Chap. 3. An indicatory instrument, showing by the virtue of a stone the degrees of declination from the horizon of each several latitude.

Chap. 4. Concerning the length of a versorium convenient for declination on a terrella.

Chap. 5. That declination does not arise from the attraction of the loadstone, but from a disposing and rotating influence.

Chap. 6. On the proportion of declination to latitude, and the cause of it.

Chap. 7. Explanation of the diagram of the rotation of a magnetick needle.

Chap. 8. Diagram of the rotation of a magnetick needle, indicating magnetical declination in all latitudes, and from the rotation and declination, the latitude itself.

Chap. 9. Demonstration of direction, or of variation from the true direction, at the same time with declination, by means of only a single motion in water, due to the disposing and rotating virtue.

Chap. 10. On the variation of the declination.

Chap. 11. On the essential magnetick activity sphaerically effused.

Chap. 12. Magnetick force is animate, or imitates life; and in many things surpasses human life, while this is bound up in the organick body.

_Book 6._

Chap. 1. On the globe of the earth, the great magnet.

Chap. 2. The Magnetick axis of the Earth persists invariable.

Chap. 3. On the magnetick diurnal revolution of the Earth's globe, as a probable assertion against the time-honoured opinion of a Primum Mobile.

Chap. 4. That the Earth moves circularly.

Chap. 5. Arguments of those denying the Earth's motion, and their confutation.

Chap. 6. On the cause of the definite time of an entire rotation of the Earth.

Chap. 7. On the primary magnetick nature of the Earth, whereby its poles are parted from the poles of the Ecliptick.

Chap. 8. On the Praecession of the aequinoxes, from the magnetick motion of the poles of the Earth, in the Arctick & Antarctick circle of the Zodiack.

Chap. 9. On the anomaly of the Praecession of the aequinoxes, & of the obliquity of the Zodiack.

[Illustration]

{1} [Illustration]

WILLIAM GILBERT

ON THE LOADSTONE, BK. I.

_CHAP. I._

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

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

only, Theophrastus the Lesbian, Dioscorides, C. Plinius Secundus, and Julius Solinus[4]. As handed down by them the loadstone merely attracted iron, the rest of its virtues were all undiscovered. But that the story of the {2} loadstone might not appear too bare and too brief, to this singular and sole known quality there were added certain figments and falsehoods, which in the earliest times, no less than nowadays, used to be put forth by raw smatterers and copyists to be swallowed of men. As for instance, that if a loadstone be anointed with garlick, or if a diamond be near, it does not attract iron[5]. Tales of this sort occur in Pliny, and in Ptolemy's _Quadripartitum_; and the errors have been sedulously propagated, and have gained ground (like ill weeds that grow apace) coming down even to our own day, through the writings of a host of men, who, to fill put their volumes to a proper bulk, write and copy out pages upon pages on this, that, and the other subject, of which they knew almost nothing for certain of their own experience. Such fables of the loadstone even Georgius Agricola himself, most distinguished in letters, relying on the writings of others, has embodied as actual history in his books _De Natura Fossilium_. Galen noted its medicinal power in the ninth book of his _De Simplicium Medicamentorum Facultatibus_, and its natural property of attracting iron in the first book of _De Naturalibus Facultatibus_; but he failed to recognize the cause, as Dioscorides before him, nor made further inquiry.

But his commentator Matthiolus repeats the story of the garlick and the diamond, and moreover introduces Mahomet's shrine vaulted with loadstones[6], and writes that, by the exhibition of this (with the iron coffin hanging in the air) as a divine miracle, the public were imposed upon. But this is known by travellers to be false. Yet Pliny relates that Chinocrates the architect had commenced to roof over the temple of Arsinoe at Alexandria with magnet-stone[7], that her statue of iron placed therein might appear to hang in space. His own death, however, intervened, and also that of Ptolemy, who had ordered it to be made in honour of his sister.

