that varies according to the elevation of regions 
we assume in magnetic demonstrations a sensible horizon, not 
what is called by astronomers the rational horizon. 



CHAPTER XIII. 

OF THE MAGNETIC AXIS AND POLES. 

A LINE drawn through the centre of the earth (or of the 
terrella) to the poles is called the axis. The poles are so 



COITION STRONGER AT THE POLE. 

called by the Greeks (TtoXoi, and rov Ttokeiv poloiirvrnpolein, 
to revolve), and by the Latins cardines (hinges, pivots) and 
vertices (centres of a whirling motion) ; and these names were 
given to signify that the world rotates and is ever whirling. 
We propose to show that the earth and the terrella are by 
the magnetic force made to revolve round these poles, whereof 
that one in the earth which points to Cynosura 1 is called the 
North, the Boreal, or the Arctic pole ; the opposite one is 
called the South, Austral, or Antarctic pole. And neither in 
earth nor in terrella do the poles exist merely for the sake of 
rotation ; they are furthermore reference points of direction 
and of position (consist 'endi), on the one hand towards one's 
destination on the earth, and on the other hand as regards 
their angular distance (turn versus destinatas mundi regiones). 



CHAPTER XIV. 

WHY THE COITION IS STRONGER AT THE POLE THAN IN 
THE PARTS BETWEEN EQUATOR AND POLE ; AND THE 
RELATIVE POWER OF COITION IN DIFFERENT PARTS OF 
THE EARTH AND THE TERRELLA. 

WE have already shown that the supreme attractional 
power is at the pole, while the weaker and more sluggish 
power is in the parts nigh the equator. And as in the decli- 
nation it is seen that this ordering and rotating force increases 
as we advance from the equator to the poles, so too does the 
coition of magnetic bodies grow stronger by the same degrees 

1 Cynosura Cynosure the constellation of the Lesser Bear ( Ursa Minor} 
containing the polar star. 



I3O WILLIAM GILBERT. 

and in the same proportion. For at points remote from the 
pole the loadstone does not pull magnetic bodies in a right 
line toward its centre, but they tend to it obliquely, and 
obliquely are attracted. For as a very small chord of a circle 
differs from the diameter, by so much do differ the attractional 
powers of different parts of the terrella. For inasmuch as the 
attraction is a coition to a body, and magnetic bodies come 
together owing to their natural tendency to turn to each other, 
in the diameter drawn from pole to pole a body impinges on the 
loadstone in a right line ; but not so in other parts. Therefore 
the less it turns toward the body, the less and the more weak 
is the coition and the cohesion. Let ab be the poles. An 




iron bar or the other magnetic body c is attracted at e ; yet 
the end that is pulled does not tend toward the centre of the 
loadstone, but obliquely toward the pole, and a chord drawn 
from that end obliquely in the direction in which the body is 
attracted is a short one ; the strength of the coition therefore 
is less, and so too the attracted object turns at a less angle to 
the terrella. But as from a body at f a longer chord pro- 
ceeds, so the action there is stronger. At g the chord is still 



MAGNETIC FORCE IMPARTED TO IRON. 13! 

longer. At a (the pole) it is longest of all (for the diameter is 
the longest line), and thither do all the parts send their forces : 
there stands, as it were, the citadel, the judgment-seat, of the 
whole region, not that the pole holds this eminence in its own 
right, but because it is the depository of forces contributed to 
it by all the other parts ; it is like soldiers bringing reinforcement 
to their commander. Hence a rather oblong loadstone attracts 
better than a spherical one, if its length stretch from pole 
to pole, and yet the two may be from the same mine, and be 
of equal size and volume. The way is longer from one pole to 
the other in the oblong stone, and the force supplied by the 
other parts are not so scattered as in a spherical loadstone 
and the terrella ; they are better massed and united, and thus 
united they are stronger and greater. But a flat or oblong 
loadstone is much less effective when the length is in the direc- 
tion of the parallels, and the pole ends neither in a point nor 
in a circle or sphere, but lies flat on a plane surface so as to 
be held for something abject and of no account, for its unfit 
and unadaptable form. 



CHAPTER XV. 

THE MAGNETIC FORCE IMPARTED TO IRON IS MORE APPAR- 
ENT IN AN IRON ROD THAN IN AN IRON SPHERE OR 
CUBE, OR IRON OF ANY OTHER SHAPE. 

IT has been already said that an oblong loadstone lifts a 
greater weight of iron : so in a long piece of iron rubbed with 
a loadstone the magnetic force is stronger if the poles are at 
the ends; for the magnetic forces, which are sent to both 



Ij 2 WILLIAM GILBERT. 

ends from the poles, are concentrated at the narrow terminals, 
and not diffused. In square and other angular figures the 
force is scattered, nor does it proceed in right lines or along 
suitable arcs. The iron sphere, too, though it hath the figure 
of the earth, still has less attraction for magnetic bodies for 
the same reason ; hence an excited iron spherule acts with 
less force on iron than does a magnetized bar of the same 
weight. 



CHAPTER XVI. 

THAT MOTION IS PRODUCED BY THE MAGNETIC FORCE 
THROUGH SOLID BODIES INTERPOSED : OF THE INTER- 
POSITION OF A PLATE OF IRON. 

AN iron wire passed through a suitable piece of cork, or a 
needle poised on a point or in a mariner's compass, is set in 
motion when a loadstone is brought near it or is passed 
beneath it, though the water, the vessel, or compass-box stand 
between. No hindrance is offered by thick boards, or by walls 
of pottery or marble, or even of metals : there is naught so 
solid as to do away with this force or to check it, save a plate 
of iron. Whatever substances are interposed, however dense 
they be, as they do not aniiul the force nor obstruct its path, 
so do they in no wise hinder or lessen or retard. Nor is the 
whole of the force suppressed by a plate of iron, but in part 
diverted. For when the force enters the middle of an iron 
plate placed within the sphere of magnetic influence or directly 
* over the pole of the loadstone, that force is distributed chiefly 
to the extremities, so that the rim of a circular plate of suit- 



MOTION PRODUCED BY MAGNETIC FORCE. 133 

able size attracts pieces of iron wire at all points. The same 
is seen in a long iron rod rubbed with a loadstone in the mid-* 




die ; it has the same verticity at both ends. In the figure, 
CD is a long rod magnetized in the middle by the north pole 
E ; C is a south end or south pole, and D is another south end. 
But here note the singular fact, that a needle magnetized by 
that pole turns to that pole, though the round plate stands 
between, the plate not hindering, but the attraction being only* 
weaker; for the force is scattered to the extremities of the 
plate, and departs from the straight track, but yet the plate in 
its middle retains the same verticity with the pole when it is 
nigh it and alongside it : hence does the needle magnetized by 
the same pole tend to the centre of the plate. If the loadstone 
is a weak one, the needle hardly turns if an iron plate be inter- 
posed ; for, being diffused out to the extremities of tlie plate, 
the loadstone's energy is less able to pass through the centre. 
But let the plate be magnetized in the middle by the pole, and * 
then let it be removed beyond the loadstone's sphere of in- 
fluence, and you shall see the point of the same needle go in 
the contrary direction and quit the centre of the plate, which 
before it sought : for outside of the sphere of influence the plate 
has the contrary verticity, but near the loadstone it has the 
same ; for near the loadstone the plate is as it were part of the 
loadstone and has the same pole. Let A be an iron plate 



134 WILLIAM GILBERT. 

near a pole ; B a needle with point tending toward the centre 
of the plate, which plate has been magnetized by the pole C 
of a loadstone. Now if the same plate be placed outside the 
sphere of magnetic influence, the point of the needle will not. 
turn to its centre, but only the crotch (the other end) of the 




same needle. But an iron sphere interposed (if it be not too 

* large) attracts the point of the needle at the other side of the 
stone, for the verticity of that side is the same as that of the 
adjoining pole of the loadstone. And this turning of the 
needle's point (i.e., the end of it magnetized by contact with 
that pole) and of its cross (other end) at a considerable distance 

* takes place with an iron sphere interposed, whereas it would 
not take place at all were the space between vacant ; for the 
magnetic force travels through bodies and is continued on by 
them. Let A be a terrella, B an iron sphere, F a needle 
between the two bodies, with its point magnetized by the pole 
C. In the second figure A is the terrella, C a pole, B an iron 
sphere : the needle tends toward C, the terrella's pole, through 
the iron sphere. The needle thus placed between terrella and 
sphere vibrates more forcibly toward the pole of the terrella, 
because the loadstone imparts instantaneous verticity to the 
opposite sphere. The earth's efficiency is the same, produced 
by the same cause. For if in a thick box made of gold (the 
densest of metals) or glass, or marble, you put a needle free to 



MOTION PRODUCED BY MAGNETIC FORCE. 135 

revolve, that needle, in spite of the box, will show that its 
forces are most closely allied to and unified with those of the 
earth ; of its own accord and instantly, regardless of the box 




that prisons it, it turns to its desiderated points of north and 
south. And it does the same though it be shut up in iron * 
vaults sufficiently roomy. Whatever bodies are produced here 
on the earth or are manufactured from nature's products by 
art, all consist of the matter of the globe : such bodies do not 
interfere with the prime potencies of nature derived from the 
primary form ; nor can they withstand them, save by contrary 
forms. But no forms of mixed bodies are inimical to the innate 
primary form, though some of them oft do not accord among 
themselves. On the other hand, in all the bodies that have a 
material cause of attraction (e.g., amber, jet, sulphur) action is 
hindered by interposition of a body (as paper, leaves, glass, etc.), 
and the way is obstructed and blocked so that that which is 
exhaled cannot reach the light body that is to be attracted. 
But coition and movement of the earth and the loadstone, 
though corporeal hindrances be interposed, are shown also in 
the efficiencies of other chief bodies that possess the primary 



13 WILLIAM GILBERT. 

form. The moon, more than the rest of the heavenly bodies, 
is in accord with the inner parts of the earth because of her 
nearness and her likeness of form. The moon causes the move- 
ment of the waters and the tides of ocean ; makes the seashore 
to be covered and again exposed twice between the time she 
passes a given point of the heavens and reaches it again in the 
earth's daily rotation : this movement of the waters is produced 
and the seas rise and fall no less when the moon is below the 
horizon and in the nethermost heavens, than when she is high 
above the horizon. Thus the whole mass of the earth, when 
the moon is beneath the earth, does not prevent the action of 
the moon ; and thus in certain positions of the heavens, when 
the moon is beneath the horizon, the seas nearest to our coun- 
tries are moved, and, being stirred by the lunar power (though 
not struck by rays nor illumined by light), they rise, approach 
with great impetus, and recede. Of the reason of this we will 
treat elsewhere : suffice it here just to have touched the thresh- 
old of the question. Hence, here on earth, naught can be 
held aloof from the magnetic control of the earth and the load- 
stone, and all magnetic bodies are brought into orderly array 
by the supreme terrene form, and loadstone and iron sympa- 
thize with loadstone though solid bodies stand between. 1 



1 In connection with the increased energy which magnets acquire by being 
armed, that is, fitted with a cap of polished iron at each pole, Dr. Whewell 
remarks, that it is only at a later period any notice was taken " of the distinc- 
tion which exists between the magnetical properties of soft iron and of hard 
steel; the latter being susceptible of being formed into artificial magnets , with 
permanent poles ; while soft iron is only passively magnetic, receiving a tempo- 
rary polarity from the action of a magnet near it, but losing this property when 
the magnet is removed. About the middle of the last century various methods 
were devised of making artificial magnets, which exceeded in power all mag- 
netic bodies previously known." ("Hist, of Ind. Sciences," 1859, Vol. II, page 
220.) 



IRON HELMET OF THE LOADSTONE. 137 



CHAPTER XVII. 

OF THE IRON HELMET (CAP) OF THE LOADSTONE, WHERE- 
WITH IT IS ARMED AT THE POLE TO INCREASE ITS 
ENERGY ; EFFICIENCY OF THE SAME. 1 

A. CONCAVE hemisphere of thin iron, a finger's width in 
diameter, is applied to the convex polar superficies of a load- 
stone and properly fastened ; or an iron acorn-shaped ball ris- 
ing from the base into an obtuse cone, hollowed out a little and 
fitted to the surface of the stone, is made fast to the pole. 
The iron must be the best (steel), smooth, polished, and even. 
Fitted with this contrivance, a loadstone that before lifted 
only 4 ounces of iron will now lift 12 ounces. But the greatest 
force of the co-operating or rather unified matter is seen 
when two loadstones fitted with these projections are so joined* 
as mutually to attract and lift each other : thus may a weight 
of 20 ounces be lifted, though either stone unarmed would lift 
only 4 ounces. Iron is held faster by an armed loadstone than 
by one not armed, and hence it lifts greater weights, because 
iron clings more strongly to the armed stone : for, by the con- 
tiguous presence of the loadstone, the iron of the armature 
and the iron attracted are bound fast together ; and when the 
armature has imbibed the magnetic energy by reason of the 
presence of the loadstone, and another piece of iron adjoining 
at the same time derives force from the presence of a loadstone, 
the two unite energetically. Hence when two powerful arma- 

1 Dr. J. Lament's " Handbuch des Magnetismus," Leipzig 1867, page 

53- 



138 WILLIAM GILBERT. 

tures are in contact they cohere strongly. This is proved in Book 
III, Chap. IV, by iron rods cohering, as also where we men- 
tion the transformation of steel-filings into a concreted mass. 
For this reason iron situate near a loadstone takes away from 
it pieces of iron of suitable weight, provided only it be in con- 
tact with them ; else, however near they may be, it does not 
match them. For masses of magnetic iron do not, within the 
field of a loadstone or near a loadstone, attract more strongly 
than the loadstone attracts any iron ; but once they are in con- 
tact with each other they unite more strongly, and become as 
it were clamped together, though with the same forces at work 
the substance remains the same. 1 



CHAPTER XVIII. 

AN ARMED LOADSTONE DOES NOT ENDOW WITH GREATER 
FORCE MAGNETIZED IRON THAN DOES AN UNARMED ONE. 

TAKE two pieces of iron, one magnetized with an armed 
and the other with an unarmed loadstone, and apply to one 
of them a weight of iron proportioned to its powers : the other 
loadstone will lift the same weight, and no more. Two needles 
also turn with the same velocity and constancy toward the 
poles of the earth, though one needle may have been touched 
by an armed magnet and the other by one unarmed. 

1 Sir Kenelm Digby, " The Nature of Bodies," 1645, Chap. XXII, page 
243; Jacobi Rohaulti, Physica, Londini 1718, Par. III. Cap. VIII, p. 403, or 
the English translation by Dr. Clarke, London, 1728, Vol. II, page 181; Ath. 
Kircheri, Magnes ; sive de arte Magnetica, 1643, Lib. I, Pars II, page 63; 
Nicolao Cabeo, Philosophia Magnetica, 1629, Lib. IV, Cap. XLII, page 407. 



AN ARMED MAGNET LIFTS ANOTHER. 139 



CHAPTER XIX. 

THAT UNITION IS STRONGER WITH AN ARMED LOADSTONE; 
HEAVIER WEIGHTS ARE THUS LIFTED ; THE COITION IS 
NOT STRONGER, BUT COMMONLY WEAKER. 

THAT an armed loadstone lifts a greater weight is evident 
to all ; but iron is drawn from the same dis- 
tance, or rather from a greater distance, to 
the loadstone when the stone is without the 
iron helmet. This is to be tried with two 
pieces of iron of the same weight and form at . 
equal distance, or with one and the same 
needle, tested first with the armed then with 
the unarmed stone, at equal distances. 



CHAPTER XX. 

THAT AN ARMED MAGNET LIFTS ANOTHER, 
AND THAT ONE A THIRD: THIS HOLDS 
GOOD THOUGH THERE BE LESS ENERGY 
IN THE FIRST. 

ARMED loadstones duly joined together 
cohere firmly and form one ; and though the 
first be weak, the second "nevertheless clings to 
it, not alone with the force of the first, but of 
the second, the stones thus helping each other : 
to the second a third will often cling, and with strong load- 
stones a fourth to the third. 



I4O WILLIAM GILBERT. 



CHAPTER XXI. 

THAT WHEN PAPER OR OTHER MEDIUM IS INTERPOSED, AN 
'.~ ARMED LOADSTONE DOES NOT LIFT MORE THAN ONE 
UNARMED. 

IT has been shown above that an armed loadstone does not 
attract at a greater distance than an unarmed one, but that it 
lifts a greater quantity of iron, if it be in contact with the iron 
and continuous therewith. But put a leaf of paper between, 
and this intimate coherence is hindered, nor are objects of 
iron held together by the action of the loadstone. 



CHAPTER XXII. 

THAT AN ARMED LOADSTONE DOES NOT ATTRACT IRON MORE 
THAN AN UNARMED ONE ; AND THAT THE ARMED STONE 
IS MORE STRONGLY UNITED TO THE IRON, IS SHOWN BY 
MEANS OF AN ARMED LOADSTONE AND A CYLINDER OF 
POLISHED IRON. 

ON a plane surface lay a cylinder too heavy for the un- 
armed loadstone to lift ; then, with paper between, apply at 
the middle of the cylinder the pole of an armed loadstone : if 
the cylinder is pulled by the loadstone, it follows after it with 
rolling motion ; but when there is no paper between, the cylin- 
der, joined to the loadstone, is pulled by it, and does not roll 



ARMED AND UNARMED LOADSTONES. 



at all. But if the same loadstone be unarmed, it pulls the roll- 
ing cylinder with the same velocity as does an armed loadstone 
with paper between, or wrapped in paper. 

Armed loadstones of different weights, force, and shape, but* 
out of the same mine, show an equal degree of 
strength in adhering to or hanging from iron 
objects of suitable size and shape. The same 
is true of unarmed ones. A suitable piece of* 
iron applied to the under side of a loadstone 
that hangs from a magnetic body heightens the * 
energy of the loadstone, so that it clings with 
greater force. For a pendent loadstone clings 
faster to the body above, to which it is at- 
tached, when a piece of iron is applied and hangs 
from it, than when a piece of lead or other non- 
magnetic material is fastened to it. 

A loadstone, whether armed or not, attached 
by its proper pole to the pole of another load-* 
stone, armed or not, makes that other lift a 
greater weight at its opposite end. The same 
thing is seen when iron is applied to the pole of 
a loadstone, viz., the opposite pole carries a greater 
weight of iron : thus, as in the figure, the load- 
stone with a bar of iron superposed carries the 
bar below, but cannot carry it if the upper piece 
be removed. Magnetic bodies in conjunction * 
form one magnetic body ; hence, the mass increasing, the mag- 
netic energy increases also. 

An armed loadstone, as also an unarmed one, leaps more* 
quickly to a large mass of iron and combines with it more 
strongly than with a small mass. 



142 WILLIAM GILBERT. 



CHAPTER XXIII. 

THE MAGNETIC FORCE MAKES MOTION TOWARD UNION, AND 
WHEN UNITED CONNECTS FIRMLY. 

MAGNETIZED objects cohere well and duly to one another 

* according to their forces. Pieces of iron in the presence of a 
loadstone, though not in contact with it, come together, 
eagerly seek and seize one another, and when in conjunction 

*are, as it were, glued together. Iron dust or iron reduced to a 
powder, packed in paper tubes, and placed on the meridian of 
a loadstone or merely brought near it, coalesces into one mass, 

* and in an instant the many particles come together and com- 
bine ; and the multitude of united grains acts on a piece of iron 

*and attracts it, as though they formed but one continuous rod 
of iron, and take the north and south direction when laid on 
the loadstone. But if they be taken away from the stone to 
any distance, the particles, resolved again to their original con- 
dition, separate, and each stands alone : thus it is that the foun- 
dations of the earth are conjoined, connected, held together, 
magnetically. So let not Ptolemy of Alexandria, and his fol- 
lowers and our philosophers, maintain that the earth will go to 
pieces, neither let them be alarmed if the earth spins round in 
a circle. 

Iron-filings when made hot are attracted by the loadstone 
not so strongly nor from as great a distance as if they were 

*not heated. A loadstone subjected to any great heat loses 
some of its energy ; for its humor is dissipated, and so its pecul- 

* iar nature is marred. So, too, a mass of iron-filings, if roasted 
in a reverberatory furnace and changed to Crocus Mar -tis, is not 



IRON HANGS SUSPENDED IN AIR. 143 

attracted by a loadstone ; l but if it has not been very highly 
heated, not quite wasted, it clings to loadstone, though more * 
feebly than iron that has not been put in fire. For Crocus 
Martis has nothing of the form of iron left ; but metal that has 
been made hot takes heat from the fire, and in its vitiated sub- 
stance the magnetic powers are less powerfully awakened by the 
loadstone, and iron that has quite lost its nature is not attracted 
by the loadstone. 



CHAPTER XXIV. 

THAT IRON WITHIN THE FIELD OF A LOADSTONE HANGS 
SUSPENDED IN AIR, IF ON ACCOUNT OF AN OBSTACLE IT 
CANNOT COME NEAR. 

IRON within the magnetic field tends toward the points of* 
the stone that have the most energy, if it be not hindered by 

1 Crocus Martis, or " Saffron of Mars," already mentioned, Book I, Chap. 
XV, was formed in ancient pharmacy by deflagrating iron filings with nitre 
and washing the residue. (Brande's "Manual of Chemistry," Vol. I, page 
715.) Geber mentions oxide of copper under the name of as ustum, the red 
oxide of iron under the name of crocus of iron. (Dr. Thomson, "Hist, of 
Chem.," Vol. I, page 130.) We read in Sir Thomas Brown's Pseudoloxia 
Epidemica, 1658, page 71 : " It is likewise true what some have delivered of 
Crocus Martis, that is, steel corroded with vineger, sulphur, or otherwise, and 
after reverberated by fire. For the loadstone will not at all attract it, nor will 
it adhere, but lie therein like sand. This to be understood of Crocus Martis well 
reverberated, and into a violet colour; for common chalybs prceparatus, or cor- 
roded and powdered steel, the loadstone attracts like ordinary filings of iron ; 
and many times most of that which passeth for Crocus Martis. So that this 
way may serve as a test of its preparation ; after which it becometh a very 
good medicine in fluxes. The like may be affirmed of flakes of iron that are 
rusty and begin to tend unto earth. For their cognation then expireth, and the 
loadstone will not regard them." Consult Lazarus Erckern's Aula Subterranea, 
Franckfurt 1672, page 294, or Sir J. Pettus' " Heta Minor," London 1683, 
although, according to Dr. Thomson, the translation is a very bad one. 



144 WILLIAM GILBERT. 

force or by the matter of an intervening body ; and this is so 
whether the iron tends downward to the loadstone, or seeks it 
from one side and obliquely, or whether it leaps up to it. But 
if on account of an obstacle it cannot reach the stone, it sticks 
to the obstacle and there remains, yet is held by a less constant 
bond, for, owing to the greater intervals and distances, the asso- 
ciation (with the loadstone) is less amicable. Fracastorio, in 
his Chapter VIII, De Sympathia, says that a piece of iron will 
be suspended in air so that it cannot move either up or down 
if a loadstone be placed above it that has an attractive force on 
the iron equal to the force by which the iron tends downward : 
thus the iron will stand fixed in mid-air. That is ridiculous : 
for the nearer the loadstone the greater always is its force ; and 
hence the iron that is lifted ever so little above the earth by 
the loadstone's force must needs be steadily drawn to it, and 
must cling to it. Baptista Porta suspends in air a piece of iron 
(with a loadstone fixed above), and holds back the iron by 
means of a thin thread fastened to it beneath, so that it shall 
not rise to the stone ; hardly a very brilliant idea. The piece 
* of iron is pulled in a perpendicular line by the loadstone, though 
the two are not in contact, but only near each other ; but, as on 
account of the greater nearness, the iron mass is stirred by the 
force that was lifting it, straightway it speeds to the loadstone 
and clings to it. For the iron, the nearer it comes to the load- 
stone, the more is excited, and the stronger is the attraction. 



INTENSIFYING THE LOADSTONE'S FORCES. H5 



CHAPTER XXV. 

INTENSIFYING THE LOADSTONE'S FORCES. 

ONE loadstone far surpasses another in energy, for one will 
snatch up almost its own weight of iron, while another is hardly 
able to move the smallest particle. All animals and plants 
that possess life have need of victual of some sort, to the end 
their powers may last and become firmer and stronger. But 
iron is not attracted by the loadstone, as Cardan and Alexander 
Aphrodiseus supposed, so that it may be nourished with mor- 
sels of it ; neither does the loadstone gain strength from iron- 
filings as from a nutritious food. Baptista Porta, having his 
doubts about this view, and wishing to make an experiment, 
took a loadstone of determinate weight and buried it in iron- 
filings of a weight not unknown ; and, after he had left it there 
many months, he found the stone heavier, the filings lighter. 
But the difference was so minute that Porta was uncertain as 
to the truth. This experiment of Porta's does not prove that 
the stone devours anything, nor does it show any process of 
nutrition, for minute quantities of filings are easily lost by 
handling. So, too, a very small quantity of the iron dust may 
adhere to some small part of the loadstone and not be noticed, 
thus adding somewhat to the weight of the stone ; but that is 
a superficial accretion, and can be brushed off without much 
difficulty. Many think that when weak and sluggish the stone 
can bring itself back to a better condition, and that a very 
strong stone can endow a weaker one with the highest degree 
of force. Is it as when animals gain strength when they feed 



146 WILLIAM GILBERT. 

and are filled ? Is a remedy found for the loadstone in addi- 
tion or subtraction of something ? Is there aught that can 
restore this primary form or give it anew? Surely nothing can 
do such a thing save what possesses magnetic properties. 
Magnetic bodies can restore soundness (when not totally lost) 
to magnetic bodies, and can give to some of them powers 
greater than they had originally ; but to those that are by their 
nature in the highest degree perfect, it is not possible to give 
further strength. Hence the more infamous becomes all the 
charlatanry of Paracelsus, who declares that the loadstone's 
force and energy may be increased and transformed to tenfold 
what it is naturally. And the way of doing this is, so to speak, 
to half-candescify the loadstone, i.e., to make it very hot, 
yet so that it does not reach white heat, and then immediately 
to dip it in oil of vitriol made from the best Corynthian steel, 
letting it become saturated. " In this way," says Paracelsus, 
" you can give to a loadstone such strength that it will pull a 
nail out of a wall, and perform many other the like marvels im- 
possible for a common loadstone." But a loadstone so dipped 
not only acquires no force, but suffers some loss it already hath. 
A loadstone rubbed and smoothed with steel is made better. 
When covered with filings of the best iron or pure steel, not 
rusty, it retains its properties. Sometimes, too, a good strong 
loadstone gains some strength when rubbed on its opposite 
pole with the pole of another loadstone : it takes in force. In 
such experiments it is well to observe the earth's pole, and to 
lay down in the direction required by the magnetic laws the 
stone that one wishes to make stronger: this point we will 
establish hereafter. A strong, large loadstone increases the 
power of another loadstone, as also the power of iron. If, on 
* the north pole of a loadstone, you place another loadstone, 
the north pole of the second becomes stronger, and a piece of 



INTENSIFYING THE LOADSTONE'S FORCES. 147 

iron clings like an arrow to the north pole a, and not at all to 
the south pole b. And the pole a, when it is in a right line 
above with the axis of both loadstones, they being joined ac- 
cording to the magnetic laws, raises the piece of iron to the 
perpendicular : this it cannot do if the larger loadstone be 
moved away, for its strength is insufficient. But as a ball of 





iron on the pole of the terrella raises the piece of iron to the * 
perpendicular, so, at the side, the iron is not directed toward 
the centre, but stands oblique and sticks everywhere ; for in 
the iron ball the pole is ever the point of contact with the ter- 
rella's pole, and it is not constant, as it is in the smaller terrella. 
The parts of the earth, as of all magnetic bodies, are in accord 
and enjoy neighborhood with each other: there is in them all 
mutual love, undying good-will. The weaker loadstones are 
refreshed by the stronger ones, and the less vigorous bring no 
damage to the more vigorous. Yet a strong loadstone exerts 
more attraction in another strong one than in one that is 
feeble, for a vigorous stone contributes forceful action, and 



WILLIAM GILBERT. 



itself hastes, flies to the other, and solicits it vehemently; 
accordingly there is co-operation, and a clearer and stronger 
cohesion. 



CHAPTER XXVI. 

WHY THE LOVE OF IRON AND LOADSTONE APPEARS GREATER 
THAN THAT OF LOADSTONE AND LOADSTONE, OR IRON 
AND IRON WHEN NIGH A LOADSTONE AND WITHIN ITS 
FIELD. 

ONE loadstone does not attract another on all its sides as 
it does iron, but only at one fixed point : hence the poles of 
the two must be properly arranged, else they do not duly and 
powerfully cohere. But this arranging is not easy nor the 
work of an instant : therefore one loadstone will seem to be 
refractory toward another, whereas they may be in perfect har- 
mony. Iron, suddenly impressed by a loadstone, is not only 
attracted by it, but is renovated and its powers enhanced, 
whereby it pursues and solicits the loadstone with a force not 
less than its own, and also makes captive other iron objects. 
Suppose a little iron bar firmly adhering to a loadstone : if 
you bring near this piece of iron an iron rod, but without 
touching the loadstone, you shall see the iron instantly follow 
the rod, relinquishing the loadstone, leaning toward the rod, 
and, on contact, firmly adhering thereto ; for iron in union and 
contact pulls more vigorously another piece of iron within the 
field of a loadstone than does the loadstone itself. The natu- 
ral magnetic force, which in iron lies confined and asleep, is 
awakened by a loadstone, associates itself with it, and comes 



LOVE OF IRON AND LOADSTONE. 149 

into sympathy with it in virtue of the primary form : ' hence 
comes the perfect magnetized iron, which is as strong as the 
loadstone itself; for as the one imparts and arouses, so the 
other conceives, and, being awakened, endures, and by its very 
act gives back the force again. But in so much as iron is 
liker to iron than is loadstone, and in two pieces of iron within 
the field of a loadstone, the nighness of the latter enhances 
the powers of both: then, their forces being equal, likeness of 
substance becomes decisive, and iron gives itself up to iron, 
and the two pieces are united by their most like (identical) 
and homogeneous forces. This is effected not only by coition, 
but by a firmer union ; and a steel cap or snout (glans vel 
nasus) properly adjusted to the pole of a loadstone lifts greater 
weights than can the stone by itself. When steel or iron is 
made from loadstone or from iron ore, the slag and impuri- 
ties are separated from the substance by a better fusion : hence 
usually such iron contains the matter of the earth purged of 
foreign admixture and dross, and more homogenic and perfect 
(than before smelting), albeit deformed by fusion. And this 
matter, when acted on by a loadstone, conceives the magnetic 
virtue, and within the magnetic field is endowed with force 
surpassing that of an inferior loadstone, which is seldom with- 
out some admixture of impurities. 



1 " Let us imagine that that which impels the iron towards the loadstone, 
or the loadstone towards the iron, is a third body, or rather a certain matter 
which is in motion, and which is very subtle, because it cannot be perceived by 
our senses." (Jacobi Rohaulti, Physica, 1718, Par. Ill, Cap. VIII, page 391, 
or Dr. Clarke's translation, 1728, Vol. II, page 167.) 



ISO 



WILLIAM GILBERT. 



CHAPTER XXVII. 

"THAT THE CENTRE OF THE MAGNETIC FORCES IN THE 
EARTH IS THE CENTRE OF THE EARTH; AND IN THE 
TERRELLA THE TERRELLA'S CENTRE. 

THE rays of magnetic force are dispersed in a circle in all 
directions ; and the centre of this sphere is not in the pole (as 
Baptista Porta deems, Chap. XXII), but in the centre of the 
stone and of the terrella. So, too, the earth's centre is the centre 
of the earth's magnetic movements, though magnetic bodies are 
not borne direct toward the centre in the magnetic movement 
save when they are attracted by the pole. For as the formal 
power of loadstone and earth promotes simply unity and con- 
formity between things separate, it follows that everywhere at 
equal distance from the centre or from the convex circum- 




ference, just as at one point it seems to attract in a right line, so 
at another it can control and rotate the needle, provided only 
the loadstone be not of unequal power. For if at the distance 






LOADSTONE DOES NOT ATTRACT TO A FIXED POINT. I$I 

C from pole D the stone is able to attract the needle, then at 
an equal distance A above its equator it can control and rotate 
the needle. Thus the centre and middle of the terrella is the 
centre of force, and thence to the circumference of its sphere 
of influence its magnetic virtues extend (for) equal distances 
in all directions. 



CHAPTER XXVIII. 

THAT A LOADSTONE DOES NOT ATTRACT TO A FIXED POINT 
OR POLE ONLY, BUT TO EVERY PART OF A TERRELLA, 
EXCEPT THE EQUINOCTIAL CIRCLE. 

COITION is always strongest when pole touches pole, for at 
the poles the force is greatest by concert of the whole : hence 
one pole seizes the other with greatest force. Points at dis- 
tances from the poles possess attractional power also, but 
somewhat weaker and sluggish in the ratio of the distance, so 
that finally in the equinoctial line they are utterly enervate 
and faint. The poles, too, do not attract as mathematical 
points, nor does magnetized iron unite at its poles only with 
the poles of a loadstone. On the contrary, the coition takes 
place all over the periphery, north and south, the force ema- 
nating from the whole mass. Magnetic bodies, however, are 
attracted feebly in the parts near the equator, but quickly in 
the parts near the poles. Wherefore not the poles alone, and 
not the parts alone that are near the poles, attract and solicit 
magnetic bodies ; but magnetic bodies are controlled and rotated 
and unite with other magnetic bodies according as parts neigh- 
boring and adjoining lend their forces, which forces are ever of 
the same potency in the same parallel, except when otherwise 
distributed by causes producing variation. 



152 WILLIAM GILBERT. 



CHAPTER XXIX. 

OF DIFFERENCE OF FORCES DEPENDENT ON QUANTITY OR 

MASS. 

LOADSTONES coming from the same mine, and not inter- 
mingled with neighboring metals or ores, have the same 
potency ; yet the stone that is largest exhibits greatest force, 
as it carries the greatest weight and has a wider sphere of influ- 
ence. A loadstone weighing an ounce does not lift an iron 
spike as does one that weighs a pound, nor does its control 
reach so far, nor does its force extend to such a distance. 
And if you take from a one-pound stone a part, somewhat of 
its power will be seen to leave also ; for when a part is taken 

*away some of the energy is lost. But when such part is duly 
applied and united to the stone, though it be not cemented 
there nor perfectly fitted in by the mere apposition, the origi- 
nal strength is recovered, and the force returns. Sometimes, 

* however, the energy is increased by detachment of a part 
because of malformation of the stone, as when the force is 
diffused through awkward corners. 

In stones of different sorts the ratio of power is different : 
one weighing a drachm may have more force than another one 
of 20 pounds. Many a loadstone is so weak that the force can 
scarcely be noticed, and such faint magnets are often surpassed 
by masses prepared of potter's earth. But we may ask : Sup- 
posing that a stone of a given kind and of definite goodness, 
and weighing a drachm, carries one drachm, whether one 
weighing an ounce will carry an ounce, a pound a pound, and 

*so on ? So it is, for in proportion to size such loadstone has 
greater or less strength : so that a loadstone of proportionate 



SHAPE AND MASS ARE IMPORTANT. 1 53 

size and weight, a drachm weight of which lifts a drachm 
weight of iron, will, when brought near a suitable great obelisk 
or enormous pyramid of iron, attract it and pull it to itself, 
and that with no greater effort of its nature and with no 
greater pains than when a drachm weight of loadstone seizes 
a drachm weight of iron. But in all such experiments the 
power of the loadstones should be equal, the form of the 
stones should be exactly proportioned : this is true not less of 
an armed than of a naked loadstone. As an experiment, take 
a loadstone weighing 8 oz., which when armed lifts 12 oz. of : 
iron ; cut off of this stone a part which, when brought to the 
form of the whole stone as it was before, shall weigh only 
2 oz. : such a stone, armed, lifts 3 oz. of iron. In this experi- 
ment it is requisite that the form of the 3-oz. piece of iron be 
the same as that of the 12-oz. piece ; if the 12 oz. mass rose in 
form of a cone, the 3-oz. piece must assume a pyramidal form 
proportioned to the figure of the original mass, 



CHAPTER XXX. 

THE SHAPE AND THE MASS OF AN IRON OBJECT ARE IM- 
PORTANT IN MAGNETIC COITIONS. 

IT was shown before that the shape and mass of a loadstone 
are weighty factors in magnetic coitions : similarly, the shape 
and mass of the iron determine whether its force shall be great 
or little. Oblong, bacilliform pieces are both more quickly at- 
tracted and cling more firmly than spherical or square pieces, and 
this for the causes we have shown with regard to the loadstone. 
It is also worthy of note, that when a smaller iron object has at- 



154 WILLIAM GILBERT 

tached to it a weight of different material, so that the weight 
*of the two shall equal that of another larger piece whose 
weight is proportioned to the power of the loadstone, it is not 
lifted by the loadstone like the larger object ; for the smaller 
piece is not so powerfully attracted by the loadstone, because 
it gives back less force, and only magnetic matter conceives 
the magnetic energy : foreign matter appended to such a body 
cannot take in magnetic force. 



CHAPTER XXXI. 
OF OBLONG AND ROUND STONES. 

IRON bodies are more forcibly attracted by an oblong stone 
than by a round one, provided only the pole of the stone is at 
the extreme end of its length. The reason is that in the 
oblong stone the magnetic body at the extremity is directed 
straight toward a body wherein the force proceeds in right 
lines and through a longer diameter. But the oblong stone 
has only little force on the side ; for, plainly, the attraction at 
a and B is stronger in a round loadstone at equal distance 
* from the pole, than in c and D. 





PROBLEMS AND MAGNETIC EXPERIMENTS. 155 



CHAPTER XXXII. 

SOME PROBLEMS AND MAGNETIC EXPERIMENTS ON THE CO- 
ITION, AND REPULSION, AND REGULAR MOVEMENT, OF 
MAGNETIC BODIES. 

LOADSTONES that are equal come together with equal* 
mutual incitation. 

Magnetized iron bodies that are in all respects equal do* 
also come together with equal mutual incitation. 

Iron bodies not magnetized, if they are equal, and not* 
hindered by their bulk, do also come together with equal 
movement. 

Two loadstones placed on suitable floats apart on the sur- 
face of water, if they be suitably arranged within their mag- 
netic field, attract each other. So, too, a proportionate piece 
of iron on one float hastes to a loadstone with the same speed 
with which the magnet itself, afloat, strives to reach the iron. 
For the two are impelled from their own places on either side 
to come together midway and coalesce. Two magnetized-iron * 
wires, floated in water by suitable corks, move forward to con- 
tact, and, with the proper end on, strike and are joined. 

With magnetic bodies that are equal, coition is more vigor-* 
ous, and quicker than repulsion and separation. That mag- 
netic bodies are more sluggish in repelling than in attracting, 
is seen in every magnetic experiment, as when loadstones are 
borne on suitable floats on water, or when magnetized iron 
wire or little bars are driven through cork and set afloat in 
water, as also in experiments with a needle. The reason is 
that, since the power of coition is one thing, the power of con- 



WILLIAM GILBERT. 

formation and of ordering in place is another, therefore repul- 
sion and aversation are the act of the force ordering in place ; 
but the coming together is the result of mutual attraction to 
contact as well as of the force that orders in place ; i.e., it is 
due to a twofold force. 

The ordering force is often only the forerunner of coition, 
so that the bodies shall stand in due position before the onset : 
hence they turn in the direction of the points of coition, if they 
be hindered from attaining those points. If a loadstone be 




cut in two equal parts along the meridian, the separated parts 
repel each other, if the poles be placed at a suitable even dis- 
tance from each other ; for they mutually repel with greater 
velocity than is the case when pole is wrongly opposed to pole. 
Thus the half B of a loadstone, placed near the other half A, 
repels A on its float, because D withdraws from F and E from 
C. But if B be again joined exactly with A, they come to- 
gether and form one magnetic body ; yet when they are only 
near each other they are mutually hostile. And if one half be 
turned about so as to bring C opposite to D and F to , then 
A follows B within the field and becomes joined to it. 



PROBLEMS AND MAGNETIC EXPERIMENTS. 1 57 

South parts of a stone retreat from south parts, and north 
parts from north. Nevertheless, if you bring the south end of 
a piece of iron near to the south part of the stone, the iron is 
seized and the two are held in friendly embrace ; as the ver- 
ticity fixed in the iron is reversed and changed by the presence 
of the more powerful loadstone, which is more constant in its 
forces than the iron. For they come together in accordance 
with nature, if either by reversal or change there be produced 
true conformity and orderly coition as well as regular direction. 
Loadstones of identical shape, size, and strength attract each 
other with equal force, and when in wrong position repel with 
like energy. 

Little rods of unmagnetized iron, though like and equal,* 
yet act on one another often with different force ; for as there 
are different grounds for the acquisition of verticity and also 
of strength and vigor, so the particles that are most strongly 
excited by the loadstones themselves in turn act with most 
force. 

Pieces of iron that have been magnetized at one same pole* 
of a loadstone repel one another at the magnetized ends ; and 
their other extremities are also mutually hostile. 

In rotating needles when the points are magnetized but* 
not the crotches, the latter repel one another, but only feebly 
and in proportion to length. 

In like rotating needles when the points are magnetized by* 
the same pole of a loadstone the crotches attract with equal 
force. 

In a long rotating needle the crotch is attracted feebly by* 
the point of a short needle ; the crotch of a short one is 
attracted strongly by the point of a long one, because the 
crotch of a long needle has feeble verticity, but the point of a 
long needle has strong verticity. 



WILLIAM GILBERT. 

* The point of a long needle repels the point of a short one 
more strongly than the point of a short needle repels that of a 
long one, if one of them be poised free on a sharp point and 
the other held in the hand ; for though both have been 
equally magnetized by the same loadstone, still the longer 
one, by reason of its greater mass, has greater force at its 
point. 

In unmagnetized iron rods the south end of one attracts 
the north end of another, and the north end the south ; 
the meridional parts, too, repel meridional parts, and north 
parts north parts. 

If magnetic bodies be divided or in any way broken up, 
each several part hath a north end and a south end. 
' A needle is stirred by a loadstone at as great a distance 
with an obstacle interposed as in air and in an open medium. 

