wmf'miM''^^' /V®' i i'J''^: b H' ..nsi WILLIAM GILBERT OF COLCHESTER, PHYSICIAN OF LONDON, ON THE LOADSTONE AND MAGNETIC BODIES, AND ON THE GREAT MAGNET THE EARTH. % NEW P)iYSIOLOGY. DEMONSTRATED WITH MANY ARGUMENTS AND EXPERIMENTS. " Elecirica, 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. ESOl Robert Druhmond, Febbis Bbos., Electrotyper, Printers, 444 & 446 Pearl Street, 326 Pearl Street, New York. New York. GVILIELMI GIL' B E R T I C O L C E ST R E N- SIS,^MEDICI LONDI- N E N S I S, D E M A G R1E T E> M A G N E T P <:lSCiVE CC>RPbRIBVS,ET DE I^AG. no magnete teJlure j Phyfiologia noua^ Ip/mmis ^ jirgumentiSy &^p^^ rimentis dcraonflrata* L O H D 1 N I XCVDEBAT PetrvLShortiANNO MDC. 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 gf 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, VI TRANSLATOR'S PREFACE. Mr. Joseph Wetzler, Dr. Joseph V. Livingston, Hon. Park Ben- jamin, and Prof. Alfred M. Mayer. I am hkevvise 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 Wrip-ht, 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 — inateria — con- stitutes the true nature of the thing. Matter /^r se is indiffer- ent, indefinite; form gives it definiteness. The earth is informed With, 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 — confonnatmn — 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 a&ormed—aj^orjnattiin (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 vm 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 lo, 1892. BIOGRAPHICAL MEMOIR. William Gilbert — or Gilberd/ as he wrote it — was born in 1540 at Colchester, County Essex, England,'' 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),' proceeding B.A. 1560, Fellow 1 560-1 561, M.A. 1564, mathematical examiner 1 565-1 566, M.D. 1569, and ' "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." {BiograpMa Britannica, London 1757, Vol. IV, page 2202.) - 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. Brayley and John Britton, London 1810. 2 Dr. Thomas Fuller, " Hist, of the Worthies of England," London 1840, page 515. * 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 lOGRAPHICAL 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," ' 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 (i 581-1582, 1584-1587, 1589-1590), Treasurer (i 587-1 591, 1 597-1 599), Con- siliarius (i 597-1 599), 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),' 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, loc. cit.. Vol. I, Book II, page 117. See, likewise, Ree's Cyclopzedia, 1819, Vol. XVI, article "Gilbert." BIOGRAPHICAL MEMOIR. XI latter of which had practically lain dormant for two thousand years — 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- Xll BIOGRAPHICAL MEMOIR. guished man of science in England during the reign of the Virgin Queen. " The year 1600," observes the EngHsh historian Henry Hallam/ "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 v/hich 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.'' 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 Litt. of Europe in the 15th, i6th, and 17th Centuries," London 1839, Vol. 11, page 463. 2 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.^ While Dr. Whewell observes^ 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^ 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 Organiim 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. Poggendorff, from whose '* Geschichte der Physik " (page 286) 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 ' Engl. Cycl., Section " Biography," Vol. Ill, page 102. * " Hist, of the Inductive Sciences," 1859, Vol. II, page 217. ^ " History of the Royal Society," London 1812. XIV 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,' Archdeacon of SaHsbury, 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 ' 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." {Athena Oxonienses, London 1S13, 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^ 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," 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.^ 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 ^ "Memoirs of the Life of Sir H. Davy," London 1836, Vol. \, page 309. ^ "Nouvelle Biog. G6n6rale," 1858, Tome VIII, page 494. ' 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^ 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 philosophising, 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 * " System of Mechanical Philosophy," London 1822, page 209. BIOGRAPHICAL MEMOIR. XVll 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 we call magnets ; that is, pieces of steel which have acquired properties similar to those of the loadstone. But he extends the term magnetism ^ 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 Hmitation 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 * Humboldt states that in Gilbert " we do not find either the abstract ex- pression electricitas, or the barbarous word magnetismus introduced in the eighteenth century." (" Cosmos," 1849, Vol. II, page 726, note.) XVni 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,' "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 f 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* . . . printed at London 1602." Of the monumental De Magnete, Prof. Robison states'' 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. Poggendorff^ and " Inter- national Encycl."* (London, Stettin); " AUgemeine Ency." ^ and " Biographic Universelle " ^ (London, Sedan) ; Three editions (1600, 1628, 1633) are given by W. T. Lowndas,' S. A. Allibone," J. G. T. Graesse," S. P. ' " Bibliotheca Britannica," Edinburgh 1824, Vol. I, Authors, by R. Watt, pages 124 and 414. 2 " 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. ' Leipzig 1858, Sec. I, page 229. 8 Bruxelles 1843-1847, Vol. VII, page 253. » "The Bibliog. Manual," 1859, Part IV, page 890. 1" "Critical Diet, of Engl. Lit.", 1859, Vol. I, page 668. " "Tresor de Livres Rares et Precieux," 1862. XX BIOGRAPHICAL MEMOIR. Thompson' (Londini, Sedini) ; Dr. J. Lamont* (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' as fol- lows : London 1600, Stettin 1628, 1633, Franckfort 1629, 1638, the same being specified in the " Ninth Britannica,"* 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,* also Sedanum in the " Diet. G6og. Port.", 1809, page 617, as well as by Em. Bowen,^ Henry Cotton,^ and M. Des- champs.* Stettin, on the Oder, in Prussia, is called in Latin Stetinum ("Diet. G^og. Port", 1809, page 652; Em. Bowen, loc. cit. Vol. I, page 701). See * " Gilbert of Colchester, an Eliz. Magn.", 1891, pages 43-44. 