Very little was written by the ancients as to the causes of attraction of iron; by Lucretius and others there are some short notices; others only make slight and meagre mention of the attraction of iron: all of these are censured by Cardan for being so careless and negligent in a matter of such importance and in so wide a field of philosophizing; and for not supplying an ampler notion of it and a more perfect philosophy: and yet, beyond certain received opinions and ideas borrowed from others and ill-founded conjectures, he has not himself any more than they delivered to posterity in all his bulky works any contribution to the subject worthy of a philosopher. Of modern writers some set forth its virtue in medicine only, as [8]Antonius Musa Brasavolus, Baptista Montanus, Amatus Lusitanus, as before them Oribasius in his thirteenth chapter _De Facultate Metallicorum_, Aetius Amidenus, Avicenna, Serapio Mauritanus, Hali Abbas, Santes de Ardoynis, Petrus Apponensis, Marcellus[9], Arnaldus. Bare mention is made of certain points relating to the loadstone in very few words by Marbodeus Callus, Albertus, {3} Matthaeus Silvaticus, Hermolaus Barbarus, Camillus Leonhardus, Cornelius Agrippa, Fallopius, Johannes Langius, Cardinal Cusan, Hannibal Rosetius Calaber; by all of whom the subject is treated very negligently, while they merely repeat other people's fictions and ravings. Matthiolus compares the alluring powers of the loadstone which pass through iron materials, with the mischief of the torpedo, whose venom passes through bodies and spreads imperceptibly; Guilielmus Pateanus in his _Ratio Purgantium Medicamentorum_ discusses the loadstone briefly and learnedly. Thomas Erastus[10], knowing little of magnetical nature, finds in the loadstone weak arguments against Paracelsus; Georgius Agricola, like Encelius[11] and other metallurgists, merely states the facts; Alexander Aphrodiseus in his _Problemata_ considers the question of the loadstone inexplicable; Lucretius Carus, the poet of the Epicurean school, considers that an attraction is brought about in this way: that as from all things there is an efflux of very minute bodies, so from the iron atoms flow into the space emptied by the elements of the loadstone, between the iron and the loadstone, and that as soon as they have begun to stream towards the loadstone, the iron follows, its corpuscles being entangled. To much the same effect Johannes Costaeus adduces a passage from Plutarch; Thomas Aquinas[12], writing briefly on the loadstone in Chapter VII. of his _Physica_, touches not amiss on its nature, and with his divine and clear intellect would have published much more, had he been conversant with magnetick experiments. Plato thinks the virtue divine. But when three or four hundred years afterwards, the magnetick movement to North and South was discovered or again recognized by men, many learned men attempted, each according to the bent of his own mind, either by wonder and praise, or by some sort of reasonings, to throw light upon a virtue so notable, and so needful for the use of mankind. Of more modern authors a great number have striven to show what is the cause of this direction and movement to North and South, and to understand this great miracle of nature, and to disclose it to others: but they have lost both their oil and their pains; for, not being practised in the subjects of nature, and being misled by certain false physical systems, they adopted as theirs, from books only, without magnetical experiments, certain inferences based on vain opinions, and many things that are not, dreaming old wives' tales. Marsilius Ficinus ruminates over the ancient opinions, and in order to show the reason of the direction seeks the cause in the heavenly constellation of the Bear, supposing the virtue of the Bear to prevail in the stone and to be transferred to the iron. Paracelsus asserted that there are stars, endowed with the power of the loadstone, which attract to themselves iron. Levinus Lemnius describes and praises the compass[13], and infers its antiquity on certain grounds; he does not divulge the hidden miracle which he propounds. In the kingdom {4} of Naples the Amalfians were the first (so it is said) to construct the mariners' compass: and as Flavius Blondus says the Amalfians[14] boast, not without reason, that they were taught by a certain citizen, Johannes Goia, in the year thirteen hundred after the birth of Christ. That town is situated in the kingdom of Naples not far from Salerno, near the promontory of Minerva; and Charles V. bestowed that principality on Andrea Doria, that great Admiral, on account of his signal naval services. Indeed it is plain that no invention of man's device has ever done more for mankind than the compass: some notwithstanding consider that it was discovered by others previously and used in navigation, judging from ancient writings and certain arguments and conjectures. The knowledge of the little mariners'