Rods magnetized by friction with the pole of a loadstone 
draw toward that pole and follow it. Baptista Porta is there- 
fore in error when he says (Chapter IV) that " if you bring a 
part nigh the part that gave it the force, it shudders, and 
repels and drives it away, and attracts the converse and oppo- 
site part." 

The laws of rotation and attraction are the same as be- 
tween loadstone and loadstone, loadstone and iron, and iron 
and iron. 

When the parts of a magnetic body that has been broken 
up by force and cut into pieces are put together again and 
properly joined, they form one body and their joint force is 
one ; nor have they separate poles. 

The separated parts, if division has not been made on the 
parallels, assume new poles, north and south ; if the division is 
along a parallel, they may retain one pole in the same place as 
before. 



PROBLEMS AND MAGNETIC EXPERIMENTS. 



159 



Iron rubbed and excited by a loadstone is seized at the 
fitting ends by a loadstone more powerfully than iron not 
magnetized. 

If a small iron bar be set erect on the pole of a loadstone,* 
another bar-iron pin in touch with its upper end becomes 
firmly attached thereto, and if it be moved away pulls the 
standing bar from the terrella. 

If, to the nether end of the erect bar you apply the end of* 
another bar, it does not cohere, nor do they unite. 

As a rod of iron pulls iron away from the terrella, so does 
a small loadstone or a smaller terrella albeit of less force. 




Here the iron bar C coalesces with the terrella A, and thus its 
force is enhanced and awakened magnetically both in the end 
in conjunction and also in the distal end by reason of its con- 
tact with the terrella ; the distal end furthermore receives 
energy from the loadstone B, and the pole D of this magnet 
also gains force by reason of its favorable position and the 
nearness of the pole E of the terrella. Hence many causes 
cooperate to make the bar C, attached to the loadstone B. 



IOO WILLIAM GILBERT. 

cling more strongly to that than to the terrella A. The 
energy called forth in the bar, also the energy called forth in 
the loadstone B, and .Z?'s native energy, all concur; therefore 
D is magnetically bound more strongly to C than E to C. 

But if you turn the pole F to the iron C, then C does not 
cling to F as it did before to D ; for, within the magnetic 
field, stones so arranged stand in an unnatural order: hence F 
does not get force from E. 

, Two loadstones, or two magnetized pieces of iron, duly 
cohering, fly apart on the coming of a stronger loadstone or a 
stronger magnetized mass of iron ; for the newcomer, present- 
ing the opposite pole, puts one to flight and overmasters it, 
and the mutual action of the two that before were conjoined 
ceases. So the forces of one of the bodies are reduced and 
fail ; and were it possible, it would shake off its fellow, and, 
turning about, would go rolling over to the stronger. For this 
reason it is that magnetic bodies held pendent in air drop to 
the ground when the opposite pole of a loadstone is presented 
to them; and this not because there is any weakening or 
numbing of the forces of both of the bodies before conjoined, as 
Baptista Porta maintains, for pole cannot be hostile to both of 
the ends that cohere, but to one only: this end the newcomer, 
the stronger loadstone, drives away from itself by presenting 
its opposite pole, and thus one of the smaller bodies is com- 
pelled to give up its friendly association with the other. 



STRENGTH AND MOVEMENT OF COITION. l6l 



CHAPTER XXXIII. 

OF THE DIFFERENCE IN THE RATIO OF STRENGTH AND 
MOVEMENT OF COITION WITHIN THE SPHERE OF IN- 
FLUENCE. 

IF the greatest weight that is attracted to a loadstone at 
the nearest distance be divided into a given number of parts, 
and the radius of the sphere of magnetic attraction into the 
same number of parts, the parts of the weight will correspond 
to the intermediate parts of the radius. 

The sphere of influence extends farther than the sphere of 
movement of any magnetic body, for a magnetic body is 
affected at the outermost edge though it may not move with 
local motion : that is done when the loadstone is brought 
nearer. A needle, even a very small one, turns round while 
remote from a loadstone, though, at the same distance and free 
to move and in no wise hindered, it does not come to the 
loadstone. 

The velocity of the movement of a magnetic body to a 
loadstone is in proportion to the strength of the loadstone, or 
its mass, or its shape, or the nature of the medium, or the dis- 
tance within the magnetic sphere of action. 

A magnetic body approaches with greater velocity a* 
powerful loadstone than a sluggish one, in the ratio of the 
respective energies of the two loadstones. A smaller mass of 
iron, as also one rather oblong in shape, is attracted with the 
greater velocity. The velocity of the movement of a mag- 
netic body to a loadstone varies according to the medium, for 



1 62 WILLIAM GILBERT. 

bodies move with greater velocity in air than in water, and in 
a serene atmosphere than in thick and foggy weather. 

In the ratio of distance, movement is quicker from anear 
than from afar. At the outermost edge of a terrella's field 
magnetic bodies move faintly and slowly. In the immediate 
neighborhood of the terrella the motor impetus is greatest. 
> A loadstone that in the outermost verge of its field of 
force, at the distance of one foot, can hardly stir a rotating 
needle, will, when connected with a long iron rod, strongly 
attract and repel (accordingly as its different poles are pre- 
sented) the needle at the distance of three feet, and this 
whether the loadstone is armed or unarmed. The iron rod 
should be of fitting quality, and of the thickness of the little 
finger. 

For the energy of the loadstone awakens verticity in the 
iron and passes in and through iron to a far greater distance 
than it extends through air. 

The force also passes through a number of pieces of iron 
conjoined at their extremities, yet not so surely as through 
one continuous rod. 

Steel-filings strewed on paper rise on end and present the 
appearance of stubby steel hairs when a loadstone is brought 
near above them ; when the loadstone is applied beneath, the 
hairlike crop rises also. 

Steel-filings, when the pole of a loadstone is brought near, 
coalesce into one body ; but when it would come to the load- 
stone, the body is broken up and rises to the steel in smaller 
masses that still hold together. 

But if the loadstone be beneath the paper, the consolidated 
mass breaks up as before, and into very many parts, each of 
which consists of a multitude of grains ; and they remain 
united, like separate bodies ; and while the lowermost parts of 



WHY A LOADSTONE IS OF DIFFERENT POWER. 163 

these eagerly follow the pole of the loadstone beneath, so the 
separate masses stand like solid magnetic bodies. In like 
manner a bit of iron wire one barley-corn or two m length 
stands on end when a loadstone is applied either beneath or 
above. 



CHAPTER XXXIV. 

WHY A LOADSTONE IS OF DIFFERENT POWER IN ITS POLES 
AS WELL IN THE NORTH AS IN THE SOUTH REGIONS. 

THE extraordinary magnetic energy of the earth is beauti-* 
fully shown in the following neat experiment : Take a terrella 
of no ordinary power, or an oblong loadstone with equal cones 
forming its polar ends ; but in any figure not exactly spheri- 
cal it is easy to fall into mistakes, and the experiment is diffi- 
cult. In northern latitudes raise the true north pole above 
the horizon straight toward the zenith. Plainly it holds erect 
on its north pole a larger bar of iron than could the south 
pole of the same terrella if turned in like manner toward the 
centre of the sky. The same demonstration is made with a 
small terrella set atop of a large one. 

Let ab be the earth or a large terrella, and ab a small ter- 
rella; a larger bar is raised erect by the north pole of the 
small terrella than the b pole of the same, if turned skyward, 
can raise to the erect position. And the a pole of the small 
terrella derives force from the greater, turning from zenith to * 
the plane of the horizon or to the level. Now if, the smaller 
terrella having its poles directed as before, you apply a piece 



164 WILLIAM GILBERT. 

of iron to its lower or south pole, that will attract and hold a 
greater weight than can the south pole if that be turned down. 
Which is thus shown : Let A be the earth or a terrella ; E the 





north pole or some point in high latitude ; let B be a large 
terrella above the earth, or a small terrella above a larger one ; 
D the south pole : it is plain that D (south pole) attracts a 
larger piece of iron, C, than can E (the north pole), if that pole 
be turned downward to the position D, looking toward the 
earth or the terrella in their northern regions. Magnetic 
bodies gain force from other magnetic bodies if they be ar- 
ranged duly and according to their nature in neighborhood 
and within the sphere of influence ; and hence, when a terrella 
is imposed on the earth or on another terrella in such way 
that the south pole looks toward the north pole, and north is 
turned away from north, the energy and forces of its poles are 
augmented. Hence the north pole of a terrella in such posi- 
tion lifts a heavier piece of iron than the south pole does if that 
be turned away. In like manner the south pole, gaining force 



WHY A LOADSTONE IS OF DIFFERENT POWER. 165 

from the earth or the larger terrella when it is duly placed as 

nature requires, attracts and holds heavier bars of iron. In * 

he other portion of the terrestrial globe, toward the south, as 




also in the southern parts of the terrella, the case is reversed, 
for, there, the south pole of the terrella is strongest when distal, 
as is the north pole of the terrella when it faces the earth 
or terrella. The farther a place is from the equinoctial line, 
whether of the earth or of a terrella, the greater is seen to be 
the accession of force ; but nigh the equator the difference is 
slight ; at the equator it is null ; at the poles it is greatest. 



WILLIAM GILBERT. 



CHAPTER XXXV. 

OF A PERPETUAL-MOTION ENGINE ACTUATED BY THE AT- 
TRACTION OF A LOADSTONE, MENTIONED BY AUTHORS. 

CARDAN writes that out of iron and loadstone may be con- 
structed a perpetual-motion engine not that he saw such a 
machine ever ; he merely offers the idea as an opinion, and 
quotes from the report of Antonius de Fantis, of Treviso ; 
such a machine he describes in Book IX, De Rerum Varietate. 
But the contrivers of such machines have but little practice in 
magnetic experiments. For no magnetic attraction can be 
greater (whatever art, whatever form of instrument you em- 
ploy) than the force of retention ; and objects that are con- 
joined, and that are near, are held with greater force than 
objects solicited and set in motion are made to move ; and as 
we have already shown, this motion is a coition of both, not 
an attraction of one. Such an engine Petrus Peregrinus, cen- 
turies ago, either devised or delineated after he had got the 
idea from others ; and Joannes Taysner published this, illus- 
trating it with wretched figures, and copying word for word 
the theory of it. May the gods damn all such sham, pilfered, 
distorted works, which do but muddle the minds of students ! * 

1 See note 2, page 9, relative to Joannes Taisnier Hannonius. 

With reference to the above-named passage, P. D. Timoteo Bertelli Barna- 
bita, at Chap. VI, page 22, of his Memoir on P. Peregrinus, says that Gilbert 
has "appropriated other observations and experiments of Peregrinus," and has 
taken from him the idea of his terrella as well as the experiments on magnetic 
polarity. Farther on (page 28) Bertelli gives the following extract from Theve- 
not : " 5 L'on voit encore que la pluspart des choses que Ton attribue a Gilbert 
et que luy ont donn6 la reputation de Pere de la Philosophic de 1'Ayman 



HOW A STRONG LOADSTONE MAY BE RECOGNIZED. 1 6? 



CHAPTER XXXVI. 

HOW A STRONG LOADSTONE MAY BE RECOGNIZED. 

A STRONG loadstone sometimes lifts in air a mass of iron 
weighing as much as itself ; a weak loadstone hardly attracts a 
bit of fine wire. Those, then, are the stronger loadstones 
which attract and hold the larger bodies, unless there is some 
defect of shape, or unless the pole of the stone is not properly 
applied. Besides, the stronger loadstone, when afloat, more 
readily turns its poles toward the poles of the earth or the 
points of variation on the horizon. But the stone that acts 
sluggishly, betrays some flaw in itself, shows that its force is 
exhausted. Loadstones are to be all prepared in the same 
way, shaped alike, and made of the same size ; for when they 
are unlike and unequal, experiments are doubtful. All load- 
stones are tested for strength in the same way, viz., w r ith a 
versorium (rotating needle) held at some distance ; the stone 
that at the greatest distance is able to make the needle go 
round is the best and strongest. Baptista Porta also rightly 
determines the power of a loadstone by thus weighing in a 

estaient sciies des le treizieme siecle." This, says he, is "doubtless an ex- 
aggeration. That Gilbert took from P. Peregrinus his terrella and many ex- 
cellent scientific plans on magnetism, the ideas of others also, is probable, but 
it is indubitable that much was his own, and that, for his time, his work is a 
veritable chef d'oeuvre of inductive and experimental method and the most 
finished treatise on magnetism which had up to that time appeared." 

Consult, also, Bertelli, page 92 ; Gilbert, De Magnete, Book VI, Chap. IV ; 
likewise, W. Wenckebach, " Sur Petrus Adsigerius . . .," Rome 1865, page 8, 
and the work therein quoted " Universal Lexicon," Leipzig 1741 ; also Nicolao 
Cabeo, Phil. Magn., Ferrara 1629, P a & e 2 3- 



1 68 WILLIAM GILBERT. 

balance. A piece of loadstone is put in one scale and an equal 
weight of another substance in the other, so that the scales 
are balanced. Then some iron lying on a board is brought 
nigh, so that it shall cleave to the loadstone in the scale, and 
the two bodies cohere perfectly at their points of attraction ; 
into the opposite scale sand is poured gradually till the scale 
in which is the loadstone separates from the iron. By weigh- 
ing the sand the force of the loadstone is ascertained. So, 
too, we can make experiment and find the stronger stone by 
weighing sand, if we put in a pair of scales loadstones that 
balance each other. Such is an experiment given by Cardinal 
Cusanus in his Statica, and from him Porta would seem to 
have learned the one he cites. The stronger loadstones turn 
readily toward the poles or the points of variation ; so, too, 
they propel their floats and cause them and other cumbrances, 
as so much wood, to wheel about. In an inclination or dip in- 
strument the greater power of a loadstone is manifested and 
there greater power is requisite. Hence loadstones are 
stronger the more speedily they do their work, and the more 
rapidly they travel from side to side and return, and the 
sooner they come to a standstill. Feeble, exhausted load- 
stones travel more sluggishly, come to a rest more slowly, 
stick at the pole less decisively, and are easily displaced 
therefrom. 



USES OF THE LOADSTONE AS IT AFFECTS IRON. 169 



CHAPTER XXXVII. 

USES OF THE LOADSTONE AS IT AFFECTS IRON. 

BY means of magnetic coition we test an iron ore. The 
ore is roasted in a furnace, is crushed, washed, dried, and so is 
freed from foreign humors. The loadstone being thrust among 
the particles collected from the bath attracts the iron dust, 
which being removed by a feather brush is caught in a cruci- 
ble ; again and again the loadstone is dipped in and the iron 
dust brushed into the crucible, till nothing remains that it will 
attract. Then the powdered iron is heated together with 
halinitro till it is melted and becomes a mass of iron. Now if 
the loadstone picks up the iron dust readily and easily, we 
deem the ore to be rich ; if slowly, the ore is poor ; if the load- 
stone seems quite to reject it, the ore is judged to have little 
or no iron. By the same method, iron particles may be sepa- 
rated from particles of any other metal. And many tricks are 
played by secretly attracting bits of iron to light bodies, or 
causing a concealed loadstone to attract the iron ; to persons 
who know not the cause, the movements of the objects seem 
amazing. Any ingenious workman may exhibit a great 
number of such tricks for sport, with the air of one dealing in 
incantations and magic. 



UNIVERSITY br CALIFORNIA 

'ARTMENT OP CIVIL 
irv 



1 70 WILLIAM GILBERT. 



CHAPTER XXXVIII. 

OF THE ATTRACTIONS OF OTHER BODIES. 

PHILOSOPHIZERS of the vulgar sort and mere copyists oft 
repeat, from others' memoirs on natural philosophy, opinions 
and errors with regard to the attractional force of various 
bodies. They will say, for example, that diamond attracts iron 
and pulls it away from loadstone ; that loadstones differ, some 
attracting gold, others silver, copper, lead yea, flesh, water, 
fish. The flame of sulphur is said to seek iron and stones ; so 
is white naphtha said to draw to itself fire. I have already said 
that inanimate natural bodies in no other wise attract or are 
attracted on this terrestrial globe, save either magnetically or 
electrically. It is therefore not true that there are loadstones 
that attract gold or other metals ; for a magnetic body attracts 
only a magnetic body. Fracastorio tells of having seen a 
loadstone attracting silver. If that were true, then it must 
necessarily have been because some iron had been artificially 
mixed with the silver and lay hidden therein, or because 
nature had mixed iron with the silver (as she does sometimes, 
though very seldom) ; for iron is now and then mixed with 
silver by nature, but silver with iron very rarely or never. By 
false coiners and by avaricious princes, when money is coined, 
iron is mixed with silver; an instance of this we have in 
Anthony's denarius, if what Pliny declares be true. So Car- 
dan (led into error, perhaps, by others) says there is a certain 
kind of loadstone which attracts silver; and he adds a very 
silly test of the thing : " If," says he, " a thin rod of silver be 



OF THE ATTRACTIONS OF OTHER BODIES. I? I 

touched with this and then poised in equilibrium, when it 
comes to a standstill after being whirled, it will point to silver 
(especially a large quantity), though the same be buried in the 
ground ; by this means anybody may easily unearth hidden 
treasures." He adds that " the stone must be of the best," 
and that he never saw such stone. Nor will he or anybody 
else ever see such a stone or such an experiment. Cardan 
cites an attraction, improperly so called, of flesh, which is 
altogether unlike magnetic attraction ; his magnes creagus (or 
flesh-attracting loadstone, so named because it clings to the 
lips) must be cast out of the company of loadstones and of the 
whole family of attractional bodies. Lemnian earth, red 
ochre, and sundry minerals have this action, but it were 
absurd to say that they attract. Cardan imagines another 
loadstone, a third species as it were ; if a needle be driven into 
this, it may be thrust into a person's body afterward without 
being felt. But what has attraction to do with numbing of 
sense, or what is there in common between stupefaction and 
the mind of a philosopher while he discourses of attraction ? 
Many are the stones, both of natural origin and artificially 
compounded, that possess the power of dulling the senses. 
The flame of sulphur is by some said to attract because that it 
consumes certain metals by reason of its penetrating force. 
So does naphtha attract flame because it emits and exhales in- 
flammable vapor, and hence is set aflame at some distance ; 
even as the smudge of a candle that has just been extinguished 
catches fire again from another flame ; for fire creeps to fire 
through an inflammable medium. Of the sucking-fish or re- 
mora (Echeneis remora), and how it stays ships, philosophers 
have discoursed variously. It is their custom oft to account with 
their reasonings for this and many other fables, before ascer- 
taining that the thing is so in fact. Wherefore, approving and 



1/2 WILLIAM GILBERT. 

indorsing the absurdities of the ancients, they published the 
most blunderous theories and ridiculous theses e.g., that there 
are rocks having the power of attraction and that there the 
remora dwells ; and they postulate of the necessity of I know 
not what vacuum or how produced. Pliny and Julius Solinus 
tell of the stone cathochites and affirm that it attracts flesh and 
holds one's hand, as loadstone holds iron and amber holds 
chaff. But that is due solely to its viscosity and its natural 
glutinousness, for it adheres most readily to a warm hand. 
The sagda, or sagdo, is a gem of leek-green color mentioned by 
Pliny, Solinus, Albertus Magnus, and Euace, who themselves 
make up or from others copy the story that this stone has the 
peculiarity of attracting wood. And there are others who 
utter the nonsense that the wood attracted cannot be pulled 
off, but has to be cut away ; while some tell of a stone of this 
kind that clings as firmly to ships' bottoms as do the barnacles 
gathered on a long voyage. But though a stone may cling to 
a surface, it does not therefore attract ; and if it did attract, 
surely it would draw to itself chips and shavings electrically. 
A stone of this sort was seen by Encelius in the hands of a 
certain seaman ; a weak stone, it was, hardly able to attract 
the smallest twigs ; and its color was not a true leek-green. 
Diamond, carbuncle, rock-crystal, and other stones attract 
in that way. I say nothing of other fabulous stones, of 
pantarbes whereof Philostratus affirms that it attracts to itself 
other stones; of amphitane, said to attract also gold. Pliny, 
in telling of the discovery of glass, makes the loadstone 
attract glass as it does iron ; for when in speaking of the mode 
of making glass he describes its nature, he adds this concern- 
ing the loadstone : " In time the skill of the workmen, clear 
sighted and resourceful, was no longer content with mixing in 
natron ; loadstone began to be added because it is believed to 



OF THE ATTRACTIONS OF OTHER BODIES. 173 

attract to itself the liquid glass even as it attracts iron." * 
Georgius Agricola asserts that "A portion of loadstone is 
added to the ingredients of glass (sand and natron), because it 
is believed in our day as in early times that that force (the 
magnetic) attracts to itself the molten glass even as it attracts 
iron, that it purifies it when attracted, and changes it from 
green or orange-yellow to clear white ; but afterward the fire 
consumes the loadstone." True it is indeed that loadstone of 
some kind (as the magnesia employed by glass-makers, which 
has no magnetic powers) is sometimes introduced into and 
mingled with the material of glass, yet not because that it 
attracts glass. But a red-hot loadstone does not attract iron 
at all, nor is iron at white heat attracted by loadstone ; and 
the loadstone is even destroyed by very strong heat and loses 
its power of attraction. Nor is this work of purifying the 
function of loadstone alone in the glass furnace, but also of 
certain pyrites and of readily combustible iron ores ; and these 
alone are used by such of our glass-makers as make clear, fine 
glass. These materials are mixed with sand, ashes, and natron 
(just as other materials are mixed with metals when they are 
smelted), so that, when the contents of the furnace become 
fluid glass, the well-known green and yellow color may be 
purged away by the penetrant heat. For no other matter 
reaches such degree of heat or endures fire for the requisite 



1 The allusion to Pliny is made by J. B. Porta: Natural Magick, London 
1658, Book VII, page 216 ; Magia Naturalis, Amstelodami 1664, Lib. VII, 
Cap. LVI, page 331. Sir Thomas Brown says (Pseudoloxia Epidemica, London 
1658, Book II, page 76): "True it is that in the making of glass it hath been 
in ancient practice to cast in pieces of Loadstone : conceiving it carried away 
all ferreous and earthy parts from the pure and running portion of glass, 
which the Loadstone would not respect ; and therefore if that attraction were 
not rather Electrical than Magnetical, it was a wonderous effect what Helmont 
delivereth concerning a glass wherein the Magistery of Loadstone was prepared; 
which after retained an attractive quality." 



1/4 WILLIAM GILBERT. 

length of time that the material of the glass may become 
perfectly fluid, and just then is burnt up by the strong fire. But 
sometimes it happens that on account of the magnetic stone, or 
magnesia, or iron ore, or pyrites, the glass hath a dusky tinge, 
these substances being too resistant to fire and hence not being 
burnt up, or having been introduced in too great quantity. 
For this reason, glass-makers procure the right sort of stone 
and carefully attend to the proportion of ingredients in the 
mixture. Thus, then, Georgius Agricola and later writers are 
badly led astray by Pliny's stupid philosophy when they de- 
clare that loadstone is needed by glass-makers for its magnetic 
virtues and attractive force. And Scaliger (De Subtil, ad Car- 
danum) strays far from truth when, in treating of magnetic 
bodies, he speaks of diamond attracting iron ; unless he means 
only that diamond electrically attracts iron as it does bits of 
wood, straws, and other small bodies of all kinds. Fallopius 
thinks that quicksilver attracts metals in virtue of an occult 
property, just as the loadstone does iron, or as amber attracts 
chaff. But there is no attraction properly so called when 
quicksilver enters into metals. For metals imbibe quicksilver 
as clay does water, but not unless the substances are in con- 
tact ; for quicksilver does not draw to itself gold or lead from 
a distance, but remains fixed in its place. 



MUTUALLY REPELLANT BODIES. 175 



CHAPTER XXXIX. 

OF MUTUALLY REPELLANT BODIES. 

AUTHORS who have treated of the forces of attracting 
bodies have discoursed of the powers of repellant bodies also ; 
and in particular those who have classified objects in nature 
according to sympathy and antipathy. It would seem, there- 
fore, that we must needs say something about the strife of 
bodies among themselves, lest widespread errors, accepted by 
all to the ruin of true philosophy, should extend farther. They 
tell us that as like things attract for conservation's sake, so 
unlike things and opposites repel and drive each other away, 
as is seen in the antiperistasis (counteraction) of many bodies ; 
but it is most potent in plants and animals, which, as they 
attract things in affinity and of kin, so do put away things 
extreme and disadvantageous to themselves. But in other 
bodies the same reason does not exist for their coming to- 
gether by mutual attraction when they are separated. Ani- 
mals take food (as do all things that live), bring it into their 
inwards, absorb their nourishment by means of certain organs 
(the vital principle acting and operating). Only things set 
before them and adjoining them do they enjoy through a 
natural instinct, not things placed afar ; herein there is no 
exercise of force, no movement on the part of those other 
things , and therefore animals neither attract bodies nor repel. 
Water does not repel oil, as some do think, for oil floats on 
water; nor does water repel mud, because when mixed with 
water it settles at last. This is a separation of bodies unlike 



WILLIAM GILBERT. 

or not perfectly mixed, because of their matter ; but after they 
have been separated, they still remain in conjunction without 
any natural strife. Thus, in the bottom of a vessel, muddy 
sediment rests quiet, and oil remains on the top of water, nor 
is it ordered away. A drop of water remains whole on a dry 
surface, nor is it chased away by the dry. Wrongly, therefore, 
do they who discourse of these things impart an antipathy 
antipathia (i.e., a power of repulsion through opposite 
passions) ; for neither is there in them any repellant force, and 
repulsion comes of action not of passion. But these people 
dearly love their Greek terms. The question for us is whether 
there is any body that drives another away to a distance with- 
out material impetus, as the loadstone attracts. Now a load- 
stone does repel another loadstone ; for the pole of one is 
repelled by the pole of another that does not agree naturally 
with it ; driving it, it makes it turn round so that they may 
come together perfectly according to nature. But if a weak 
loadstone floating freely in water cannot, on account of obsta- 
cles, readily turn about, then it is repelled and driven farther 
away by the other. All electrics attract objects of every 
kind ; they never repel or propel. What is told of some 
plants (e.g., of the cucumber, which, when oil is placed beneath 
it, moves away) is a material change from neighborhood, not a 
hidden sympathy. But when they show you a candle's flame 
that touches a cold solid (as iron) turning to one side, and pre- 
tend that here is antipathy, they talk nonsense. The reason 
of this they will see clearer than light when we come to treat 
of heat and what it is. As for Fracastorio's belief that a 
loadstone may be found that shall repel iron, in virtue of some 
principle latent in it that is opposed to iron, it is without any 
foundation. 




BOOK III. 



CHAPTER I. 

OF DIRECTION. 

IN the roregoing books it has been shown that a loadstone 
has its poles, iron also poles, and rotation, and fixed verticity, 
and finally that loadstone and iron direct their poles toward 
the poles of the earth. But now we have to set forth the 
causes of these things and their wonderful efficiencies known 
aforetime but not demonstrated. Of these rotations all the 
writers who went before us have given their opinions with such 
brevity and indefiniteness that, as it would seem, no one could 
be persuaded thereby, while the authors themselves could 
hardly be contented with them. By men of intelligence, all 
their petty reasonings as being useless, questionable, and 
absurd, and based on no proofs or premises are rejected with 
the result that magnetic science, neglected more and more and 
understood by none, has been exiled. The true south pole,* 

177 



WILLIAM GILBERT. 

and not the north (as before our time all believed), of a load- 
stone placed on its float in water turns to the north ; the south 
end of a piece of magnetized and of unmagnetized iron also 
moves to the north. An oblong piece of iron of three or four 
finger-breadths, properly stroked with a loadstone, quickly 
turns to north and south. Therefore artificers place such a 
bar, balanced on a point, in a compass-box or in a sun-dial ; or 
they construct a versorium out of two curved pieces of iron 
that touch at their extremities so that the movement may be 
more constant ; thus is constructed the mariner's compass, an 
instrument beneficial, salutary, and fortunate for seamen, show- 
ing the way to safety and to port. But it is to be understood 
at the threshold of their argument, before we proceed farther, 
that these directions of loadstone or of iron are not ever and 
always toward the world's true poles, that they do not always 
seek those fixed and definite points, nor rest on the line of the 
true meridian, but that at places, more or less far apart, they 
commonly vary either to the east or to the west; sometimes, 
too, in certain regions of land or sea, they point to the true 
poles. This discrepance is known as the variation of the 
needle and of the loadstone ; and as it is produced by other 
causes and is, as it were, a sort of perturbation and depravation 
of the true direction, we propose to treat here only of the true 
direction of the compass and the magnetic needle, which would 
all over the earth be the same, toward the true poles and in 
the true meridian, were not hindrances and disturbing causes 
present to prevent : in the book next following we will treat of 
its variation and of the cause of perturbation. 

They who aforetime wrote of the world and of natural 
philosophy, in particular those great elementarian philosophers 
and all their progeny and pupils down to our day ; those, I 
mean, who taught that the earth is ever at* rest, and is, as it 



DIRECTION. 179 

were, a dead-weight planted in the centre of the universe at 
equal distance everywhere from the heavens, of simple uncom- 
plex matter possessing only the qualities of dryness and cold 
these philosophers were ever seeking the causes of things in 
the heavens, in the stars, the planets ; in fire, air, water, and in 
the bodies of compounds ; but never did they recognize that 
the terrestrial globe, besides dryness and cold, hath some 
principal, efficient, predominant potencies that give to it firm- 
ness, direction, and movement throughout its entire mass and 
down to its inmost depths ; neither did they make inquiry 
whether such things were, and, for this reason, the common 
herd of philosophizes, in search of the causes of magnetic 
movements, called in causes remote and far away. Martinus 
Cortesius, who would be content with no cause whatever in 
the universal world, dreamt of an attractive magnetic point 
beyond the heavens, acting on iron. Petrus Peregrinus holds 
that direction has its rise at the celestial poles. Cardan was 
of the opinion that the rotation of iron is caused by the star 
in the tail of Ursa Major. The Frenchman Bessard thinks 
that the magnetic needle turns to the pole of the zodiac. 
Marsilius Ficinus will have it that the loadstone follows its 
Arctic pole, and that iron follows the loadstone, and chaff 
follows amber : as for amber, why, that, mayhaps, follows the 
Antarctic pole : emptiest of dreams ! Others have come down 
to rocks and I know not what " magnetic mountains " ! So 
has ever been the wont of mankind : homely things are vile ; 
things from abroad and things afar are dear to them and the 
object of longing. As for us, we are habitants of this very 
earth, and study it as cause of this mighty effect. Earth, the 
mother of all, hath these causes shut up in her recesses : all 
magnetic movements are to be considered with respect to her 
law, position, constitution, verticity, poles, equator, horizon, 



ISO WILLIAM GILBERT. 

meridians, centre, periphery, diameter, and to the form of her 
whole inward substance. So hath the earth been ordered by 
the Supreme Artificer and by nature, that it shall have parts 
unlike in position, terminal points of an entire and absolute 
body, and such points dignified by distinct functions, whereby 
it shall itself take a fixed direction. For like as a loadstone, 
when in a suitable vessel it is floated on water, or when it is 
suspended in air by a slender thread, does by its native ver- 
ticity, according to the magnetic laws, conform its poles to the 
poles of the common mother, so, were the earth to vary from 
her natural direction and from her position in the universe, or 
were her poles to be pulled toward the rising or the setting 
sun, or other points whatsoever in the visible firmament (were 
that possible), they would recur again by a magnetic move- 
ment to north and south, and halt at the same points where 
now they stand. But why the terrestrial globe should seem 
constantly to turn one of its poles toward those points and 
toward Cynosura [constellation of the Lesser Bear], or why 
her poles should vary from the poles of the ecliptic by 23 
deg. 29 min., with some variation not yet sufficiently studied 
by astronomers, that depends on the magnetic energy. The 
causes of the precession of the equinoxes and of the progres- 
sion of the fixed stars, as well as of change in the declinations 
of the sun and the tropics, are traceable to magnetic forces : 
hence we have no further need of Thebit Bencora's " move- 
ment of trepidation," which is at wide variance with observa- 
tions. 1 A rotating needle turns to conformity with the situa- 

1 Abu 1'Hasan Thabet Ben Korrah, celebrated philosopher and geome- 
trician, born in Mesopotamia A.D. 835-836, was appointed by Mo'tadhed 
Billah, sixteenth of the 'Abbaside Khalifs, one of his astrologers, and is the 
author of numerous treatises on mathematics and other scientific subjects, as 
well as of several works in Syriac, and many translations in Arabic, the bare 
mention of the titles of which take up nearly two folio pages of Casiri's Cata- 
logue. 



DIRECTION. 



iSi 



tion of the earth, and, though it be shaken oft, returns still to 
the same points. For in far northern climes, in latitude 70 to 
80 deg. (whither in the milder season our seamen are wont to 
penetrate without injury from the cold), and in the middle 
regions, in the torrid zone under the equinoctial line, as also 
in all maritime regions and lands of the southern hemisphere, 
at the highest latitudes yet known, the magnetic needle ever 
finds its direction and ever tends in the same way (barring dif- 
ference of variation) on this side of the equator where we 
dwell and in the other, the southern part, which, though less 
known, has been to some extent explored by our sailors : and 
the lily of the mariner's compass ever points north. Of this, 
we are assured by the most illustrious navigators and by many 
intelligent seamen. The same was pointed out to me and 
confirmed by our most illustrious Neptune, Francis Drake, 
and by Thomas Candish [Cavendish], that other world-ex- 
plorer. 

Our terrella teaches the same lesson. The proposition is 
demonstrated on a spherical loadstone. Let A, B be the poles ; 
CD, an iron wire placed on the stone, always tends direct in 




the meridian to the poles A, B, whether the centre of the wire 
be in the middle line or equator of the stone, or whether it be 
in any other region between equator and poles, as H, G, F y E. * 



1 82 WILLIAM GILBERT. 

So the point of a magnetized needle looks north on this side 
of the equator : on the other side the crotch is directed to the 
south ; but the point or lily does not turn to the south below 
the equator, as somebody has thought. Some inexperienced 
persons, however, who, in distant regions below the equator, 
have at times seen the needle grow sluggish and less prompt, 
have deemed the distance from the Arctic pole or from the 
magnetic rocks to be the cause. But they are very much 
mistaken, for it has the same power and adjusts itself as 
quickly to the meridian as the point of variation in southern 
regions as in northern. Yet at times the movement appears 
to be slower, the point on which the compass needle is poised 
becoming in time, during a long voyage, rather blunt, or the 
magnetized needle itself having lost somewhat of its acquired 
force through age or from rusting. This, too, may be tested 
experimentally by poising the versorium of a sun-dial on a 
rather short-pointed needle rising perpendicularly out of the 
surface of the terrella. The magnetized needle turns to the 
poles of the terrella, and quits the earth's poles ; for a general 
cause that is remote is overcome by a particular cause that 
is present and strong. Magnetized bodies incline of their 
own accord to the earth's position, and they conform to the 
terrella. Two loadstones of equal weight and force conform 
to the terrella in accordance with magnetic laws. Iron 
gets force from the loadstone and is made to conform to 
the magnetic movements. Therefore true direction is the 
movement of a magnetized body in the line of the earth's ver- 
ticity toward the natural position and unition of both, their 
forms being in accord and supplying the forces. For we have, 
after many experiments in various ways, found that the dis- 
posing and ranging of the magnetized bodies depends on the 
differences of position, while the force that gives the motion is 



DIRECTIVE FORCE. 183 

the one form common to both ; also that in all magnetic 
bodies there is attraction and repulsion. For both the load- 
stone and the magnetized iron conform themselves, by rota- 
tion and by dip, to the common position of nature and the 
earth. And the earth's energy, with the force inhering in it 
as a whole, by pulling toward its poles and by repelling, ar- 
ranges in order all magnetic bodies that are unattached and 
lying loose. For in all things do all magnetic bodies conform 
to the globe of earth in accordance with the same laws and in 
the same ways in which another loadstone or any magnetic 
body whatsoever conforms to the terrella. 



CHAPTER II. 

DIRECTIVE (OR VERSORIAL) FORCE, WHICH WE CALL VER- 
TICITY: WHAT IT IS; HOW IT RESIDES IN THE LOAD- 
STONE; AND HOW IT IS ACQUIRED WHEN NOT NAT- 
URALLY PRODUCED. 

THE directive force, which by us is also called verticity, is 
a force distributed by the innate energy from the equator in 
both directions to the poles. That energy, proceeding north 
and south to the poles, produces the movement of direction, 
and produces also constant and permanent station in the sys- 
tem of nature, and that not in the earth alone but in all mag- 
netic bodies also. Loadstone occurs either in a special vein 
or in iron mines, for, being a homogenic earth-substance pos- 
sessing and conceiving a primary form, it becomes converted 
into or concreted with a stony body which, in addition to the 



1 84 WILLIAM GILBERT. 

prime virtues of the form, derives from different beds and 
mines, as from different matrices, various dissimilitudes and 
differences, and very many secondary qualities and varieties of 
its substance. A loadstone mined in this debris of the earth's 
surface and of its projections, whether it be (as sometimes 
found in China) entire in itself, or whether it be part of a con- 
siderable vein, gets from the earth its form and imitates the 
nature of the whole. All the inner parts of the earth are in 
union and act in harmony, and produce direction to north and 
south. Yet the magnetic bodies that in the topmost parts of 
the earth attract one another are not true united parts of the 
whole, but are appendages and agnate parts that copy the 
nature of the whole; hence, when floating free on water, they 
take the direction they have in the terrestrial order of nature. 
:We once had chiselled and dug out of its vein a loadstone 20 
pounds in weight, having first noted and marked its extremi- 
ties ; then, after it had been taken out of the earth, we placed 
it on a float in water so it could freely turn about ; straight- 
way that extremity of it which in the mine looked north 
turned to the north in water and after a while there abode ; 
for the extremity that in the mine looks north is austral and is 
attracted by the north parts of earth, just as in the case of 
iron, which takes verticity from the earth. Of these points we 
will treat later under the head of " Change of Verticity." 

But different is the verticity of the inward parts of the 
earth that are perfectly united to it and that are not separated 
from the true substance of the earth by interposition of bodies, 
as are separated loadstones situated in the outer portion of the 
globe, where all is defective, spoilt, and irregular. Let AB 
be a loadstone mine, and between it and the uniform earthen 
globe suppose there are various earths and mixtures that in 
a manner separate the mine from the true globe of the earth. 



DIRECTIVE FORCE. 18$ 

It is therefore informated by the earth's forces just as CD, 
a mass of iron, is in air ; hence the extremity B of the mine or 
of any part thereof moves toward the north pole G, just as 
does C, the extremity of the mass of iron, but not A nor D. 
But with the part EF, which comes into existence continuous 
with the whole and which is not separated from it by any 




mixed earthy matter, the case is different. For if the part 
EF, being taken out, were to be floated, it is not E that would 
turn to the north pole, but F. Thus, in those bodies which 
acquire verticity in the air, C is the south extremity and is at- 
tracted by the north pole G. In those which come into exist- 
ence in the detrital outermost part of the earth, B is south, 
and so goes to the north pole. But these parts which, deep 
below, are of even birth with the earth, have their verticity 
regulated differently. For here F turns to the north parts of 
the earth, being a south part ; and E to the south parts of the 
earth, being a north part. So the end C of the magnetic body 
CD, situate near the earth, turns to the north pole ; the end B of 
the agnate body BA to the north ; the end E of the inborn 
body EF to the south pole as is proved by the following 
demonstration and as is required by all magnetic laws. 



1 86 WILLIAM GILBERT. 

Describe a terrella with poles A, B ; from its mass sepa- 
rate the small part EF, and suspend that by a fine thread in a 
cavity or pit in the terrella. E then does not seek the pole A 
but the pole B, and F turns to A, behaving quite differently 
from the iron bar CD\ for, there, C, touching a north part of 
the terrella, becomes magnetized and turns to A, not to B. 
But here it is to be remarked that if pole A of the terrella 
were to be turned toward the southern part of the earth, still 




the end E of the solitary part cut out of the terrella and not 
brought near the rest of the stone would turn to the south : 
but the end C of the iron bar would, if placed outside the 
magnetic field, turn to the north. Suppose that in the un- 
broken terrella the part EF gave the same direction as the 
whole ; now break it off and suspend it by a thread, and E will 
turn to B and F to A. Thus parts that when joined with 
the whole have the same vefticity with it, on being separated 
take the opposite ; for opposite parts attract opposite parts, 
yet this is not a true opposition, but a supreme concordance 
and a true and genuine conformance of magnetic bodies in 
nature, if they be but divided and separated ; for the parts thus 
divided must needs be carried away some distance above the 
whole, as later will appear. Magnetic bodies seek formal unity, 
and do not so much regard their own mass. Hence the part 



DIRECTIVE FORCE. 



187 



FE is not attracted into its pit, but the moment it wanders * 
abroad and is away from it, is attracted by the opposite pole. 
But if the part FE be again placed in its pit or be brought 




near without any media interposed, it acquires the original 
combination, and, being again a united portion of the whole, 
co-operates with the whole and readily clings in its pristine 
position, while E remains looking toward A and F toward B, 
and there they rest unchanging. 

The case is the same when we divide a loadstone into two* 
equal parts from pole to pole. In the figure, a spherical stone 
is divided into two equal parts along the axis AB ; hence, 
whether the surface AB be in one of the two parts supine (as 
in the first diagram), or prone in both (as in the second), the end* 
A tends to B. But it is also to be understood that the point 
B does not always tend sure to A, for, after the division, the 
verticity goes to other points, for example to F, G, as is shown 



i88 



WILLIAM GILBERT. 



in Chapter XIV of this Third Book. LM, too, is now the 
axis of the two halves, and AB is no longer the axis; for, 
once a magnetic body is divided, the several parts are integral 
and magnetic, and have vertices proportional to their mass, 
new poles arising at each end on division. But the axis and 
poles ever follow the track of a meridian, because the force 



M 








B 




proceeds along the stone's meridian circles from the equinoc- 
tial to the poles invariably, in virtue of an innate energy that 
belongs to matter, owing to the long and secular position, and 
bearings toward the earth's poles, of a body possessing the fit 
properties ; and such body is endowed with force from the 
earth for ages and ages continuously, and has from its first be- 
ginning stood firmly and constantly turned toward fixed and 
determinate points of the same. 