2 " Handb. des Magnetismus," Leipzig 1867, page 434. 3 London "Engineering" for the month of December, 1889. * Volume X, page 592. 5 "Grand Diet, de G6og. Univ.", 1857, Tome IV, page 560. fi "Compl. Syst. of Geog.", 1747, Vol. I, page 401. ' " Typog. Gazetteer," 1825, page 146. 8 "Diet, de Geog.", 1870, page 1158. BIOGRAPHICAL MEMOIR. XXI Sedmum — likewise Sideni, Sidini, Sudeni, in " Lexi- con Geog.", 1657, page 361; " Diet. Geog.", Nice 1 79 1, page 308, "Diet. Geog. Univ.", 1832, pages 453-454 ; as well as by Larousse/ Cotton,* Des- champs/ and W. Smith.* Gilbert alludes to the Sudini of Prussia, Book 2, Chap. 2. Sedini, Sedinu, Seduni, Sedunum (French Sion, Ger- man Sitten), were names attaching to place and people along the banks of the Rhone in Switzer- land (Phil. Brietio, " Parallela Geographiae," 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 goUts, 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 ' "Grand Diet. Univ.", 1875, Tome XIV, pages 477, 1099. ' H. Cotton, loc. cit. page 152. ^ Deschamps, loc. cit. pages 1161, 1175. * "Diet, of Gr. and Rom. Geog.", 1857, Vol. II, pages 995, 1042. XXU 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 orbis virtutis^ 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 Httle 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 30th November of the same year. He was buried in the chancel of the Church of the Holy Trinity in Colchester, where a monu- > See cuts of Orbis Virtutis in De Magnete, Book II, Chapters VI and XXVII, also Book V, Chap, II. BIOGRAPHICAL MEMOIR. XXlll ment ' was erected to him by his brothers, who placed upon it a Latin inscription ^ 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 ai 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. ' 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." ' "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," 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.' " ' 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." " 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 Oyian^' (AthencB Oxonienses, by Anthony a Wood [1st edi- tion, 1691-2], London 1813, Vol, I, page 738). ^ 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 anjd retired a person." Besides Gilbert's folio De Magnete, there appeared at Am- sterdam, in 165 1, 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 165 1 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 14th 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 Worshipfull 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 dinars 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 Effingham, 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 v/ell learned, whose name is Johannes Franciscus Sagredus, he is a great Magneticall man, and writeth that hee hath conferred with diners learned men of Venice and with the Readers of Padua, and re- porteth wonderfuU 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. XXVll 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. Gilbertiis Jo. Sherwood propriis inanibus." 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." ^ In his epistle ' to Dr. Walter Charleton (physician in ordi- nary to King Charles I.), the celebrated EngHsh poet, John Dryden, predicts that " Gilbert shall live till loadstones cease to draw, Or British fleets the boundless ocean awe." ' " 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. ^ 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 Magneiica, 1629, Lib. IV, Chap. XVIII, page 335. * 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 • IL 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 XL 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 XXXll 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 115 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 XI. Parallels 127 XII. The magnetic horizon 128 XIII. Of the magnetic axis and poles 125 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 , 138 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. XXXlll 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 XXXI V 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 VI I. 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,Y) 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 XX. The variation in the Eastern Ocean 272 XXI. How the deviation of the needle is greater or less according to the distance oif 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- tioM of the instrument; its uses 285 IV. Of a suitable length of needle on the terrella for showing the dip 288 XXXVl CONTENTS. TAGS 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 XI. 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 3^7 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 equinoxes 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 35^ 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 XXXVIU 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 ^ 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, * 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 ED WARD 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 iii 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.* 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 inclinatorium, 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. H, page 658). ADDRESS BY EDWARD WRIGHT. xH 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 EngHsh 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/ 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,^^ 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. * 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' (a most diligent student not so much of geography as ^ Peter Plancius, Dutch theologian and astronomer, 1 552-1622. xliv ADDRESS BY EDWARD WRIGHT, of magnetic observations) and Simon Stevinius/ 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}xvev- periKTiv 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 Homeri, (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.)* 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 Jiabent veri vatum prcesagia, (If the presages of poets have aught of truth)* 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. * 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 rriatters taken out of lofty mountains, or the depths of seas, or deepest caverns, or hidden mines, we gave much atten- xlvii xlviii 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. xHx 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 difificult 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 {^physiologid) 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 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.' Verticity.'