compass seems to have been brought into Italy by Paolo, the Venetian[15], who learned the art of the compass in the Chinas about the year MCCLX.; yet I do not wish the Amalfians to be deprived of an honour so great as that of having first made the construction common in the Mediterranean Sea.

Goropius[16] attributes the discovery to the Cimbri or Teutons, forsooth because the names of the thirty-two winds inscribed on the compass are pronounced in the German tongue by all ship-masters, whether they be French, British, or Spaniards; but the Italians describe them in their own vernacular. Some think that Solomon, king of Judaea, was acquaint with the use of the mariners' compass, and made it known to his ship-masters in the long voyages when they brought back such a power of gold from the West Indies: whence also, from the Hebrew word _Parvaim_[17], Arias Montanus maintains that the gold-abounding regions of Peru are named But it is more likely to have come from the coast of lower aethiopia, from the region of Cephala, as others relate. Yet that account seems to be less true, inasmuch as the Phoenicians, on the frontier of Judaea, who were most skilled in navigation in former ages (a people whose talents, work, and counsel Solomon made use of in constructing ships and in the actual expeditions, as well as in other operations), were ignorant of magnetick aid, the art of the mariners' compass: For had it been in use amongst them, without doubt the Greeks and also Italians and all barbarians would have understood a thing so necessary and made famous by common use; nor could matters of much repute, very easily known, and so highly requisite ever have perished in oblivion; but either the learning would have been handed down to posterity, or some memorial of it would be extant in writing. Sebastian Cabot was the first to discover that the magnetick iron varied[18]. Gonzalus Oviedus[19]

is the first to write, as he does in the _Historia_, that in the south of the Azores it does not vary. Fernelius in his book _De Abditis Rerum Causis_ says that in the loadstone there is a hidden and abstruse cause, elsewhere calling it celestial; and he brings forth nothing but the unknown by means of what is still more unknown. {5} For clumsy, and meagre, and pointless is his inquiry into hidden causes. The ingenious Fracastorio, a distinguished philosopher, in seeking the reason for the direction of the loadstone, feigns Hyperborean magnetick mountains attracting magnetical things of iron: this view, which has found acceptance in part by others, is followed by many authors and finds a place not in their writings only, but in geographical tables, marine charts, and maps of the globe: dreaming, as they do, of magnetick poles and huge rocks, different from the poles of the earth. More than two hundred years earlier than Fracastorio there exists a little work, fairly learned for the time, going under the name of one Peter Peregrinus[20], which some consider to have originated from the views of Roger Bacon, the Englishman of Oxford: In which book causes for magnetick direction are sought from the poles of the heaven and from the heaven itself. From this Peter Peregrinus, Johannes Taisnier of Hainault[21]

extracted materials for a little book, and published it as new. Cardan talks much of the rising of the star in the tail of the Greater Bear, and has attributed to its rising the cause of the variation: supposing that the variation is always the same, from the rising of the star. But the difference of the variation according to the change of position, and the changes which occur in many places, and are even irregular in southern regions, preclude the influence of one particular star at its northern rising. The College of Coimbra[22] seeks the cause in some part of the heaven near the pole: Scaliger in section CXXXI. of his _Exercitationes_ on Cardan suggests a heavenly cause unknown to himself, and terrestrial loadstones nowhere yet discovered. A cause not due to those sideritic mountains named above, but to that power which fashioned them, namely that portion of the heaven which overhangs that northern point. This view is garnished with a wealth of words by that erudite man, and crowned with many marginal subtilities; but with reasonings not so subtile. Martin Cortes[23]

considers that there is a place of attraction beyond the poles, which he judges to be the moving heavens. One Bessardus[24], a Frenchman, with no less folly notes the pole of the zodiack. Jacobus Severtius[25], of Paris, while quoting a few points, fashions new errors as to loadstones of different parts of the earth being different in direction: and also as to there being eastern and western parts of the loadstone. Robert Norman[26], an Englishman, fixes a point and region respective, not attractive; to which the magnetical iron is collimated, but is not itself attracted.