HO W IRON A CQ UIRES VER TICITY FROM THE LOADSTONE. 1 89 



CHAPTER III. 

HOW IRON ACQUIRES VERTICITY FROM THE LOADSTONE, 
AND HOW THIS VERTICITY IS LOST OR ALTERED. 

AN oblong piece of iron, on being stroked with a loadstone, 
receives forces magnetic, not corporeal, nor inhering in or con- 
sisting with any body, as has been shown in the chapters on 
coition. Plainly, a body briskly rubbed on one end with a 
loadstone, and left for a long time in contact with the stone, 
receives no property of stone, gains nothing in weight ; for if 
you weigh in the smallest and most accurate scales of a gold- 
smith a piece of iron before it is touched by the loadstone you 
will find that after the rubbing it has the same precise weight, 
neither less nor more. And if you wipe the magnetized iron* 
with cloths, or if you rub it with sand or with a whetstone, it 
loses naught at all of its acquired properties. For the force is 
diffused through the entire body and through its inmost parts, 
and can in no wise be washed or wiped away. Test it, there- 
fore, in fire, that fiercest tyrant of nature. Take a piece of iron 
the length of your hand and as thick as a goose-quill ; pass it 
through a suitable round piece of cork and lay it on the sur- 
face of water, and note the end of the bar that looks north. 
Rub that end with the true smooth end of a loadstone ; thus 
the magnetized iron is made to turn to the north. Take off 
the cork and put that magnetized end of the iron in the fire* 
till it just begins to glow ; on becoming cool again it will re- 
tain the virtues of the loadstone and will show verticity, though 
not so promptly as before, either because the action of the fire 



WILLIAM GILBERT. 

was not kept up long enough to do away all its force, or be 
cause the whole of the iron was not made hot, for the property 
is diffused throughout the whole. Take off the cork again, 
drop the whole of the iron into the fire, and quicken the fire 
with bellows so that it becomes all alive, and let the glowing 
iron remain for a little while. After it has grown cool again 
(but in cooling it must not remain in one position) put iron and 

* cork once more in water, and you shall see that it has lost its 
acquired verticity. All this shows how difficult it is to do 
away with the polar property conferred by the loadstone. 
And were a small loadstone to remain for as long in the same 
fire, it too would lose its force. Iron, because it is not so 
easily destroyed or burnt as very many loadstones, retains its 
powers better, and after they are lost may get them back again 
from a loadstone ; but a burnt loadstone cannot be restored. 

Now this iron, stripped of its magnetic form, moves in a way 
different from any other iron, for it has lost the polar prop- 
erty; and though before contact with the loadstone it may 
have had a movement to the north, and after contact toward 

* the south, now it turns to no fixed and determinate point ; 
but afterward, very slowly, after a long time, it turns un- 
steadily toward the poles, having received some measure of 
force from the earth. There is, I have said, a twofold cause 
of direction, one native in the loadstone and in iron, and the 
other in the earth, derived from the energy that disposes 
things. For this reason it is that after iron has lost the 
faculty of distinguishing the poles and verticity, a tardy and 
feeble power of direction is acquired anew from the earth's 
verticity. From this we see how difficultly, and how only by 
the action of intense heat and by protracted firing of the iron 
till it becomes soft, the magnetic force impressed in it is done 
away. When this firing has suppressed the acquired polar 



HOW IRON ACQUIRES VERTICITY FROM THE LOADSTONE. IQI 

power, and the same is now quite conquered and as yet has 
not been called to life again, the iron is left a wanderer, and 
quite incapable of direction. 

But we have to inquire further how it is that iron remains 
possessed of verticity. It is clear that the presence of a load- 
stone strongly affects and alters the nature of the iron, also 
that it draws the iron to itself with wonderful promptness. 
Nor is it the part rubbed only, but the whole of the iron, that 
is affected by the friction (applied at one end only), and 
therefrom the iron acquires a permanent though unequal 
power, as is thus proved. 

Rub with a loadstone a piece of iron wire on one end so as* 
to magnetize it and to make it turn to the north ; then cut off 
part of it, and you shall see it move to the north as before, 
though weakly. For it is to be understood that the loadstone 
awakens in the whole mass of the iron a strong verticity (pro- 
vided the iron rod be not too long), a pretty strong verticity in 
the shorter piece throughout its entire length, and, as long as 
the iron remains in contact with the loadstone, one somewhat 
stronger still. But when the iron is removed from contact it 
becomes much weaker, especially in the end not touched by 
the loadstone. And as a long rod, one end of which is thrust 
into a fire and made red, is very hot at that end, less hot in 
the parts adjoining and midway, and at the farther end may 
be held in the hand, that end being only warm, so the mag- 
netic force grows less from the excited end to the other ; but 
it is there in an instant, and is not introduced in any interval 
of time nor successively, as when heat enters iron, for the 
moment the iron is touched by the loadstone it is excited 
throughout. For example, take an unmagnetized iron rod,* 
4 or 5 inches long : the instant you simply touch with a load- 



192 WILLIAM GILBERT. 

stone either end, the opposite end straightway, in the twink- 
ling of the eye, repels or attracts a needle, however quickly 
brought to it. 1 



CHAPTER IV. 

WHY MAGNETIZED IRON TAKES OPPOSITE VERTICITY ; AND 
WHY IRON TOUCHED BY THE TRUE NORTH SIDE OF 
THE STONE MOVES TO THE EARTH'S NORTH, AND WHEN 
TOUCHED BY THE TRUE SOUTH SIDE TO THE EARTH'S 
SOUTH: IRON RUBBED WITH THE NORTH POINT OF THE 
STONE DOES NOT TURN TO THE SOUTH, NOR vice versa, 
AS ALL WRITERS ON THE LOADSTONE HAVE ERRONE- 
OUSLY THOUGHT. 

IT has already been shown that the north part of a load- 
stone does not attract the north part of another stone, but the 
south part, and that it repels the north end of another stone 
applied to its north end. That general loadstone, the terres_ 
trial globe, does with its inborn force dispose magnetized iron, 
and the magnetic iron too does the same with its inborn force, 
producing movement and determining the direction. For 
whether we compare together and experiment on two load- 
stones, or a loadstone and piece of iron, or iron and iron, or 
earth and loadstone, or earth and iron conformated by the 
earth or deriving force from the energy of a loadstone, of 
necessity the forces and movements of each and all agree and 
harmonize in the same way. 

1 Dr. J. Lament's " Handbuch des Magnetismus," Leipzig 1867, page 
383. 



WHY MAGNETIZED IRON TAKES OPPOSITE VERTICITY. 193 

But the question arises, Why does iron touched with load- 
stone take a direction of movement toward the earth's opposite 
pole and not toward that pole of earth toward which looked 
the pole of the loadstone with which it was magnetized? Iron 
and loadstone, we have said, are of the same primary nature : 
iron when joined to a loadstone becomes as it were one body 
with it, and not only is one extremity of the iron altered, but 
the rest of its parts are affected. Let A be the north pole of 
a loadstone to which is attached the tip of an iron pointer: 
the tip is now the south part of the iron, because it is con- 




tiguous to the north part of the stone; the crotch of the 
pointer becomes north. For were this contiguous magnetic 
body separated from the pole of the terrella or the parts nigh 
the pole, the other extremity (or the end which when there 
was conjunction was in contact with the north part of the 
stone) is south, while the other end is north. So, too, if a 
magnetized needle be divided into any number of parts 
however minute, those separated parts will take the same direc- 
tion which they had before division. Hence, as long as the 
point of the needle remains at A, the north pole, it is not aus- 
tral, but is, as it were, part of a whole ; but when it is taken 
away from the stone it is south, because on being rubbed it 
tended toward the north parts of the stone, and the crotch (the 



194 WILLIAM GILBERT. 

other end of the pointer) is north. The loadstone and the 
pointer constitute one body : B is the south pole of the whole 
mass ; C (the crotch) is the north extremity of the whole. Even 
divide the needle in two at E, and E will be south as regards 
the crotch, E will also be north with reference to B. A is the 
true north pole of the stone, and is attracted by the south pole 
of the earth. The end of a piece of iron touched with the true 
north part of the stone is south, and turns to the north pole of 
the stone A if it be near ; if it be at a distance from the stone, 
it turns to the earth's north. So whenever iron is magnetized 
it tends (if free and unrestrained) to the portion of the earth 
opposite the part toward which inclines the loadstone at which 
it was rubbed. For verticity always enters the iron if only it 
be magnetized at either end. Hence all the needle points at 
B acquire the same verticity after being separated, but it is 




the opposite verticity to that of the pole B of the stone ; and 
all the crotches in the present figure have a verticity opposite 
to that of the pole E, and are made to move and are seized by 
E when they are in suitable position. The case is as in the 
oblong stone FH, cut in two at , where F and H t whether the 
stone be whole or be broken, move to opposite poles of the 



WHY MAGNETIZED IRON TAKES OPPOSITE VERTICITY. 19$ 

earth, and O and P mutually attract, one being north, the other 
south. For if in the whole stone H was south and F north, 
then in the divided stone P will be north with respect to H and 
O, south with respect to F\ so, too, F and H tend toward con- 
nection if they be turned round a little, and at length they 
come together. But if the division be made meridionally, i.e., 
along the line of the meridian and not on any parallel circle, 
then the two parts turn about and A pulls B, and the end B 




is attracted to A, until, being turned round, they form connec- 
tion and are held together. For this reason, iron bars placed * 
on parallels near the equator of a terrella whose poles are AB, 
do not combine and do not cohere firmly ; but when placed 




alongside on a meridian line, at once they become firmly joined, * 
not only on the stone and near it, but at any distance within 



196 WILLIAM GILBERT. 

the magnetic field of the controlling loadstone. Thus they are 
held fast together at E, but not at C of the other figure. For 
the opposite ends C and F of the bars, come together and 
cohere, as the ends A and B of the stone did. But the ends 
are opposite, because the bars proceed from opposite poles and 
parts of the terrella ; and C is south as regards the north pole 

*A, and F is north as regards the south pole B. Similarly, too, 
they cohere if the rod 7 (not too long) be moved further toward 
A f and the rod F toward , and they will be joined on the 
terrella just as A and B of the divided stone were joined. But 

now if the magnetized needle point A be north, and if with 
this you touch and rub the point B of another needle that ro- 
tates freely but is not magnetized, B will be north and will turn 
to the south. But if with the north point B you touch still 
another new rotatory needle on its point, that point again will 
be south, and will turn to the north : a piece of iron not only 
takes from the loadstone, if it be a good loadstone, the forces 
needful for itself, but also, after receiving them, infuses them 
into another piece, and that into a third, always with due regard 
to magnetic law. 

In all these our demonstrations it is ever to be borne in 
mind that the poles of the stone as of the iron, whether mag- 
netized or not, are always in fact and in their nature opposite to 
the pole toward which they tend, and that they are thus named 
by us, as has been already said. For, everywhere, that is north 
which tends to the south of the earth or of a terrella, and that 
is south which turns to the north of the stone. Points that are 

north are attracted by the south part of the earth, and hence 
when floated they tend to the south. A piece of iron rubbed 
with the north end of a loadstone becomes south at the other 
end and tends always (if it be within the field of a loadstone 
and near) to the north part of the loadstone, and to the north 



MAGNETIZING STONES OF DIFFERENT SHAPES. 

part of the earth if it be free to move and stand alone at a dis- 
tance from the loadstone. The north pole A of a loadstone 
turns to the south of the earth, G ; a needle magnetized on 




its point by the part A follows A, because the point has been 
made south. But the needle C, placed at a distance from the * 
loadstone, turns its point to the earth's north, F, for that point 
was made south by contact with the north part of the loadstone. 
Thus the ends magnetized by the north part of the stone 
become south, or are magnetized southerly, and tend to the 
earth's north ; the ends rubbed with the south pole become 
north, or are magnetized northerly, and tend to the earth's south. 



CHAPTER V. 
OF MAGNETIZING STONES OF DIFFERENT SHAPES. 

OF a magnetized piece of iron one extremity is north, the 
other south, and midway is the limit of verticity : such limit, in 
the globe of the terrella or in a globe of iron, is the equinoctial 
circle. But if an iron ring be rubbed at one part with a load-, 
stone, then one of the poles is at the point of friction, and the 
other pole at the opposite side ; the magnetic force divides the 
ring into two parts by a natural line of demarkation, which, 



WILLIAM GILBERT. 

though not in form, is in its power and effect equinoctial. But 
if a straight rod be bent into the form of a ring without weld- 
ing and unition of the ends, and it be touched in the middle 
with a loadstone, the ends will be both of the same verticity. 

* Take a ring, whole and unbroken, rubbed with a loadstone at 

* one point ; then cut it across at the opposite point and stretch 
it out straight : again both ends will be of the same verticity, 
just like an iron rod magnetized in the middle, or a ring not 
cohering at the joint. 



CHAPTER VI. 

WHAT SEEMS TO BE A CONTRARY MOVEMENT OF MAGNETIC 
BODIES IS THE REGULAR TENDENCE TO UNION. 

IN magnetic bodies nature ever tends to union not merely 
to confluence and agglomeration, but to agreement, so that the 
force that causes rotation and bearing toward the poles may 
not be disordered, as is shown in various ways in the following 
example. Let CD be an unbroken magnetic body, with C 



looking toward B, the earth's north, B and D toward A, the 
* earth's south. Now cut it in two in the middle, in the equator, 



CONTRARY MOVEMENT OF MAGNETIC BODIES. 199 

and then E will tend to A and F to B. For, as in the whole, 
so in the divided stone, nature seeks to have these bodies 
united ; hence the end E properly and eagerly comes together 
again with F t and the two combine, but E is never joined to D 
nor F to C, for, in that case, C would have to turn, in opposition, 
to nature, to A, the south, or D to B, the north which were 
abnormal and incongruous. Separate the halves of the stone 
and turn D toward C : they come together nicely and combine. 
For D tends to the south, as before, and C to the north ; E and 
F, which in the mine were connate parts, are now greatly at 
variance, for they do not come together on account of material 
affinity, but take movement and tendence from the form. 
Hence the ends, whether they be conjoined or separate, tend 
in the same way, in accordance with magnetic law, toward the 
earth's poles in the first figure of the stone, whether unbroken 
or divided as in the second figure ; and FE of the second figure, 
when the two parts come together and form one body, is as 
perfect a magnetic mass as was CD when first produced in the 
mine ; and FE, placed on a float, turn to the earth's poles, * 
and conform thereto in the same way as the unbroken stone. 

This agreement of the magnetic form is seen in the shapes 
of plants. Let AB be a branch of ozier 1 or other tree that * 




sprouts readily ; and let A be the upper part of the branch 
and be the part rootward. Divide the branch at CD. Now, 

1 Ozier, osier, a species of willow (salix). 



2OO 



WILLIAM GILBERT. 



the extremity CD, if skilfully grafted again on Z>, begins to 
grow, just as B and A, when united, become consolidated and 
germinate. But if D be grafted in A, or C on B, they are at 
variance and grow not at all, but one of them dies because of 
the preposterous and unsuitable apposition, the vegetative 
force, which tends in a fixed direction, being now forced into 
a contrary one. 



CHAPTER VII. 

A DETERMINATE VERTICITY AND A DIRECTIVE POWER MAKE 
MAGNETIC BODIES ACCORD, AND NOT AN ATTRACTIONAL 
OR A REPULSATIVE FORCE, NOR STRONG COITION ALONE 
OR UNITION. 

IN the equinoctial circle A there is no coition of the ends 
of a piece of iron wire with the terrella ; at the poles the 




coition is very strong. The greater the distance from the 
equinoctial the stronger is the coition with the terrella itself, 



DISAGREEMENTS OF IRON ON THE SAME POLE. 2OI 

and with any part thereof, not with the pole only. But the 
pieces of iron are not made to stand because of any peculiar 
attracting force or any strong combined force, but because of 
the common energy that gives to them direction, conformity, 
and rotation. For in the region B not even the minutest bit* 
of iron that weighs almost nothing can be reared to the per- 
pendicular by the strongest of loadstones, but adheres ob- 
liquely. And just as the terrella attracts variously, with unlike* 
force, magnetic bodies, so, too, an iron hump (or protuberance 
nasus) attached to the stone has a different potency according 
to the latitude : thus the hump Z, as being strongly adherent, 
will carry a greater weight than M, and M a heavier weight 
than N. But neither does the hump rear to perpendicular a 
bit of iron except at the poles, as is shown in the figure. The 
hump L will hold and lift from the ground two ounces of solid 
iron, yet it is unable to make a piece of iron wire weighing* 
two grains stand erect ; but that would not be the case if 
verticity arose from strong attraction, or more properly coi- 
tion, or from unition. 



CHAPTER VIII. 

OF DISAGREEMENTS BETWEEN PIECES OF IRON ON THE 
SAME POLE OF A LOADSTONE ; HOW THEY MAY COME 
TOGETHER AND BE CONJOINED. 

IF two pieces of iron wire or two needles above the poles 
of -a terrella adhere, when about to be raised to the perpen- 
dicular they repel each other at their upper ends and present * 
a furcate appearance ; and if one end be forcibly pushed toward 



202 WILLIAM GILBERT. 

the other, that other retreats and bends back to avoid the asso- 
ciation, as shown in the figure. A and B y small iron rods, 




adhere to the pole obliquely because of their nearness to each 
other : either one alone would stand erect and perpendicular. 
The reason of the obliquity is that A and B, having the same 
verticity, retreat from each other and fly apart. For if C be the 
north pole of a terrella, then the ends A and B of the rods are 
also north, while the ends in contact with and held fast by the 
pole C are both south. But let the rods be rather long (say 

, two finger-breadths), and let them be held together by force : 
then they cohere and stand together like friends, nor can they 
be separated save by force, for they are held fast to each other 
magnetically, and are no longer two distinct terminals but one 
only and one body, like a piece of wire bent double and made 
to stand erect. 

But here we notice another curious fact, viz., that if the 
rods be rather short, not quite a finger's breadth in length, or 

* as long as a barley-corn, they will not unite on any terms, nor 
will they stand up together at all, for in short pieces of wire 
the verticity at the ends farthest from the terrella is stronger 
and the magnetic strife more intense than in longer pieces. 



DISAGREEMENTS OF IRON ON THE SAME POLE. 203 

Therefore they do not permit any association, any fellowship. 
Again, if two light pieces of wire, A and B, be suspended 




by a very slender thread of silk filaments not twisted but 
laid together, 1 and held at the distance of one barley-corn's 
length from the loadstone, then the opposite ends, A and B, 
situate within the sphere of influence above the pole, go a 
little apart for the same reason, except when they are very 
near the pole C of the stone : in that position the stone at- 
tracts them to the one point. 

1 See Book I, Chapter XII. 



204 



WILLIAM GILBERT. 



CHAPTER IX. 

DIRECTIONAL FIGURES SHOWING THE VARIETIES OF ROTA- 
TION. 

HAVING now sufficiently shown, according to magnetic laws 
and principles, the demonstrable cause of the motion toward 
determinate points, we have next to show the movements. 
On a spherical loadstone having the poles A, , place a rotating 
needle whose point has been magnetized by the pole A : that 
point will be directed steadily toward A and attracted by A, 




because, having been magnetized by A, it accords truly and 
combines with A ; and yet it is said to be opposite because 
when the needle is separated from the stone it moves to the 
opposite part of earth from that toward which the loadstone's 
pole A moves. For if A be the north pole of the terrella, the 
point of the needle is its south end, and its other end, the 
crotch, points to B : thus B is the loadstone's south pole, 
while the crotch of the needle is the needle's north end. So, 
too, the point is attracted by EFGH and by every part of a 



FIGURES SHOWING THE VARIETIES OF ROTATION. 2O5 

meridian from the equator to the pole, because of the power 
of directing ; and when the needle is in those places on the 
meridian the point is directed toward A ; for it is not the 
point A but the whole loadstone that makes the needle turn, 
as does the whole earth in the case of magnetic bodies turning 
to the earth. 

The figure following shows the magnetic directions in the 
right sphere of a loadstone and in the right sphere of the 
earth, also the polar directions to the perpendicular of the 
poles. All the points of the versorium have been magnetized 
by pole A. All the points are directed toward A except the 
one that is repelled by B. 




The next figure shows horizontal directions above the 
body of the loadstone. All the points that have been made 
south by rubbing with the north pole or some point around the 
north pole A, turn to the pole A and turn away from the 
south pole B, toward which all the crotches are directed. 

I call the direction horizontal because it coincides with 
the plane of the horizon ; for nautical and horological instru- 
ments are so constructed that the needle shall be suspended 
or supported in equilibrium on a sharp point, which prevents 
the dip of the needle, as we shall explain later. And in this 



206 



WILLIAM GILBERT. 



way it best serves man's use, noting and distinguishing all the 
points of the horizon and all the winds. Otherwise in every 
oblique sphere (whether terrella or earth) the needle and all 




magnetized bodies would dip below the horizon, and, at the 
poles, the directions would be perpendicular, as appears from 
our account of the dip. 

The next figure shows a spherical loadstone cut in two at 
the equator; all the points of the needles have been mag- 




netized by pole A. The points are directed in the centre of 
the earth and between the two halves of the terrel-la, divided 



FIGURES SHOWING THE VARIETIES OF ROTATION. 2O? 

in the plane of the equator as shown in the diagram. The 
case would be the same if the division were made through the 
plane of a tropic and the separation and distance of the two 
parts were as above, with the division and separation of the 
loadstone through the plane of the equinoctial. For the 
points are repelled by C, attracted by D, and the needles are 
parallel, the poles or the verticity at both ends controlling 
them. 

The next figure shows half of a terrella by itself, and its 
directions differing from the directions given by the two parts 
in the preceding figure, which were placed alongside. All 




the points have been magnetized by A ; all the crotches below, 
except the middle one, tend not in a right line but obliquely, 
to the loadstone, for the pole is in the middle of the plane 
that before was the plane of the equinoctial. All points mag- 
netized by parts of the loadstone away from the pole move 
to the pole (just as though they had been magnetized by the 
pole itself) and not to the place of friction, wherever that may 
be in the whole stone at any latitude betwixt pole and equa- 
tor. And for this reason there are only two differences of 
regions they are north and south as well in the terrella as in 
the great globe of earth ; and there is no east, no west place, 



208 WILLIAM GILBERT. 

no regions truly eastern or western, but, with respect to each 
other, east and west are simply terms signifying toward the 
east or west part of the heavens. Hence Ptolemy seems in 
the Quadripartitum to err in laying out eastern and western 
divisions, to which he improperly annexes the planets ; he is 
followed by the rabble of philosophasters and astrologers. 



CHAPTER X. 

OF THE MUTATION OF VERTICITY AND MAGNETIC PROPER- 
TIES, OR OF THE ALTERATION OF THE FORCE AWA- 
KENED BY THE LOADSTONE. 

IRON excited by the magnetic influx has a verticity that is 
pretty strong, yet not so stable but that the opposite parts 
may be altered by the friction not only of a stronger but of 
the same loadstone, and may lose all their first verticity and 
take on the opposite. Procure a piece of iron wire and with 
the self-same pole of a loadstone rub each end equally ; pass 
the wire through a suitable cork float and put it in the water. 
Then one end of the wire will look toward a pole of the earth 
whereto that end of the loadstone does not look. But which 
* end of the wire ? It will be just the one that was rubbed 
last. Now rub with the same pole the other end again, and 
straightway that end will turn in the opposite direction. 
Again rub the end that first pointed to the pole of the load- 
stone, and at once that, having, as it were, obtained its orders 
(jmpertum nactus), will go in the direction opposite to the one 
it took last. Thus you will be able to alter again and again 



MUTATION OF VERTICITY. 

the property of the iron, and the extremity of it that is last 
rubbed is master. And now merely hold for a while the 
north end of the stone near the north end of the wire that 
was last rubbed, not bringing the two into contact, but at the . 
distance of one, two, or even three finger-breadths, if the* 
stone be a powerful one ; again the iron will change its prop- 
erty and will turn to the opposite direction: so it will, too, 
though rather more feebly, if the loadstone be four finger- 
breadths away. The same results are had in all these experi- 
ments whether you employ the south or the north part of the 
stone. Verticity can also be acquired or altered with plates* 
of gold, silver, and glass between the loadstone and the end of 
the piece of iron or wire, provided the stone be rather power- 
ful, though the plates of metal be touched neither by the 
stone nor by the iron. And these changes of verticity occur 
in cast-iron. But what is imparted or excited by one pole of 
the loadstone is expelled and annulled by the other, which 
confers new force. Nor is a stronger loadstone needed to 
make the iron put off the weaker and sluggish force and to 
put on a new. Neither is the iron " made drunken" (inebri- 
atur) by equal forces of loadstone, so that it becomes " unde- 
cided and neutral," as Baptista Porta maintains. But by one 
same loadstone, and by loadstones endowed with equal power 
and strength, the force is altered, changed, incited, renewed, 
driven out. The loadstone itself, however, is not robbed, by 
friction with another bigger or stronger stone, of its property 
and verticity, nor is it turned, when on a float, to the oppo- 
site direction or to another pole different from that toward 
which, by its own nature and verticity, it tends. For forces 
that are innate and long implanted inhere more closely, nor* 
do they easily retire from their ancient seats ; and what is the 
growth of a long period of time is not in an instant reduced 



210 WILLIAM GILBERT. 

to nothing unless that in which it inheres perishes. Neverthe- 
less change comes about in a considerable interval of time, 
e.g., a year or two, sometimes in a few months to wit, when 
a weaker loadstone remains applied, in a way contrary to 
the order of nature, to a stronger, i.e., with the north pole of 
one touching the north pole of the other, or the south of one 
touching the other's south. Under such conditions, in the 
lapse of time the weaker force declines. 



CHAPTER XL 

OF FRICTION OF IRON WITH THE MID PARTS OF A LOAD- 
STONE BETWEEN THE POLES, AND AT THE EQUINOCTIAL 
CIRCLE OF A TERRELLA. 

TAKE a piece of iron wire not magnetized, three finger- 
widths long ('twill be better if its acquired verticity be rather 
weak or deformated by some process) ; touch and rub it with 
the equator of the terrella exactly on the equinoctial line 
along its whole tract and length, only one end, or both ends, 
or the whole of the iron, being brought into contact. The 
wire thus rubbed, run through a cork and float it in water. 
It will go wandering about without any acquired verticity, and 
the verticity it had before will be disordered. But if by chance 
it should be borne in its wavering toward the poles, it will be 
feebly held still by the earth's poles, and finally will be en- 
dowed with verticity by the energy of the earth. 



EXISTENCE OF VERTICITY IN SMELTED IRON. 211 



CHAPTER XII. 

HOW VERTICITY EXISTS IN ALL SMELTED IRON NOT EXCITED 
BY THE LOADSTONE. 

HITHERTO we have declared the natural and innate causes 
and the powers acquired through the loadstone ; but now we 
are to investigate the causes of the magnetic virtue existing 
in manufactured iron not magnetized by the loadstone. The 
loadstone and iron present and exhibit to us wonderful subtile 
properties. It has already oft been shown that iron not ex- 
cited by the loadstone turns to north and south ; further, that 
it possesses verticity, i.e., distinct poles proper and peculiar to 
itself, even as the loadstone or iron rubbed with the loadstone. 
This seemed to us at first strange and incredible : the metal, 
iron, is smelted out of the ore in the furnace, flows out of the 
furnace, and hardens in a great mass ; the mass is cut up in 
great workshops and drawn out into iron bars, and from these 
again the smith fashions all sorts of necessary implements and 
objects of iron. Thus the same mass is variously worked and 
transformed into many shapes. What, then, is it that pre- 
serves the verticity, or whence is it derived? First take a 
mass of iron as produced in the first iron-works. Get a smith 
to shape a mass weighing two or three ounces, on the anvil, 
into an iron bar one palm or nine inches long. Let the smith 
stand facing the north, with back to the south, so that as he 
hammers the red-hot iron it may have a motion of extension 
northward ; and so let him complete the task at one or two 
heatings of the iron (if needed) ; but ever while he hammers 



212 



WILLIAM GILBERT. 



and lengthens it, have him keep the same point of the iron 
looking north, and lay the finished bar aside in the same direc- 
tion. In this way fashion two, three, or more, yea one hun- 
dred or four hundred bars: it is plain that all the bars so 
hammered out toward the north and so laid down while cool- 
ing will rotate round their centres and when afloat (being 




passed through suitable pieces of cork) will move about in 
water, and, when the end is duly reached, will point north. 
And as an iron bar takes verticity from the direction in which 
it lies while being stretched, or hammered, or pulled, so too 
* will iron wire when drawn out toward any point of the horizon 
between east and south or between south and west, or con- 
versely. Nevertheless, when the iron is directed and stretched 



EXISTENCE OF VERTICITY IN SMELTED IRON. 21$ 

rather to a point east or west, it takes almost no verticity, or 
a very faint verticity. This verticity is acquired chiefly 
through the lengthening. But when inferior iron ore, in 
which no magnetic properties are apparent, is put in the fire* 
(its position with reference to the world's poles being noted) 
and there heated for eight or ten hours, then cooled away 
from the fire and in the same position with regard to the 
poles, it acquires verticity according to its position during 
heating and cooling. 

Let a bar of iron be brought to a white heat in a strong* 
fire, in which it lies meridionally, i.e., along the track of a 
meridian circle ; then take it out of the fire and let it cool and 
return to the original temperature, lying the while in the same 
position as before : it will come about that, through the like 
extremities having been directed toward the same poles of the 
earth, it will acquire verticity; and that the extremity that 
looked north when the bar, before the firing, was floated in 
water by means of a cork, if now the same end during the 
firing and the cooling looked southward, will point to the 
south. If perchance the turning to the pole should at any 
time be weak and uncertain, put the bar in the fire again, take 
it out when it has reached white heat, cool it perfectly as it 
lies pointing in the direction of the pole from which you wish 
it to take verticity, and the verticity will be acquired. Let it 
be heated again, lying in the contrary direction, and while yet* 
white-hot lay it down till it cools ; for, from the position in 
cooling (the earth's verticity acting on it), verticity is infused 
into the iron and it turns toward points opposite to the 
former verticity. So the extremity that before looked north 
now turns to the south. For these reasons and in these ways 
does the north pole of the earth give to that extremity of the* 
iron which is turned toward it south verticity ; hence, too, that 



214 WILLIAM GILBERT 

extremity is attracted by the north pole. And here it is to be 
observed that this happens with iron not only when it cools 
lying in the plane of the horizon, but also at any inclination 
thereto, even almost up to perpendicular to the centre of the 
earth. Thus heated iron more quickly gets energy (strength) 
and verticity from the earth in the very process of returning 
to soundness in its renascence, so to speak (wherein it is trans- 

* formated), than when it simply rests in position. This experi- 
ment is best made in winter and in a cold atmosphere, when 
the metal returns more surely to the natural temperature 
than in summer and in warm climates. 1 

Let us see also what position alone, without fire and heat, 
and what mere giving to the iron a direction toward the earth's 
poles may do. Iron bars that for a long time twenty years 

* or more have lain fixed in the north and south position, as 
bars are often fixed in buildings and in glass windows such 
bars, in the lapse of time, acquire verticity, and whether sus- 
pended in air or floated by corks on water turn to the pole 
toward which they used to be directed, and magnetically 
attract and repel iron in equilibrium ; for great is the effect of 
long-continued direction of a body toward the poles. This, 
though made clear by plain experiment, gets confirmation for 
what we find in a letter written in Italian and appended to a 
work by Master Philip Costa, of Mantua, also in Italian, Of 
the Compounding of Antidotes ; which, translated, is as follows: 
"At Mantua, an apothecary showed to me a piece of iron 
completely turned to loadstone, so attracting other iron that it 
might be compared to a loadstone. But this piece of iron, 
after it had for a long time supported a terra-cotta ornament 
on the tower of the Church of San Agostino at Rimini, was at 

1 See John Farrar's "Elem. of Elect, and Magn.," 1826, pages 201, 202. 



EXISTENCE OF VERTICITY IN SMELTED IRON. 21$ 

last bent by the force of the winds and so remained for ten 
years. The friars, wishing to have it restored to its original 
shape, gave it to a blacksmith, and in the smithy Master 
Giulio Cesare, prominent surgeon, discovered that it resembled 
loadstone and attracted iron. The effect was produced by 
long-continued lying in the direction of the poles. 1 It is well, 
therefore, to recall what has already been laid down with 
regard to alteration of verticity, viz., how that the poles of 
iron bars are changed when a loadstone simply presents its 
pole to them and faces them even from some distance. Surely 
in a like way does that great loadstone the earth affect iron 
and change verticity. For albeit the iron does not touch the 
earth's pole nor any magnetic portion of the earth, still the 
verticity is acquired and altered not that the earth's pole, that 
identical point lying thirty-nine degrees of latitude, so great a 
number of miles, away from this City of London, changes the 
verticity, but that the entire deeper magnetic mass of the 
earth which rises between us and the pole, and over which 



1 It is said by Humboldt (Cosmos, 1849, Vol. II, page 718, note) that this 
observation, the first of the kind, was made on the tower of the Church of the 
Augustines at Mantua (Mantova), and that Grimaldi and Gassendi were ac- 
quainted with similar instances (the cross of the Church of Saint Jean, at Aix, 
in Provence), all occurring in geographical latitudes where the inclination of the 
magnetic needle is very considerable. Some writers give Gassendi's observa- 
tion as occurring during 1632. (See Rohaulti, Physica, 1718, Par. Ill, Cap. 8, 
p. 399; or Rohault's "System of Nat. Phil.," 1728, page 176.) 

" As the iron cross of an hundred weight upon the Church of Saint John in 
Ariminum, or that Load-ston'd iron of Csesar Moderatus, set down by Aldro- 
vandus." (Sir Thomas Brown, Pseudoloxia Epidcmica, 1658, page 66.) 

Consult " Lettera dell' Eccel. Cavallara ....," Mantova 1586, for a de- 
tailed account of this discovery, made January 6 of the last-named year. The 
iron rod supported a brick ornament in the form of an acorn, and stood on a 
pyramid at the summit of the belfry of the Church of St. John the Baptist at 
Rimini, belonging to the monks of St. Augustine. See Cabeo, Philos. Magn., 
page 62 ; " Ulysses Aldrovandi, Patr. Bonon. . . .Barthol. Ambros ....," Lib. 
I, Cap. VI, p. 134- 



2l6 WILLIAM GILBERT. 

stands the iron that this, with the energy residing within the 
field of the magnetic force, the matter of the entire orb con- 
spiring, produces verticity in bodies. For everywhere within 
the sphere of the magnetic force does the earth's magnetic 
effluence reign, everywhere does it alter bodies. But those 
bodies that are most like to it and most closely allied, it rules 
and controls, as loadstone and iron. For this reason it is not 
altogether superstitious and silly in many of our affairs and 
businesses to note the positions and configurations of coun- 
tries, the points of the horizon and the locations of the stars. 
For as when the babe is given forth to the light from the 
mother's womb and gains the power of respiration and certain 
animal functions, and as the planets and other heavenly bodies, 
according to their positions in the universe and according to 
their configuration with the horizon and the earth, do then 
impart to the new-comer special and peculiar qualities ; so a 
piece of iron, while it is being wrought and lengthened, is 
affected by the general cause, the earth, to wit ; and while it is 
coming back from the fiery state to its original temperature it 
becomes imbued with a special verticity according to its posi- 
tion. Long bars have sometimes the same verticity at both 
ends, and hence they have a wavering and ill-regulated motion 
on account of their length and of the aforesaid manipulations, 
just as when an iron wire four feet long is rubbed at both ends 
with one same pole of a loadstone. 



ONLY MAGNETIC BODIES IMBUED WITH VERTICITY. 



CHAPTER XIII. 

WHY NO OTHER BODIES SAVE THE MAGNETIC ARE IMBUED 
WITH VERTICITY BY FRICTION WITH A LOADSTONE ; 
AND WHY NO BODY NOT MAGNETIC CAN IMPART AND 
AWAKEN THAT FORCE. 

WOOD floating on water never turns by its own forces 
toward the poles of the world save by chance : so neither 
threads of gold, silver, copper, zinc, lead, nor glass, when 
passed through cork and floated, have ever sure direction ; 
and, therefore, when rubbed with a loadstone they show 
neither poles nor points of variation ; for bodies that do not 
of their own accord turn toward the poles and are not obedi- 
ent to the earth are in no wise governed by the loadstone's 
touch ; neither has the energy of the loadstone entrance into 
their interior, nor are their forms excited magnetically ; nor, if 
the energy did enter in, could it effect aught, for the reason 
that there are no primary qualities in such bodies, mixed as 
they are with a variety of efflorescent humors and degenerate 
from the primal property of the globe. On the other hand the 
properties of iron which are primal are awakened by approach 
of a loadstone: like brute animals and men when awakened 
out of sleep, the properties of iron now move and put forth 
their strength. 

Here we must express wonder at a manifest error of Bap- 
tista Porta, who, though he properly refuses assent to the 
inveterate falsehood about a force the opposite of the mag- 
netic, imparts a still falser opinion, to wit, that iron rubbed 



218 WILLIAM GILBERT. 

with diamond turns to the north. "If," he writes, "we rub an 
iron needle on diamond, and then put it in a boat or on a 
straw or suspend it properly with a thread, at once it turns to 
the north like iron rubbed on a loadstone, or perhaps a little 
more sluggishly. Nay and this is worthy of remark the 
opposite part, like the loadstone itself at its south end, repels 
iron, and when we experimented with a multitude of small 
iron rods in water, they all stood at equal distances apart and 
pointed north." Now this is contrary to our magnetic rules ; 
and hence we made the experiment ourselves with seventy-five 
* diamonds in presence of many witnesses, employing a number 
of iron bars and pieces of wire, manipulating them with the 
greatest care while they floated in water, supported by corks ; 
yet never was it granted me to see the effect mentioned by 
Porta. He was led astray by the verticity of the iron in the 
bars or wires got from the earth (as shown above) ; the iron of 
itself tended toward its determinate pole, and Porta, ignorant 
of this, supposed the thing was done by the diamond. But let 
searchers of the things of nature beware lest they be further 
deluded by their own faultily observed experiments, and lest, 
with errors and blunders, they throw into confusion the repub- 
lic of letters. Diamond (adamas) is sometimes called siderite 
(siderites), not because it is ferruginous or that it attracts iron 
(crtdrfpos, sideros), but on account of its glister, like that of 
shining iron ; this brilliance is possessed by the finest diamonds. 
On account of this confusion of names many effects are cred- 
ited to diamond that in fact belong to the loadstone siderite. 1 

1 See Book I, Chap. II. 



POSITION DOES NOT AFFECT VERTICITY. 2Ip 



CHAPTER XIV. 

THE POSITION OF A LOADSTONE, NOW ABOVE, ANON BENEATH, 
A MAGNETIC BODY SUSPENDED IN EQUILIBRIUM, ALTERS 
NEITHER THE FORCE NOR THE VERTICITY OF THE MAG- 
NETIC BODY. 

THIS point we may not rightly pass by, because we must 
correct an error that has lately arisen out of a faulty observa- 
tion of Baptista Porta ; out of this erroneous judgment, Porta, 
by vain repetition, makes three chapters, viz., the eighth, the 
thirty-first, and the sixty-second. Now, if a loadstone or a 
piece of iron suspended in equilibrium or floating in water is 
attracted or controlled by another piece of iron or another 
loadstone held above it, the stone or the iron does not turn to 
the opposite direction when you apply the second iron or stone 
beneath ; on the contrary, the ends of the floating loadstone or 
of the floating iron will ever turn to the same points of the 
stone, however the loadstone or the iron may be suspended in 
equilibrium or whether they be mounted on a point so that 
they may revolve freely. Porta was led into error by the un- 
even shape of some loadstone or by the fact that he did not 
manage the experiment aright. Thus he is badly mistaken, 
thinking it fair to infer that, as the loadstone has a north and 
a south pole, it has also an east and a west, a superior and an 
inferior, pole. So do many vain imaginations arise out of mis- 
takes committed and accepted as true judgments. 



22O WILLIAM GILBERT. 



CHAPTER XV. 

THE POLES, EQUATOR, CENTRE, ARE PERMANENT AND STABLE 
IN THE UNBROKEN LOADSTONE; WHEN IT IS REDUCED 
IN SIZE AND A PART TAKEN AWAY, THEY VARY AND 
OCCUPY OTHER POSITIONS. 

LET AB be a terrella, E its centre, DF its diameter (and 
also its equinoctial circle). If you cut out a piece (for instance 
along the Arctic circle) 677, it is evident that the pole which 
before was at A now has its seat at /. But the centre and the 




* equinoctial circle recede only toward B, so as always to be in 
the middle of the mass that remains between the plane of the 
Arctic circle 6777 and the Antarctic pole B. Thus the segment 
of the terrella between the plane of the former equinoctial cir- 
cle DEF (that is of the equinoctial circle which existed before 



THE POLES IN BROKEN AND UNBROKEN LOADSTONE. 221 

the part was cut away) and the newly acquired equator MLN 
will always be equal to one half of the part cut off, GIHA. 
But if the part be cut from the side CD then the poles and the* 
axis will not be in the line AB but in EF\ and the axis is 




changed in the same proportion as the equator in the previous 
figure. For these points of forces and of energy, or rather 
these terminals of forces that flow from the entire form, are 
moved forward by change of mass or of figure ; as all these 
points result from the joint action of the whole and of all the 
parts united, and verticity or polarity is not a property innate in 
the part or in any fixed point, but a tendency of the force to 
such part. And as a terrella dug out of the earth has no longer 
the poles and the equator of the earth but special poles and 
equator of its own, so, too, if the terrella be cut in two again, 
these points and distinctions of its forms and powers migrate 
to other parts. But if the loadstone be in any way divided 
either on the parallels or on the meridians so that in conse- 
quence of the change of its shape either the poles or the equator 
migrate to other seats, then if the part that has been cut off 



222 WILLIAM GILBERT. 

be but set in its natural position and conjoined to the rest, 
though they be not cemented or otherwise fastened together, 
the terminal points go back again to the former places as 
though no part of the body had been cut away. When the 
body is whole the form remains whole ; but when the mass of 
the body is reduced, a new whole results, and a new wholeness 
necessarily arises in each minutest piece of loadstone, even in 
magnetic gravel and fine sand. 