^ 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 convertens). ^' * 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^) 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.* Meridionally. In the direction of a meridian. Paralleletically. In the direction of a parallel of latitude. Cuspis (point). The end of a magnetized versorium. ' See Kenelm Digby's allusion to terrella in the Biographical Memoir, also De Magnete, Book I, Chap, III. ^ See De Magnete, Book I, Chap. X. 2 See De Magnete, Book II, Chap. VI, also Prof, Sir Wm. Thomson's allu- sion to the orbis virtutis in the Biographical Memoir. * "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 Efidemica, 1658, Book II, Chapter II, page 63). ^ 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 ctirvis ferramentis). « 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.^ 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 iiifiuence. The entire space over which the force of a load- stone extends.'^ 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) — '^Ojj.odpourf, the coition is always vigorous, even though heavy substances make opposition. Declinatorium. A bar or needle movable vertically on its axis and that is excited with a loadstone ; used in the dip instrument. » See De Magnete, Book II, Chap. XXXII. 2 See note 3, page xxxi. ^ 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 iron, then many ancient philosophers and physicians discoursed of it, and briefly (but briefly only) made it matter of record: as, for instance, Plato in the lo, 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 appended 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.' The like of this is found in Pliny and in Ptolemy's Quadripar- titum; and errors have steadily been spread abroad and been ' " 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, Quasi. Conviv. Lib. II, Qusest 7) ; Barthol. de Glanvil, Zz^^. 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 A UTHORS 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.* 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 cofifin 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.* 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. '•^ " 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, $>o 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.' Of later authors, some tell only of its efificacy in medicine, as Antonius Musa Brasevolus, Baptista Montanus, Amatus Lu- sitanus, as did before them Oribasius in book 13th 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 Callus, Albertus, Matthseus 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 dearte 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, LIT, Tr. Ill, c. vi, p. 243, Lione 165 1 ; Ausonio L. Ampelius, Lib, Memorialis, c. viii, Paris 1827 ; J. H. Martin, " Observ. et Theories . . .," Rome, 1865, pp. 5, 6, 7. ^ For a better list than Cardan's, of authors who have written on the load- stone, consult "Petri Peregrini . . . Achillem T. Gasserum . . . Augs- burg! . . . 1558." ■^■■'^ ANCIENT AND MODERN AUTHORS ON THE LOADSTONE. 5 passes through bodies and spreads in an occult way. Guliel- mus Puteanus in his Ratio Purgantiutn 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 Fhysica, 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 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 1300.' 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 * 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. 7 appears to have been brought into Italy by the Venetian Paolo [Paulum Veftetum — Marco Polo] who about the year 1260 learned the art of the compass in China/ 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 Phcenicians, next neighbors of Judea, most skilful navigators in early times ^ 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 (" Historise Hierosolimitanae," Cap. 89), and Dante (" Paradiso," 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/ Gonzales Oviedo first made mention in his history that in the meridian of the Azores there is no varia- tion. [Jean Frangois] Fernel, in his book De Abditis Rerum CausiSf 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,'' asks what gives direction to the loadstone ^ At page 150 of the 1869 London edition of Mr. J. F. Nicholls' Life of Seb. Cabot, it is said the latter represented' 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"). '^ 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. 9 [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.' 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" 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 "...De Natura Magnetis et ejus effectibus . . . ,"Coloniae 1562, an English translation of which, by Richarde Eden, was published in London about 1579. The 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, T/ziL 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 Il.Chap.XXXV), is said by Bertelir 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.) lO 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 131st 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 * discusses a few problems regarding the loadstone, adopting the current opinions of others ; he believes that the variation is caused by ' 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 Itahan) 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.' Nor will ' Olaus Magnus, Historia de Gentibus Septentrionalibus, Romae 1555, Book II, Chap. XXVI, page 8g. 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 AUTHORS ON THE lOADSTONE- 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 mseus, Geographia, Lib. vii, c. 2; Klaproth Boussole, Paris 1834, p. 116, etc.; Taisnier's Z>^ iVfls/^ra, 1562, Eden tr. p. 12; " Beati 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, v/ill 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, Williani Barlo (Barlowe) in his 1 Consult: Simon, Clavis Sanationis, Padua 1474; C. G. Solino, Folykisior, 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/ 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 ' 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. 