CHAPTER XVI. 

IF THE SOUTH PART OF A LOADSTONE HAVE A PART BROKEN 
OFF, SOMEWHAT OF POWER IS TAKEN AWAY FROM THE 
NORTH PART ALSO. 

FOR though the south part of magnetic iron is attracted by 
the north part of the loadstone, still the south part of the stone 
does not reduce but increases the power of the north part. 
Hence if a loadstone be cut and divided at the Arctic circle, 
or at the tropic of Cancer, or at the equator, the south part 
does not so powerfully attract at its pole as before ; for a new 
'whole arises and the equator leaves its former place and ad- 
vances poleward, because of the division of the stone. In the 
former state, inasmuch as the opposite part of the stone be- 
yond the plane of the equator increases the mass, it also 
strengthens the verticity and the force and the movement 
toward unition. 



ROTARY NEEDLES AND THEIR ADVANTAGES. 22$ 



CHAPTER XVII. 

OF THE USE OF ROTARY NEEDLES AND THEIR ADVANTAGES ; 
HOW THE DIRECTIVE IRON ROTARY NEEDLES OF SUN- 
DAILS AND THE NEEDLES OF THE MARINER'S COMPASS 
ARE TO BE RUBBED WITH LOADSTONE IN ORDER TO 
ACQUIRE STRONGER VERTICITY. 

MAGNETIZED versoriums (or magnetized rotary needles) 
serve so many purposes in the life of man, that it will not be 
out of place to show the best process for rubbing and magnet- 
ically exciting them and the proper method of applying the 
process. With the aid of a small bar of iron magnetically pre- 
pared and suspended in equilibrium, rich iron ores and those 
containing most metal are recognized, and magnetic stones, 
clays, and earths, whether crude or prepared, are distinguished. 
A little iron bar that soul of the mariner's compass, that 
wonderful director in sea- voyages, that finger of God, so to 
speak points the way and has made known the whole circle 
of earth, unknown for so many ages. Spaniards (and English- 
men too) have again and again circumnavigated the whole 
globe on a vast circle by the help of the mariner's compass. 
They who travel on land or who remain at home have sun-dial 
horologes. The magnetic needle pursues and searches for 
veins of iron in mines : with its help mines are driven when 
cities are besieged ; cannons and military engines are trained 
at night in the desired directions. The needle is of use for to- 
pography, for determining the areas and position of buildings, 
and in constructing underground aqueducts. On it depend 



224 WILLIAM GILBERT. 

the instruments invented for investigating its own dip and its 
own variation. When iron is to be quickened by the loadstone, 
let it be clean and neat, not disfigured by rust or dirt, and have 
it of the best steel. Let the stone be wiped dry so that there 
shall be no moisture, and scrape it gently with some well- 
polished iron tool. But beating it with a hammer is of no 
avail. And let the naked iron be applied to the naked stone 
and rubbed at it in such a way that they may come into closer 
contact not in order that the corporeal matter of the stone 
may be joined to the stone and stick to it, but the two are 
slightly worn away by the friction, and (useless parts being 
ground off) are united closely : hence arises in the excited iron 
a grander force. In the figure, A shows the best mode of ap- 
plying the versorium to the stone its point touches the pole 
and is directed toward the pole B is a passable mode, for 
though it is at a little distance from the pole it is directed 




toward it ; so, too, C is only a passable mode, the point being 
turned away from the pole ; D is a worse mode on account of 
the greater distance from the pole ; F is a bad mode because 
it lies on a parallel across the stone ; the magnetic needle L 



ROTARY NEEDLES AND THEIR ADVANTAGES. 22 5 

that is rubbed on the equator is of no value and plainly is neg- 
ative and forceless ; the oblique indirect mode G and the 
oblique indirect averse H are both bad. 

The purpose of all this is to show the different powers of a 
globular loadstone. But the artificers often use a stone rather 
tending toward the conical form, and, therefore, more power- 
ful, its topmost projection being the pole, at which they rub 
the needles. Sometimes, also, the stone has at the top and 
above the very pole an artificial cap or snout of steel to give 
more strength ; on this cap iron versoriums are rubbed, and 
thereafter they turn to that same pole as though they had been 
magnetized at that part without the cap. 

The stone should be of good size and strong ; the versorium, 
even if it be long, must be pretty thick, not too thin, with 
moderate-sized point, not too sharp, though the energy is not 
in the point itself but in the whole needle. Any powerful, 
large loadstone serves well for rubbing versoriums, though 
sometimes, owing to its powerfulness, it causes, when the 
needle is long, some dip and perturbation, so that the needle, 
that before friction stood in equilibrium in the plane of the 
horizon, now, after friction and excitation, dips with one end 
as low as the fulcrum on which it is supported permits. Hence 
in the case of a long versorium the end that is to be north 
should be, before friction, a little lighter than the other end, so 
that it may remain in exact equipoise after friction. But a 
versorium so prepared performs its function poorly at any con- , 
siderable distance from the equinoctial circle. 

When the versorium has been magnetized, put it back in 
its box, and do not let it come in contact with other magnetic 
bodies, nor remain in close neighborhood with them, lest it 
become unsteady and sluggish through the action of opposite 
forces, whether potent or feeble. And if you rub the other 



226 WILLIAM GILBERT. 

end of the needle at the opposite pole of the stone, the needle 
will act with more steadiness, especially if it be rather long. 
Iron rubbed with loadstone keeps constant and strong, even 
for several centuries, the magnetic power awakened in it, if it 
be laid in the natural position, meridionally, not on a parallel, 
and is not spoilt by rust or any external ill coming from the 
ambient medium. 

Porta seeks amiss a ratio between loadstone and iron : a 
small mass of iron, saith he, cannot hold a great measure 
of power, for it is wasted by the mighty energy of the load- 
stone. Clearly, the iron takes to the full its own virtue, though 
it weigh only one scruple and the mass of the loadstone more 
than 100 Ibs. It is vain also to make the versorium rather flat 
at the end that is rubbed in order that it may become a better 
and stronger magnetic body, and that it may better seize and 
hold certain magnetic particles, but few of which can adhere 
to a sharp point ; for it was Porta's belief that the energy is 
transmitted and retained by adhesion of particles of the load- 
stone, like hairs, whereas these particles are simply scrapings 
detached by the iron from the softer stone ; besides, the mag- 
netized iron points steadily north and south if, after friction, it 
be scoured with sand or emery or other material, and even 
though by long-continued friction its outer parts be ground 
down and worn away. In stroking the loadstone with a ver- 
sorium each stroke should terminate at one end of the verso- 
rium, else, if the stroke is made toward the middle, a less degree 
of verticity, or none at all, or very little, is excited in the iron. 
For where the contact ends there is the pole and the point 
of verticity. To produce stronger verticity in iron by friction 
* with a loadstone, it is necessary in northern latitudes to turn the 
loadstone's true north pole toward the zenith; on such pole 
that end of the versorium is to be rubbed which afterward will 



ROTARY NEEDLES AND THEIR ADVANTAGES. 22/ 

turn to the earth's north ; the other end of the versorium must 
be rubbed on'the south pole of the terrella turned toward the 
earth ; so excited, it will incline to the south. In southern 
latitudes, below the equator, the case is different, and the cause 
of the difference is given in Book II, Chap. 34, where is shown 
(by means of a combination of earth and terrella) why the poles 
of a loadstone are, for diverse reasons, one stronger than the 
other. 

If between the ends of two loadstones in conjunction and ! 
equal in power, shape, and mass, you rub a versorium, it 




acquires no property. A, B are two loadstones conjoined nat- 
urally at ; their opposite ends ; 7, the point of a versorium, * 
touched simultaneously by both, is not excited, if the load- 
stones be equal (though the loadstones are connected with it 
in the natural way); but if the loadstones be unequal, force is 
gained from the stronger. 

In magnetizing a versorium with a loadstone begin at its 
middle and so draw it over the stone that one end quits the 
stone last ; finally let the application be continued by a gentle 
stroking of the stone with the end of the needle for a while, 
say one or two minutes. The movement from middle to end 
must not, as is the wont, be repeated, for so the verticity is 
spoilt. Some delay is needed, for though the energy is infused 
and the iron is excited instantaneously, still the verticity is 



228. WILLIAM GILBERT. 

more steady and endures more surely in the iron when the ver- 
sorium is left near the loadstone and abandoned at rest for a 
proper length of time ; although an armed stone lifts a greater 
weight of iron than an unarmed, still a versorium is not more 
powerfully magnetized by the armed than by the unarmed 
stone. Take two pieces of iron wire, of equal length, cut off 
the same coil of wire, and let one be excited by the armed end, 
the other by the unarmed end : it will be found that they begin 
to move and make a perceptible inclination toward the load- 
stone at the same distances : this can be ascertained by meas- 
urement with a long rod. But objects powerfully excited turn 
quickly to the pole, those that are feebly excited turn slowly 
and only when brought nearer : the experiment is made in 
water with corks of equal size. 





BOOK IV. 



CHAPTER I. 



OF VARIATION. 

So far we have been treating of direction as if there were 
no such thing as variation ; for we chose to have variation left 
out and disregarded in the foregoing natural history, just as if 
in a perfect and absolutely spherical terrestrial globe variation 
could not exist. But inasmuch as the magnetic direction of 
the earth, through some fault and flaw, does depart from the 
right track and the meridian, the occult and hidden cause o( 
variance which has troubled and tormented, but to none effect, 
the minds of many has to be brought to light by us and 
demonstrated. They who hitherto have written of the mag- 
netic movements have recognized no difference between direc- 
tion and variation, but hold that there is one only movement 
of the magnetized needle. But the true direction is a move- 
ment of the magnetic body to the true meridian, and continu- 

229 



230 WILLIAM GILBERT. 

ance therein, with the ends pointing to the respective poles. 
Yet very oft it happens, afloat and ashore, that a magnetic 
needle does not look toward the true pole, but is drawn to a 
point in the horizon nigh to the meridian, and that there is a 
deflection not only of the needle and magnetized iron in gen- 
eral and of the mariner's compass, but also of a terrella on its 

* float, of iron ore and ironstone, and of magnetic clays artifi- 
cially treated ; for they often look with their poles toward 
points different from the meridian. The variation, then, as 
observed with the aid of instruments or of the mariner's com- 
pass, is an arc of the horizon between the intersection of the 
horizon by the meridian and the term of the deflection on the 
horizon, or the range of deviation of the magnetized body. 
This arc varies and is different according to locality. 1 So the 
terminus of the variation is commonly assigned to a great circle 
the circle of variation, as it is called and a magnetic merid- 
ian passing through the zenith and the point of variation on 
the horizon. 

In northern terrestrial latitudes this variation takes place 
either in the direction from north toward east, or from north 
toward west ; in southern latitudes, in like manner, it is from 
south toward east, or south toward west. Hence in northern 

latitudes we must heed the end of the needle that tends north, 
and in southern latitudes the end looking south : this naviga- 



1 Gilbert defines variation to be the arc intersected between the point 
where the meridian of the place cuts the horizon and that point to which the 
magnetic needle looks ; the length of this arc varying with the place of observa- 
tion." ("Nature " for April 27, 1876, page 523.) The variation is now known 
by scientific writers as the declination. As expressed by Commander A. W. 
Greely, "declination is the variation of the magnetic meridian from the geo- 
graphical meridian. It is measured by the angle between the two meridians, 
and is expressed in degrees of azimuth from zero either to the east or to the west 
of the true north. When the magnetic north is west of the true north it is west 
declination, and east when the reverse occurs." 



VARIATION. 231 

tors and sciolists seldom understand, for on both sides of the 
equator they note only the north point terminal of the com- 
pass, or the one that looks north. As we have already said, 
every movement of loadstone and needle, every turn and dip, 
and their standing still, are effects of the magnetic bodies 
themselves and of the earth, mother of all, which is the fount 
and source and producer of all these forces and properties. 
Thus, then, the earth is the cause of this variation and ten- 
dence to a different point in the horizon ; but we have to 
inquire further how and by what potencies it acts. 

Here we must first reject the common opinion of modern 
writers concerning magnetic mountains or a certain magnetic 
rock or a distant phantom pole of the world controlling the 
movement of the compass or of the versorium. This opinion 
Fracastorio adopted and developed after it had been broached 
by others ; but it does not agree with the experiments at all. 
For, if it were correct, in different places on land and sea the 
variation point would in geometrical ratio change to east or to 
west, and the versorium would always regard the magnetic 
pole; but experience teaches that there is no determinate 
pole, no fixed terminus of variation in the globe. For the arc 
of variation changes in different ways erratically, so that in* 
different meridians and even in the same meridian, and when, 
according to the opinion of recent writers, the magnetized 
needle would deviate toward east, suddenly, on a trifling 
change of place, it goes from north toward west, as -in the 
northern regions near Nova Zemlya (Nova Zembla). 1 In 
southern latitudes also, and at sea, far away from the equator 
and toward the Antarctic, and not in northern latitudes near 
those magnetic mountains, is variation frequent and great. 

1 See Book IV, Chap. XVI. 



232 WILLIAM GILBERT. 

But still more vain and silly are the imaginations of other 
writers Cortesius, for example, who speaks of a motive force 
beyond the farthest heavens ; Marsilius of Ficino, who finds 
the cause of variation in a star of Ursa ; Petrus Peregrinus, 
who finds it in the pole of the world ; Cardan, referring it to 
the rising of a star in the tail of Ursa ; the Frenchman Bessard, 
to the pole of the zodiac ; Livius Sanutus, to a certain mag- 
netic meridian ; Franciscus Maurolycus, to a magnetic island ; 
Scaliger, to the heavens and to mountains ; the Englishman 
Robert Norman, to the "respective point." 1 

Quitting, therefore, those opinions that are at odds with 
every-day experience, or that at least are by no means proven, 
let us look for the true cause of variation. The Great Load- 
stone, or the terrestrial globe, gives, as I have said, to iron a 
north and south direction ; magnetized iron readily conforms 
itself to those points. But as the globe of earth is at its sur- 
face broken and uneven, marred by matters of diverse nature, 
and hath elevated and convex parts that rise to the height of 
some miles and that are uniform neither in matter nor in con- 
stitution but opposite and different, it comes about that this 
entire earth-energy turns magnetic bodies at its periphery 
toward stronger massive magnetic parts that are more power- 
ful and that stand above the general level. Wherefore at the 
outmost superficies of the earth magnetic bodies are turned a 
little away from the true meridian. And since the earth's sur- 
face is diversified by elevations of land and depths of seas, 
great continental lands, ocean, and seas differing in every 
way, while the force that produces all magnetic movements 
comes from the constant magnetic earth-substance, which is 
strongest in the most massive continent and not where the 

i See Book I, Chap. I; Book III, Chap. I; Book IV, Chap. VI. 



VARIA TION. 233 

surface is water or fluid or unsettled, it follows that toward a 
massive body of land or continent rising to some height in any 
meridian (passing whether through islands or seas) there is a 
measurable magnetic leaning from the true pole toward east or 
west, i.e., toward the more powerful or higher and more ele- 
vated magnetic part of the earth's globe. 1 For as the earth's 
diameter is more than 1700 German miles, these continents 
may rise above the general superficies to a height equal to the 
depth of the ocean bed, or more than four miles, and yet the 
earth keep the spherical shape, albeit slightly uneven at the 
top. For this reason a magnetic body under the action of the 
whole earth is attracted toward a great elevated mass of land 
as toward a stronger body, so far as the perturbed verticity 
permits or abdicates its right. Yet the variation takes place 
not so much because of these elevated but less perfect parts of 
the earth and these continental lands, as because of the inequal- 
ity of the magnetic globe and of the true earth-substance which 
projects farther in continents than beneath sea-depths. We 
have therefore to inquire how the demonstration of this new 
natural philosophy may be drawn from unquestionable experi- 
ments. 

From the coast of Guinea to Cape Verde, the Canaries, and 
the frontier of the empire of Morocco, thence along the 

1 Gilbert "refers the curvatures of the isogonic lines to the configuration 
of continents and the relative positions of sea basins, which possess a weaker 
magnetic force than the solid masses rising above the ocean." He considers 
" that the inflections of the lines of equal declination and inclination depend 
upon the distribution of mass, the configuration of continents, or the form and 
extent of the deep intervening oceanic basins. It is difficult to connect the 
periodic variations which characterize the three principal forms of magnetic 
phenomena (the isoclinal, isogonic, and isodynamic lines) with this rigid sys- 
tem of the distribution of force and mass, unless we represent to ourselves the 
attractive force of the material particles modified by similar periodic changes of 
temperature in the interior of the terrestrial planet." (" Cosmos," 1849, Vol. I, 
page 170; Vol. II, pages 717, 718.) 



234 WILLIAM GILBERT. 

coasts of Spain, France, England, Holland, Germany, Den- 
mark, Norway, the land on the right and to the east is all 
continent, vast regions forming one mass ; on the left, immense 
seas and the mighty ocean extend far and wide: now we 
should expect that (as has in fact been observed by diligent 
investigators) magnetic bodies would deflect a little eastward 
from the true pole toward those more powerful and extraordi- 
nary elevations of the terrestrial globe. Very different is the 
case on the east coasts of North America, for, from the region 
of Florida through Virginia and Norumbega ' to Cape Race 
and away to the north, the needle turns to the west. But in 
the mid spaces, so to speak, for example in the western 
Azores, it regards the true pole. 2 But it is not on account of 
that meridian or of the coincidence of the meridian with any 
magnetic pole, as the philosophastric crew suppose, that a 
magnetic body turns in like manner to the same regions of the 
world ; neither does the variation take place along the entire 

* meridian, for on the same meridian near Brazil the case is very 
different, as later we will show. 

Other things equal, variation is less along the equator, 
greater in high latitude, save quite nigh the very pole. 

* Hence it is greater off the coast of Norway and Holland than 
off Morocco or Guinea ; greater, too, at Cape Race than in the 

1 Norumbega, "the lost city of New England," was called Arambec, or 
"Arambe" in 1523, " Aranbega " in 1529, " Norumbega" in 1539, and, sub- 
sequently, " Norumbdega," " Narembegue." Norumbega, in the Indian 
tongue, means the place of a fine city. Its site was indicated as on the bank of 
the Penobscot, the province of that name extending from the Kennebec River 
to the St. Croix River in that section of the country which afterwards became 
the State of Maine. (See " Magazine of Am. Hist." for 1877, pages 14, 321, 
and for 1886, page 291, " New England's lost city found "; also, " Antiquitates 
Americans," Roy. Soc. of Copenhagen; Lang's "Sagas of the Kings of 
Norway; Shea's "Catholic Church in Colonial Days;" Horsford, "Cabot's 
Landfall in 1497 and the site of Norumbega.") 

2 Humboldt, "Cosmos," London 1849, Vol. I, page 175, note. 



VARIATION IS DUE TO EARTH'S ELEVATIONS. 2$$ 

ports of Norumbega or of Virginia. In the Guinea littoral, 
the magnetized needle inclines to the east one-third part of a 
point ; in the Cape Verde Islands two thirds ; in England, at 
the mouth of the Thames, one point : the higher the latitude 
the stronger the moving force, and the masses of land toward 
the pole exert most influence : all this is easily seen in a ter- 
rella. For just as, when the direction is true, magnetic bodies 
tend toward the pole (i.e., the greater force and the entire earth 
co-operating), so do they tend a little toward the more power- 
ful elevated parts under the action of the whole and in virtue 
of the concurrent action of their iron. 1 



CHAPTER II. 

THAT VARIATION IS DUE TO INEQUALITY AMONG THE 
EARTH'S ELEVATIONS. 

THIS very thing is clearly demonstrated on the terrella 
thus : take a spherical loadstone imperfect in any part or de- 
cayed (I once had such a stone crumbled away at a part of its 
surface and so having a depression comparable to the Atlantic 
sea or great ocean); lay on it bits of iron wire two barley- 
corns in length, as in the figure. AB is a terrella imperfect in 
parts and of unequal power on the circumference ; the needles 
, F do not vary but regard the pole straight, for they are 
placed in the middle of the sound and strong part of the ter- 
rella at a distance from the decayed part : the surface that is 

1 Ath. Kircheri, Magnes ; si-ve de arte magnetica, 1643, Lib. II, Pars. V, page 
410. 



236 



WILLIAM GILBERT. 



dotted and that is marked with cross-lines is weaker. Neither 
does the needle O vary because it is in the middle line of the 
decayed part, but turns to the pole just as off the western 
Azores. H and L vary, for they incline toward the sound 




parts. And as this is shown on a terrella whose surface has 
sensible imperfections, so, too, in terrellas that are whole and 
perfect, for often one part of a stone is of greater strength on 
the outside than another, though no difference is plain to 
sense. With such a terrella variation is demonstrated and the 
* strong points are discovered in the following way : Here A is 
the pole, B the place of variation, C the more powerful region. 
The horizontal needle at B varies from the pole 7-ward. So 
is the variation shown and the regions of greater force recog- 
nized. The more powerful surface is found also by means of 
a slender iron wire two barley-corns long : for though it will 
stand upright on the pole of the terrella and in other parts 



VARIATION IS DUE TO EARTH'S ELEVATIONS. 

will lean toward the equator, still if on the same parallel circle 
it stands more nearly erect at one point than at another, the 
terrella's surface has more power where the needle is the more 




erect ; and also when a piece of iron wire laid on the pole in- 
clines more to one side than the other. For experiment take * 




a piece of iron wire three finger-widths long, resting on the 
pole A so that its middle lies over the pole. One of the ends 
turns toward C and will not rest in position toward B ; yet, in 
a terrella that is flawless and even all over, it will be at rest on 



2 3 8 



WILLIAM GILBERT. 



the pole no matter toward what point of the equator it be 
* directed. Or make another experiment : Suppose two merid- 
ians meeting at the poles A, B in equal arcs DA and CA ; at 




their extremities D, and C, let pieces of iron wire be reared : at 
D (which is the region of greater force) the wire will be reared 
more near perpendicular than at C, the region of less force. 
Thus can we discern the stronger and more powerful part of a 
loadstone, else not recognizable by the senses. In a terrella 
that is perfect, even, and alike in all its parts, there is at equal 
distances from the pole no variation. 

Variation may be shown by means of a terrella having a 




H 



onsiderable part of its surface projecting a little above the 
rest : such terrella, though not decayed nor spoilt, attracts out 



VARIATION IS DUE TO EARTH'S ELEVATIONS. 239 

of the true direction, its whole mass operating. The figure 
shows a terrella with uneven surface. The demonstration is * 
made with small bars or short needles placed on the terrella : 
they turn from the terrella toward the projecting mass and 
the great eminences. In this way is verticity disturbed on the 
earth by the great continents which mostly rise above the 
beds of the seas and which at times cause the needle to devi- 




ate from the straight track, i.e., from the true meridian. The 
tip of the versorium A does not point toward the pole P if 
there be a large projection B on the terrella ; so, too, the 
point C varies from the pole because of the projection F. 
Midway between the two eminences, the needle G points to 
the true pole, because, being equidistant from both projections 
B and F, it deviates to neither but keeps the true meridian. 



2 4O WILLIAM GILBERT. 

particularly when the energy of the projections is equal. But 
elsewhere, at N, the needle varies from the pole M toward the 
eminence H, nor is hindered nor stayed nor checked by the 
small eminence D on the terrella, which is like some island of 
the earth in the ocean. But L unhindered tends poleward. 

In another mode may variation be shown, whether in a 
terrella or on the earth. Let A be the earth's pole ; B its 
equator ; C a parallel circle at latitude 30 degrees ; D an emi- 
nence reaching poleward ; E another eminence stretching from 
the pole equatorward. Evidently the versorium F in the 
middle line of D does not vary ; but G deflects very much, C 
very little as being more remote from D. So, too, the needle 
/, placed directly toward E, does not deflect from the pole : 
but L and M turn from the pole toward the eminence E. 



CHAPTER III. 

VARIATION IS CONSTANT AT A MIVEN PLACE. 1 

As the needle hath ever inclined toward east or toward 
west, so even now does the arc of variation continue to be the 
same in whatever place or region, be it sea or continent ; so, 

1 Henry Gellibrand, English mathematician, professor of geometry at 
Gresham College, discovered, 1633-1635, the secular variation of the declination. 
In the words of Dr. Whewell (" Hist, of the Ind. Sciences," 1859, Vol. II, page 
219) : " Gellibrand discovered that the variation is not constant, as Gilbert im- 
agined, but that in London it had diminished from eleven degrees east in 1580 
to four degrees in 1633. Since that time the variation has become more and 
more westerly; it is now about twenty-five degrees west, and the needle is sup- 
posed to have begun to travel eastward again. 

It may be added that the diurnal -variation was subsequently found by 
George Graham, during the year 1722, whilst the annual variation was made 
known by Jean Jacques Dominique Cassini between 1782 and 1791. 



VARIATION IS CONSTANT AT A GIVEN PLACE. 24! 

too, will it be forevermore unchanging, save there should be a 
great break-up of a continent and annihilation of countries, as 
of the region Atlantis, whereof Plato and ancient writers telL 
The constancy of the variation and the regard of the verso- 
rium toward a fixed point of the horizon in each region is 
shown by laying a very small versorium on a terrella of uneven 
surface : the needle always diverges from the meridian over 
an equal arc. It is shown also by the inclination of the needle 
toward a second loadstone, though in truth this is done by a 
changed direction of all within the earth and the terrella. 
Lay upon a plane surface a versorium with its point looking 




toward A, north ; bring alongside the loadstone B, at such 
distance as to make the versorium turn to C and no further. 
Move the needle of the versorium as often as you will (yet 
without stirring either its case or the loadstone) and the 
needle will ever surely return to the point C. Thus if you so 
hold the stone as to make the needle turn to E, its point ever 
returns to E and not to any other point of the compass. Just 
so, by reason of the position of countries and the differing 
nature of the uppermost parts of the earth's globe (certain 
more magnetic projections of the terrestrial sphere prevailing), 



242 WILLIAM GILBERT. 

variation is ever fixed in a given place, but it differs and is 
unequal between one place and another, for the true and polar 
direction, having its birth in the entire globe of earth, is 
slightly diverted toward particular eminences of great mag- 
netic force on the broken surface. 



CHAPTER IV. 

THE ARC OF VARIATION DOES NOT DIFFER ACCORDING TO 
DISTANCE BETWEEN PLACES. 

ON the broad ocean, while a ship is borne by favoring wind 
along the same parallel, if the variation be reduced just one 
degree in a voyage of 100 miles, it does not follow that the 
next IOO miles will reduce it another degree. For the needle 
varies according to the position and conformation of the land 
and the magnetic force ; also according to distance. For 
example, when a ship from the Scilly Islands bound for New- 
foundland has proceeded so far that the compass points to 
the true magnetic pole, then, as she sails on, the borrholybic 
variation begins, but faintly and with small divergence. But 
after a while the arc increases in a higher ratio as equal distances 
are traversed, till the ship comes nigh the continent, when the 
variation is very great. Yet before she comes quite to land 
or enters port, while at some distance away, the arc is again 
lessened a little. But if the ship in her course departs much 
*from that parallel, either to north or south, the needle will 
vary more or less according to the position of the land and the 
latitude of the region ; for, other things equal, the higher the 
latitude the greater the variation. 



VARIATION NOT ALTERED BY AN OCEAN ISLAND. 243 



CHAPTER V. 

AN ISLAND IN OCEAN DOES NOT ALTER THE VARIATION ; 
NEITHER DO MINES OF LOADSTONE. 

ISLANDS, albeit they are more magnetic than the seas, still 
do not alter magnetic direction nor variation. For direction 
being a movement produced by the energy of the entire earth, 
and not due to the attractive force of any prominence but to 
the controlling power and verticity of the whole mass, there- 
fore variation (which is a perturbation of the directive force), 
is a wandering from the true verticity and arises out of the 
great inequalities of the earth, by reason of which the earth 
itself, when very large and powerful magnetic bodies are 
present, has but little power of turning away magnetic bodies 
that revolve freely. As for the wonders that some do 
report about the Island Elba : loadstones do there abound, 
but, nevertheless, the versorium (or the mariner's compass) 
makes no special inclination toward it when ships sail by in the 
Tyrrhenian Sea. 1 The reasons already given sufficiently 
account for this ; but, furthermore, a reason may be found 
in the fact that the energy of minor loadstones reaches of it- 
self but little beyond their own site ; for variation is not pro- 
duced by a pulling to, as they would make it who have 
thought out magnetic poles. Besides, mines of loadstone are 
only agnate, not innate, in the true earth-substance, and, there- 
fore, the globe as a whole does not heed them ; neither are 
magnetic bodies borne toward them, as is proved in the dia- 
gram of prominences. 

1 See note relative to Elba, Book I, Chap. VIII. 



244 WILLIAM GILBERT. 



CHAPTER VI. 

THAT VARIATION AND DIRECTION ARE PRODUCED BY THE 
CONTROLLING FORCE OF THE EARTH AND THE ROTA- 
TORY MAGNETIC NATURE, NOT BY AN ATTRACTION OR A 
COITION, OR BY OTHER OCCULT CAUSE. 

INASMUCH as the loadstone is deemed by the philoso- 
phizers of the vulgar sort to seize and snatch objects away, as it 
were, and pretenders to science have, in fact, noticed no other 
properties save this much-lauded force of attraction, therefore 
they have supposed that the whole movement to north and 
south is produced by some natural force soliciting bodies. But 
the Englishman Robert Norman first strove to show that this 
is not done by attraction ; he, therefore, originated the idea 
of the " respective point " looking, as it were, toward hidden 
principles, and held that toward this the magnetized needle 
ever turns, and not toward any attractional point ; but he was 
greatly in error, albeit he exploded the ancient false opinion 
about attraction. Norman proves his theory as follows : Take 
a round vessel full of water ; on the mid surface of the water 
float a small bit of iron wire supported by just so much cork 
as will keep it afloat while the water is in equilibrium ; the 
wire must have been first magnetized so as to show plainly the 
variation point D. Let it remain in the water for a while. 
Clearly the wire with its cork does not move toward the rim 
D of the vessel, as it would do if attraction came to the iron 
from D y and the cork would move from its place. This asser- 
tion of the Englishman Robert Norman is demonstrable, and 



VARIA TION AND DIRECTION. 245 

it does seem to do away with attraction, inasmuch as the iron 
remains in the still water both in the direction toward the 
very pole (if the direction be true) and in variation and irreg- 
ular direction ; and it revolves on its iron centre, and is not 
borne toward the vessel's rim. Yet the direction is not pro- 
duced by attraction, but by a disposing and conversory power 




existing in the earth as a whole, not in a pole or any attra- 
hent part of the stone, neither in any mass projecting beyond 
the circle of the periphery, so that the variation should result 
because of the attraction of that mass. Besides, the directive 
force of the stone and of iron, and their natural power of re- 
volving on their centre, produce the movement of direction and 
of collimation, in which is included also the motion of dip or 
inclination (declinationis). Nor does the earth's pole attract as 
though the force of the globe resided in the pole only : the 
magnetic force exists in the whole, but in the pole it is pre- 
eminent and surpassing. Therefore that the cork abides 
quietly in the midst, and that the magnetic needle does not 
move toward the rim of the vessel, is a fact in accord and 
agreement with the loadstone's nature, as is shown with the 
aid of a terrella. Here a little iron bar, placed on the stone at* 



246 WILLIAM GILBERT. 

C, clings there, nor is it pulled farther away by the pole A or 
by the parts near the pole. So, too, it continues at D and 
takes direction toward the pole A y but it sticks at D, and dips 




also toward D in virtue of its power of rotation whereby it 
conforms itself to the terrella. On this point we shall treat 
further when we consider inclination or the dip of the com- 
pass. 



CHAPTER VII. 

WHY THE VARIATION DUE TO THIS LATERAL CAUSE IS NOT 
GREATER THAN HITHERTO IT HAS BEEN OBSERVED TO 
BE, SELDOM APPEARING TO AMOUNT TO TWO POINTS 
OF THE COMPASS, EXCEPT NEAR THE POLE. 

THE earth, by reason of lateral elevations of the more 
energic globe, causes iron and loadstone to diverge a few 
degrees from the true pole or true meridian. For example, 
here in England, at London, it varies \\\ degrees; in some 
other places the variation is somewhat greater, yet in no region 
does the end of the needle diverge very many degrees more 
from the meridian. 1 For as the needle always gets its direction 

1 Consult Cabeo, Philos. Magn., Ferrara 1629, Lib. I, Cap. XVI. 



WHY VARIATION IS NOT GREATER THAN HITHERTO. 



from the true verticity of the earth, so the polar nature of a 
continent tends poleward, even 
as does that of the whole globe 
of earth ; and though the mass of 
a continent may turn magnetic 
bodies away from the meridian, 
still the verticity of that same 
land (as of the whole earth also) 
controls and directs those bodies 
so that they shall not turn east- 
ward in too large an arc. It were 
not easy to determine according 
to any general method how great 
the arc of variation is in every 
place, nor how many degrees and 
minutes it covers on the horizon, 
because it becomes greater or 
less according to divers causes. 
For we must take account of 
the force of true verticity of 
each place and of the elevated 
regions, also of the distances 
of those regions from the place 
under consideration and from the 
world's poles ; and these distances 
are to be compared a thing that 
cannot be done with precision. 
Still, by our method, the variation 
is ascertained in such way that no 
serious error is left to perturb the 
course of a sea-voyage. Were the 
positions of masses of land uniform, if the land lay on a 




WILLIAM GILBERT. 

meridian line, and did not present a broken and indented 
contour, the variations near the land would be without com- 
plexity, as in the figure. 

This is demonstrated with the aid of a long loadstone 
whose poles are at the ends A, B: the middle of the load- 
stone and the equinoctial is CD ; and the lines GH and EF 
are meridians on which are arranged versoriums, the deviations 
of which are greater the greater their distance from the 
equator. But the inequalities of the seaboard parts of the 
habitable globe, the great promontories, the wide gulfs, the 
mountainous and the more elevated regions, and the more 
uneven and precipitous regions make the variations more 
difficult of determination, and in high latitudes less certain 
and more irregular. 



CHAPTER VIII. 

OF THE CONSTRUCTION OF THE COMMON MARINER'S COM- 
PASS, AND OF THE DIFFERENT COMPASSES OF VARIOUS 
NATIONS. 

IN a round wooden box (bowl), having its top covered over 
with glass, a fly-card (versorium) rests on a pretty long pin 
fixed in the middle. The glass cover keeps out wind and 
draughts of air produced by outer causes. All that is within can 
be distinctly seen through the glass. The versorium (rotating 
part) is circular, made of light material, as pasteboard, to the 
under side of which is attached the magnetized iron or needle. 
On the upper side 32 spaces (points as they are called) are 
distributed to as many mathematical intervals in the horizon, 



THE CONSTRUCTION OF COMPASSES. 249 

or winds, which are distinguished by certain marks and by a 
lily (fleur-de-lis) indicating the north. The compass-box is 
suspended in equilibrium in the plane of the horizon, within a 
ring of brass, which is also pivoted (equilibrated) in another 
ring suspended in a roomy stand, a leaden weight being 
attached to the box so that it shall remain in the plane of the 
horizon though the ship may be tossed by the sea in all direc- 
tions. There are either two magnetized-iron bars (with ends 
united) or one piece of a rather oval shape with the ends pro- 
jecting : this style is the surer and quicker of the two in 
performing its function. 1 This is to be so fitted to the paste- 
board disk (or card of the compass) that the centre of the disk 
shall be in the middle of the magnetized iron. But as varia- 
tion begins in the horizon from the point where the meridian 
intersects it at right angles, therefore, on account of the 
variation, instrument-makers in different countries and cities 
inscribe the compass variously, and have different ways of 
attaching the magnetized iron to the card whereon are marked 
the bounds of the 32 spaces or points. 

There are in general use in Europe four different con- 
structions and forms of compass. First, the form adopted 
throughout the Mediterranean, and in Sicily, Genoa, and the 
Venetian republic. In all of these compasses the pieces of 
iron are so attached beneath to the rotating card that (where 

1 This opinion of Gilbert's is not borne out by advanced knowledge of the 
laws of magnetization, which shows that the oval ring needle cannot be trusted 
to for keeping its magnetic axis securely in a constant direction under whatever 
disturbing influence it may be subjected to as does a thin rod or bar. The 
oval form was authoritatively condemned on this account by the British Admi- 
ralty Committee of 1837, who found the theoretical objection amply confirmed 
by experience. They actually found compasses of this pattern, which had been 
in use for some time at sea, presenting errors of as much as three degrees on 
account of the displacement of the magnetization in the substance of the needle. 
(Sir Wm. Thomson, " Good Words " for 1879, page 445.) 



25O WILLIAM GILBERT. 

there is no variation) they turn to the true points of north 
and south. Hence the mark for north, designated by a lily, 
always indicates exactly the point of variation : for the point 
of the lily on the card, together with the ends of the pieces of 
magnetized iron beneath, come to a standstill at the point of 
variation. Another form of compass is that of Dantzic, em- 
ployed in the Baltic Sea and in the Netherlands. Here the 
magnetized iron underneath diverges three fourths of one 
point eastward from the lily ; for a voyage to Russia the 
divergence (recognized difference) is two thirds. But the 
compasses made at Seville, Lisbon, Rochelle, Bordeaux, 
Rouen, as well as throughout all England, have an interval of 
one half of a point. 

Out of these differences have grown very serious errors in 
seafaring and in the science of navigation. For, after the 
directional positions of sea-coasts, of promontories, ports, 
islands, have been found by the aid of the compass, and the 
tides of the seas or the times of full sea have been determined 
from the moon's position above one or another point of the 
compass (as the phrase is), we have still to inquire in what 
country or according to what country's usage the compass 
was constructed by which the directions of said places and the 
times of the marine tides were observed and determined. For 
the mariner, who, using British compass, should follow the 
directions of the Mediterranean marine charts, must needs 
stray far from his true course ; so, one who should use an 
Italian compass in the North Sea, the German Sea, or the 
Baltic, in connection with the marine charts commonly used in 
those parts, would oft stray from the right direction. These 
differences were introduced by reason of the unlike variations, 
that navigators might escape grave errors in those parts of the 
world. Yet Petrus Nonius seeks the meridian with a mariner's 



CAN LONGITUDE BE FOUND FROM VARIATION? 251 

compass or versorium (the Spaniards call it a needle), taking no 
account of variation ; and he brings forward many geometric 
proofs that rest on utterly vicious foundations : for he had 
small acquaintance or experience of things magnetic. In like 
manner Pedro de Medina, who does not accept variation, 1 
has with many errors disgraced the art of navigation. 



CHAPTER IX. 

WHETHER TERRESTRIAL LONGITUDE CAN BE FOUND FROM 

VARIATION. 

THAT were a welcome service to mariners and would 
advance geography very much. But Porta (Book VII, Chap. 
38) is deluded by a vain hope and by a baseless theory. For 
he thinks that, in moving along a meridian, the needle observes 
order and proportion, so that the nearer it is to east the more 
it will deviate eastward, and, according as you advance west, 
the needle takes a westerly direction : all of which is false as 
false can be. Porta thinks he has found a true index of 
longitude ; but he is mistaken. Taking, however, and assum- 
ing for true these premises, he constructs a large compass 
showing degrees and minutes for observing these proportional 
changes of the needle. But his principles are erroneous and 
illogically taken and very poorly studied ; for a versorium does 
not vary more to the east because it is carried to the east ; and 
though in the countries of western Europe and the seas 

1 Pedro de Medina, Arte de Navegar, Valladolid 1545 (Ronalds, page 341). 
Consult Larte del Navegar^ Dottor M. Pietro da Medina, Vinetia 1555, Libro 
Sesto, " Delia Aguggia, over bossolo da navegar," pages cviii-cxvi. 



252 WILLIAM GILBERT. 

adjoining the variation is to the east, and beyond the Azores 
it is changed a little toward the west, nevertheless variation is 
in divers ways ever uncertain, both because of latitude and 
longitude and because of approach to great masses of land, 
also because of the altitude of dominant terrestrial elevation ; 
but it does not follow the rule of any meridian, as we have 
already shown. Livius Sanutus sorely tortures himself and 
his readers with like vanities. As for the opinion of the 
common run of philosophizers and mariners, that the meridian 
which passes through the Azores is the limit of variation, so 
that on the opposite side of that meridian a magnetic body 
will point to the poles exactly as at the Azores an opinion 
held also by Joannes Baptista Benedictus and sundry other 
writers on the art of navigation it is in no wise true. 
Stevinus (quoted by Hugo Grotius), in his Portuum Invenien- 
darum Rationed distinguishes variation according to meridians. 
"In the island Corvo," 2 says he, "the magnetic pointer 
indicates the true north, 3 but the farther one advances thence 
toward the east the more will he see the needle 'easting* 



1 Simon Stevinus, Portuum Investigandorum Ratio, Leyden 1599. This 
was printed in English, the same year, by the celebrated mathematician, 
Edward Wright, who afterwards attached it to the third edition of his " Cer- 
taine errors in navigation detected and corrected" (Engl. Cycl., "Biography," 
Vol. VI, page 834). 

8 Corvo, one of the Azores, the northernmost of the whole group, lying ten 
miles north of Flores. 

3 "The fact that the needle does not point at all places to the true north was 
early known, but the discovery that it changed its direction with a change of 
place is generally attributed to Columbus, This is incorrect, for the needle's 
departure from the geographic meridian (called its variation or declination) is 
marked down for different points of the sea, on the atlas of Andrea Bianco, 
which was made in the year 1436; but what Columbus really did discover was 
a line of no variation 2^ east of the island of Corvo on the I3th of September 
1492" (A. M. Mayer, " The Earth a great Magnet," 1872, page 253). 

See Thomas Brown, Pseudoloxia Epidemica, 1658, Book II, patres 68, 69. 