1 6 ■ WILLIAM GILBERT. were held fast in a magnetic region while he was pasturing his cattle), or after the district Magnesia in Macedonia/ abound- ing in loadstones ; or after the City of Magnesia in Ionia of Asia Minor, on the river Maender ; hence Lucretius writes, Quern Magneta vacant patrio de nomine Graii, Magnetum quia sit patriis in montibus ortus^ It is called Heracleus from the City Heraclea,^ 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 ' 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. '^ Transl. — Which the Greeks call magnetes, from the name of its country, for it had its origin in the native hills of the Magnesians. ' Heraclea, a town of uncertain site in Lydia, perhaps not far from (the Lydian) Magnesia at the foot of Mount Sipylus {ad Sipylum) (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. 1 7 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 ' 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 lo, by Nicander of Colophon, Theophrastus, Dioscorides, Pliny, Soli- nus, Ptolemy, Galen, and other investigators of nature. But considering tbe 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 sufiEicient 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. Phny 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.' > Porta has it: "The Ethiopian, the Magnesian from Magnesia near Macedonia, as the way lies to the Lake Boebis, 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). lo 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.' For the ancients, the differences were based on the color : The magnets from Magnesia in Macedonia were red and black, those from Boeotia 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 ' Consult Johann S. T. Gehler's " Physikalisches Worterbuch," article " Magnetismus." THE LOADSTONE: WHAT IT IS: ITS DISCOVERY. 1 9 along the Cattegat. Blue-black and dusky-blue loadstones are likewise powerful and highly prized.' 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 Hke 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 ' "They are proved to be the best which are most of blewe or heavenly- colour " (Taisnier, Z>^ A^a^wrrt, 1562, Eden tr. p. ii). — "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, Lib. de Prop., Lyons 1480, fol.. Lib. XVI, Cao. 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 dihgently 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/ 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 bbdy, 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 v»^ith 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 'HpocKXeioZ, as by Theo- phrastus, and Mayvf/ris and Mayvijs, as by Euripides, quoted by Plato in the lo; by Orpheus it is called also MayvT^ocra and 2idrjpitr)Z {quasi ironstone) ; by the Latins it is called Magnes Herculeus ; by the French Aimant, a corruption of adamas ; hy the SpsLniards Ptedramanf ; by the Italians Calamita ; by the English XoabStOne an& HC)amant stone; 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.^ The magnet is called ^idrjpitij's because ' "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. * Consult Vincentii Burgundi, Spec. Mai., Douai ed. 1624, T. I, LVIII, C. 34, 39-41; 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 2i6rfpiTT/5 from the glistening of polished iron- Aristotle merely names the loadstone in his work De Anima, I. : "Eoiks 6e Kai ©aXfjS e^ d)v oc7iojj.vejxovevov(Tif Kivr/riKOv n rrfv ipvx^y iTtoXafx^aveiv, eirtep rov Xidov ipvx'ijy e(prf exeiv^ on tor cridr/pov Kivet. (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 Katsensilber 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 confused 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, Exercitationes Plin., Rhenuni 1689, page log. The Macedonian diamond, as well as the adamas cyprius and siderites, were obviously not dianaonds, 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 termini 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 ojff- 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 MiKpoyr} (microge) or Terrella (earthkin, little earth).' 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. 25 On top of the stone AB is set the versorium in such a way that its pointer may remain in equihbrium : 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. ^ 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 unruflfled 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. ^7 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 lo, 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 he just in the plane of the horizon, or at least in a plane not very obhque to it ; take in your hand another stone the poles of which are also known, and hold it so that its south pole shall he toward the north pole of the floating stone, and near it alongside ; the floating loadstone wiU 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 bear- 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 30 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 6 and c, before connected, now separated from each other, are not what they were before. 3 is now south while c is north. d 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 d 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 unju?^ 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 1 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.* 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- ^ Dr. J. Lamont's " Handbuch des Magnetisniius," 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,' 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- avtddes" (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.' 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 exphcation of difificulties connected with the loadstone, ' Somewhat in this connection, Gilbert has already (Book I, Chap. I) alluded to Albertus Magnus, of whom mention was inade in note i, page 9. In his De Miner alibus — 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* 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 difificulty. 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 36 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.' 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 ' 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, 118). WHAT IRON IS; WHAT ITS MATTER; ITS USE. 37 them enter bodies often and change them into marchasites' 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 pecuhar 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 saflfron, India its ivory, the Sabaens their frankincense, the naked Chalybes iron, Pontus the malodorous castor, Epirus the mares that have won at Olympia? (Virgil ius, Georgica, Book I, pages 56-59.) ' 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. 38 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 efiflorescences 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 {bractecs) ' ; 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 gel (schniergel), 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 Adniirandis 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 Gtojxwfxa^ 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 {gesscs), Mace- donian pikes {sarisscB)^ 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 //V 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 looo 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' 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 • "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 a.^aine of the same mettall as at first " (Geo. Hakewill's " Apologie," 1635, Lib. II, Sec. 7, pages 164-165). 4^ 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 120, 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. 4/ 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 WILLIAM 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 XL 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 follov/s, 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. so WILLIAM GILBERT. CHAPTER XII. A LONG PIECE OF IRON, EVEN NOT MAGNETIZED, ASSUMES A NORTH AND SOUTH DIRECTION. I 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. $1 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, 52 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. DiOSCORlDES tells that loadstone blended in water is ad- ministered in a dose of three oboli' to expel gross humors. Galen writes that it has virtues like those of bloodstone. ' 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 ivictus). " The man who was ordered to do this thing told me," says Gartias.* 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 I'Ecluse, Antwerp 1567, 1574, 1579, 1593, under title "Aromatumet 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 T>e Magneie, Lib. I, Cap. LVI, pages 178, 179. Hakewill observes (" Apologie," 1635, Lib. II, page 165), "Remarkable indeed that is which Garziasab Horto writes concerning the load-stone in Simpl Indice, 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.' 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. * 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 $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.' 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,"" 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 efificiency and a constringent rather than a resolvent ; but it does this neither by heat nor by cold, but by its own dryness ' " 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 , § i8). 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." '■* See Book II, Chap. XXIII. THE MEDICINAL POWER OF THE IRON. 5/ 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 hoo\i mvA!i\. 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 58 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 acies, 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 6o 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. 6l is kept in iron filings not as though it fed on iron, or as though it were a hving 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 eacli 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 looo pounds of iron. For if one were to drive into a wall a number of iron nails weighing all together lOOO 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 quahties 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 66 WILLIAM GILBERT. 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 Peripateties 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- genic 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 locaHty, 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- 6S 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 earths — 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 v/hole interior of this our globe to be of rock or of iron, albeit the learned Franciscus Maurolycus ^ 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 ' Francis Maurolico — Maurolycus, MaruUo (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 aflfinity 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, 70 WILLIAM GILBERT. moreover, shown in a previous proposition {Libro de Proper- tionibus) that the loadstone is true earth. ' A strong loadstone 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 ^ Consult Cardan's Works, Lugduni (Lyons), 1663 ed., Vol. II, De Ex- emplo. . . ., pages 539, 546, Vol. HI, Lib. V, Cap. XVII-XIX, Vol. X, Cap. VI, page 12. THE TERRESTRIAL GLOBE A LOADSTONE. 71 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 L 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.' 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 : CoiTlON ^ (commonly called attraction), an impulsion to magnetic union ; DIRECTION ' toward the earth's poles, and verticity of the earth toward determinate points in the universe, and the standstill there ; VARIATION," deflection from the meridian, — this we call a per- verted motion ; DECLINATION ' (inclination or dip), a descent of the magnetic pole beneath the horizon ; and circular move- ment, or REVOLUTION.^ 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 jy 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 J'j 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 ' See Plato's Timceus (tr. of Mr. Henry Davis), London 1849, Vol. II, pages 372-374. * See Book II, Chap. II, et seq. 3 See Book III. ^ See Book IV. « See Book V. « 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.' 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 ^ 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, ^$ cf 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 whicli they cannot set fortli, 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 t/XeKzpor, because, when heated by rubbing, it attracts to itself chaff ; whence it is also called aprta^, and from its golden color, jpi»o-o0opon' But the Moors call it carabe, because they used to offer it in sacrifices and in the ' 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 o^ 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 first 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).' Many call this substance ambra (amber), especially that which is brought from India and Ethiopia." The Latin name succi- num appears to be formed from succus, juice.^ The Suda- vienses or Sudini call the substance geniter, as though genitmn 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 {csternis 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. » 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.) "^ Consult the very interesting tables given by Joannes Zahn, at page 51, Chap. VII, Vol. II, of his "Specula physico-raathematico-historica notabi- lium. . . .", Norimbergse 1696. 