CAN LONGITUDE BE FOUND FROM VARIATION? 253 



^eiv}, till he comes to within one mile of Plymouth 
on the east, where the variation, reaching maximum, is 13 
deg. 24 min. Then the anatolism (easting) begins to grow 
less as far as Helmshud, which place is not far from North 
Cape in Finmark : there the north is pointed to again. There 
are 60 degrees of longitude between Corvo and Helmshud, 
but the variation is greatest at Plymouth, whose longitude 
is 30 degrees." But though these statements are in part 
true, still along the entire meridian of the island of Corvo the 
compass does by no means point due north. Neither in the 
whole meridian of Plymouth at other places is the variation 
13 deg. 24 min., nor in other parts of the meridian of Helms- 
hud does the needle point to the true pole. For, on the 
meridian passing through Plymouth at lat. 60 deg., the 
north by east variation is greater ; in lat. 40 deg. it is much 
less ; in lat. 20 deg. it is very small indeed. On the meridian 
of Corvo, though the variation near the island is nil, yet 
in lat. 55 deg. the variation north by west is about -J; in lat. 
20 deg. the variation is ^ of a point toward the east. Hence 
the bounds of variation are not properly defined by great 
meridian circles, and far less are the ratios of increase or 
decrease toward a given region of the heavens investigated by 
that method. Therefore the rules of clattumen (declining) or 
auxanomen (increasing), anatolism (easting) or dysism (west- 
ing), cannot possibly be found by that device. The grounds 
of variation in the southern regions of the earth, which 
Stevinus thereafter searches into in the same way, are utterly 
vain and absurd ; they have been put forth by some Portuguese 
mariners, but they do not agree with investigations: equally 
absurd are sundry observations wrongly accepted as correct. 
But the method of rinding the port on long voyages to distant 
parts by means of accurate knowledge of the variation (a 



254 WILLIAM GILBERT. 

method invented by Stevinus and recorded by Grotius) is of 
great importance, if only fit instruments be at hand wherewith 
the deviation may positively be ascertained at sea. 



CHAPTER X. 

WHY IN VARIOUS PLACES NEAR THE POLE THE VARIATIONS 
ARE MUCH AMPLER THAN IN LOWER LATITUDES. 

ON the equator or near it, the variation of a needle is often 
trifling, not unusually it is null. In higher latitudes, as 60, 
70, 80 degrees, the variations are not infrequently very great. 
The reason of this is found partly in the nature of the earth, 
partly in the position of the versorium. The earth causes 
magnetic bodies to rotate and directs them poleward strongly 
at the equator ; at the poles there is no direction, but only fast 
coition of terminals that agree. Hence direction is weaker at 
the poles, because the versorium, by reason of its tendency to 
turn to the pole, dips greatly, and is but feebly directed ; but 
the force of the lands and eminences is strong, with an energy 
proceeding from the entire earth, and, besides, the causes of 
variation are nearer: therefore the versorium deflects more to 
those eminences. It must be known also that the direction of 
a versorium poised on a needle toward the plane of the 
horizon is much stronger at the equator than anywhere else 
by reason of the lie of the versorium ; and in proportion as 
latitude increases the direction is less strong, for at the 
equator the versorium is directed naturally toward the plane 
of the horizon, but in other places it is forced to be in equilib- 



CARDAN'S ERROR. 2$$ 

rium and remains in equilibrium because of an external force : 
by its nature it dips under the horizon as the latitude in- 
creases, as will be shown in the Book on Inclination or Dip. 
Wherefore direction becomes weaker and at the pole itself is 
null. For this reason a weak direction is easily overcome by 
powerful causes of variation, and near the pole the needle 
deflects more from the meridian. This is demonstrated with 
a terrella, on which is put an iron wire of two finger-breadths : 
the wire is quickly and strongly directed toward the poles on 
a meridian, but in the intervals between equator and pole it is 
directed weakly ; herein we may see the great tendency to 
variation near the poles. 



CHAPTER XL 

CARDAN'S ERROR IN SEEKING TO DETERMINE THE DISTANCE 
OF THE EARTH'S CENTRE FROM THE CENTRE OF THE 

WORLD BY MEANS OF THE LOADSTONE (IN HIS De Pro- 
portionibus, V). 

How very easy it is to make mistakes and errors in the 
absence of trustworthy experiments, while investigating the 
hidden causes of things, is well shown by a gross blunder of 
Cardan, who thinks he has discovered the distances of the 
centres of the earth and the world through the variation of the 
magnetic needle over nine degrees; for he believed that the 
variation point in the horizon is everywhere distant eastward 
nine degrees from due north: on this basis he establishes a 
demonstrative ratio of the different centres. 



WILLIAM GILBERT. 



CHAPTER XII. 

OF FINDING THE AMOUNT OF THE VARIATION; WHAT THE 
QUANTITY IS OF THE ARC OF THE HORIZON FROM ITS 
ARCTIC OR ANTARCTIC INTERSECTION BY A MERIDIAN 
TO THE POINT TOWARD WHICH THE NEEDLE TURNS. 

THE true meridian is the principal basis of the whole ques- 
tion ; when that is surely known it is easy, with the mariner's 
compass (when you know its construction and how the iron 
bars are fixed in it), or with any large horizontal versorium, to 
show the arc of variation on the horizon. A variation com- 
pass of good size, after you have made two observations of the 
sun before and after noon, shows the variation by the shadow : 
the sun's altitude is observed with a radius 1 or with a large 
quadrant. On account of the greater size of the instrument, 
there is an easier and surer way of finding the variation on 
shore. Get a thick plank of suitable timber, two feet long, 
sixteen inches broad ; on it describe several semicircles, as in 
the accompanying plate, but more numerous. In the centre 
erect perpendicularly a brass stilus ; let there be also a rotatory 
pointer reaching from the centre to the outermost semicircle, 
and a magnetized versorium in a box with glass cover. Then 

1 Radius radius astronomicus measuring-rod, same as radiometer. An 
old instrument for measuring angles; the cross-staff; Jacob's-staff ; a kind of 
astrolabe. (For Radius and Quadrant, etc., consult R. Ainsworth's " Latin 
Diet.;" the "Century Diet.," Volumes III, page 3213; V, pp. 4883, 4934-4935 ; 
J. E. Worcester, " Diet, of Eng. Lang.," 1881, Vol. I, page 786; Vol. II, page 
1163; Noah Webster, "Int. Diet.," 1891, pp. 1171, 1399; Dr. John Ogilvie, 
" The Imp. Diet.," 1882, Vols. I, page 631; II, page 657; III, page 585 ; John- 
son's "Diet, of Eng. Lang.," London 1876, Vol. II, pp. 5 and 676). 



FINDING THE AMOUNT OF THE VARIATION. 2$ 7 




258 WILLIAM GILBERT 

when the plank is placed accurately to the level of the horizon 
by the plane instrument with its perpendicular (instrumento 
piano cum suo perpendiculo), turn the extremity of the pointer 
toward the north, so that the versorium shall rest just on the 
midline of its case, which regards the point of variation in the 
horizon. Afterwards, at some convenient hour in the morning 
8 or 9 o'clock observe the point of the shadow cast by the 
stilus when it reaches the nearest semicircle, and mark with 
chalk or ink the place of the shadow's point ; now bring the 
pointer round to that mark and note with another mark the 
number of the degree in the horizon shown by the pointer. 
In the afternoon, see when the extremity of the shadow again 
reaches the periphery of the same semicircle, and, bringing the 
pointer around to the tip of the shadow, find the degree at the 
other side of the lily. From the difference in degrees, you find 
the variation : the less being substracted from the greater, the 
half of the remainder is the arc of variation. The amount of 
variation is sought to be determined with many other instru- 
ments and in many other ways, in conjunction with the mar- 
iner's compass by means of a globe, number, and by the ratio 
of triangles and of sines, the latitude being known and one 
observation of the altitude of the sun being made. But these 
methods and means are of little advantage, for it is useless to 
seek in roundabout ways and by intricate paths what you may 
find more quickly and more surely by taking a shorter road. 
The whole trick consists in proper use of the instruments by 
which the sun's position is ascertained readily and quickly (as 
the sun does not stand still but moves on), for either the hand 
trembles, or the eyesight is defective, or the instrument does 
not work aright. Besides, to observe the sun's altitude on both 
sides of the meridian, is as easy as to observe it on one side 
only and at the same time to ascertain the elevation of the 



FINDING THE AMOUNT OF THE VARIATION. 

pole. And he who can take one altitude with an instrument 
can take another, and if the one is doubtful, the whole work 
with globe, number, sines, and triangles is thrown away. Never- 
theless, these exercises of mathematical minds are praise- 
worthy. It is easy for anyone who stands on the land, by 
means of accurate observations and with the use of fit instru- 
ments, to ascertain the variation, especially in a rather right 
sphere ; but at sea, in view of the motion and the turning of 
the waters, experiments cannot be made with exactness as to 
degrees and minutes, and, in fact, with the instruments in com- 
mon use, hardly within one third or one half of a point, partic- 
ularly in high latitude : hence so many incorrect and faulty 
records of observations by navigators. As for us, we have 
contrived a method of finding the variation, by means of a 
convenient, handy instrument, from the rising of certain stars, 
the rising or setting of the sun, in northern regions, from the 
pole-star ; for, at sea, when the ship is tossed by the waves, 
even the skilled observer determines the variation more surely 
with the aid of a simple instrument and one of no great preci- 
sion. Such an instrument is constructed as follows : 

After the pattern of a true and meridional mariner's com- 
pass (with a bare versorium or with a versorium fastened to a 
card circle), make an instrument at least one foot in diameter ; 
divide its rim into four quarters, each subdivided into 90 de- 
grees. Let the movable compass-box be balanced below (sub- 
tuslibratd) with a heavyweight of 16 pounds. On the edge of 
the suspended box at beginnings opposite quadrants, a semi- 
circle rising in the middle to a point (conuni) is to be erected 
(the feet of the semicircle at both sides being fastened in holes 
on the margin) so that the top of the conum shall be perpen- 
dicular to the plane of the compass ; on its top a rule sixteen 
digits long is to be fastened at its middle over the central axis, 



260 



WILLIAM GILBERT. 




FINDING THE AMOUNT OF THE VARIATION. 26 1 

as it were (of the compass-box), like the beam of a balance, 
with such a joint that it may move. At the ends of the rule 
are small sights with holes through which we may observe the 
sun and stars. By means of the rising or the setting sun at 
the equinoxes, the variation can be taken very well and very 
readily with this instrument. When the sun is in other parts 
of the zodiac, the variation can also be determined when we 
have the altitude of the pole : that known, any one may find, 
with a globe, or maps, or with the instrument, the amplitude (of 
the sun or star) on the horizon and the distance from the true 
east as well of the sun as of the following fixed stars. Then, 
having counted the degrees and minutes of the ortive ampli- 
tude (time of rising) from the true east, we readily find the 
variation. Observe the foremost star of the three in Orion's 
belt when first it appears on the horizon ; direct the instru- 
ment toward it, and observe the versorium, for as that star 
rises in the true east, generally one degree toward the south, 
we can see how far the versorium diverges from the meridian, 
allowance made for that one degree. You may also observe 
the Arctic pole-star when it is on the meridian or at greatest 
distance from the meridian (about 3 degrees: according to 
the observations of Tycho Brahe the pole-star is 2 deg. 55 min. 
from the pole), and with the aid of the instrument you may 
determine the variation scientifically, by adding or subtract- 
ing the due prostapharesis ' of the star's distance from the 

1 Prostaphseresis (Gr. previous subtraction), (i) The reduction to bring 
the apparent place of a planet or moving point to the mean place. (2) A 
method of computing by means of a table of natural trigonometrical functions 
without multiplying. It was invented by a pupil of Tycho Brahe, named Wit- 
tig, but was entirely superseded by logarithms ("The Century Diet.," 1890, 
Vol. IV, page 4790). It is more generally called eqitation of the centre (L. N. 
Bescherelle, "Nouv. Diet. Nat." 1887, Vol. Ill, page 1084). Eqtiation of the 
centre is the difference between the place of a planet as supposed to move uni- 
formly in a circle, and its place as moving in an ellipse (Noah Webster's 



262 WILLIAM GILBERT. 

meridian (if it is not in the meridian). You will find when the 
pole-star is in the meridian, the sun's place and the hour of the 
night being known : even the practised observer will easily 
know that without much error, by the visible inclination of the 
asterism as we do not care for a matter of a few minutes, as 
some do, who while striving to get at the minutes at sea often 
miss by a whole point. The experienced observer will allow 
somewhat for refraction in noting the rise of the sun or stars, 
so that his calculation may be more exact. 

List of bright, brilliant stars not far from the equator, that 
can be observed in rising or in setting from the altitude of the pole 
and the declination of the stars, the ortive amplitude on the hori- 
zon being ascertained on a globe, or map, or the instrument whence 
the variation is determined by artful calculation. 

Right Ascension. Declination, 

deg. min. deg. min. 

Aldebaran Eye of Taurus 62 55 15 53 N. 

Bellatrix Left shoulder of Orion 72 24 4 5 N. 

Betelgeuze Right " " " 83 30 6 19 N. 

Mintaka Foremost star in belt of Orion. 77 46 I 16 S. 

Sirius Canis Major 97 ro 15 55 S. 

Procyon Canis Minor 109 41 5 55 N. 

Alphard Bright star in Hydra 137 10 5 3 S. 

Pollux South head of Gemini no 21 28 30 N. 

Castor North " " " 107 4 32 10 N. 

Regulus Heart of Leo 146 8 13 47 N. 

Denebola Tail " " 171 38 16 30 N. 

Spica Spica Virginis 195 44 8 34 S. 

Arcturus and BoOtae 29 13 21 54 N. 

Altair Heart of Aquila 291 56 7 35 N. 

" Int. Diet." 1891, page 504). In ancient astronomy, it is usually the difference 
between the true and mean place of the centre of the epicycle (Short, Kepler, 
Par. 43); but in the case of the moon, generally the angle at the centre of the 
epicycle between the true and mean apogee (Clavius; Ozanari), though some- 
times the first inequality (Halma, Almagest, Vol. VII). In modern astronomy, 
it is the excess of the true over the mean anomaly (Gauss, Theoria Motus, I. 7). 
See the "Century Diet.," 1890, Vol. II, page 1982; also, P. Larousse, " Grand 
Diet. Univ.," 1875, Volumes VII, page 771, and XIII, page 288; also Dr. John 
Ogilvie, "The Imp. Diet./' 1882, Vol. II, page 185. 



FINDING THE AMOUNT OF THE VARIATION. 263 

An instrument for finding the ortive amplitude on the horizon. 
Describe the periphery of a circle and divide it into quarters 
by two diameters intersecting at right angles. One of the 
diameters indicates the equinoctial circle, the other the axis of 
the world. Divide the four quarters in the usual way, each 
into 90 degrees, and to every fifth or every tenth degree from 
each end of the two diameters in both directions assign num- 
bers on the two margins (outside of this periphery) provided 
for the purpose. Then from each degree draw a right line 
parallel to the equator. Next make a rule, or alidade, of the 
same length as the diameter of the circle and divided into the 
same parts exactly as the diameter which represents the axis 
of the world. In the middle of this rule let a small projecting 
piece be left attached whereby the middle of the linea fiduci- 
alis * of the rule may be connected with the centre of the 
circle ; and to each fifth or tenth part of the rule give a num- 
ber, beginning in the middle and numbering right and left. 
The circle represents the plane of the meridian ; its centre rep- 
resents the very point of rising or setting, i.e., the intersection 
of horizon and equator. All these lines equidistant from the 
equator, represent parallels of the sun and stars ; the linea 
fiducialis of the rule or alidade represents the horizon, and its 
parts degrees of the horizon, beginning at the point of rising 
or setting. Therefore, if to the given latitude of the place, 
as numbered at each end of the diameter that represents the 

1 Linea fidicialis fiducial line : (i) The straight edge of the alidade of a 
plane table. (2) The initial line of a graduated circle or vernier. (3) Any line 
which is intended to be taken as a standard straight line. The term fiducial, 
in physics, denotes a fixed position or character, and hence is used as a basis of 
reference or comparison ("Century Dictionary," 1889, Vol. II, page 2202, 
and Vol. Ill, page 3463. See, likewise, Noah Webster's " International Dic- 
tionary," 1891, page 556 ; L. N. Bescherelle, " Nouv. Diet. Nat.," 1887, Vol. 
II, page 1576; Larousse, "Diet. Universe!," 1872, Vol. VIII, page 336; M. 
P. E. Littre's " Dictionnaire," 1863, Vol. I, page 1665). 



264 



WILLIAM GILBERT. 



axis of the world, the linea . fiducialis of the rule be applied ; 
and if the given declination (less the complement of the lati- 







tude of the station) of sun or any star from the equator be 
found on the rim of the instrument, then a section of a parallel 



OBSERVATIONS MADE BY SEAMEN UNTRUSTWORTHY. 26$ 

drawn from the point of this declination in the horizon, or in 
the linea fiducialis, will show the ortive amplitude of the given 
star or of the sun at the stated latitude of the place. 



CHAPTER XIII. 

OBSERVATIONS MADE BY SEAMEN COMMONLY VARY AND ARE 
UNTRUSTWORTHY, PARTLY THROUGH MISTAKES AND 
WANT OF KNOWLEDGE AND THE IMPERFECTNESS OF THE 
INSTRUMENTS, AND PARTLY BECAUSE THE SEA IS SEL- 
DOM SO CALM BUT SHADOWS OR LIGHTS MAY REST ON 
THE INSTRUMENTS. 

FROM the time when first the variation of the needle was 
noticed, many alert navigators have in sundry ways striven to 
investigate the difference in the direction of the mariner's 
compass ; but this has not been done with the exactness that 
was requisite, much to the disadvantage of the art of naviga- 
tion. For, either, being unlearned, they knew of no sure 
method, or they used ill-constructed and unsuitable instru- 
ments, or they adopted some conjecture based merely on the 
false hypothesis of some prime meridian or magnetic pole ; 
while many copy others' writings and pass off for their own the 
observations of earlier writers : and these early authors, how- 
ever stupid the writings in which they entered their observa- 
tions, are held in high respect just because of their antiquity ; 
and their posterity hold it to be not safe to differ from them. 
Hence on long voyages, especially to the East Indies, the in- 
exact records of variation of the compass kept by the Portu- 



266 WILLIAM GILBERT. 

guese are prized ; but whoever reads what the Portuguese have 
written will quickly see that in very many respects they are 
mistaken, and that they did not rightly understand the con- 
struction and the use, in taking the variation of the compass of 
Portugal (in which the lily points one half point west from the 
magnetized needle). Hence while they exhibit the variation 
of the compass in different places, it is not certain whether 
they measure the deviation with a true meridional compass or 
with some other kind, in which the magnetized iron points 
away from the lily. The Portuguese (as is seen in their writ- 
ings) employ the compass of Portugal, in which the magnetized 
iron is one half of a point to the east of the lily. 

Even expert navigators find it very difficult to observe the 
variation at sea on account of the ship's motions and her toss- 
ing in every direction, though they may employ the best in- 
struments yet devised and in use. Hence have arisen various 
opinions about magnetic deviation. For example, the Portu- 
guese navigator Roderigues de Lazos takes it to be one half 
point off the island of St. Helena ; the Dutch, in their nauti- 
cal journal, make it one point there ; Kendall, an expert Eng- 
lish navigator, makes it only one sixth of a point, using a true 
meridional compass. Diego Alfonso finds no variation at a 
point a little southeast of Cape das Agulhas, and by the astro- 
labe shows that the compass stands in the true meridian ; but 
Roderigues declares that the compass points due north and 
south at Cape das Agulhas if it be of the Portuguese style, in 
which the variation is one half point to the southeast. 1 There 

1 Cape Agulhas Cape Aguilhas Capo d'Aguhas southernmost point of 
Africa. This name was given by the Portuguese on account of the magnetic 
derangement of their compass needles in its locality when Vasco de Gama 
sailed round it Aguilhas, in Portuguese, signifying needles. (Walker, " Magn. 
of Ships," 1853, page 2.) 

" And so likewise, because the Cape de las Agullas hath sea on both sides 



VARIATION OF THE MAGNETIZED NEEDLE. 267 

Is the same degree of confusion, carelessness, and falsity in 
most of the other records. 



CHAPTER XIV. 

OF THE VARIATION UNDER THE EQUINOCTIAL LINE AND 

NEAR BY. 

IN northern regions the compass varies because of the 
northern eminences ; in southern regions because of the south- 
ern eminences ; on the equator, if the eminences on both sides 
were equal, there would be no variation. But because this sel- 
dom happens, therefore oftimes variation is observed under 
the equator ; and even at some distance from the equator, 
three or four degrees, variation may be produced by austral 
eminences, if extensive and potent austral continents lie near 
on one side. 



CHAPTER XV. 

THE VARIATION OF THE MAGNETIZED NEEDLE IN THE GREAT 
SEA, ETHIOPIC AND AMERICAN, BELOW THE EQUATOR. 

WE have already spoken of the mode and reason of varia- 
tion in the great Atlantic Sea ; but below the equator, on the 

near it, and other land remote, and as it were aequidistant from it, therefore at 
that point the needle conforms unto the true meridian, and is not distracted by 
the vicinity of Adjacencies. This is the general and great cause of variation " 
(Sir Thomas Brown, Pseudoloxia Epidemica, 1658, Book II, page 70). See the 
extract from unpublished letter of Mr. Archibald Smith to Lord Cardwell, dated 
February 13, 1866, relative to the loss of the iron steamer " Eastern Province" 
near Cape Agulhas, at page 387 of " Good Words " for 1879. 



268 WILLIAM GILBERT. 

east coast of Brazil, the needle swerves toward the continent ; 
with the end that looks south : thus, at that end, it declines 
from the true meridian, toward the west ; this is noticed by 
navigators as a movement of the point of the needle, and so 
they think that the variation is to the east. But, over the whole 
route from the first eastern promontory of Brazil, past Cape 
Sao Agostino to Cape Frio and as far as the mouth of the 
Strait of Magelhan, the variation is always from south to west, 
the crotch of the needle tending to the Antartic pole. For it 
always turns with the proper end toward a continent. Yet the 
variation takes place not only on the coast itself, but at some 
distance from the land over a space of 50 or 60 German miles 
or more. 

But at a great distance from the land the arc begins to 
grow less, for the needle turns less toward distant promi- 
nences ; and it is not made to diverge much by such promi- 
nences when present and on the spot, for it then shares with 
them. On the island of St. Helena (whose longitude is less 
than it is usually given in maps) the compass varies one or 
perhaps two degrees. The Portuguese, and others who have 
learnt of them, in sailing beyond the Cape of Good Hope to 
the Indies, in order to have favorable winds, shape their course 
toward the islands of Tristan de Acunha, and on the first half 
of the voyage find no considerable difference of variation ; but 
near those islands the difference is greater than anywhere else 
in the entire voyage. For the great promontory of the 
southerly continent which lies to the southwest pulls and 
solicits that end of the versorium which points south (and at 
that end is the principal cause of the variation). But as the 
ship approaches the Cape of Good Hope the variation grows 
steadily less. In the prime meridian, at latitude 45 degrees, 
the needle points southeast by south ; and so, too, he who 



VARIATION IN NOVA ZEMBLA. 269 

sails along the coast from Manicongo to the tropic and a little 
beyond will find the needle tending from the south to the 
southeast, but not much. At Cape das Agulhas it still keeps 
a little of the variation it showed near the islands of Tristan 
de Acunha, but it is much diminished owing to the remoteness 
from the cause of the variation ; and the south end of the 
needle does not yet point due south. 



CHAPTER XVI. 

OF THE VARIATION IN NOVA ZEMBLA. 

THE variations are greatest in regions nigh to the poles, as 
has been proved, and there, too, the changes of variation are 
sudden, as Dutch observers noted some years ago, though 
their observations were not exact ; yet the inexactitude can 
be excused, for, with the ordinary instruments, it is hard to 
get at the truth in such high latitudes about 80 degrees. 
But now the variation of the compass gives the clear evidence 
of the existence of an open passage eastward through the 
North Sea Arctic Ocean (Mare Scythicum\ for, since the 
compass has so great an arc of variation to the west, it is evi- 
dent that no continent stretches for any great distance along 
that whole route eastward. Therefore we can strive and ex- 
plore more hopefully for a passage to the Moluccas by the 
northeast than by the northwest. 



27 WILLIAM GILBERT. 



CHAPTER XVII. 

VARIATION IN THE SOUTH SEA. 

AFTER passing through the Strait of Magellan, the varia- 
tion off the Peruvian coast is to the southeast ; and a like 
deflection continues all along the coast of Peru to the equator. 
In higher latitude, up to 45 degrees, the variation is greater 
than near the equator ; and, just as on the eastern coast of 
South America, the deflection was from south toward west, 
so now it is to the southeast. From the equator northward 
the variation is very small or null till you reach New Galicia ; 
thence along the whole coast as far as Quivira the inclination 
is from the north to the east. 



CHAPTER XVIII. 

OF THE VARIATION IN THE MEDITERRANEAN SEA. 

SICILIAN and Italian manners declare that in the Sicilian 
sea and eastward to the meridian of Peloponnesus (as Francis 
Maurolycus relates) the needle grecizes, i.e., is diverted from 
the pole toward the wind called Graecus (Greek), or north 
wind ; that on the coast of Peloponnesus it points to the true 
pole ; but that when you proceed farther, then it mistralizes, 
inclining from the pole to the mistral or northwest wind : this 
is in accordance with our rule of the variation. For, as the 



VARIATION IN INTERIOR OF CONTINENTS. 

Mediterranean Sea stretches away from that meridian toward 
the west, so, on the side toward the east, there is open sea as 
far as Palestine, and toward the north and east is the whole 
archipelago, and hard by the Black Sea. From Peloponnesus 
to the north pole, that meridian passes through the largest 
and most elevated regions of all Europe : through Achaia, 
Macedonia, Hungary, Transylvania, Lithuania, Livonia, Novo- 
goroda, Corelia and Biarmia. 1 



CHAPTER XIX. 

THE VARIATION IN THE INTERIOR OF THE GREAT CONTI- 
NENTS. 

GREAT seas usually have great variations ; in some parts, 
however, there is no variation, but true direction poleward. 
On the continents, too, the needle often deflects from the 
meridian, as on the margin of the land and the confines, but 
the arc of variation is wont to be small : in the middle regions 
of great continents there is no variation. Hence in the heart 
of northern Europe and of Asia, in the interior of Africa, Peru, 
and of North or Mexican America, the versorium rests in the 
meridian. 

1 Biarmia is the name given by Scandinavian writers to that section of N. E. 
Russia bordering upon the White Sea. See reference thereto in note, Book I, 
Chap. I, of present work. 



272 WILLIAM GILBERT. 

CHAPTER XX. 

THE VARIATION IN THE EASTERN OCEAN. 

THE variation in the Eastern Ocean, all the way to Goa 
and the Moluccas, is noted by the Portuguese, but they are 
mistaken in very many points, for they follow the first observ- 
ers who set down the variations for sundry places, ascertained 
by the use of unfit instruments, or by inaccurate observations, 
or by conjecture. Thus in the island of Brando 1 they make 
the compass vary 22 degrees to the northwest. Now, in no 
region, in no place on earth that has not a higher latitude 
than that, is the variation so much as 22 degrees : in fact the 
deviation on that island is trifling. So, when they say that in 
Mozambique the compass varies to the northwest one point, 
they are in error even though the compass they use is that of 
Portugal ; for, without a doubt, the needle varies in Mozam- 
bique to the southwest one quarter of a point or more. 
Again, they are all wrong in holding that beyond the equator, 
on the route toward Goa, the compass varies westward one 
point and one half ; better had they said that in the first part 
of the route the compass of Portugal inclines one point, but 
that a true or meridional compass varies only one-half point. 
Yet to determine the amount of the variation in the Eastern 
Ocean according to our rules, we need a more exact and cor- 
rect reconnoissance of the austral continent, which stretches 
farther from the south toward the equinoctial than it is de- 
scribed in current charts and globes. 

1 The island of Brando lies in the Gulf of Bothnia, close by the east 
coast of Sweden. 



DEVIATION VARIES ACCORDING TO DISTANCE. 273 



CHAPTER XXI. 

HOW THE DEVIATION OF THE NEEDLE IS GREATER OR LESS 
ACCORDING TO THE DISTANCES OF PLACES. 

In the heart of great continents there is no variation; so, 
too, in the midst of great seas. On the edge of such lands and 
seas the variation is often large, but not as great as it is a little 
out at sea : thus off Cape Sao Agostino there is variation, but 
50 miles away to the east there is a larger variation ; still larger 
80 miles away and 100 miles away. But from 100 miles dis- 
tance the reduction of the deviation is slower as you approach 
the continent than from the distance of 80 miles, and from 80 
miles than from 50; for the deviation is changed and reduced 
somewhat more quickly as you come toward the shore from 
anear then from afar. So, for mariners approaching New- 
foundland, the change of the variation is quicker (i.e., a degree 
of variation is lost in a less arc of the route on a parallel) when 
they are not far from land than when they are 100 miles away ; 
but when they journey inland the changes are more tardy at 
first than when they come farther into the interior. 

The figure shows the ratio of the arcs on a parallel circle 
while a versorium is brought toward a continent that reaches 
to the pole ; the ratio answers to the degrees of the variation. 
Let A be the pole, B the elevation of a great mass of land. 
At C there is no variation caused by B, which is too distant ; 
at D the variation is greatest, because there the needle is at- 
tracted or is made by the whole earth to turn to the projecting 
land B ; nor is the needle hindered, nor checked, nor led towp~d 



274 WILLIAM GILBERT. 

the pole by the verticity of this land, but, tending to the pole, 
it is nevertheless deflected therefrom, because of the site or 
position and convenient distance of the overmastering eleva- 
tions of land. 




But, now, from C to D the variation grows, yet the 
versorium does not deviate so quickly in the first stages as 
it does when near D. But you sail more miles on the parallel 
circle CD as long as you are near C, to register one degree of 
variation, than you sail when near D ; so, too, in travelling from 
D toward E you must make a greater number of miles when 
near D than when near E. Thus there are equal deviations 
for unequal distances sailed, both for rising and falling varia- 
tion ; yet it falls within a less space than it rises. There are, 
however, several other incidental cases that confuse this ratio. 




BOOK V. 



CHAPTER I. 



OF THE DIP OF THE MAGNETIC NEEDLE. 

WE come at last to that fine experiment, that wonderful 
movement of magnetic bodies as they dip beneath the horizon 
in virtue of their natural verticity ; after we have mastered this, 
the wondrous combination, harmony, and concordant interac- 
tion of the earth and the loadstone (or magnetized iron), being 
made manifest by our theory, stand revealed. This motion we 
have so illustrated and demonstrated with many experiments, 
and purpose in what follows so to point out the causes and 
reasons, that no one endowed with reason and intelligence may 
j ustly contemn, or refute, or dispute our chief magnetic principles. 
Direction, as also variation, is demonstrated on the plane of the 
horizon whenever a magnetic needle poised in equilibrium 
comes to a rest in any fixed point of it. But inclination (dip) 
is seen to be the motion of the iron bar, first balanced on its 
axis and then excited by a loadstone, from that point in the 

275 



WILLIAM GILBERT. 

horizon, one end or pole tending toward the earth's centre. 
And we have found that this inclination differs in the ratio of 
the latitude of each region. Now this movement is produced 
not by any motion away from the horizon toward the earth's 
centre, but by the turning of the whole of the magnetic body to 
the whole of the earth, as later we will show. Nor does the 
needle descend below the horizon in the ratio of the degrees of 
the elevation of the pole in the given region, and with an equal 
arc of the quadrant in any oblique sphere, as later will be seen. 
But how much the needle dips in every horizon can now first 
be ascertained by means of an instrument (which, however, is 
not very easily constructed), just as in sun-dials when the needle 
returns to points in the horizon, or as in the mariner's compass. 
Get a circular planed board with diameter at least six finger- 
lengths, which is to be fastened to one face of an upright square 
post and to rest on a wooden base. Divide the periphery of 
the instrument into four quadrants, and then each quadrant 
into ninety degrees. In the centre of the instrument drive a 
brass nail, and in the centre of its head bore a small hole well 
reamed and smoothed. Adjust to the instrument a circle or 
ring of brass about two finger-breadths wide, with a transverse 
plate or flat bar of the same metal fastened across the middle 
of the ring and serving for horizon. In the middle of this 
horizon bar bore another hole which shall be exactly opposite 
to the centre of the instrument, in which a hole was already 
bored. Next get a steel wire such as is used for compass 
needles, and at the exact middle of it and at right angles to it 
pass a very thin iron axis through it so that the middle of the 
axis and the middle of the needle shall exactly meet ; let this 
inclination (dipping) needle, the ends of the axis having been 
inserted into the holes, be suspended so that it may move freely 
and evenly on itself in most exact equilibrium, and so accu- 



DIP OF THE MAGNETIC NEEDLE. 




DIP INSTRUMENT. 



278 WILLIAM GILBERT 

rately that it may not turn away from any one degree or point 
marked on the circumference more than from any other, but 
may rest easily at any one point. Have the instrument fastened 
upright to the face of the post, and on the edge of the base 
set a very small magnetized versorium. The needle thus 
nicely balanced, now rub skilfully at both ends with the oppo- 
site poles of a loadstone, but do this with the greatest care lest 
the wire be in the least bent ; for unless you do all this with 
great skill and dexterity, you will reach no result. Next get a 
second brass ring, a little larger than the first, so as to go round 
it, and to one rim fit a cover of glass or of very thin mica ; this, 
when placed over the other ring, encloses the whole space, and 
the needle is protected from dust and currents of air. The in- 
strument being now complete, set it up perpendicularly with 
the small versorium on the base, so that when thus erected 
exactly upright it may tend to the true point of the magnetic 
direction. Then that one of the needle's ends which in north- 
ern latitudes looks to the north dips below the horizon ; but in 
southern latitudes the end of the needle that looks south tends 
toward the earth's centre in a certain ratio (afterward to be ex- 
plained) of the latitude of the region in question from the 
equator on either side. But the needle must be rubbed with a 
powerful loadstone, else it does not dip at the true point or 
goes beyond it and is not always at rest in it. A larger instru- 
ment can also be employed, of ten or twelve finger-lengths diam- 
eter, but in that case there is more trouble in balancing the 
needle exactly. Care must be taken to have the needle of 
steel, also that it be straight, and that the sharp points of the 
axis on both ends be at right angles with the needle itself, and 
that it pass through the very centre. 

As in other magnetic movements there is strict agreement 
and a clearly visible, sensible accordance between the earth and 



DIP OF THE MAGNETIC NEEDLE. 2/9 

the loadstone in our demonstration, so in this inclination is 
the accordance of the globe of the earth and the loadstone 
positive and manifest. The true and definite cause of this 
great and hitherto unknown effect is as follows : The loadstone 
moves and revolves until one of its poles, being impelled toward 
the north, comes to rest in its predetermined point on the 
horizon ; the pole that comes to a stand looking north is (as 
appears from the foregoing rules and demonstrations) southern, 
not northern, though till now every one has supposed it to be 
northern because it turns to the north. An iron wire or ver- 
sorium touched with this pole of the stone turns south, and is 
made northern because rubbed at the south end of the stone; 
just as when the point of a versorium is magnetized in that way 
it will be directed toward the earth's south pole and to that 
will turn, while the other end, the crotch, will be southern and 
will turn to the northern regions of the earth (the earth itself 
causing the motion), for thus does direction result from the 
bearings of the stone and the needle, and from the earth's ver- 
ticity. But inclination (dip) is when the needle turns to the 
body of the earth, its south end pointed to the north, in any 
latitude away from the equator. For it is a fixed and unchang- 
ing law that exactly beneath the celestial equator, or rather on 
the equator of the terrestrial globe, the magnetic inclination or 
dip of the needle is nil; and in whatever way it may have been 
excited or rubbed, it rests exactly on the plane of the horizon 
in the inclination instrument, provided it be first duly balanced. 
The reason of this is, that the needle, being at equal distance 
from the two poles, does not in its rotation dip toward either, 
but stands balanced, pointing to the level of the equator, as it 
does when mounted on a sharp point or floating free and un- 
hindered on water. 

But when the needle is in any latitude from the equator, or 



28O WILLIAM GILBERT. 

when one of the earth's poles is raised (I do not say raised 
above the visible horizon, like what is commonly reputed to be 
the pole of the revolving world in the heavens, but raised 
above the horizon of the centre or above its own diameter, 
equidistant from the plane of the visible horizon, which is the 
true elevation of the earth's pole), then inclination appears and 
the needle dips in its meridian towards the body of the earth. 
Thus, let AB be the visible horizon of a region ; CD the 
earth's horizon, dividing the earth into equal parts ; EF the 
earth's axis ; G a place within the region : plainly the north pole 
E rises above the point C by as much as G is distant from the 
equator ; therefore, since at E the magnetized needle is raised 




to perpendicular just by its turning (to the north), as has already 
been shown, so now at G there is a sort of beginning of such 
a turning, proportioned to the latitude (the magnetized body 
departing from the plane of the horizon), and the needle inter- 
sects at unequal angles the horizon and shows dip beneath the 
horizon ; for this reason, if the dipping needle be placed at G, 
its south end (that which points north) descends below the 
plane of the visible horizon AB. Thus there is very great dif- 
ference between a right and a polar or parallel sphere, in which 



DIP OF THE MAGNETIC NEEDLE. 



281 



the pole is in the true zenith. For in a right sphere the needle 
is parallel to the plane of the horizon. But when the celestial 
pole is in the vertical point, or when the earth's pole is itself 
the place in question (locus regionis), then the needle is perpen- 
dicular to the horizon. This is shown on a terrella ; suspend 
in air, like the beam of a balance, a small dip needle of only 
two fingers-width (duorum digitorum) rubbed at a loadstone, and 
carefully bring the terrella under it, and first let the terrella 
stand properly (recta) as in a right sphere, and, as in the first of 
the figures following, the needle will now remain in equilibrium. 
But in an oblique position of the terrella, as in an oblique 
sphere and in the second figure, the needle dips at one end 
obliquely toward the neighboring pole, but does not rest on 
the pole, nor is its dip governed by the pole, but by the whole 
body and mass ; for the dipping needle in a higher latitude sinks 
passes (labitur) beyond the pole. But in the third position * 
of the terrella the needle is perpendicular, because the pole of 




the stone is uppermost, and the needle tending straight toward 
the body attains the pole. The crotch in the foregoing figures 
always turns toward the north pole of the terrella, having been 
touched with its north pole ; the point having been touched 



282 



WILLIAM GILBERT. 



by the south pole of the terrella tends toward its south pole. 
Thus may we see the level, the oblique, and the perpendicu- 
lar position of the needle on a terrella. 1 



CHAPTER II. 

DIAGRAM SHOWING DIP OF THE MAGNETIC NEEDLE IN DIF- 
FERENT POSITIONS OF A SPHERE AND HORIZONS OF THE 
EARTH IN WHICH THERE IS NO VARIATION OF DIP. 

Let AB be the equator, C the Arctic and D the Antarctic 
pole, E y G dipping needles in northern regions, and H, F in 




southern regions of the earth or the terrella. All the needles 
have been touched with the true Arctic pole of the terrella. 

i 

1 At two points of the earth's globe, the needle will rest in a vertical 
position. These are the magnetic poles of the earth. The northern mag- 
netical pole was discovered June i, 1831, by Sir James Clark Ross, during the 
second voyage he made to the Arctic Regions under his uncle Sir John Ross, 






DIAGRAM SHOWING DIP OF MAGNETIC NEEDLE. 283 

The figure shows the needles in horizontal position at A and 
B y the earth's and the terrella's equator ; they are perpendicular 
at the poles C and D ; but in the mid spaces, at distances of 45 
degrees, the crotches dip toward the south, but the points 
look toward the north at the same angle. 

Diagram showing the direction and dip ofaterrella represent-' 
ing the earth relative to the standard representation of the globe 
of the earth, at north latitude 50 degrees. 

A is the north pole of the earth or of the large terrella ; B 
its south pole, C is the smaller terrella, and E the south pole of 
the smaller terrella that dips toward the north region (of the 
larger). Its centre C is placed on the superficies of the larger 
terrella, because the smaller terrella varies a little on account 
of the length of the a.x.is(guia terrella minor aliquantulum vari- 
at propter axis longitudineiri), but in the earth the variation is 
very little. As the needle dips in the latitude of a region of 
50 degrees, so, too, the axis of the stone which is spherical 
is depressed beneath the horizon, and its south pole, which is 
within the circumference of the larger terrella dips, while 



and lies near Boothia Felix Land in 70 5' 17" N. lat. and 96 46' 45" W. 
long., the dip being 89 59', or " within one minute of the vertical." He was 
not successful, however, in reaching the southern magnetic pole, but he 
assigned to it a position in 75 5' S. lat. and 154 8' E. long. The north 
magnetic pole is the point of the earth's surface where the dipping-needle rests 
with its magnetic axis vertical and its true south pole downwards ; the south 
magnetical pole is the point where the dipping-needle rests with its axis ver- 
tical and its true north pole downwards. As the magnetism of the north mag- 
netic pole corresponds to that of the south pole of the magnet, Prof. Silvanus P. 
Thompson named the latter " the north-seeking pole." By Prof. Faraday the 
north-seeking end was designated as the " marked " and the other end the 
"unmarked," the French calling them the "astral" and the "boreal," while 
others allude to them as the "negative" and "positive" ends, respectively. 
(See Capt. Sir John Ross' " Narrative of a Second Voyage. . . .," published in 
1835; Humboldt, "Cosmos," article on Magnetic Inclination; Sir Wm. Thom- 
son's " Terrestrial Magn. and the Magn. Compass ;" " The Earth a Magnet," 
in "Cornhill Mag.," Vol. XVII, page 727.) 



284 WILLIAM GILBERT. 

in the south (of the larger terrella) its (the smaller terrella's) 
north pole is raised toward the zenith. And a flat circular 
piece of iron carefully magnetized at opposite points of its 




circumference acts in the same way ; but these magnetic ex- 
periments are less striking because in iron disks the magnetic 
force is rather sluggish. The figure below shows, with bits of 
iron, the differences in dip at various latitudes in the terrella. 1 

Below is shown the dip of the needle on a terrella by 
means of a number of bits of iron wire of equal size, one bar- 
ley-corn in length, and placed in a meridian. At the equator 
the bits of iron are directed toward the poles, and lie upon the 



1 Consult Airy's " Magnetism," more particularly for figures and explana- 
tions of the magnetic dip and the variations of total terrestrial magnetic in- 
tensity. 



INSTRUMENT FOR SHOWING DEGREE OF DIP. 285 

body of the terrella in the plane of its horizon. The nearer 
they are placed to the poles the more do they rise from the 




horizontal by reason of their turning poleward ; at the poles 
they tend straight to the centre. But bits of iron will not 
stand up aright, save on a good loadstone, if they be too long. 



CHAPTER III. 

AN INSTRUMENT FOR SHOWING BY THE ACTION OF A LOAD- * 
STONE THE DEGREE OF DIP BELOW THE HORIZON IN 
ANY LATITUDE. 

Description of the instrument ; its uses. 

MAKE a perfectly round terrella of a superior strong load- 
stone, one homogeneous throughout, not injured anywhere by 



286 



WILLIAM GILBERT. 




INSTRUMENT FOR SHOWING DEGREE OF DIP. 287 

decay or corrosion, of proper size, so that its diameter shall be 
six or seven finger-breadths. Having, by the method hereto- 
fore given, found the poles, mark them with some iron instru- 
ment, also mark the equinoctial circle. Next, in a squared 
block of wood, one foot in diameter, make a hemispherical 
cavity to hold half of the terrella, so that just one half of the 
terrella shall rise above the block. Where the limb of the 
terrella is nearest the rim of this cavity draw a circle around it 
for a meridian, and then divide it into four equal parts or 
quadrants, and the quadrants each into 90 degrees. Let one 
end of the quadrants on the limb be near the centre of a quad- 
rant on the block, and divide this also into 90 degrees. At 
that centre, place a small short versorium having one of its 
ends sharp and longer than the other, for use as a pointer, and 
let it be poised on a fitting sharp fulcrum. Evidently, when- 
ever the poles of the terrella are at the beginnings (zero) of 
the quadrants, then the versorium will lie in a right line on the 
terrella as in equilibrium. But, if the terrella be moved so 
that one of the poles rises on the left, then the needle elevates 
itself in the meridian according to the latitude, just as a piece 
of magnetized iron rises ; and the needle indicates upon the 
quadrant described on the block the degrees of the dip. The 
rim of the cavity in the block represents a meridian circle, and 
to it answers some meridian circle of the terella, for the poles 
on both sides are upon the inner circumference of the rim. 
This is precisely what takes place on the earth itself where 
there is no variation ; but when there is variation either of di- 
rection or of dip, i.e., a disordering of the proper magnetic 
revolution for causes later to be set forth, then there is some 
difference. The quadrant described on the block must be 
near the limb of the terrella, or its centre must be at the limb 
itself, and the needle must be very short so as not to touch 



288 WILLIAM GILBERT. 

the terrella ; for there is error when the needle is long or 
placed at a distance, as it has a truly proportionate movement 
only at the superficies of the terrella. But were the quadrant 
being remote from the terrella to be moved into its sphere 
of influence toward the pole on a circle concentric with the 
terrella, then the needle would indicate on the quadrant the 
degrees of dip in ratio and symmetry with that circle, not with 
the terrella. 



CHAPTER IV. 

OF A SUITABLE LENGTH OF NEEDLE ON THE TERRELLA FOR 
SHOWING THE DIP. 

WHEN it is sought to define the dip by means of a dip- 
indicating instrument on the earth itself, we may use either a 
short versorium or one ever so long, provided only the mag- 
netic property of the loadstone with which it has been stroked 
is able to pervade its whole substance and length. For the 
greatest length of a versorium, as compared with the earth's 
diameter, is insignificant and has no ratio perceptible by sense. 
But on a terrella, or on a plane nigh a meridian of a terrella, a 
short needle is required, one barley-corn's length ; for longer 
versoria (because they reach farther), in the first degrees of dip, 
descend suddenly and irregularly, and turn to the body of the 
terrella. For example, as soon as the long versorium in the 
figure is moved onward from the equator A to C, it lays hold 
of the stone with its point C as though with a long outspread 
wing, when the point reaches the parts around B, which give 
it a greater revolution than those at C. And the ends of 



DIP NOT CAUSED BY ATTRACTION OF LOADSTONE. 289 

rather long pieces of wire or little rods are also made to rotate 
irregularly, just as pieces of iron wire and iron balls and other 
spherical loadstones are made to rotate irregularly by an ob- 
long loadstone not rounded into a ball. Yet magnetic bodies.. 




or pieces of iron on the surface of a terrella should not have a 
long but a very short axis, so that they may dip true and nat- 
urally ; for a long versorium situated near a terrella does not 
easily stand in a right sphere on the horizon, and wavers and 
suddenly dips to one side or the other, especially its magnet- 
ized end, or, if both ends are magnetized, then the end mag- 
netized last. 



CHAPTER V. 

THAT DIP IS NOT CAUSED BY THE ATTRACTION OF A LOAD- 
STONE, BUT BY ITS POWER OF GIVING DIRECTION AND 
ROTATION. 

THROUGHOUT nature we have to recognize that wondrous 
work of the Maker whereby the principal bodies are restricted 
within particular localities and, as it were, hedged round with 
fences, nature so ordering. Hence it is that heavenly bodies 
do not get confused in their motions and in their progressions 



2QO WILLIAM GILBERT. 

beyond each other. Similarly are the magnetic revolutions 
produced by the force of a greater and dominant body as well 
as by that of a lesser and subject body, though that be of very 
small volume. For the work is not done by attraction but by 
incitation on the part of both, and that with a proportionate 
movement toward fixed points beyond which there is no further 
motion. For did the versorium dip under the action of an at- 
tractive force, then a terrella fashioned out of a very powerful 
loadstone would pull it to itself more than would one made of 
an indifferent loadstone, and iron stroked by a strong loadstone 
would have greater dip ; but that is never so. Further, a piece 
of iron attached to and projecting from the terrella at any lati- 
tude does not cause a little iron bar to rise more to perpendic- 
ular than does the unarmed stone, though when so armed the 
stone does seize and lift far heavier weights. But if a load- 
stone be somewhat fashioned to a point at one end, and rather 
obtuse at the other, the acute end or pole solicits with greater 
force magnetized iron, the obtuse, thick end makes the iron 
turn to itself more powerfully ; but a spherical stone makes it 
*turn to itself powerfully and in true direction according to 
magnetic laws and the form of spheres ; while a loadstone of 
some length from pole to pole stirs the versorium unequally, 
for in such a stone the pole of the versorium always is pointed 
toward the pole of the loadstone itself. So, too, if the load- 
stone take a disk shape, with the poles in the circumference, 
but with the body plane and not spherical, when the plane is 
brought near to the versorium, the versorium does not move 
with the regular magnetic movement as with a terrella, but 
turns round always pointing toward the pole of the loadstone 
situated in the circumference of the plane. Besides, if the 
stone caused the versorium to revolve by attraction, then in 
the first degrees of latitude it would attract toward the mass 



DIP NOT CAUSED BY ATTRACTION OF LOADSTONE. 

of the terrella itself the end of a short versorium ; but it does 
not so attract as to bring the two together and into coition 
the versorium simply revolves so far as nature demands, as is 
shown in the following instance. 




For here the point of a versorium in a low latitude neither 
touches the stone nor comes into coition with it, only inclines 
toward it. Further, when the versorium rotates as it dips, the 
pole of the versorium is not stayed nor held by the pole of the 
earth or the terrella, but revolves regularly, nor remains in any 
point or terminus, nor looks straight to the pole toward which 
the centre of the versorium advances, save at the pole itself, 
and that only once between the pole and the equator ; but the 
inclination goes on according as the change in the site of the 
centre produces a dip in conformity to magnetic laws. The 
dip of the needle in water, demonstrated in the sequel, is also 
constant : the needle does not dip toward the bottom of the 
vessel, but stands in mid direction poised on its centre accord- 
ing to its due dip ; yet this would not be the case if the earth 
or its poles by attraction made the extremity of the needle to 
dip. 



WILLIAM GILBERT. 



CHAPTER VI. 

OF THE RATIO OF DIP TO LATITUDE AND THE CAUSES 

THEREOF. 

WE have spoken of the construction of the instrument for 
determining the dip, of the causes and modes of the dip, and of 
the different inclinations of the needle for different localities ; 
of the inclination of the loadstone, too, and of an instrument 
for showing the power of the stone at any latitude, as well as 
of the demonstrated rotation (by erection) of pieces of iron on 
a meridian of the stone, according to latitude. We have now 
to treat more at length of the causes of this proportionate 
inclination. A loadstone and a piece of iron wire, when moved 
in a meridian from the equator to the pole, turn toward a 
spherical loadstone, and toward the earth also, with a circular 
motion. In a right horizon (as also upon the equinoctial circle 
of the stone) the axis of the iron, which is its middle, is a line 
parallel with the earth's axis. When that axis reaches the pole, 
which is its centre, it stands still in the same right line with 
the earth's axis. The same end of the iron that at the equator 
points south turns to the north ; for it is not a movement of 
centre to centre, but of one magnetic body to another, and a 
natural turning of the axis of the body to the axis of the 
terrella, not caused by the pole's attraction, so that the iron 
should regard the earth's polar point. On the equator the 
magnetic iron stands in horizontal equilibrium, but toward the 
pole on either side of the equator, at every latitude from the 



RA TIO OF DIP TO LA TITUDE. 



293 



beginning of the first degree even to the goth, it dips; yet, 
not in ratio to the number of degrees or the arc of the latitude 
does the magnetic needle dip so many degrees or over a like 
arc; but over a very different one, for this movement is in 
truth not a dipping movement, but really a revolution move- 
ment, and it describes an arc of revolution proportioned to 
the arc of latitude. Hence the magnetic body A, while it 




passes round the earth, or an earthkin or terrella, from the 
equinoctial circle G toward B (the pole), rotates on its centre, 
and, midway in its progress from the equator to pole B t points 
to the equator F as the mean of the two poles : therefore 
ought the versorium to rotate much more quickly than the 
centre travels in order to regard the point F in a right line by 
rotating. For this reason the movement of this rotation is 
quick in the first degrees from the equator, from A to Z-, but 
slower in the subsequent degrees, from L to B, that is, with 
reference to the equatorial point F, toward C (in respectibus ab 
cequatore F ad C). But were dip equal to the latitude, i.e., 
always so many degrees from the horizon as the centre of the 



294 



WILLIAM GILBERT. 



versorium has gone away from the equator, then the magnetic 
needle would obey the potency and the peculiar virtue of the 
centre as a point operating of itself ; but it obeys the whole 
and its mass and outer limits, the powers of both cooperating, 
*to wit, those of the magnetized versorium and of the earth. 




EXPLANATION OF DIAGRAM OF ROTATION. 295 



CHAPTER VII. 

EXPLANATION OF THE DIAGRAM OF THE ROTATION OF 
MAGNETIZED IRON. 

LET ACDL be the body of the earth or of a terrella, M 
the centre, AD the equator, CL the axis, AB the horizon, 
which changes according to the locality. From the point F 
in the horizon, at a distance from the equator A equal to the 
semi-diameter CM of earth or terrella, is described an arc to 
H as terminus of the quadrants of dip ; for all quadrants of 
dip that belong (inserviuni) to the parts between A and C 
begin at that arc and terminate in the earth's centre, M. The 
semi-diameter of this arc is a chord drawn from the equator 
A to the pole C. And a line equal to that chord, drawn in 
the horizon to B, gives the starting point (principmm) of the 
arc of the termini of the arcs of revolution and rotation, which 
arc is continued on to G. For as the quadrant of a circle 
around the earth's centre (the starting-point of it being in the 
horizon, at a distance from the equator equal to the earth's 
semi-diameter) is the terminus of all the quadrants of dip pro- 
duced from every horizon to the centre, so a circle round the 
centre from the starting point of the first arc of rotation B to 
G is the terminus of the arcs of rotation. Between the arc of 
rotation BL and BG are intermediate arcs of revolution and 
rotation of the magnetic needle. The centre of the arc is the 
region or place where the observation is obtained ; the begin- 
ning of the arc is taken from the circle that is terminus of the 
revolutions, and it ends at the opposite pole, as from O to Z, 



296 WILLIAM GILBERT. 

in 45 degrees latitude. Divide any arc of revolution into 90 
equal parts from the terminus of the arcs of revolution to the 
pole ; for whatever the degree of latitude of the place, that 
part of the arc of revolution is to be reckoned as cognominal 
to it which the magnetic pole in rotating upon or around 
terrella or earth regards: in the large diagram that follows, 
this is indicated by the right lines. In the middle latitude of 
45 degrees the magnetic rotation is directed to the equator, 
and there also the arc from its terminus to the pole is the 
quadrant of a circle ; but at latitudes above this (ante htmc, i.e., 
nearer the equator) all the arcs of revolution are greater than 
a quadrant ; in latitudes below this (post hunc, i.e., higher, 
farther from the equator) they are less : in the former the 
needle rotates quickly ; in the latter it gradually rotates more 
slowly. Each region has its own arc of revolution, in which 
is, according to the number of the degree of latitude of the 
place, the terminus toward which the needle turns ; so that a 
right line drawn from the region to a point in that arc cog- 
nominal to the number of the degree of latitude indicates the 
magnetic direction, and shows the degree of the inclination at 
the intersection of the quadrant of dip that belongs (inservii) 
to the given region. Take away the arc of the quadrant of 
dip from the centre to the line of magnetic direction, and 
what remains is the arc of dip beneath the horizon. Thus, in 
the rotation of the versorium N, whose line of magnetic direc- 
tion extends to D, take away from the quadrant of dip SM 
its arc RM, and what remains will be the arc of dip, that is, it 
shows how much the needle dips in latitude 45 degrees- 



DIAGRAM OF THE ROTATION OF MAGNETIZED IRON. 2Q/ 



CHAPTER VIII. 

DIAGRAM OF THE ROTATION OF MAGNETIZED IRON, SHOW- 
ING THE MAGNETIC DIP IN ALL LATITUDES, AND SHOW- 
ING THE LATITUDE FROM THE ROTATION AND DIP. 

IN the foregoing diagram, around the body of the earth or 
of the terrella are drawn a circle of rotation and a circle of 
dip, together with a first, a last, and a middle arc of rotation 
and dip. Now from each one fifth part of that arc which 
terminates all the arcs of rotation (and each of which also is 
supposed to be divided into 90 equal parts) are drawn arcs to 
the pole, and from every fifth degree of the arc terminating 
the quadrants of dip are drawn quadrants to the centre, and 
at the same time is drawn a spiral line indicating (by the aid 
of a movable quadrant) the dip in every latitude. Right lines 
of magnetic direction are drawn from the degrees marked on 
the meridian of earth or terrella to their proper arcs and to 
the parts answering to those arcs. 

How to ascertain the elevation of the pole, or the latitude of 
any place, by means of the following diagram, turned into a mag- 
netic instrument, in any part of the world, without the help of 
the heavenly bodies, sun, planets, or fixed stars, and in foggy 
weather as well as in darkness. 

We can see how far from idle is the magnetic philoso- 
phy; on the contrary, how delightful, how beneficial, how 
divine ! Seamen tossed by the waves and vexed with incessant 
storms, while they cannot learn even from the heavenly lumi- 
naries aught as to where on earth they are, may with the great- 



298 



WILLIAM GILBERT. 



est ease gain comfort from an insignificant instrument, and 
ascertain the latitude of the place where they happen to be. 
With a dip instrument an observation is taken of the degree of 
the needle's dip beneath the horizon ; that degree is noted on 




the inside arc of the quadrant, and the quadrant is turned round 
at the centre of the instrument until that degree on the quad- 
rant touches the spiral line : then in the open space B, at the 
centre of the quadrant, the latitude of the region on the pe- 
riphery of the globe is found by the linea fiducice AB. Draw 
the diagram on a suitable planed board, and to its centre attach 



DIAGRAM OF THE ROTATION OF MAGNETIZED IRON. 299 

the centre of the angle of the quadrant A, so that the quad- 
rant may rotate on that centre. But it must be remembered 
also that in some places there is variation in dip for the causes 
aforesaid (albeit the variation is not great) : this variation also 
it will be well to study, and to account for on some probable 




hypothesis, and it will be of very great interest to observe it in 
different localities, for this variation of dip seems to present 
more difficulty than the variation of direction ; but it is readily 
understood with dip instruments when it disagrees either by 
plus or by minus with the diagram. 



300 WILLIAM GILBERT. 

Observing the magnetic dip at sea. 

Place the dip instrument upon our variation instrument, a 
wooden ball being put between the round movable compass- 
box and the dip instrument ; but first remove (eximitd] the verso- 
rium, lest it interfere with the dip instrument. In this way, 
when the sea is in commotion the compass box will remain 
erect on the level of the horizon. The dip compass is to be 
directed, by means of a small versorium at its base, to the point 
of the variation, to the greater circle of which (commonly called 
the magnetic meridian) the plane of the upright compass con- 
forms ; thus the dip instrument, in virtue of its property of 
rotating, shows the degree of the dip. 

In a dip instrument the magnetic needle which when on a 
meridian circle descends, hangs perpendicular when it lies on a 
parallel. 

The magnetic needle, in due position, while it conforms 
itself to the earth in virtue of its rotatory property, dips in an 
oblique sphere to a certain extent. But when the plane of the 
instrument is removed from the plane of the meridian, the 
needle (which tends poleward) no longer remains in the degree 
of its dip, but inclines more toward the centre, for the direc- 
tional force is greater than that of the dip ; and all power of 
dip is taken away if the plane of the instrument be on a 
parallel. For then the needle, its axis being transverse, cannot 
take its due position, and so tends perpendicular to earth, and 
remains only in its own meridian, or in what is commonly 
called the magnetic meridian. 



DEMONSTRATION OF DIRECTION. 30 1 



CHAPTER IX. 

DEMONSTRATION OF DIRECTION, OR OF VARIATION FROM 
THE TRUE DIRECTION, TOGETHER WITH DIP, SIMPLY 
BY THE MOVEMENT IN WATER, DUE TO THE POWER 
OF CONTROLLING AND ROTATING. 

PASS through a round cork three finger-breadths of thin iron* 
wire, so that the cork may support the iron in water. Let the 
water be contained in a vase or large goblet of glass. With a 
very sharp knife pare the cork away gradually (still preserving 
its rotundity) till it will stand a finger-breadth or two under 
the surface motionless, with the wire evenly balanced. Then 
stroke one end of the wire on the north pole of a loadstone, 
the other end on the south pole (very carefully, so that the cork 
may not be moved ever so little out of its place), and put the 
instrument again in the water. The wire will dip with a cir- 
cular movement on its centre below the plane of the horizon, 
according to the latitude of the place, and even as it dips will 
show (the true direction being disordered) the point of varia- 
tion. The loadstone with which it is rubbed should be a 
powerful one, such as is required in all magnetic demonstra- 
tions. When the wire having been thus put in the water, and 
treated with the loadstone, comes to a standstill in the line of 
the dip, its lower end remains in the point of variation in an 
arc of a great circle, or meridian, passing through the zenith 
and the point of variation in the horizon, and through that 
lowermost point of the heavens called nadir : all this is demon- 
strated by bringing a rather long magnetized needle near 



302 WILLIAM GILBERT. 

the vessel on one side. This is a demonstration of the absolute 
conforming of a magnetic body to unity with the earth's body ; 
here in the natural way is manifested direction with variation 
thereof and dip. But it is to be understood that delicate and 




difficult as this experiment is, so it does not continue, for the 
apparatus does not remain in the midst of the water, but at 
last sinks to the bottom when the cork has taken in too much 
water. 1 

l " It is also manifest in a needle pierced through a globe of cork so cut 
away and pared by degrees that it will swim under water, yet sink not unto 
the bottom, which may be well effected ; for if the cork be a thought too light 
to sink under the surface, the body of the water may be attenuated with spirits 



VARIATION OF DIP. 303 



CHAPTER X. 

OF VARIATION OF DIP. 

WE have already spoken of direction and of variation as a * 
sort of derangement of direction. Now we observe a like 
irregular movement in the dip, when it descends beneath the 
limits or when, as sometimes happens, it does not reach its due 
bounds. Thus the variation of the dip is an arc of the mag- 
netic meridian betwixt the true and the apparent dip. For as, 
because of elevations of the earth, magnetized bodies are pulled 
to one side, so, too, the needle (its rotation being a little in- 
creased) dips beyond the due measure. And as variation is 
a deviation in direction, so, for the same reason, there is some 
error of dip, albeit usually a trifling one. Sometimes, too, 
though there be no variation of direction on the horizon, there 
may nevertheless be a variation of the dip, to wit, when either 
in a direct meridian line, i.e., on -the meridian itself, there pro- 
jects some magnetically powerful earthmass, or when such ele- 
vations have less force than is called for by the general con- 



of wine ; if too heavy, it may be incrassated with salt ; and if by chance too 
much be added, it may again be thinned by a proportionable addition of fresh 
water. If then the needle be taken out, actively touched and put in again, it 
will depresse and bow down its Northern head toward the bottom, and ad- 
vance its Southern extremity toward the brim. This way invented by Gilbertus 
may seem of difficulty ; the same with lesse labour may be observed in a 
needled sphere of cork equally contiguous unto the surface of the water ; for if 
the needle be not exactly equiponderant, that end which is a thought too light, 
if touched becometh even ; that needle also which will but just swim under 
water, if forcibly touched, will sink deeper and sometime unto the bottom " 
(Dr. Thos. Brown, Pseudoloxia Epidemica, 1658, Book II, page 67). 



304 WILLIAM GILBERT. 

stitution of the globe, or when the energy is overconcentrated 
in one part, and in another is diffused, as we may see in the 
Atlantic Ocean. And this discrepancy of constitution, this 
variance of effect, we easily recognize in certain parts of every 
spherical loadstone. The inequality of force in the various 
regions of a terrella is shown by the conclusive experiment 
described in Chapter 2 of this Book. And the effect is clearly 
shown by the demonstrational (ostensivum) instrument, an 
account of which is contained in Chapter 3 of the same Book. 



CHAPTER XL 

OF THE FORMAL MAGNETIC ACT SPHERICALLY EFFUSED. 

* REPEATEDLY we have spoken of the poles of earth and 
terrella and of the equinoctial circle ; last we treated of the dip 
of magnetized bodies earthward and terrellaward, and the 
causes thereof. But having with divers and manifold con- 
trivances labored long and hard to get at the cause of this dip, 
we have by good fortune discovered a new and admirable 
science of the spheres themselves a science surpassing the 
marvels of all the virtues magnetical. For such is the prop- 
erty of magnetic spheres that their force is poured forth and 
diffused beyond their superficies spherically, the form being 
exalted above the bounds of corporeal nature ; and the mind 
that has diligently studied this natural philosophy will dis- 
cover the definite causes of the movements and revolutions. 
The potencies of a terrella, too, are of the same kind through- 
out the whole sphere of its influence, and the spheres (of influ- 
ence) themselves, at whatever distance from the body of the 



FORMAL MAGNETIC ACT SPHERICALLY EFFUSED. 30$ 

terrella, have, in the ratio of their diameter and the quantity 
of their superficies, termini of their forces, or, in other words, 
there are points whereat magnetic bodies turn toward them ; 
and these bodies do not regard the same part or point of the 
terrella at every distance whatever therefrom (unless they be 
in the axis of the spheres and the terrella), but ever do tend 
toward those points of the spheres (of influence) which are 
equal arcs distant from their common axis. Thus in the 
following diagram we show the body of a terrella, with its 
poles and equator ; also a magnetic needle in three other con- 
centric spheres around the terrella and at some distance there- 
from. In these spheres (and they may be imagined as infinite) 
the magnetic needle or versorium regards its own sphere in 
which it is placed and its diameter, poles, and equator, not 
those of the terrella ; and it is by these and in accordance with 
the magnitude of these that it is made to rotate and is directed, 
both while its centre stands still and while it advances in any 
arc whatever of that sphere. Still we do not mean that the 
magnetic forms and spheres exist in the air, or water, or any 
other medium not magnetical, as though the air or water took 
them on or were by them informated ; for the forms are only 
effused and really subsist when magnetic bodies are present : 
hence the magnetic body within the forces and limits of the 
spheres is taken hold of, and in the several spheres magnetic 
bodies control other bodies magnetical and excite them even 
as though the spheres of influence were solid materiate load- 
stones ; for the magnetic force does not proceed through the 
whole of the medium, nor exists really as in a continuous 
body ; and so the spheres are magnetical, and yet are not real 
spheres existing by themselves. 

AB is the axis of a terrella and its spheres ; CD the equa- 
tor. In all the spheres, as on the terrella, at the equator the 



306 



WILLIAM GILBERT. 



versorium lies in the plane of the horizon ; in the axis it 
everywhere regards the centre perpendicularly ; in the mid 
spaces, E regards D> and G regards H, not F, which is re- 




DlAGRAM OF THE MOVEMENTS IN THE MAGNETIC SPHERES. 

garded by the versorium L on the superficies of the terrella. 
But as is the proportion of L to F on the terrella's superficies, 
such is that of G to H in its own sphere, and of E to D in its 
own sphere ; so all the revolutions in the spheres to the ter- 
mini of the spheres are such as are the revolutions at the sur- 



FORMAL MAGNETIC ACT SPHERICALLY EFFUSED. 307 

face of the terrella or to its termini. But if in the more distant 
spheres there is now and then some error, that is to be charged 
to the inertia of the loadstone or to weakened power, because 
of the too great distance of the spheres from the terrella. 

DEMONSTRATION. 

Upon the instrumental diagram above described, place, a 
small board or a strong disk of brass or tin on which are in- 
scribed the magnetic spheres, as in the diagram ; and in the 
middle make a hole proportioned to the size of the terrella, so 
that the board may lie evenly on the middle of it along the 
meridian circle above the wood. Then in one of the spheres 
of influence place a small versorium one barley-corn long ; the 
versorium, as it there moves into various positions in the same 
circle, will always have regard to the dimensions of that sphere 
and not those of the terrella, as is seen in the diagram of the 
effused magnetic forms. While some writers posit as causes 
of the wonderful effects of the loadstone occult and recondite 
virtues of things, and others regard a property of the load- 
stone's substance as the cause, we have discovered the primary 
substantial form not in some more or less probable foreshad- 
owing of truth or in reasons that admit of controversy ; but as 
in many other demonstrations, so in this most indisputable dia- 
gram of the forces magnetical effused by the form, we grasp 
the true efficient cause. And this (the form), though it is 
subject to none of our senses and is therefore less perceptible 
to the intellect, now appears manifest and visible before our 
very eyes through this formal act, which proceeds from it as 
light proceeds from a source of light. And here it is to be 
noted that a magnetic needle moved over the earth, or over a 
terrella, or over the effused spheres, rotates completely twice 
in one circuit of its centre, like an epicycle round its circle. 



308 WILLIAM GILBERT. 



CHAPTER XII. 

THE MAGNETIC FORCE IS ANIMATE, OR IMITATES A SOUL; 
IN MANY RESPECTS IT SURPASSES THE HUMAN SOUL 
WHILE THAT IS UNITED TO AN ORGANIC BODY. 

WONDERFUL is the loadstone shown in many experiments 
to be, and, as it were, animate. And this one eminent prop- 
erty is the same which the ancients held to be a soul in the 
heavens, in the globes, and in the stars, in sun and moon. For 
they deemed that not without a divine and animate nature 
could movements so diverse be produced, such vast bodies 
revolve in fixed times, or potencies so wonderful be infused 
into other bodies ; whereby the whole world blooms with most 
beautiful diversity through this primary form of the globes 
themselves. The ancient philosophers, as Thales, Heraclitus, 
Anaxagoras, Archelaus, Pythagoras, Empedocles, Parmenides, 
Plato and all the Platonists, nor Greek philosophers alone, but 
also the Egyptian and Chaldean, all seek in the world a cer- 
tain universal soul, and declare the whole world to be endowed 
with a soul. Aristotle held that not the universe is animate, 
but the heavens only ; his elements he made out to be inani- 
mate ; but the stars were for him animate. As for us, we find 
this soul only in the globes and in their homogenic parts, and 
albeit this soul is not in all globes the same (for that in the sun 
or in certain stars is much superior to that in other less noble 
globes). Still in very many globes the souls agree in their 
powers. Thus, each homogenic part tends to its own globe 
and inclines in the direction common to the whole world, and 



MAGNETIC FORCE IS ANIMATE. 309 

in all globes the effused forms reach out and are projected in 
.a sphere all round, and have their own bounds hence the 
order and regularity of all the motions and revolutions of the 
planets, and their circuits, not pathless, but fixed and deter- 
minate, wherefore Aristotle concedes to the spheres and 
heavenly orbs (which he imagines) a soul, for the reason that 
they are capable of circular motion and action and that they 
move in fixed, definite, tracks. And I wonder much why the 
globe of earth with its effluences should have been by him 
and his followers condemned and driven into exile and cast 
out of all the fair order of the glorious universe, as being 
brute and soulless. In comparison with the whole creation 
'tis a mere mite, and amid the mighty host of many thousands 
is lowly, of small account, and deformate. And to it the 
Aristotelians add allied elements that by like ill-fortune are 
also beggarly and despicable. Thus Aristotle's world would 
seem to be a monstrous creation, in which all things are per- 
fect, vigorous, animate, while the earth alone, luckless small 
fraction, is imperfect, dead, inanimate, and subject to decay. 
On the other hand, Hermes, Zoroaster, Orpheus, recognize a 
universal soul. As for us, we deem the whole world animate, 
and all globes, all stars, and this glorious earth, too, we hold to 
be from the beginning by their own destinate souls governed 
and from them also to have the impulse of self-preservation. 
Nor are the organs required for organic action lacking, whether 
implanted in the homogenic nature or scattered through the 
homogenic body, albeit these organs are not made up of 
viscera as animal organs are, nor consist of definite members; 
indeed in some plants and shrubs the organs are hardly recog- 
nizable, nor are visible organs essential for life in all cases. 
Neither in any of the stars, nor in the sun, nor in the planets 
that are most operant in the world, can organs be distinguished 



3IO WILLIAM GILBERT. 

or imagined by us ; nevertheless, they live and endow with 
life small bodies at the earth's elevated points. If there is 
aught of which man may boast, that of a surety is soul, is 
mind ; and the other animals, too, are ennobled by soul ; even 
God, by whose rod all things are governed, is soul. But who 
shall assign organs to the divine intellects, seeing that they are 
superior to all organ-structure, nor are comprised in material 
organs? But in the bodies of the several stars the inborn 
energy works in ways other than in that divine essence which 
presides over nature ; and in the stars, the sources of all 
things, in other ways than in animals; finally, in animals in 
other ways than in plants. Pitiable is the state of the stars, 
abject the lot of earth, if this high dignity of soul is denied 
them, while it is granted to the worm, the ant, the roach, to 
plants and morels ; for in that case worms, roaches, moths, 
were more beauteous objects in nature and more perfect, inas- 
much as nothing is excellent, nor precious, nor eminent, that 
hath not soul. But since living bodies spring from earth and 
sun and by them are animate, and since in the earth herbage 
springs up without sowing of seeds (e.g., when soil is taken 
out of the bowels of the earth and carried to some great eleva- 
tion or to the top of a lofty tower and there exposed to the 
sunshine, after a little while a miscellaneous herbage springs 
up in it unbidden), it is not likely that they (sun and earth) 
can do that which is not in themselves ; but they awaken 
souls, and consequently are themselves possessed of souls. 
Therefore the bodies of the globes, as being the foremost 
parts of the universe, to the end they might be in themselves 
and in their state endure, had need of souls to be conjoined to 
them, for else there were neither life, nor prime act, nor move- 
ment, nor unition, nor order, nor coherence, nor conactus, nor 
sympathia, nor any generation, nor alternation of seasons, and 



MAGNETIC FORCE IS ANIMATE 3 11 

no propagation ; but all were in confusion and the entire 
world lapse into chaos, and, in fine, the earth were void and 
dead and without any use. But only on the superficies of the 
globes is plainly seen the host of souls and of animate exist- 
ences, and in their great and delightful diversity the Creator 
taketh pleasure. But the souls (in the interior of the globes) 
confined, as it were, by prison bars send not forth their effused 
immaterial forms beyond the limits of the body, nor are bodies 
put in motion by them without labor and exertion ; a breath 
carries and bears them forth ; but if that breath be fouled or 
stilled by mischance, the bodies lie like the world's recrement 
or as the waste matter of the globes. But the globes them- 
selves remain and endure, rotate and move in orbits, and 
without wasting or weariness run their courses. The human 
soul uses reason, sees many things, investigates many more ; 
but, however well equipped, it gets light and the beginnings of 
knowledge from the outer senses, as from beyond a barrier 
hence the very many ignorances and foolishnesses whereby 
our judgments and our life-actions are confused, so that few 
or none do rightly and duly order their acts. But the earth's 
magnetic force and the formate soul or animate form of the 
globes, that are without senses, but without error and without 
the injuries of ills and diseases, exert an unending action, 
quick, definite, constant, directive, motive, imperant, harmoni- 
ous, through the whole mass of matter ; thereby are the gen- 
eration and the ultimate decay of all things on the superficies 
propagated. For if it were not for the movement whereby the 
daily revolution is accomplished, all things here on earth were 
wild and disordered, and worse than desert and unused would 
they ever remain. Yet these movements in nature's founts 
are not produced by thoughts or reasonings or conjectures, 
like human acts, which are contingent, imperfect, and indeter- 



312 WILLIAM GILBERT. 

minate, but connate in them are reason, knowledge, science, 
judgment, whence proceed acts positive and definite from the 
very foundations and beginnings of the world : these, because 
of the weakness (imbecillitatem) of our soul, we cannot com- 
prehend. Wherefore, not without reason, Thales, as Aristotle 
reports in his book De Anima, declares the loadstone to be 
animate, a part of the animate mother earth and her beloved 
offspring. 





BOOK VI. 
CHAPTER I. 

OF THE GLOBE OF EARTH AS A LOADSTONE. 

HITHERTO we have spoken of the loadstone and magnetic 
bodies, how they conspire together and act on each other, 
and how they conform themselves to the terrella and to the 
earth. Now we have to treat of the globe of earth itself sep- 
arately. All the experiments that are made on the terrella, 
to show how magnetic bodies conform themselves to it, may 
at least the principal and most striking of them be shown 
on the body of the earth ; to the earth, too, all magnetized 
bodies are associate. And first, on the terrella the equinoctial 
circle, the meridians, parallels, the axis, the poles, are natural 
limits: similarly on the earth these exist as natural and not 
merely mathematical limits. As on the periphery of a terrella 
a loadstone or the magnetic needle takes direction to the pole, 
so on the earth there are revolutions special, manifest, and 
constant, from both sides of the equator : iron is endowed 

313 



3H WILLIAM GILBERT. 

with verticity by being stretched toward the pole of the earth 
as toward the pole of a terrella; again, by being laid down 
and suffered to grow cool lying toward the earth's pole, after 
its prior verticity has been destroyed by fire, it acquires new 
verticity conformed to the position earthward. And iron rods 
that have fora long time lain in the poleward direction acquire 
verticity simply by regarding the earth; just as the same rods, 
if they be pointed toward the pole of a loadstone, though not 
touching it, receive polar force. There is no magnetic body 
that draws nigh in any way to a loadstone which does not in 
like manner obey the earth. As a loadstone is more powerful 
at one end and at one side of the equator, so the same thing 
is shown with a small terrella on a large one. According to 
the difference in amount and mode of friction in magnetizing 
a piece of iron at a terrella, it will be powerful or weak in per- 
forming its functions. In movements toward the body of the 
earth, just as on a terrella, variation is produced by unlikeness 
and inequality of prominences and by imperfections of the 
surface; and all variation of the versorium or the mariner's 
compass all over the earth and everywhere at sea a thing 
that has so bewildered men's minds is found and recognized 
through the same causes. The dip of the magnetic needle 
(that wonderful turning of magnetic bodies to the body of the 
terrella by formal progression) is seen also in the earth most 
clearly. And that one experiment reveals plainly the grand 
magnetic nature of the earth, innate in all the parts thereof 
and diffused throughout. The magnetic energy, therefore, 
exists in the earth just as in the terrella, which is a part of 
the earth and homogenic in nature with it, but by art made 
spherical so it might correspond to the spherical body of the 
earth and be in agreement with the earth's globe for the capi- 
tal experiments. 



EARTH'S MAGNETIC AXIS INVARIABLE. 



CHAPTER II. 

THE MAGNETIC AXIS OF THE EARTH REMAINS INVARIABLE. 

THE earth's magnetic axis, just as it passed through the mid- 
earth in the very beginnings of the moving world, so to-day 
tends through the centre to the same points of the superficies, 
the equinoctial line and plane also persisting the same. For not, 
save with a vast demolition of the terrestrial mass, may these 
natural bounds be altered, as is easily shown by magnetic dem- 
onstrations. Wherefore the opinion held by Dominicus Maria 
of Ferrara, a man of rare ability, and who was the preceptor of 
Nicolaus Copernicus, is to be rejected. It was based on cer- 
tain observations, and was as follows: "Some years ago," he 
writes, " while considering Ptolemy's geography, I found the 
elevations of the north pole given by him for the several 
regions to fall short by one degree and ten minutes of what 
they are in our time, which difference can by no means be 
referred to an error of the table, for it is not credible that the 
whole book should be throughout equally wrong in the figures 
contained in the tables ; therefore we must suppose the north 
pole brought toward the vertical point. Thus a protracted 
observation began to disclose to us things hid from our ances- 
tors not through any sloth on their part, but because they 
lacked observation of a long period by their predecessors. 
For very few places before Ptolemy's time were observed in 
elevations of the pole, as he himself testifies in the beginning 
of his Cosmographia : ' Hipparchus alone,' he writes, * hath 
handed down to us the latitudes of a few places ; but many 



WILLIAM GILBERT. 

latitudes of distances, especially of distances to east and west, 
have been fixed on a basis of general tradition, and this is not 
from any indolence of writers, but because they were unac- 
quaint with a more accurate mathematic.' Hence it is no 
wonder if our predecessors have not noted the very slow 
movement, seeing that in 1700 years it has advanced about 
one degree toward the uttermost point of human habitation. 
This is shown at the Strait of Gibraltar, where in Ptolemy's 
day the north pole was raised 36J degrees above the horizon, 
while now it is 37! degrees. A like difference is shown by 
Leucopetra (Capo dell' Armi) in Calabria and sundry other 
places in Italy, namely, places that have not changed from 
Ptolemy's time to ours. Thus, in consequence of this move- 
ment, places that now are inhabited will one day be deserted, 
while those that now are scorched by the tropic sun will, 
albeit after a long time, be reduced to our temperature. For 
this very slow movement will be completed in 395,000 years.'* 
Thus, according to Dominicus Maria's observations, the 
north pole is raised higher and the latitudes of places are 
greater now than in the past : from this he infers a change of 
latitudes. But Stadius, holding the directly opposite opinion, 
proves by observations that the latitudes have grown less. 
" The latitude of Rome," says he, " is given in the Geographica 
of Ptolemy as 41% degrees ; and lest any one should say that 
some error has crept into the text of Ptolemy, Pliny relates, and 
Vitruvius in his ninth book testifies, that at Rome on the day 
of the equinox the ninth part of the gnomon's shadow is lack- 
ing. But recent observation (as Erasmus Rheinhold states) 
gives the latitude of Rome in our age as 41^ degrees ; so that 
you are in doubt whether one half of a degree has been lost 
(decrevisse) in the centre of the world, or whether it is the re- 
sult of an obliquation of the earth." From this we may see 



DAILY MAGNETIC REVOLUTION OF THE GLOBES. 

how, on the basis of inexact observations, men conceive new 
and contrary opinions as to the earth's mechanism, and postu- 
late absurd motions. For, as Ptolemy simply took from Hip- 
parchus a few latitudes and did not himself observe them in 
many places, it is likely that, knowing the position of the 
countries, he made a conjectural estimate of the latitude of 
cities, and set such conjectures down in his tables. So, here, 
in Britain, the latitudes of cities vary two or three degrees, as 
we know by experience. Hence no new movement is to be 
postulated on the ground of these miscalculations, nor is the 
grand magnetic nature of the earth to be deformed for the 
sake of a judgment so rashly arrived at. And these errors have 
crept into geography all the more easily because the mag- 
netic force was quite unknown to authors. Besides, observa- 
tions of latitudes cannot be made with exactitude save by 
experts, with the help of large instruments, and by taking 
account of refraction of lights. 



CHAPTER III. 

OF THE DAILY MAGNETIC REVOLUTION OF THE GLOBES, AS 
AGAINST THE TIME-HONORED OPINION OF A primum 
mobile : A PROBABLE HYPOTHESIS. 

AMONG the ancients, Heraclides of Pontus, and Ecphantus, 
the Pythagoreans Nicetas of Syracuse and Aristarchus of 
Samos, and, as it seems, many others, held that the earth 
moves, that the stars set through the interposition of the 
earth, and that they rise through the earth's giving way : they 



318 WILLIAM GILBERT. 

do give the earth motion, and the earth being, like a wheel, 
supported on its axis, rotates upon it from west to east. The 
Pythagorean Philolaus would have the earth to be one of the 
stars, and to turn in an oblique circle toward the fire, just as 
the sun and moon have their paths : Philolaus was an illus- 
trious mathematician and a vefy experienced investigator of 
nature. But when Philosophy had come to be handled by 
many, and had been given out to the public, then theories 
adapted to the capacity of the vulgar herd or supported with 
sophistical subtleties found entrance into the minds of the 
many, and, like a torrent, swept all before them, having gained 
favor with the multitude. Then were many fine discoveries 
of the ancients rejected and discredited at the least were no 
longer studied and developed. First, therefore, Copernicus 
among moderns (a man most worthy of the praise of scholar- 
ship) undertook, with new hypotheses, to illustrate the phce- 
nomena of bodies in motion ; and these demonstrations of 
reasons, other authors, men most conservent with all manner 
of learning, either follow, or, the more surely to discover the 
alleged ((/Hxivojtevrjr) " symphony " of motion, do observe. 
Thus the suppositions and purely imaginary spheres postulated 
by Ptolemy and others for finding the times and periods of 
movements, are not of necessity to be accepted in the physical 
lectures of philosophers. 