3 Pliny considers amber as the juice of a tree concreted into a solid form (Dr. Thos. Thomson, "Hist, of Chem.", 1830, Vol. I, page loi). 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/ 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,^ 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.'' Like powers of attracting are ^ " 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 loi). Cardan states, Gagates non lapis est (Lugduni ed. 1663, Vol. X, page 528). ''' 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. 78 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.* This we may observe when in mid-winter the atmosphere is very cold, clear, and thin ; when the electrical ef^uvia 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 ^ 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, Vol. II, page 192), 2 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 {Psetcdoloxia 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.' 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,'^ 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., seaHng-wax and other unctuous mixtures. But why this inclination and what ' 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; Rohaulti Physica, London 1718, Par, III, Cap. VIII, page 408). ' 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. 51 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 [versoriiini) 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 medica, 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 other 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 does 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 subjectutn : " now the proper sub- fectum" 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, L, 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,' pearls, jasper, chalcedony, alabaster, porphyry, coral, the marbles, lapis lydius (touch- stone, basanite), flint, bloodstone, emery or corundum {tnugris), 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 liumid, and a matter that is firm and dry. From this two- old 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 ' 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 sufiicient 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. 85 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 shi-ne. 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 Hnen 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 * 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 QucBstiones Platonic(2, 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 O'J 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 efHuvia 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 1 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.' 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 efHuvia 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. ' Consult Robert Boyle's "Of the Strange Subtilty of EfBuviums," 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 Httle 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 ; ie.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 E, 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 efiflu- 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.' 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, Philosopkia 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/ 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 ^ "In these obscure axioms we trace the recognition of terrestrial electric- ity' — 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). 98 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.' 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 Timcsus, 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." ' 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'v in confused fashion or in a circle. The Epicurean poet Lucretius thus presents his master's theory : Principio, fluere e lapide hoc permulta necesse est Semina sive sestum, 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.^ * In his note to the translation of the TimcBus (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. ^ 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 draff with them the mass to which they're joined ; For nothing- is than steel more closely knit, lOO WILLIAM GILBERT. A similar explication is offered by Plutarch in the Qucss- 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. LUCRETTI Cari, De Reruni Natura, London 1824, Book VI, v. IOOO-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. lOI and their return movements : that is Epicurus's theory, so oft repeated by others. Galen errs in his first book, De Naturali- bus Faeultatibus, cap. 14, when he expresses the opinion that whatever agents draw out the venom of serpents or arrows possess the same powers as the loadstone. As 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 beHef 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 I02 WILLIAM GILBERT. a property of its whole substance unknown to any one and in- capable of demonstration (as Galen held, and after him nearty all physicians), but from '' its substantial form as from a prime motor and self-motor, and as from its own most potent nature and its natural temperament, as the instrument which the efificient 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 honiim 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,^ "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 fights, 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,' in Book 7 of his Pkysica, treating of the * 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 Theologice, 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. I04 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 were 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 efifluvia from humor ; magnetic bodies by formal efificiencies 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 ; * 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, * Whewell, " Hist, of Ind. Sciences," 1859, Vol. II, Chap. II, page 220. I06 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. lO/ 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.' ^ " 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. I08 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.* 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 » 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 no 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 evrekexeioc, not epyov- it is (Tvvevrekexeia 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. 1 1 1 from the