It is then an ancient opinion, handed down from the olden 
time, but now developed by great thinkers, that the whole earth 
makes a diurnal rotation in the space of twenty-four hours. 
But since we see the sun, the moon, and the other planets, and 
the whole heavenly host, within the term of one day come and 
depart, then either the earth whirls in daily motion from west 
to east, or the whole heavens and all the rest of the universe 
of things necessarily speeds about from east to west. But in 



DAILY MAGNETIC REVOLUTION OF THE GLOBES. 319 

the first place, it is not probable that the highest heaven and 
all those visible splendors of the fixed stars are swept round 
in this rapid headlong career. Besides, what genius ever has 
found in one same (Ptolemaic) sphere those stars which we 
call fixed, or ever has given rational proof that there are any 
such adamantine spheres at all ? No man hath shown this 
ever ; nor is there any doubt that even as the planets are at 
various distances from earth, so, too, are those mighty and 
multitudinous luminaries ranged at various heights and at dis- 
tances most remote from earth : they are not set in any 
sphaeric framework or firmament (as is supposed), nor in any 
vaulted structure. As for the intervals (between the spheres) 
imagined by some authors, they are matters of speculation, 
not of fact ; those other intervals do far surpass them and are 
far more remote ; and, situated as they are in the heavens, at 
various distances, in thinnest aether, or in that most subtile 
fifth essence, or in vacuity how shall the stars keep their 
places in the mighty swirl of these enormous spheres composed 
of a substance of which no one knows aught ? Astronomers 
have observed 1022 stars ; besides these, innumerable other 
stars appear minute to our senses ; as regards still others, our 
sight grows dim, and they are hardly discernible save by the 
keenest eye ; nor is there any man possessing the best power 
of vision that will not, while the moon is below the horizon 
and the atmosphere is clear, feel that there are many more 
indeterminable and vacillating by reason of their faint light, 
obscured because of the distance. Hence, that these are many 
and that they never can be taken in by the eye, we may well 
believe. What, then, is the inconceivably great space between 
us and these remotest fixed stars? and what is the vast im- 
measurable amplitude and height of the imaginary sphere in 
which they are supposed to be set ? How far away from earth 



32O WILLIAM GILBERT. 

are those remotest of the stars : they are beyond the reach of 
eye, or man's devices, or man's thought. What an absurdity 
is this motion (of spheres). 

It is evident, therefore, that all the heavenly bodies, being, 
as it were, set down in their destined places, in them are con- 
globed whatever elements bear to their own centres, and 
around them are assembled all their parts. But if they have 
a motion, it will be motion of each round its proper centre, 
like the earth's rotation ; or it will be by a progression in an 
orbit, like that of the moon ; in so multitudinous a scattered 
flock there will be no circular motion. And of the stars, those 
situate nigh the equator would seem to be borne around with 
greatest rapidity, while others nigher the pole have a rather less 
rapid movement ; and others still, as though motionless, have 
but a small revolution. Yet no differences in the light, the 
mass, or the colors of the light are perceptible for us ; for they 
are as brilliant, as clear, as resplendent, or as faint (sombre, 
fuscce) toward the poles as nigh the equator and the zodiac ; 
and in their seats do they remain and there are they placed, 
nor are they suspended from aught, nor fastened nor secured 
in any vault. Far more extravagant (insanior) yet is the idea 
of the whirling of the supposititious primum mobile, which is 



1 Primum mobile (first cause of motion), name given in the Ptolemaic 
System to the imaginary huge outermost sphere, in the centre of which stood 
the earth, and by the revolutions of which from east to west diurnal motion 
was given to all the heavens, creating the phenomena of day and night. Ac- 
cording to Aristotle, the FIRST heaven was that of the Moon, the SECOND Mer- 
cury, THIRD Venus, FOURTH the Sun, FIFTH Mars, SIXTH Jupiter, SEVENTH 
Saturn, and the EIGHTH that of the fixed stars. Two more heavens were added 
by later theorists : a NINTH, moving slowly round the poles of the ecliptic and 
carrying the entire system forward in longitude, to produce the phenomena 
arising from the precession of the equinoxes, the TENTH being the primum 
mobile beyond which was the empyreal heaven. 

" It was the errour of Aristotle," says Hakewill, "that via lactea was a 
meteor ; and not onely of Aristotle, but almost all before him. that there were 



DAILY MAGNETIC REVOLUTION OF THE GLOBES. 321 

still higher, deeper, more immeasurable ; and yet this incom- 
prehensible primum mobile would have to be of matter, of 
enormous altitude, and far surpassing all the creation below in 
mass, for else it could not make the whole universe down to 
the earth revolve from east to west, and we should have to 
accept a universal force, an unending despotism, in the govern- 
ance of the stars, and a hateful tyranny. This primum mobile 
presents no visible body, is in no wise recognizable ; it is a 
fiction believed in by some philosophers, and accepted by 
weaklings who wonder more at this terrestrial mass here than 
at those distant mighty bodies that baffle our comprehension. 
But there cannot be diurnal motion of infinity or of an 
infinite body, nor, therefore, of this immeasurable primum 
mobile. The moon, neighbor of earth, makes her circuit in 
twenty-seven days ; Mercury and Venus have a tardy move- 
ment ; Mars completes his period in two years, Jupiter in 
twelve, Saturn in thirty. And the astronomers who ascribe 
motion to the fixed stars hold that it is completed, according 
to Ptolemy, in 36,000 years, or, according to Copernicus's 
observations, in 25,816 years ; thus in larger circles the motion 
and the completion of the course are ever more slow ; and yet 
this primum mobile, surpassing all else in height and depth, 
immeasurable, has a diurnal revolution. Surely that is super- 

but EIGHT Celestial! Spheres ; after this Timocaris, about 330 years B.C., found 
out NINE; but about the yeare of Christ 1250, Alphonsus discovered TEN, and 
the received opinion now is that there are ELEVEN, the highest of all being held 
immoveable, the seate of Angels and blessed spirits." 

Tycho Brahe was of the same opinion with Ptolemy, viz., that the earth is 
at rest in the centre of the world and that the whole machine of the heavens is 
turned about it from east to west in the space of a day, by action of the 
primum mobile (Jacobi Rohaulti, Physica, Londini 1718, Par. II, Cap. VIII 
and XXIII, or Rohault's "System of Nat. Phil./' London 1728, Vol. II, pages 

24, 58). 

As is well known, the doctrine of a fixed central earth was doomed by the 
brilliant investigations of Galileo, Kepler, and Newton. 



3 22 WILLIAM GILBERT. . 

stition, a philosophic fable, now believed only by simpletons 
and the unlearned ; it is beneath derision ; and yet in times 
past it was supported by calculation and comparison of move- 
ments, and was generally accepted by mathematicians, while 
the importunate rabble of philophasters egged them on. 

The motions of the heavenly bodies (i.e., of the planets) 
seem all to be eastward, and according to the succession of the 
zodiacal signs ; and mathematicians and philosophers of the 
vulgar sort do also believe that the fixed stars progress in the 
same way with a very slow movement : to these stars they 
must needs, through their ignorance of the truth, add a ninth 
sphere. But now this inadmissible primum mobile, this fiction, 
this something not comprehensible by any reasoning and evi- 
denced by no visible star, but purely a product of imagination 
and mathematical hypothesis, accepted and believed by philos- 
ophers, and reared into the heavens and far beyond all the 
stars, this must needs by a contrary incitation wheel from 
east to west, counter to the tendence of all the rest of the 
universe. 

Whatever in nature moves naturally, the same is impelled 
by its own forces and by a consentient compact of other 
bodies. Such is the motion of the parts to a whole, of the 
globes and stars throughout the universe with each other 
accordant ; such is the circular propulsion of the planets' 
bodies, each the other's career observing and inciting. But as 
regards this primum mobile with its contrary and most rapid 
career, where are the bodies that incite it, that propel it? 
Where is the nature conspiring with it? and what mad force 
lies beyond the primum mobile ? for the agent force abides in 
bodies themselves, not in space, not in the interspaces. 

But he who supposes that all these bodies are idle and in- 
active, and that all the force of the universe pertains to those 



DAILY MAGNETIC REVOLUTION OF THE GLOBES. 323 

spheres, is as foolish (insanit) as the one who, entering a man's 
residence, thinks it is the ceilings and the floors that govern 
the household, and not the thoughtful and provident good-man 
of the house. So, then, not by the firmament are they borne, 
not from the firmament have they movement or position ; and 
far less are those multitudes of stars whirled round en masse 
by the primum mobile, and taken up at random and swept 
along in a reversed direction at highest velocity. 

Ptolemy of Alexandria, it seems to me, was over-timid and 
scrupulous in apprehending a break-up of this nether world 
were earth to move in a circle. Why does he not apprehend 
universal ruin, dissolution, confusion, conflagration, and stu- 
pendous celestial and supercelestial calamities from a motion 
that surpasses all imagination, all dreams and fables and poetic 
licenses a motion ineffable and inconceivable ? So, then, we 
are borne round and round by the earth's daily rotation a 
more congruous sort of motion ; and as a boat glides over the 
water, so are we whirled round with the earth, the while we 
think we stand still and are at rest. This seems to some phi- 
losophers wonderful and incredible, because of the ingrained 
belief that the mighty mass of the earth makes an orbital move- 
ment in twenty-four hours : it were more incredible that the 
moon should in the space of twenty-four hours traverse her 
orbit or complete her course ; more incredible that the sun 
and Mars should do so ; still more that Jupiter and Saturn ; 
more than wonderful would be the velocity of the fixed stars 
and firmament ; and let them imagine as best they may the 
wonders that confront them in the ninth sphere. But it is ab- 
surd to imagine a primum mobile, and, when imagined, to give 
to it a motion that is completed in twenty-four hours, denying 
that motion to the earth within the same space of time. For 
a great circle of earth, as compared to the circuit of \hz primum 



324 WILLIAM GILBERT., 

mobile is less than a stadium 1 as compared to the whole earth. 
And if the rotation of the earth seems headlong and not to be 
permitted by nature because of its rapidity, then worse than 
insane, both as regards itself and the whole universe, is the 
motion of the primum mobile, as being in harmony or propor- 
tion with no other motion. Ptolemy and the Peripatetics 
think that all nature must be thrown into confusion, and the 
whole structure and configuration of this our globe destroyed 
by the earth's so rapid rotation. The diameter of the earth is 
1718 German miles ; the greatest elongation of the new moon 
is 65, the least 55, semi-diameters of the earth ; but probably 
its orbit is still larger, The sun at his greatest eccentricity is 
distant 1142 semi-diameters from earth; Mars, Jupiter, Saturn, 
as they are slow in movement, so are far more distant from the 
earth. The best mathematicians regard the distances of the 
firmament and the fixed stars as indeterminable ; to say noth- 
ing of the ninth sphere, if the convexity of \hzpmmum mobile be 
fairly estimated in its proportion to the rest, it must travel 
over as much space in one hour as might be comprised within 
three thousand great circles of the earth, for on the convexity 
of the firmament it would travel over more than eighteen 
hundred such circles : but what structure of iron can be 
imagined so strong, so tough, that it would not be wrecked and 
shattered to pieces by such mad and unimaginable velocity ? 
The Chaldees believed the heavens to be light. But in light 
there is no such firmness, neither in the fire-firmament of 
iPlotinus, nor in the fluid or watery heavens of God-inspired 
Moses, nor in the supremely tenuous and transparent firma- 
ment that stands between our eye and the lights of the stars, 
but does not intercept the same. Hence we must reject the 

1 Stadium ancient measure of length, equal to 600 Greek or 625 Roman 
feet, or 125 Roman paces, or to 606 feet 9 inches English. 



DAILY MAGNETIC REVOLUTION OF THE GLOBES. 

deep-seated error about this mad, furious velocity, and this 
forceful retardation of the rest of the heavens. Let the theo- 
logues reject and erase these old wives' stories of a so rapid 
revolution of the heavens which they have borrowed from cer- 
tain shallow philosophers. The sun is not swept round by 
Mars' sphere (if sphere he have) and its motion, nor Mars by 
Jupiter's sphere, nor Jupiter by Saturn's : the sphere of the 
fixed stars, too, seems moderate enough, save that movements 
are attributed to the heavens that really are earth movements, 
and these produce a certain change in the phenomena. The 
higher do not tyrannize over the lower, for the heaven both of 
the philosopher and of the divine must be gentle, happy, 
tranquil, and not subject to changes ; neither will the violence, 
fury, velocity, and rapidity of the primum mobile bear sway. 
That fury descends through all the celestial spheres and heav- 
enly bodies, enters the elements of the philosophers, sweeps 
the fire along, whirls the air around, or at least the greater part 
thereof ; leads in its train the universal ether, and causes it to 
whirl round as though it were a solid and firm body, whereas 
it is a most tenuous substance, that neither offers resistance nor 
is ductile ; and leads captive the fires of the upper heavens. O 
wondrous steadfastness of the globe of earth, that alone is 
unconquered ! And yet the earth is holden nor stayed in its 
place by any chains, by no heaviness of its own, by no con- 
tiguity of a denser or a more stable body, by no weights. 
The substance of the terrestrial globe withstands and resists 
universal nature, 

Aristotle imagines a philosophy of motions simple or com- 
plex, holds that the heavens move with a simple circular 
motion, and his elements with motion in a right line ; that the 
parts of the earth tend to the earth in right lines ; that they 
impinge upon it at the superficies at right angles and seek its 



32(5 WILLIAM GILBERT. 

centre, and there always rest ; and that hence the whole earth 
stands in its place, held together and compacted by its own 
weight. This coherence of parts and this consolidation of 
matter exists in the sun, the moon, the planets, the fixed stars, 
in short, in all those spherical bodies whose parts cohere and 
seek their several centres ; else would the heavens rush to de- 
struction and their grand order disappear. But these heavenly 
bodies have a circular motion, and hence the earth, too, may 
have its motion, for this motion is not, as some suppose, ad- 
verse to cohesion nor to production. For, inasmuch as this 
motion is intrinsic in the earth and natural, and as there is 
nothing without that may convulse it or with contrary motions 
impede it, it revolves untroubled by any ill or peril ; it moves 
on under no external compulsion ; there is nought to make 
resistance, nothing to give way before it, but the path is open. 
For since it revolves in a space void of bodies, the incorporeal 
aether, all atmosphere, all emanations of land and water, all 
clouds and suspended meteors, rotate with the globe : the 
space above the earth's exhalations is a vacuum ; in passing 
through vacuum even the lightest bodies and those of least 
coherence are neither hindered nor broken up. Hence the 
entire terrestrial globe, with all its appurtenances, revolves 
placidly and meets no resistance. Causelessly, therefore, and 
superstitiously, do certain faint-hearts apprehend collisions, in 
the spirit of Lucius Lactantius, who, like the most unlearned 
of the vulgar, or like an uncultured bumpkin, treats with ridicule 
the mention of antipodes and of a round globe of earth. 1 



1 " Yet that which to me seemeth more strange, is that those two learned 
Clearkes, Lactantius ('Divinarum Institut.,' 31, c. 24) and Augustine (' De 
Civitat. Dei/ i. 16, c. 9), should with that earnestnesse deny the being of any 

Antipodes Zachary, Bishop of Rome, and Boniface, Bishop of Mentz, led 

(as it seemes) by the authority of these Fathers, went farther herein, condemn- 



THE EARTH HATH A CIRCULAR MOTION. 327 

From these arguments, therefore, we infer, not with mere 
probability, but with certainty, the diurnal rotations of the 
earth ; for nature ever acts with fewer rather than with many 
means ; and because it is more accordant to reason that the 
one small body, the earth, should make a daily revolution than 
that the whole universe should be whirled around it. I pass 
by the earth's other movements, for here we treat only of the 
diurnal rotation, whereby it turns to the sun and produces the 
natural day (of twenty-four hours) which we call nycthemeron. 
And, indeed, nature would seem to have given a motion quite 
in harmony with the shape of the earth, for the earth being a 
globe, it is far easier and far more fitting that it should revolve 
on its natural poles, than that the whole universe, whose bounds 
we know not nor can know, should be whirled round ; easier 
and more fitting than that there should be fashioned a sphere 
of the primum mobile a thing not received by the ancients, 
and which even Aristotle never thought of or admitted as 
existing beyond the sphere of the fixed stars ; finally, which 
the holy Scriptures do not recognize, as neither do they recog- 
nize a revolution of the whole firmament. 



CHAPTER IV. 

THAT THE EARTH HATH A CIRCULAR MOTION. 

AND now, though philosophers of the vulgar sort imagine, 
with an absurdity unspeakable, that the whole heavens and the 
world's vast magnitude are in rotation, it remains that the 

ing one Virgilius, a Bishop of Saltzburg, as an heretique, only for holding that 
there were antipodes" (Dr. Geo. Hakewill, "An Apologie . . . .," Oxford 1635, 
Lib. Ill, page 281). 



3 2 8 WILLIAM GILBERT. 

earth daily makes one revolution ; for in no third mode can the 
apparent revolutions be accounted for. The day, therefore, 
which we call the natural day is the revolution of a meridian 
of the earth from sun to sun. And it makes a complete revolu- 
tion from a fixed star to the same fixed star again. Bodies 
that by nature move with a motion circular, equable, and con- 
stant, have in their different parts various metes and bounds. 
Now the earth is not a chaos nor a chance medley mass, but 
through its astral property has limits agreeable to the circular 
motion, to wit, poles that are not merely mathematical expres- 
sions, an equator that is not a mere fiction, meridians, too, and 
parallels ; and all these we find in the earth, permanent, fixed, 
and natural ; they are demonstrated with many experiments 
in the magnetic philosophy. For in the earth are poles set at 
fixed points, and at these poles the verticity from both sides of 
the plane of the equator is manifested with greatest force 
through the co-operation of the whole ; and with these poles 
the diurnal rotation coincides. But no revolutions of bodies, 
no movements of planets, show any sensible, natural poles in 
the firmament or in any primum mobile ; neither does any argu- 
ment prove their existence ; they are the product of imagina- 
tion. We, therefore, having directed our inquiry toward a cause 
that is manifest, sensible, and comprehended by all men, do 
know that the earth rotates on its own poles, proved by many 
magnetical demonstrations to exist. For not in virtue only of 
its stability and its fixed permanent position does the earth 
possess poles and verticity ; it might have had another direc- 
tion, as eastward or westward, or toward any other quarter. 
By the wonderful wisdom of the Creator, therefore, forces were 
implanted in the earth, forces primarily animate, to the end the 
globe might, with steadfastness, take direction, and that the 
poles might be opposite, so that on them, as at the extremities 



THE EARTH HATH A CIRCULAR MOTION. 329 

of an axis, the movement of diurnal rotation might be per- 
formed. Now the steadfastness of the poles is controlled by 
the primary soul. Thus it is for the good of the earth that the 
collimations of the verticities do not continually regard a fixed 
point in the firmament and in the visible heavens. For the 
changes of the equinoxes are caused by a certain inflection of 
the earth's axis, yet in this inflection the earth hath from her 
own forces a steadfastness in her motion. In her rotation 
the earth bears on her own poles ; for since the verticity is 
fixed in A and B, and the axis horizontal, at C and D 
(equinoctial line) the parts are free, all the forces being diffused 




on both sides from the plane of the equator toward the poles 
in the aether, 1 which is without resistance, or in vacuum; 

1 Aether, according to Sir Isaac Newton, is a thin subtile matter much 
finer and rarer than air. Sometimes it is termed by him a subtil spirit, as in 
the latter part of his Prindpia, and sometimes a subtil aetherial medium, as in 
his Optics. By many it is supposed to pervade all space, also the interior of 
solid bodies, and to be the medium of the transmission of light and heat. The 
aether of Descartes was his materia subtilis or his First Element ; by which he 
understood a "most subtil matter very swiftly agitated, fluid, and keeps to no 
certain figure, but which suits itself to the figure of those bodies that are about 



330 



WILLIAM GILBERT. 



and, A and B remaining constant, C revolves toward D both 
by natural conformity and fitness, as also for the sake of a nec- 
essary good and avoidance of ill, but most of all because the 
effused spheres of solar influence and of solar light do impel. 
And it revolves not in a new track or one assigned from with- 




out, but, in the general trend of all the rest of the planets, tends 
from west to east. For all planets have a like movement to 
the east, in accordance with the succession of the zodiacal 
signs, whether it be Mercury or Venus within the sun's orbit, or 
whether they revolve round the sun. That the earth is fitted 

it. n His Second Element consists of small globules ; that is, bodies exactly 
round and very solid, which do not only, like the First Element, fill up the 
pores of bodies, but also constitute the purest substance of the ./Ether and 
Heaven (Blome's translation of Descartes' Philos., page 101 ; R. Lovett, " The 
Subtil medium prov'd," London 1756, pages 14, 15). 



THE EARTH HATH A CIRCULAR MOTION. 331 

for circular movement is proved by its parts, which, when sepa- 
rated from the whole, do not simply travel in a right line, as 
the Peripatetics taught, but rotate also. A loadstone placed 
in a wooden vessel is put in water so that it may float freely, 
rotate, and move about. If the pole B of the loadstone be 
made to point, unnaturally, toward the south F, the terrella 
revolves round its centre in a circular motion on the plane of 
the horizon toward the north E, where it comes to a rest, and 
not at C or at D. So acts a small stone weighing only four 
ounces; and a powerful loadstone of 100 pounds will make the 
same movement as quickly ; and the largest mountain of load- 
stone would revolve in the same way were it to be set afloat 
on a wide stream or in the deep sea ; and yet a magnetic body 
is far more hindered by water than is the whole earth by the 
air. The whole earth would act in the same way, were the 
north pole turned aside from its true direction ; for that pole 
would go back, in the circular motion of the whole, toward 
Cynosura. 

Yet this motion is nothing by that circular motion where- 
with the parts naturally tend to their own places. The whole 
earth regards Cynosura by its steadfast nature ; and similarly 
each true part of the earth seeks a like place in the world, and 
turns with circular motion to that position. The natural move- 
ments of the whole and of the parts are alike : hence, since the 
parts move in a circle, the whole, too, hath the power of cir- 
cular motion. A spherical loadstone, when floated in water, 
moves circularly on its centre to become (as it seems) con- 
formed to the earth on the plane of the equator. Thus, too, 
would it move on any other great circle if it were free to move, 
so that in the dip compass there is circular movement on the 
meridian (if there be no variation), or, if there is variation, on 
a great circle drawn from the zenith through the variation point 



33 2 WILLIAM GILBERT. 

in the horizon. And this circular movement of the loadstone 
to its true and natural position shows that the whole earth is 
fitted, and by its own forces adapted for a diurnal circular mo- 
tion. I omit what Petrus Peregrinus so stoutly affirms, that a 
terrella poised on its poles in the meridian moves circularly 
with a complete revolution in twenty-four hours. We have 
never chanced to see this : nay, we doubt if there is such move- 




ment, 1 both because of the weight of the stone itself, and also 
because the whole earth, as it moves of itself, so is propelled 
by the other stars ; but this does not occur proportionately in 
any part of the earth, a terrella for example. The earth moves 
by its primary form and natural desire, for the conservation, 
perfecting, and beautifying of its parts, toward the more ex- 

1 Father Nicolao Cabeo clearly explains what Peregrinus advanced, in Lib. 
Ill, Cap. IV, of his Philosophia Magnetica. 



THE EARTH HATH A CIRCULAR MOTION. 333 

cellent things : this is more probable than that those fixed 
luminous orbs, and the planets and the sun, foremost of all and 
divine, while they get no aid of any sort from earth, no refresh- 
ment, no force whatever, should vainly circle round it, and that 
the whole host of heaven should make everlasting rounds 
about the earth, without any profit whatever to those stars 
themselves. 

The earth therefore rotates, and by a certain law of neces- 
sity, and by an energy that is innate, manifest, conspicuous, 
revolves in a circle toward the sun ; through this motion it 
shares in the solar energies and influences ; and its verticity 
holds it in this motion lest it stray into every region of the sky. 
The sun (chief inciter of action in nature), as he causes the 
planets to advance in their courses, so, too, doth bring about 
this revolution of the globe by sending forth the energies of his 
spheres his light being effused. 

And were not the earth to revolve with diurnal rotation, 
the sun would ever hang with its constant light over a given 
part, and, by long tarrying there, would scorch the earth, re- 
duce it to powder, and dissipate its substance, and the upper- 
most surface of earth would receive grievous hurt : nothing of 
good would spring from earth, there would be no vegetation ; 
it could not give life to the animate creation, and man would 
perish. In other parts all would be horror, and all things frozen 
stiff with intense cold : hence all its eminences would be hard, 
barren, inaccessible, sunk in everlasting shadow and unending 
night. And as the earth herself cannot endure so pitiable and 
so horrid a state of things on either side, with her astral mag- 
netic mind she moves in a circle, to the end there may be, by 
unceasing change of light, a perpetual vicissitude, heat and 
cold, rise and decline, day and night, morn and even, noonday 
and deep night. So the earth seeks and seeks the sun again, 



334 WILLIAM GILBERT. 

turns from him, follows him, by her wondrous magnetical 
energy. 

And not only from the sun would ill impend, were the 
earth to stand still and be deprived of the benefit of his rays ; 
from the moon also great dangers would threaten. For we 
see how the ocean swells and comes to flood under certain 
positions of the moon. But if by the daily rotation of the 
earth the moon did not quickly pass, the sea would rise unduly 
at some parts and many coasts would be overwhelmed by 
mighty tides. Lest the earth, then, should in divers ways 
perish and be destroyed, she rotates in virtue of her magnetic 
and primary energy. And such are the movements in the rest 
of the planets, the motion and light of other bodies especially 
urging. For the moon also turns round during its menstrual 
circuit that it may on all its parts successively receive the 
sun's light, which it enjoys, with which it is refreshed like the 
earth itself ; nor could the moon without grave ill and sure 
destruction stand the unceasing incidence of the light on one 
of its sides only. 

Thus each of the moving globes has circular motion, either 
in a great circular orbit or on its own axis or in both ways. 
But that all the fixed stars, and the planets, and all the higher 
heavens, still revolve simply for the earth's sake is for the 
mind of a philosopher a ridiculous supposition. The earth 
then revolves, and not the whole heavens ; and this movement 
brings growth and decay, gives occasion for the generation of 
animated things, and arouses the internal heat to productive- 
ness. Hence does matter vegetate to receive forms, and from 
this primary revolution of the earth natural bodies have prime 
incitation and original act. The motion of the whole earth, 
therefore, is primary, astral, circular about its poles, whose 
verticity rises on both sides from the plane of the equator, and 



ARGUMENT AGAINST EARTH'S MOTION REFUTATION. 335 

the energy is infused into the opposite ends, so that the globe 
by a definite rotation might move to the good, sun and stars 
inciting. But the simple right-downward motion assumed by 
the Peripatetics is the movement of weight, of coacervation, 
of separated parts, m the ratio of their matter, by right lines 
toward the earth's centre, these tending to the centre by the 
shortest route. The motions of separate magnetical parts of 
the earth are, besides that of coacervation, those of coition, 
revolution, and direction of the parts to the whole, into har- 
mony and agreement of the form. 



CHAPTER V. 

ARGUMENTS OF THOSE WHO DENY THE EARTH'S MOTION; 
AND REFUTATION THEREOF. 

IT will not be superfluous to weigh also the arguments of 
those who deny that the earth moves, to the end we may the 
better satisfy the herd of philosophers who deem the stead- 
fastness and immobility of the globe to be proved by incon- 
trovertible arguments. Aristotle does not allow that the 
earth moves circularly, for, says he, then every part thereof 
would take the same motion ; but inasmuch as all separated 
parts tend to the middle point in right lines, that circular 
motion were something imposed by force, were contrary to 
nature, were not perpetual. But we have already proven that 
all true parts of the earth do move circularly, and that all 
magnetic bodies (when fitly arranged) are borne round in a 
circle. But they tend to the earth's centre in a right line (if 



33^ WILLIAM GILBERT. 

the way is open) by the motion of coacervation, as to their 
origin ; they move with various motions to conformation of 
the whole; a terrella moves circularly by its inborn forces. 
"Besides," says Aristotle, "all things that move in a circle 
seem afterward to lose the first movement and to be carried 
on by several motions other than the first. The earth, too, 
whether situate in the middle or near the middle of the world, 
must needs have two movements ; and were that the case 
there must needs be progressions and retrogressions of the 
fixed stars : no such thing is seen, however, but evermore the 
same stars are rising and setting in the same places." Yet it 
by no means follows that a twofold motion is attributed to 
the earth. And if there be but the one diurnal motion of the 
earth round its poles, every one sees that the stars must 
always rise and set in the same way, at the same points of the 
horizon, even though there be another movement for which 
we are not contending ; because the changes in the smaller 
sphere produce in the fixed stars no variation of aspect on 
account of the great distance, unless the earth's axis changes 
position : of this we treat in the chapter treating of the cause 
of the precession of the equinoxes. 

In this reasoning (of Asritotle's) are many flaws. For if the 
earth rotates, that, as we have shown, must be due not to the 
action of the first sphere, but to its own native forces. And if 
the motion were produced by the first sphere, there would be 
no alternations of days and nights, for the globe would then 
make her revolution along with the primum mobile. And it 
does not follow, because the rest of the heavenly bodies move 
with a twofold motion, that the earth has a twofold motion 
when it rotates round its centre. Then, too, Aristotle does 
not clearly apprehend the reason of the case, nor do his trans- 
lators either, rovrov de avufiairovTOS, avayKaiov yiyrecr- 



ARGUMENT AGAINST EARTH'S MOTION REFUTATION. 337 

Oai Ttapodovs KOI rportaS TGOV evdedefjievcov ao-rpcov (de 
Caelo, Cap. 14) i.e., if that be so there must needs be muta- 
tions and regressions of the fixed stars. Some translate 
rponas " regressions " or " retrogressions/' others " diver- 
sions": these terms can in no wise be understood of axial 
motion unless Aristotle means that the earth is whirled by the 
primum mobile round other poles different even from those of 
the first sphere which is quite absurd. 

More recent writers hold that the Eastern Ocean must 
needs, in consequence of this motion, so be driven toward the 
regions to the west that parts of the earth which are dry and 
waterless would of necessity be daily submerged beneath the 
waters. But the ocean gets no impulsion from this motion, as 
there is no resistance, and even the whole atmosphere is 
carried round also ; for this reason, in the rapid revolution of 
the earth, things in the air around are not left behind nor do 
they have the appearance of moving westward ; the clouds 
stand motionless in the atmosphere, save when impelled by 
the force of the winds ; and objects thrown up into the air fall 
back again to their places. B'lt they are dullards who think 
that steeples, churches, and tJth^r edifices must necessarily be 
shaken and topple down if tne earth moves : antipodes might 
fear lest they should slip over to the other side of the globe ; 
navigators might dread lest in making the circle of the whole 
globe they might, once they had descended below the plane of 
our horizon, drop down into the opposite part of the sky. 
But these are old-wives' imaginings and ravings of philoso- 
phasters who, when they undertake to discourse of great 
things and the fabric of the world and attempt aught, are 
unable to understand hardly anything ultra crepidam. The 
earth they hold to be the centre of a circle and to stand 
motionless in the general revolution. But the stars or the 



33 8 WILLIAM GILBERT. 

planetary globes do not move in a circle round the centre of 
the earth ; nor is the earth the centre if it be in the centre 
but a body around the centre. 

And it is inconsistent that the Peripatetics' heavenly bodies 
should rest on so frail, so perishable, a thing as the earth's 
centre. 

Now generation results from motion, and without motion 
all nature would be torpid. The sun's motions, the moon's 
motions, produce changes ; the earth's motion awakens the 
inner life of the globe ; animals themselves live not without 
motion and incessant working of the heart and the arteries. 
As for the single motion in a right line to the centre, that this 
is the only movement in the earth, and that the movement of 
an individual body is one and single, the arguments for it 
have no weight, for that motion in a right line is but the incli- 
nation toward their origin, not only of the earth, but also of the 
parts of the sun, the moon, and all the other globes ; but these 
move in a circle also. Joannes Costeus, who is in doubt as to 
the cause of the earth's motion, regards the magnetic energy 
to be intrinsic, active, and controlling ; the sun he holds to be 
an extrinsic promovent cause ; nor is the earth so mean and 
vile a body as it is commonly reputed to be. Hence, according 
to him, the diurnal motion is produced by the earth, for the 
earth's sake and for the earth's behoof. 

They (if such there be) who assert that this movement of 
the earth takes place not only in longitude but also in latitude, 
speak nonsense ; for nature has set in the earth definite poles 
and has established definite and not confused revolutions. 
Thus the moon turns round to the sun in its monthly course, 
the while ever regarding with definite poles definite parts .of 
the heavens. It were absurd to suppose that the atmosphere 
moves the earth ; for the air is but exhalation and the effluvium 



ARGUMENT AGAINST EARTH'S MOTION REFUTATION. 339 

of the earth given out in every direction ; winds, too, are only 
motions of the exhalation here and there along the earth's sur- 
face ; the depth of the air current is trifling, and there are in 
every region various winds from different and opposite points. 
Some authors, not finding the cause of the revolution in the 
earth's matter for there they say they find only solidity and 
consistence maintain that it is not to be found in the form, 
and will admit as qualities of the earth only cold and dryness, 
which cannot produce the earth's motion. The Stoics attribute 
to the earth a soul, and hence they declare, amid the derision 
of the learned, that the earth is an animal. This magnetical 
form, be it energy or be it soul, is astral. Let the learned 
lament and weep for that neither the early Peripatetics, nor 
the common run of philosophasters, nor Joannes Costeus, who 
mocks at this sort of thing, were capable of appreciating this 
grand and most extraordinary fact of nature. As for the ob- 
jection that the superficial unevenness produced by mountains 
and valleys would prevent diurnal revolution, it is of no weight ; 
for mountains do not mar the rotundity of the earth as com- 
pared with the entire earth, mountains are but trifling excres- 
cences : besides, the earth does not rotate without carrying 
along with it its effluences. Beyond the effluences there is no 
resistance. The earth's motion is performed with as little labor 
as the motions of the other heavenly bodies : neither is it 
inferior in dignity to some of these. To say that it is folly to 
suppose the earth is more eager for the face of the sun than 
the sun for the face of the earth, is mere wilfulness and igno. 
ranee. Of the cause of the rotation I have oft spoken. If any 
one were to look for the cause of the rotation or any other 
tendency of the earth on the globe-encircling ocean, or in the 
movement of the atmosphere, or in the heaviness of the earth's 
mass, he would reason as stupidly as do those who obstinately 



34 WILLIAM GILBERT. 

cling to an opinion because it was held by the ancients. Ptol- 
emy's arguments are of no account ; for our true principles 
once laid down, the truth is visible, and it is useless to refute 
Ptolemy. So let Costeus and the philosophers recognize how 
'inprofitable and vain a thing it is to take their stand on the 
Joctrines and unproved theories of certain ancient writers. 
Many persons cannot see how it is (if the earth rotates) that a 
ball of iron or lead dropped from a very high tower falls 
exactly on the spot right below ; or how cannon-balls fired 
from a large culverin with equal charges of gunpowder of the 
same quality, and with the gun pointed at the same angle with 
the horizon, have exactly the same range to eastward and to 
westward, the earth moving to the east. But they who urge 
such arguments are mistaken through not understanding the 
nature of primary globes and the combination of parts with 
their globes, albeit not conjoined thereto with bonds of solid 
matter. But the earth in its diurnal revolution does not so 
move that its more solid circumference is separated from the 
bodies circumfused ; on the contrary, all the circumfused efflu- 
ences, and all heavy bodies therein, howsoever shot thereinto, 
advance simultaneously and uniformly with the earth because 
of the general coherence. This is the case in all primary 
bodies, the sun, moon, earth, the parts betaking themselves 
to their origin and founts, whereunto they are attached with 
the same appetence with which what we call heavy bodies are 
attached to earth. Thus lunar bodies tend to the moon, solar 
to the sun, within the respective spheres of their effluences. 
These effluences cohere through continuity of substance ; and 
heavy bodies, too, are united to earth by their heaviness and 
advance with it in the general movement, especially when no 
resistance of bodies hinders. And, for this reason, the diurnal 
revolution of the earth does not sweep bodies along nor retard 



ARGUMENT AGAINST EARTH'S MOTION REFUTATION. 341 

them : they neither outstrip the earth's motion nor fall behind 
when shot with force, whether to east or to west. Let EFG 




be the earth, A the centre, LE the ascending effluences. As 
the sphere of the effluences moves with the earth, so the part 
of the sphere on the right line LE proceeds undisturbed in the 
general rotation. In LE the heavy body M falls perpendicu- 
larly to E, the shortest route centreward ; nor is this right 
motion of M a composite motion, i.e., resultant of a motion 
of coacervation and a circular motion, but simple and direct, 
never going out of the line LE. And an object shot with 
equal force from E toward F, and from E toward G, has the 
same range in both directions, though the diurnal rotation of 
the earth goes on ; even as twenty steps taken by one man 
cover the same distance eastward as westward. Hence the 
diurnal revolution of the earth is not at all refuted by the illus- 
trious Tycho Brahe through such arguments as these. 

The tendence to its centre (called by philosophers, weight) 



34 2 WILLIAM GILBERT. 

works no resistance to the diurnal revolution, neither does it 
give direction to the earth, nor keep in place the parts of the 
earth, which have no weight when resting in the earth's solid 
substance : there they have no longer any tendence, but are at 
rest in its mass. If there be a flaw in the mass, a cavity of 
1000 fathoms for example, a homogenic part of the earth or 
compacted terrestrial matter descends through that space, be 
it rilled with water or with air, to a more definite centre (prin- 
cipium) than air or water, and seeks the solid globe. But the 
centre of the earth, as also the whole earth itself, has no weight: 
separated parts tend to their principium, and this tendence we 
call weight : parts in union are at rest, and even if they had 
weight, they would cause no impediment to the diurnal revo- 
lution. For if around the axis AB a weight be at C t it is 




balanced by E ; at F it is balanced by G ; if at H, by 7. And, 
similarly, if it is at , it is balanced by M. Thus the whole 
globe, having a natural axis, is balanced in equilibrium and is 
set in motion easily by the slightest cause, but chiefly for the 
reason that the earth, in its own place, is in no wise heavy nor 



DEFINITE TIME OF THE REVOLUTION OF THE EARTH. 343 

needs any balancing. Hence no weight hinders the diurnal 
revolution, and no weight gives to the earth direction or con- 
tinuance in its place. It is therefore plain that no argument of 
sufficient force has yet been formed by philosophers to refute 
the earth's motion. 



CHAPTER VI. 

OF THE CAUSE OF THE DEFINITE TIME OF THE TOTAL 
REVOLUTION OF THE EARTH. 

THE causes of the diurnal motion are to be found in the 
magnetic energy and in the alliance of bodies : that is to say, 
why a revolution of the earth is performed in the term of 24 
hours. For no ingenious artifice, whether of clepsydra, 1 or of 
hour-glasses, or of time-pieces with toothed wheels and driven 
by the tension of a steel plate, can show any difference of time. 
But the diurnal revolution once accomplished comes on again. 
Now we will take a day to mean a complete revolution of a 
meridian of the earth from sun to sun. This is a little less 
than the total revolution ; for in 365 J turnings of a meridian 
to the sun a year is completed. Because of this fixed and 

1 The Clepsydra, or water clock, is said by Vitruvius to have been first 
made by the Egyptians or Persians. Perhaps the most remarkable one was 
that sent as a present by Haroun, grandson of Almansor, to Charlemagne in 
A.D. 799. In the dial-plate were 12 doors, equally distant, upon which were 
inscribed the hours successively ; each door opened in its turn, and let fall, 
upon a brazen bell, a sufficient number of balls to strike the proper hour. The 
doors continued open till 12 o'clock, when 12 little knights, mounted on horse- 
back, issued simultaneously from a part of the machine, paraded around the 
dial, and, having closed the 12 doors, as suddenly retired (Morel, " Elem. 
Ph. and Sc.," London 1827, P ars - 2IO 22 4- Consult M. Delambre, "Hist, de 
1'Astr. Anc ," Paris 1817, Vol. I, Table page Ivii). 



344 WILLIAM GILBERT. 

constant motion of the earth the number and time of 365 days 
5 hours 55 minutes are always fixed and settled, barring that 
for other causes there are certain trifling differences. Thus 
the earth revolves, not fortuitously nor by chance, nor with a 
headlong motion, but evenly, with a certain high intelligence 
and with a wonderful steadiness, even like the rest of the 
movable stars which have fixed periods for their movements. 

Thus, inasmuch as the sun itself is the mover and inciter 
of the universe, the other planets that are situate within the 
sphere of his forces, being impelled and set in motion, do also 
with their own forces determine their own courses and revolve 
in their own periods, according to the amplitude of their greater 
rotation and the differences of the forces effused and the per- 
ception of a greater good. Hence it is that Saturn, having a 
greater course to run, revolves in a longer time, while Venus 
revolves in nine months, and Mercury in 80 days, according to 
Copernicus ; and the moon makes the circuit of the earth in 
29 days 12 hours 44 minutes. We have asserted that the 
earth turns on its centre, making one day in its revolution sun- 
ward. The moon goes round the earth in a monthly course, 
and when after its prior conjunction with the sun it comes to 
conjunction again, it constitutes one month, or one lunar day. 
The mean distance of the moon's orbit, according to the calcu- 
lations of Copernicus and other later astronomers, is distant 
from the earth's centre about 29^ diameters of the earth. A 
solar revolution of the moon in her orbit takes 29 days 12 
hours 44 minutes. We reckon her periodic time by her re- 
turn to the same position relatively to the sun, making the 
moon's solar revolution, not by her return to the same absolute 
position, making the complete or stellar revolution, just as one 
day on earth is reckoned as the planets return to the same 
position relatively to the sun, and not absolutely ; because the 



DEFINITE TIME OF THE DEVOLUTION OF THE EARTH. 345 

sun is the cause of both the earth's and the moon's motions. 
Also, because (as more recent astronomers suppose) the month, 
as measured between solar conjunctions, is really the full period 
of revolution, because of the earth's motion in her great orbit. 
Diameters bear a constant ratio to circumferences. And the 
moon's orbit is a little more than twice 29^ times the length 
of great circles on the earth. 

Thus the moon and the earth agree in a twofold ratio of 
motion, and the earth rotates in its diurnal motion in the 
space of 24 hours; because the moon has a motion propor- 
tioned to the earth, and the earth has a motion agreeing in a 
twofold proportion with the moon's motion. There is some 
difference in minutes, for the distances of the stars are not 
sufficiently determined in minutes, nor are astronomers agreed 
thereupon. So, then, the earth rotates in the space of 24 
hours, even as the moon does in her monthly course, by a 
magnetical compact of both, the globes being impelled for- 
ward according to the ratio of their orbits, as Aristotle admits 
(de Ccelo, Book II, Chap. X). " It comes about," says he, " that 
the motions of each are performed in a ratio, to wit, in the 
same intervals whereby some are quicker, others slower." But 
as between the moon and the earth, it is more reasonable to 
believe that they are in agreement, because, being neighbor 
bodies, they are very like in nature and substance, and be- 
cause the moon has a more manifest effect on the earth than 
have any of the other stars, except the sun ; also the moon 
alone of all planets directs its movements as a whole toward 
the earth's centre, and is near of kin to earth, and as it were 
held by ties to earth. 

Such, then, is the symmetry and harmony of the moon's 
and the earth's movements, very different from the oft-men- 
tioned harmony of the celestial motions, which requires that 



34^ WILLIAM GILBERT. 

the nearer any sphere is to the primum mobile and to the 
imaginary and fictitious rapid first motion, the less it opposes 
it (contranitatur) and the more slowly it is borne by its own 
motion from west to east ; but that the farther it is away the 
more rapidly and the more freely it performs its motion, and 
hence that the moon (being farthest from the primum mobile) 
revolves with greatest rapidity. These absurdities have been 
accepted for the sake of the primum mobile, and so that it 
might seem to have some effect in retarding the movements 
of the nether heavens ; as though the motion of the stars was 
due to retardation, and was not inborn and natural to them, 
and as though the rest of the heavens (the primum mobile 
alone excepted) were ever driven by a mighty force with a 
mad impulsion. Far more probable is it that the stars revolve 
symmetrically, with a certain mutual concert and harmony. 1 

1 Dr. Wm. Whewell says (" Hist, of the Ind. Sc.," 1859, Vol. I, page 
394) that Gilbert had only some vague notions that the magnetic virtue of the 
earth in some way determines the direction of the earth's axis, the rate of its 
diurnal rotation, and that of the revolution of the moon about it. He died in 
1603, and in his posthumous work (De Mundo nostro Sublunari Philosophia 
nova, 1631) we have already a more distinct statement of the attraction of one 
body by another. " The force which emanates from the moon reaches to the 
earth, and, in like manner, the magnetic virtue of the earth pervades the region 
of the moon: both correspond and conspire by the joint action of both, accord- 
ing to a proportion and conformity of motions, but the earth has more effect in 
consequence of its superior mass ; the earth attracts and repels the moon, and 
the moon, within certain limits, the earth ; not so as to make the bodies come 
together, as magnetic bodies do, but so that they may go on in a continuous 
course." Though this phraseology is capable of representing a good deal of 
the truth, it does not appear to have been connected, in the author's mind, 
with any very definite notions of mechanical action in detail. 



THE EARTH'S PRIMARY MAGNETIC NATURE. 347 



CHAPTER VII. 

OF THE EARTH'S PRIMARY MAGNETIC NATURE, WHEREBY 
HER POLES ARE MADE DIFFERENT FROM THE POLES OF 
THE ECLIPTIC. 

HAVING shown the nature and causes of the earth's diurnal 
revolution, produced partly by the energy of the magnetic 
property and partly by the superiority of the sun and his light, 
we have now to treat of the distance of the earth's poles from 
those of the ecliptic a condition very necessary for man's 
welfare. For if the poles of the world or the earth were 
fixed at the poles of the zodiac, then the equator would lie 
exactly under the line of the ecliptic, and there would be no 
change of seasons, neither winter, nor summer, nor spring, 
nor fall, but the face of things would persist forever unchang- 
ing. Hence (for the everlasting good of man) the earth's axis 
declined from the pole of the zodiac just enough to suffice for 
generation and diversification. Thus the declination of the 
tropics and the inclinations of the earth's pole always stand 
in the 24th degree, but is at present only 23 deg. 28 min., or, 
according to others, 29 minutes ; but formerly the declination 
was 23 deg. 52 min., and that is the uttermost limit of declina- 
tion so far observed. This has been wisely ordered by nature 
and settled by the earth's primary eminency. For were those 
p l es _those of the earth and the ecliptic to be much farther 
apart, then as the sun approached the tropic all things would 
be waste and ruin, in any high latitude of the other and 
neglected portion of the globe, because of the protracted 



348 WILLIAM GILBERT. 

absence of the sun. But now all things are so disposed that 
the entire globe of earth has its own changes in due succession, 
its own fitting and needful seasons, either through a more 
direct radiation from overhead or by a longer tarrying of the 
sun above the horizon. 

Around these poles of the ecliptic the bearing of the 
earth's poles rotates, and because of this motion we have the 
precession of the equinoxes. 



CHAPTER VIII. 

OF THE PRECESSION OF THE EQUINOXES BY REASON OF 
THE MAGNETIC MOVEMENT OF THE EARTH'S POLES IN 
THE ARCTIC AND ANTARCTIC CIRCLE OF THE ZODIAC. 

THE early astronomers, not noting the inequality of years, 
made no distinction between the equinoctial or solstitial re- 
volving year and the year determined from a fixed star. They 
also deemed the Olympian years, which were reckoned from 
the rising of the Dog Star or Sirius (Caniculd) to be the same 
as those reckoned from the solstice. Hipparchus the Rhodian 
was the first to notice that there is a difference between the 
two, and found another year, calculated from fixed stars, of 
greater length than the equinoctial or solstitial : hence he sup- 
posed that the stars too have a consequent motion, though a 
very slow one, nor readily noticeable. After Hipparchus, 
Menelaus, a Roman geometer, then Ptolemy, and, a long time 
afterward, Machometes Aracensis and several others, in all 
their writings have held that the fixed stars and the whole fir- 



THE PRECESSION OF THE EQUINOXES. 349 

mament have a consequent forward movement (in consequentia 
procedere), for they contemplated the heavens and not the earth, 
and knew nothing of the magnetic inclination. But we will 
prove that this motion proceeds from a certain revolution of 
the earth's axis, and that the eighth sphere, so called, the fir- 
mament, or aplanes, with its ornament of innumerable globes 
and stars (the distances of which from earth have never been 
by any man demonstrated, nor ever can be), does not revolve. 
And surely it must seem more probable that the appearances 
of the heavens should be produced by a deflection and inclina- 
tion of the small body, the earth, than by a whirling of the 
whole system of the universe especially as this movement is 
ordered for the good of the earth alone, and is of no benefit at 
all to the fixed stars or the planets. For by this motion the 
rising and setting of stars in all horizons are changed, as also 
their culminations in the zenith, so that stars that once were 
vertical are now some degrees distant from the zenith. Pro- 
vision has been made by nature for the earth's soul or its 
magnetic energy just as in attempering, receiving, and divert- 
ing the sun's rays and light in fitting seasons, it was necessary 
that the bearings of the earth's pole should be 23 degrees and 
more distant from the poles of the ecliptic ; so that now in 
regulating and in receiving in due order and succession the lu- 
minous rays of the fixed stars, the earth's poles should revolve 
at the same distance from the ecliptic in the arctic circle of 
the ecliptic, or rather that they should creep with slow gait, 
because the actions of the stars do not always persist in the 
same parallel circles, but have a slower change ; for the influ- 
ences of the stars are not so powerful that the desired course 
should be more rapid. So the axis is inflected slowly, and the 
rays of the stars are changed in such length of time as the di- 
ameter of the arctic or polar circle extends ; hence the star in 



35 WILLIAM GILBERT. 

the extremity of the tail of Cynosura, which pnce (i.e., in the 
time of Hipparchus) was 12 degrees 24 minutes distant from 
the pole of the world or from the point which the earth's pole 
regarded, now is distant from it only 2 degrees $2 minutes ; 
hence from its nearness to the pole it is called by the moderns 
the Pole Star. 1 It will not be only degree from the pole, but 
thereafter will begin to recede till it reaches a distance of 48 
degrees ; that, according to the Prutenic tables, 8 will be A.D. 
15,000. So the bright star (which for us here, in southern 
Britain, now almost culminates) will in time come within five 
degrees of the world's pole. Thus do all the stars change 
their light rays at the earth's surface, because of this admirable 
magnetic inflection of the earth's axis. Hence the ever new 
changes of the seasons ; hence are regions more or less fruitful, 
more or less sterile ; hence changes in the character and the 
manners of nations, in governments and in laws, according to 
the power of the fixed stars, the strength thence derived or 
lost, and according to the individual and specific nature of the 
fixed stars as they culminate ; or the effects may be due to 



1 Hakewill alludes (Apologie, 1635, Lib. ii, page 97) to Hipparchus, 
"who reports that in his time the starre commonly called the Polar Starre, 
which is in the tayle of the lesser Beare, was 12 degrees and two-fifths distant 
from the Pole of the Equator. This starre, from age to age, hath insensibly 
still crept nearer to the Pole, so that at this present it is not past three de- 
grees distant from the Pole of the ^Equator. When this starre then shall come 
to touch the Pole, there being no farther place left for it to go forward (which 
may well enough come to pass with five or six hundred yeares) it is likely that 
then there shall be a great change of things, and that this time is the period 
which God hath prefixed to Nature." (See Morell's "Elem. . . .Phil, and Sc.," 
London 1827, pp. 116-119 et seg.) 

2 The Prutenic (Prussian) Astronomical Tables, Pruteniccz Tabula Cceles- 
tium Afotuum, 1551, 1571, 1585, based upon the observations of Copernicus, 
Hipparchus, and Ptolemy, were the result of seven years' labor on part 
of the German astronomer Erasmus Reinhold, who named the work after his 
benefactor, Albert, Duke of Prussia, 



THE PRECESSION OF THE EQUINOXES. 351 

their risings and settings or to new conjunctions in the me- 
ridian. 

The precession of the equinoxes from the equal motion of 
the earth's pole in the zodiacal circle is here demonstrated. 




Let ABCD be the ecliptic; IEG the Arctic zodiacal circle. 
Now if the earth's pole looks toward E, then the equinoxes 
are at D, C. Suppose this to be in the time of Metho, 1 when 

1 The celebrated astronomer Meton flourished at Athens B.C. 432-430. 
The mean length of the Metonic Cycle, or Metonic Year, was 6939! days, 
which coincides with 19 Julian Years and nearly corresponds to 235 lunations. 
An improvement on the Metonic Cycle was proposed by Calippus of Cyzicus, 
a disciple of Plato. The Calippic Period consisted of 76 years, representing 
four Metonic Cycles, or about 940 complete lunations, 1020 nodal and 1016 
complete sidereal revolutions. After this, says Hake will, (Apologie 1635, Lib. 
Ill, page 279), Hipparchus framed another Cycle, "containing foure of Calippus 
his periods, each of them (all in turn) finding some errour in the former obser- 



35 2 WILLIAM GILBERT. 

the horns of Aries were in the equinoctial colure. 1 But if the 
earth's pole has advanced to /, then K, L will be the equinoxes, 
and stars in the ecliptic C will seem to have moved forward 
over the whole arc KC, following the signs; L advances by 
precession over the arc DL, counter to the order of the signs ; 
but the opposite would be the case if the point G were to 
regard the earth's poles, and the motion be from E toward G ; 
for then M, A 7 " would be the equinoxes, and the fixed stars would 
anticipate at C and D, counter to the order of the signs. 



CHAPTER IX. 

OF THE ANOMALY OF THE PRECESSION OF THE EQUINOXES 
AND OF THE OBLIQUITY OF THE ZODIAC. 

THE change in the equinoxes is not always equal, but 
becomes sometimes more rapid, sometimes more slow ; for the 
earth's poles travel unequally in the Arctic and in the Antarc- 
tic zodiacal circle, and recede from the middle line on both 

vations which they diligently amended. ..." Hipparchus, first and greatest of 
Greek astronomers, is the inventor of the astrolabe as well as the discoverer of 
the "precession of the equinoxes," and left many important works including a 
catalogue showing the latitude and longitude of over 1000 stars. It was Coper- 
nicus, however, who first gave the true explanation of the phenomenon known 
as the precession of the equinoxes, and Newton who discovered its physical cause 
(G. J. Chambers, " Descrip. Astronomy," Oxford 1867, page 240). 

1 The colure is one of two great circles which intersect at right angles in 
the poles of the equator. To Eratosthenes, the Librarian at Alexandria, who 
flourished about A.c. 280, is attributed the invention and construction of an in- 
genious and useful instrument or machine, having some resemblance to the 
armillary sphere, which exhibited the relations of the meridian to the 
equatorial and ecliptic lines, and thus indicated the solstitial and equinoctial 
colures. 



ANOMALY OF THE PRECESSION OF THE EQUINOXES. 353 

sides ; hence the obliquity of the zodiac seems to change to 
the equator (ad (zquatorem immutari). And when this became 
known through protracted observations, it was apparent that 
the true equinoctial points were elongated from the mean 
equinoctial points 70 minutes to one side or the other in 
the greatest prostaph&resi ; while the solstices either approach 
the equator equally by 12 minutes or recede to the same 
extent ; so that the nearest approach is 23 deg. 28 min. 
and the greatest elongation 23 deg. 52 min. Astron- 
omers in accounting for this inequality of precession and 
of declination of the tropics have offered "various theories. 
Thebitius, to establish a law for these great inequalities in the 
movements of the stars, held that the eighth sphere does not 
advance by continued motion from west to east, but that it has 
a sort of tremulous motion (motu quodam trepidationis concuti) 
whereby the leading stars in Aries and in Libra of the eighth 
heavens describe around the leading stars of Aries and Libra 
of the ninth sphere certain small circles with diameters equal 
to about nine degrees. But as this " motion of trepidation" 1 
is full of absurdities and impossible motions, this movement 
has gone out of fashion. Other astronomers, therefore, are 
compelled to ascribe motion to the eighth sphere, and atop of 
this to construct a ninth heaven, nay a tenth and an eleventh. 2 
We .must pardon slips in mathematicians, for one may be per- 
mitted in the case of movements difficult to account for to offer 
any hypotheses whatever in order to establish a law and to 
bring in a rule that will make the facts agree. But the phil- 
osopher never can admit such enormous and monstrous celes- 
tial constructions. 



1 See note, Book III, Chap. I. 
See note, Book VI, Chap. III. 



354 WILLIAM GILBERT. 

Now though we see in all this how loath these mathema- 
ticians are to ascribe any motion to the earth, which is a very 
small body, nevertheless they drive and whirl the heavens, 
which are vast and immense beyond human comprehension and 
human imagination : they construct three heavens, postulate 
three inconceivable monstrosities, to account for a few unex- 
plained motions. Ptolemy, comparing with his own observa- 
tions those of Timochares and Hipparchus, of whom the one 
lived 260 years before his day and the other 460 years, deemed 
this to be the motion of the eighth sphere and of the whole 
firmament, and proved it with many phenomena on the poles 
of the zodiac ; and, still thinking its motion to be equal, he 
held that the fixed stars in 100 years travel only one degree 
beneath the primum mobile. Seven hundred and fifty years 
after him, Abitegnius found that one degree is travelled over 
in 66 years, so that the whole period would be 23,760 years. 
Alphonsus would have this motion still slower I degree 28 
minutes in 200 years ; and thus would the course of the fixed 
stars proceed, but unequally. At last Copernicus, through his 
own observations and those of Timochares, Aristarchus the 
Samian, Menelaus, Ptolemy, Machometes Aracensis and Al- 
phonsus, discovered the anomalies of the motion of the earth's 
axis ; though I have no doubt that other anomalies also will 
appear some centuries hence, for it is difficult, save in periods 
of many ages, to note so slow a movement, wherefore we still 
are ignorant of the mind of nature, what she is aiming at 
through this inequality of motion. Let A be the pole of the 
ecliptic, BC the ecliptic, D the equator ; when the earth's pole 
regards the point J/near the arctic circle of the zodiac let the 
anomaly of the precession of the equinox be at F t but when it 
regards N, let the anomaly of the precession be at E. So 



ANOMALY OF THE PRECESSION OF THE EQUINOXES. 355 

long as it regards / directly there is observed the maximum 
obliquity G in the solstitial colure ; but while it regards Z, 




then there is minimum obliquity H in the colure of the sol- 
stices. 



356 



WILLIAM GILBERT. 



Copernicus' 3 intorta corolla in the arctic zodiacal circle. 

FGB is one half of an arctic circle described around the 
pole of the zodiac ; ABC is the colure of the solstices ; A the 
pole of the zodiac ; DE the anomaly of longitude 140 minutes 
on either side, with twofold terminus (duplici termind) ; BC 
anomaly of obliquity, 24 minutes ; B the greater obliquity, 
23 degrees 52 minutes ; D the mean obliquity, 23 degrees 40 
minutes ; C the minimum obliquity, 23 degrees 28 minutes. 




True movement and natural axis (or poles) of the earth directed 
toward the arctic circle of the zodiac. 

Let AI be part of the arctic circle of the zodiac in which is per- 
formed one period of the obliquity. From A to E is the period 
of the anomaly or variation of the precession of the equinoxes. 
AI is the curved line described by the earth's pole in a true mo- 
tion made up of three motions, i.e., of the motion of the preces- 
sions, and of the anomaly of the precessions, and of obliquity. 



ANOMALY OF THE PRECESSION OF THE EQUINOXES. 357 

The period of the precession of the equinoxes is 25,816 Egyptian 
years ; the period of the obliquity of the zodiac is 3434 years 
and a little more ; the period of the anomaly of the precession 
of the equinoxes is 1717 years and a little more. If we divide 
the whole time of the motion from A to / into eight equal 
parts, in the first eighth part the pole travels faster from A to 




B ; in the second more slowly from B to C ; in the third, with 
the same slowness from C to D ; in the fourth, more rapidly 
again from D to E\ in the fifth, with equal rapidity from 
E to F; again more slowly from Fto G\ with the same slow- 
ness from G to H\ in the last eighth again more rapidly from 
H to /, and this is Copernicus's intorta corolla * with mean 
motion fused into a curved line, which is the true path of the 

1 See Nicolai Copernid Torinensis, De Revolutionibus orbium ccelestium, 
Norimbergise 1543, pages 66, 67, or the Amstelrodami ed. of 1617, pages 154- 
157. The intorta corolla is not an inverted but an irregular crown : a figure 
representing the successive positions produced by the projection of the earth's 
pole upon the stellar sphere, resembling a crown, but distorted by the irregular- 
ities of motion. (Consult, also, Rheticus, " Narratio prima de Lib. Rev. Co- 
pernici;" Kepler, "De Temporis aequatione plenaria et muu octavae sphaerae.) 



358 WILLIAM GILBERT. 

motion. And so the pole reaches the extreme limit of varia- 
tion of the precession of the equinoxes twice, but the limit of 
inclination or obliquity once only. Thus do the moderns, and 
in particular Copernicus, restorer of astronomy, describe the 
variations of the movement of the earth's axis, so far as the 
same is made possible by the observations of the ancients down 
to our day ; but we still lack many and more exact observations 
to fix anything positively as to the anomaly of the movement 
of the precessions, as also of the obliquity of the zodiac. For 
since the time when in various observations this anomaly was 
first noted, only one half of a period of obliquity has passed. 
Hence all these points touching the unequal movement of 
precession and obliquity are undecided and undefined, and so 
we cannot assign with certainty any natural causes for the 
motion. 

Wherefore we here bring to an end and conclusion our 
arguments and experiments magneticaL 



FINIS. 




Siue 

PHYSIOLOGIANOV^A 
DEMAGNETE, 

MAGNETICISQVE CORPO 



RIBVS ET WA.GNO MA.0NETE 
tclfurcScx 



Guiliclwo Oilier! o Colceflrctifi 

Medico 



ddiua quamantem 
^ illu 




FAC-SIMILE TITLE PAGE OF GILBERT'S " DE MAGNETI, " SECOND EDITION, 1628. 

359 



Traftatus,fi e ve Phyfiologia Nova 

M A G N E T E , 

MagneticifqiCbrporibus & magno 

Magnete tellure, fcx libris comprehenfus* 

aGulLlELMO GlLBERTO CoIcC- 

ftrenfi, Medico LondinenfL 

In quilt** ea,qu& adbancmateriamfjseffant,p!urimis 

if Arguments tf experlmentis exafli/ime abfolutifii- 
me traftantur & 



Oinnia nunc diligenter recognita,& emendafiusquam ante 
in lucem ediu , aufta & figuris illollrata , opera & ftadio D 

WOLFGANGI LOCHMANS, I. 17- D. 

& Mathematics 



Ad calcetn libri adiunflus eft Index capltum , 

loctyletifsims, qui inpnoye tditione defiderabatw. 




E D I N I , 



Typis G O T Z I A N I S 
M. DC. xxxui, 



FAC-SIMILE TITLE PAGE OF GILBERT'S " DE MAGNETE," THIRD EDITION. 



G V I L I E L M I GILBERT I 
CPXC E S T REN SI $, 
Medici Regii, 

De Mundo noftro Sublunari 

PHILOSOPHIA 

NOVA. 

Opus pofthumum, 



rt collegium pridem 
w v & c 

Ex duobus M S S. codicibus cditum. 
ExMuftioviri perilluftrb 

;i :;t i E L M i B o s w E L L i Equitis aurati 8cc 
'& Pratoris apud Foederatos Belgas Angli., 




J M S TE I Q D A M I, 

Apud Liidovicum Elzevirium i 

C I O 1 3 C L i. 

FAC-SIMILE TITLE PAGE OF GILBERT'S " DE MUNDO NOSTRO SUBLUNARI PHILO- 
SOPHIA NOVA." 



GENERAL INDEX. 



Abano Pietro di, (Petrus Aponus, 

1250-1316,) 2, 33 
Abitegnius, 354 

Abohali (Hali Abbas), 4, 13, 76 
Acies, Aciarum, 32, 40, 55, 59 
Adamant stone, 21 
Adamas, 21, 22, 218 
Affaitatus, Fortunius, 4 
Afformed iron, 112 
Agricola, George, 3, 5, 20, 34, 45, 173, 

174 

Agrippa, Cornelius, 4 
Agulhas, Cape, 266 
Aimant, 21 

Airy, G. B., " Magnetism," 284 
Albertus Magnus, 4, 9, 13, 21, 33, 172 
Aldrovandi, Ulysses, 215 
Alexander of Aphrodisias (in Caria), 

5, 78, 145 

Alfonso, Diego, 266 
Allibone, S. A., "Critical Diet.," xix 
Alphonsus Alfonso X., El Sabio, 

321, 354 
Ambra, 76 

Ampelius, Ansonio L., 4 
Amphitane, 172 
Anaxagoras, 98, 308 
Anelectrics, 83 

Antiperisastis (counteraction), 175 
Appian, Peter, 8 
Apponensis, Petrus, 4 
Aquinas, Thomas, 5, 103 
Archelaus, 308 
Ardoniis, Santes de, 4 
Arias, Montanus, Benedictus, (Benito 

Arias Montano, 1527-1598,) 7 
Arnaldus, 4 

Aristarchus of Samothrace, 317, 354 
Aristotle, vi, li, 2, 22, 32, 34, 35, 40, 

57, 63, 69, 72, 98, 105, 309, 312, 320, 

325, 335, 336, 337 345 



Arsinoe, temple of, 3 

Asterisks (throughout the present 

work), xlix 
Attraction, 97 
Augustine, St., (Aurelius Augustinus, 

354-430,) 326 
Averroes, (Ibn-Roshd, 1149-1198,) 

2,9 
Avicenna, (Aben Sina, Ibn-Sina, 980- 

1037,) 4, 9, 45, 56, 58, 80 
Azuni, Domenico Alberto, (1749-1827,) 

7 

Bacon, Francis, xii, xiii, xv, xvi, xxv 

Bacon, Roger, 9 

Barbatus, Hermolaus, 4 

Barlo (Barlowe), William, xiii, xiv, xv, 

xxv, xxvi, 14 

Benedictus, Joannes Baptista, 252 
Benjamin, Dr. Park, vi xxi > xxv 
Bertelli Barnabita o l66 > IO 7 
Bescherelle, M., " Gr and Diet.," xx 
Bessard, 10, 179, 232 
Bianco, Andrea, 252 
Biarmia, 12, 271 

" Biographia Britannica" ix, xxiii 
Blunderville, Thomas, "The Theo- 

nques . . . ," xix 

Bodies, electric and magnetic, 97 
"Bone of Horus," 17 
Boniface, Saint, (archbishop of Mainz, 

680-755.) 326 
Borough, William, 14 
Boswell, Sir William, xxv 
Bowen, Mr., " Comp. Sys. of Geog.," 

xx 

Boyle, Robert, 78, 92 
Bractea (see Scales of Iron) 
Brande, W. T., 143 
Brando", 272 
Brasevolus, Antonius Musa, 4 

363 



3^4 



GENERAL INDEX. 



Brayley and Britton's " Beauties of 

England and Wales," ix 
Brewster, Sir David, xv, 77 
Brietio, Philip, " Paral. Geog.," xxi 
Brown, Thos., (Pseudoloxia,) xxvii, 2, 

4, 12, 53, 78, 107, 143, 173, 215, 252, 

267, 303 
Brunei, J. C. "Manuel," xix 

Cabeo, Nic. (Phil Magn.\ xxvii, 9, 96, 

127, 138, 167, 215, 246, 332 
Cabot, Sebastian, 8 
Cselius Calcaguinius, 14 
Calaber, Hannibal Roserius, 4 
Calamita, 21 

Calippus of Cyzicus, 351 
Candish Cavendish, Thomas, xxxvii, 

181 

Carabe, 75 
Cardan, 214, 10, 32, 33, 45, 61, 69, 70, 

77, 80, 101, 108, 145, 166, 170, 171, 

179, 232, 255 
Carnelian, 83 
Cassini, J. J. D., 240 
Cathochites, 172 
Cesare, Giulio, 215 
Chalybes, ckalybs, 32, 37, 40, 43, 55 
Charleton, Dr. Walter, xxvii 
Chinocrates, 3 

Church of San Agostino at Rimini, 214 
Church of Saint Jean at Aix, 215 
Church of the Augustines at Mantua, 

215 

Clark, Latimer, F.R.S., vi 
Clarke, Charles L., xxi, xxvii 
Clepsydra, 343 
Coition, magnetic, xxix, 74, 97, 105, 

129, 153, 155, 161, 200 
Coition, sphere of, xxxii 
Columbus, 252 

Colures, solstitial and equinoctial, 352 
Conactus (mutual action), no, in, 310 
Con formated (iron and earth), 192 
Conformed, 114, 331 
Constable, William, F. R. S., xxvii 
Cooke, Conrad W., xiii, xx 
Copernicus, Nicolaus, 315, 318, 321, 

344, 350, 352, 354, 356, 357, 358 
Cortesius, 232 
Corvo, 252 
Costa, Josephus, II 
Costa, Philip, 214 
Costaeus, Joannes, 5, loo, 338, 339, 

340 
Cotton, Henry, "Typog. Gaz.," xx, 

xxi 

Creech, Thomas, 100 
Crocus Martis (see " Saffron of Mars"). 



Curtius, 57 

Cusanus, Michael (Cardinal), 2, 4. 104, 

168 

Cuspis, xxviii 
Cynosura, 26, 129, 180, 331, 350 

Dante, 7 

Davis, Henry, 73, 99 

Davy, Dr. John, xv, xxv, 75 

Declinatorium, xxix 

Deformated, 210; deformate, 309 

Descartes, Rene, (1596-1650, )xv, 329, 

330 
Deschamps, M. " Diet, de Geog.," xx, 

xxi 

Dias, 56 

Diego, Alfonso, 266 
Digby, Sir Kenelm, xv, xviii, 24, 107, 

123, 138 

Dioscorides, 2, 17, 52 
Dip or inclination, Book V 
Directive (vexsorial) force, called ver- 

ticity, 183 

Dominicus Maria of Ferrara, 315, 316 
Doria, Andrea, 6 
Drake, Francis, xxxvii, 181 
Dryden, John, vii, xxvii 

Ecphantus, 317 
Electric attraction, 82, 83 
Electric bodies, 83, 97 
Electric emanation, 85 
Electric force, 85 
Electric motion, 97 
Electrical effluvia, 78 
Electrical movements, 85 
Electricity, terrestrial, 97 
Electrics, xxviii, 86, 95, 96, 176 
Electron, 75 
Emerelstone, 39 
Empedocles, 308 
Encelius, 5, 172 

English Institute of Electrical Engin- 
eers, xxi 
Epicurus, 98, 101 
Equation of the centre, 261 
Erastus, Thomas, 5, 39 
Erastosthenes, 352 
Erckern, Lazarus, 143 
Euace, 172 
Euriprides, 17, 21, 31 

Fallopius Falloppio, Gabriello, (1513 

-1562,) 4, 56, 57, 174 
Fantis, Antonius, 9, 166 
Faraday, Michael, xxii, 283 
Farrar, John, 214 
Fernel, J. F., 8 



GENERAL INDEX. 



365 



Ferrarius lapis, 1 6 

Ficinus, Marcilius, (1433-1499,) 6, 13, 

179 

Fjndlay, A. G., " Class. Atlas," xxi 
Fitzgerald, Joseph, v 
Flavius Blondus, 6 
Form, primary, 146, 149 
Forma, vi, 85, 106 
Formate soul, 311 
Fracastorio, 8, 9, 82, 109, 114, 115, 

144, 170, 176, 231. 
Frost, Alfred J., xx 
Fuller, Dr. Thomas, ix, xxiv, xxvii 

Galen, li, 3, 17, 52, 57, 63, 74, 80, 99, 

IOI, IO2 

Galileo Galilei (1564-1642), xii, xiii, 

xv, 321 

Gama, Vasco da, 266 
Garcias ab Horto Garcia d'Orta, 53 
Gassendi, xv, 215 
Gaudentius, Merula, 13 
Geber, 36, 37, 38, 143 
Gehler, J. S. T., 18 
Gellibrand, Henry, 240 
Gemma, Cornelius, 101 
Gilbert's " De mundo nostro," xxv, 

xxvii, 346 
Gilgil, 34 

Glanvil, Barthol. de, 2, 19 
Glanvill, Jos., 6 
Goia, Joannes, 6 
Gold magnet, 75 
Goropius, 7 
Graesse, J.G. T.,"Tresor de Livres," 

xix 

Graham, George, 240 
Greely, Com. A. W., 230 
Grimaidi, 215 

Grotius, Hugo, xliv, 252, 254 
Gruter John, xxv 
Guyot de Provins, 7 

Hematites, 39 

Hakewill, George, 45, 53, 320, 327, 

350, 351 

Hakluyt, Richard, xxxviii 
Hali Abbas (Abohali), 4, 13, 76 
Hall, Dr. Isaac H., vi 
Hallatn, Henry, " Intr. to Lit.," xii 
Harding, S. & E. " Biogr. Mirrour," 

xxiv 

Hariot, Thomas, 14 
Harvey, xv 
Heliodoras, 75 
Heraciea, 16 

Heracleitus, of Ephesus, 308 
Heraclides (Ponticus), 317 



Hermes, 309 

Hero the elder, 95 

Herschel, F. W., xi, 15 

Hipparchus the Rhodian the Bithy- 

nian, 315, 317, 348, 350, 351, 352, 

354 
Hippocrates (B.C. 460-357), li, 57, 82, 

99 

Hues, Robert, 14 
Humboldt, Alex., ("Cosmos,") xiii, 

xvii, xl, 7, 8, 9, 78, 97, 215, 233, 234, 

283 
Humor (unifier of all things), 85, 92, 

96 
Hunt, Arthur Ackland, xxiv 

Ibn-Roshd (see Averroes). 
Ibn-Sina (see Avicenna). 
Inclination or dip, Book V 
Informated mine, air or water, 185, 

305; informed, 113 
Intorta Corolla, of Copernicus, 356, 

357 

Johnson, C. F., 99 

Kendall, Abraham, 14, 266 

Kepler, Johann, (1571-1630,) 321, 357 

Kircheri, Ath.,(Magnes . . . magnetica,) 

4, 138, 235 ( 
Klaproth, Julius Heinrich von, (1783- 

1835,) 13 

Lactantius, Lucius Ccelhis, 326 

Lamont, Dr. J., xx, 31, 137, 192 

Langius Joannes, 4 

Larousse M., "Grand Diet.," xxi 

Lazos, Roderigues de, 266 

Leandro, Francis, 45 

Leonhardus, Camillus, 4 

Leslie, Sir John, xix 

Levinus Lemnius, 6 

Lewis, Dr. Charlton T., vi 

Linea fiducialis, 263 

Linschooten, Jan Hugo van, xxxviii 

Livingston, Dr. Jos. V., vi 

Livio Sanuto, II, 232, 252 

Loadstones, armed and unarmed, 

xxviii, 137, 138, 139, 140 
Lochmann Lochmans, Wolfgang, 

xxi 

Long, George, " Atlas," JUH 
Lovett, R., ("Subtil medium provM ",) 

330 
Lowndes, W. T., " Bibl. Manual," 

xix 

Lucas Gaurtous, 13 
Lucretius, 4, 5, 16, 81, 98, 99, 100 



366 



GENERAL INDEX. 



Lully, Raymond, (1234-1315,) 7 
Lusitanus, Amatus, 4 
Lyncurium, 75 
Lynschetensis, Hugo, xxxviii 

Machometis Aracensis, 348, 354 

Maclean, Alex., "Diet, of Am.Geog.," 
xxi 

MacMillan, E., v 

Magnes, 21 

Magnesia, 16 

Magness, 21 

Magnetic axis and poles, 128 

Magnetic body, excited, xxxi 

Magnetic bodies, 97 

Magnetic coition (see Coition, mag- 
netic). 

Magnetic horizon, 128 

Magnetic meridians, 126 

Magnetic movements, 72 

Mahomet's shrine, 3 

Manardus, 57 

Marbodaeus, 4, 14 

Marcellus, 4 

Marchasites, marcasites, 37 

Maria, Dominicus, of Ferrara, 315, 316 

Marsilius of Ficino, 232 

Martin, T. H., (Observ. et Theories,} 4, 

13 

Martinus Cortesius, 10, 179 

Materia, vi, 85 

Matthiolus, 3, 4 

Mauritanus, Serapio, 4 

Maurolycus, Franciscus, 10, 68, 232, 
270 

Mayer, Alfred M., vi, 252 

Medicinal power of the iron, 55 

Medicinal virtue of the loadstone, 52 

Medina, Pedro de, 251 

Menelaus Milieus, Roman geome- 
ter, 348, 354 

Menzies, James, li 

Metonic Cycle, 351 

Microge, or terrella, 24 

Miller, Geo., D.D., 7 

Monro, H. A. J., 100 

Montagnana, 58 

Montanus, Baptista, 4 

Morant, Philip, " Hist, of Essex," ix, 
x, xxiii 

" Movement of trepidation," 180, 353 

Munk, " Roll of the Coll. of Ph. and 
Surgeons," xii, xxiii 

Myseni, 40 

Newton, Sir Isaac, (1642-1727,) 321, 
329, 352 



Nicander, Colophonius, 15, 17 

Nicaulaus, Myrepsus, 54 

Nicetas Acominatus or Choniates, 

(1150-1216,) 317 
Niebuhr, Barthold Georg, 16 
Non-electrics, 83 
Nonius, Petrus, 250 
Norman, Robert, xi, 10, 15, 232, 244 
Norumbeja, 234 
Nova Zembla, 231, 269 

Offusius, Jofrancus, 73 
Olaus Magnus, n, 12 
Orbis virtutis, xxii, xxxi, 122, 150, 285 
Oribasius, 4 
Orpheus, 21, 98, 309 
Oviedo y Valdes, Gonzalo Fernandez 
de, (1478-1557,) 8 

Pantarbes, 172 

Parocelsus, 5, 6, 54, 146 

Parmenides, 308 

Peirce, Prof. Charles Sanders, vi 

Peregrini, Petri, 4, 9, 19, 166, 167, 179, 

232, 332 

Perpetual-motion engine, 166 
Pettus, Sir J., 143 
Philolaus, of Crotona, 318 
Philostratus, Flavius, of Lemnos, 172 
Pictorius (Quintus Fabius Pictor) 13, 

80 

Piedramant, 21 
Pieters, Charles, "Ann. de 1' Impr.," 

xxvii 

Plancius, Peter, xliii 
Plat, Sir Hugh, 2 
Platea, 56 
Plato, 2, 5, 17, 21, 31, 73, 98, 99, 241, 

308 
Pliny, 2, 3, 15, 17, 30, 32,43, 7&, 77, 

170, 172, 173, 174, 316 
Plotinus of Alexandria (204-274), 324 
Plutarch, 2, 54, 87, 99, 100 
Poggendorff, J. C., xiii, xix, xxi 
Poles of the earth, xv, 9 
Polo, Marco, 7, n 
Porta, J. B., xxvii, 2, n, 12, 17, 19, 32, 

37, 41, 102, 107, 108, 117, 144, 145, 

150, 158, 160, 173, 209, 217, 218, 219, 

226, 251 

Precession of the equinoxes, 348, 352 ' 
Priestley, Dr. Joseph, xiii 
Primary confluence, 98 
Primum mobile, xiii, 126, 317, 320 et 

eq., 328, 336, 346, 354 
Prostapharesis, 261 
Prutenic (Prussian) tables, 350 



GENERAL INDEX. 



367 



Ptolemseus, Claudius, li, 2, 12, 17, 43, 

54, 142, 208, 315, 316, 317, 318, 321, 

323, 324, 340, 348, 350, 354 

Ptolemy (Ptolemseus Philadelphus), 3 

Puteanus, G., (Ratio Purg. Meet.,) 5, 

101, 102 

Pyrimachus, 40 
Pythagoras, 92, 308 

Quaritch, Bernard, xxvii 

Radius (of a loadstone's sphere), xxix 
Radius, radius astronomicus, 256 
Razes Rhazes, 57, 58 
Reaumur, R. A, F. de, (1683-1757,) 

39 

Reinhold Rheinhold, Erasmus, (1511- 
1553,) 3i6, 350 
" Respective points " (Norman's), xli, 

10, 244 

Revolution of the Globes, Book VI 
Rheticus George Joachim, (1514- 

1576,) 357 

Richardson, Dr. B. W., xxiii, li 
Riley, Henry T., xlv 
Robison, Dr. John, xvi, xix, xxv 
Rohault, J. Rohaulti Jacobi, 2, 79, 

138, 149, 215, 321 
Ross, Sir James Clark, 282 
Ross, Sir John, 282, 283 
Rotary needles, use of, 223 
Ruellius, 13 
Rueus, Francisciis, 12 
Ruffinus (Toranus), 3 

Saccheti, F., 56 

" Saffron of Mars," 56, 142, 143 

Sagda Sagdo, 172 

Salmanasar, 33 

Salmasius, 76 

Sardonyx, 83 

Sarpi, Fra Paolo, xv 

Scales of Iron (bractea), 39 

Scaligerjulius Caesar, (1484-1558,) IO, 

61, 76, 103, 109, 113, 174, 232 
Scarella, Giambattista, " De Mag- 

nete," xviii 

Schmergel, smeargel, 39 
Serapion, 12 
Serapis, temple of, 3 
Severtius, Jacobus, 10 
Side-rites, 10, 21, 22, 2l8 
Siege Is tein, 21 
Silvaticus, Matthaeus, 4 
Simon (Clams Sanationis), 14 
Smiris, 39 
Smith, Dr. W., xxi, 16 



Solino, C. G., (Caius Julius Solinus,) 
Polyhistor, 2, 14, 17, 22, 172 

Solomon, 7, 8 

Sotacus, 17 

Sphere of coition, xxix 

Sphere of influence, xxix 

Stadius, 316 

Stevin, Simon, xliv, 252, 253, 254 

Stomoma, 40, 55> 59 

Succinum, 76 

Sudini Sudavienses, 76 

Tacitus, Cornelius, 43 

Taisner, Joannes, (Taisnier,) 9, 13, 19, 

1 66 
Terrella, xviii, xxii, xxiv, xxviii, 24, 

121, 124, 126, 150, 151, 210 
Terrestrial electricity, 97 
Thabet ben Korrah, 180 
Thales, xi, 22, 98, 109, 308, 312 
Theamedes, 32 

Themistius, " Euphrades," 114 
Theophrastus, xi, li, 2, 17, 21 
Thevenot, 166 
Thompson, Silvanus P., xx, xxvi, 

xxvii, 283 
Thomson, Thomas, M.D., (1773-1852,) 

xiii, 22, 32, 36, 37, 39, 40, 76, 77, 

83, 143 
Thomson, William, (Lord Kelvin,) 

xxii, 249, 283 

Timocaris Timochares, 321, 354 
Topaz, 75 
Tourmaline, 75 
Transformated, 214 
Tycho Brahe, 261, 321, 341 

Variation, Book IV 
Vasco da Gama, 266 
Versorium magnetized, xxviii 
Versorium non-magnetized, xviii, 

xxviii, 79, 81 
Vertices (centres of whirling motion), 

129 
Verticity, xxviii, 48, 183, 189, 192, 

200, 208, 211, 217, 219, 223 
Vieta, Francis, xv 
Vigor (primary native strength), 105 
Villanova, Arnoldus de, 14 
Vincentii Burgundi, (Vincent de Beau- 

vais), 4, 14, 2T 

Virgilius, bishop of Salzburg, 327 
Virgilius ( Vergilius), Marco P. , 37 
Vitruvius Pollio, Marcus, 316, 343 
Vitry, Jacques de, 7 

Wenckebach, W., 167 



368 



GENERAL INDEX. 



Wetzler, Joseph, vi 

Whevvell, William, xiii, 15, 74, 77, 78, 

105, 136, 240, 346 

Willems, Alph., "Les Elzevter/'xxvii 
Wood, Anthony A, Athena Oxionenses, 

ix, xiv 
Wright, Edward, vi, xxxvii, xl, 14 



Wright, Thomas, " Hist. ... of Es- 
sex," ix, xxxiii 

Zachary Zacharias, bishop of Rome, 

326 

Zahn, Johannes, 76 
Zoroaster, 309 



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