Franciscus Maurolycus[27] treats of a few problems on the loadstone, taking the trite views of others, and avers that the variation is due to a certain magnetical island mentioned by Olaus Magnus[28]. Josephus Acosta[29], though quite ignorant about the loadstone, nevertheless pours forth vapid talk upon the loadstone. Livio Sanuto[30] in his Italian _Geographia_, discusses at length the question whether the prime magnetick {6} meridian and the magnetick poles are in the heavens or in the earth; also about an instrument for finding the longitude: but through not understanding magnetical nature, he raises nothing but errors and mists in that so important notion. Fortunius Affaytatus[31] philosophizes foolishly enough on the attraction of iron, and its turning to the poles. Most recently, Baptista Porta[32], no ordinary philosopher, in his _Magia Naturalis_, has made the seventh book a custodian and distributor of the marvels of the loadstone; but little did he know or ever see of magnetick motions; and some things that he noted of the powers which it manifested, either learned by him from the Reverend Maestro Paolo, the Venetian[33], or evolved from his own vigils, were not so well discovered or observed; but abound in utterly false experiments, as will be clear in due place: still I deem him worthy of high praise for having attempted so great a subject (as he has done with sufficient success and no mean result in many other instances), and for having given occasion for further research. All these philosophizers of a previous age, philosophizing about attraction from a few vague and untrustworthy experiments, drawing their arguments from the hidden causes of things; and then, seeking for the causes of magnetick directions in a quarter of the heavens, in the poles, the stars, constellations, or in mountains, or rocks, space, atoms, attractive or respective points beyond the heavens, and other such unproven paradoxes, are whole horizons wrong, and wander about blindly. And as yet we have not set ourselves to overthrow by argument those errors and impotent reasonings of theirs, nor many other fables told about the loadstone, nor the superstitions of impostors and fabulists: for instance, Franciscus Rueus'[34] doubt whether the loadstone were not an imposture of evil spirits: or that, placed underneath the head of an unconscious woman while asleep, it drives her away from the bed if an adulteress: or that the loadstone is of use to thieves by its fume and sheen, being a stone born, as it were, to aid theft: or that it opens bars and locks, as Serapio[35]

crazily writes: or that iron held up by a loadstone, when placed in the scales, added nothing to the weight of the loadstone, as though the gravity of the iron were absorbed by the force of the stone: or that, as Serapio and the Moors relate, in India there exist certain rocks of the sea abounding in loadstone, which draw out all the nails of the ships which are driven toward them, and so stop their sailing; which fable Olaus Magnus[36]

does not omit, saying that there are mountains in the north of such great powers of attraction, that ships are built with wooden pegs, lest the iron nails should be drawn from the timber as they passed by amongst the magnetick crags. Nor this: that a white loadstone may be procured as a love potion: or as Hali Abbas[37] thoughtlessly reports, that if held in the hand it will cure gout and spasms: Or that it makes one acceptable and in favour with princes, or eloquent, as Pictorio[38] has {7} sung; Or as Albertus Magnus[39] teaches, that there are two kinds of loadstones, one which points to the North, the other to the South: Or that iron is directed toward the Northern stars by an influence imparted by the polar stars, even as plants follow the sun, as Heliotrope does: Or that there is a magnet-stone situated under the tail of the Greater Bear, as Lucas Gauricus the Astrologer stated: He would even assign the loadstone, like the Sardonyx and onyx, to the planet Saturn, yet at the same time he assigns it with the adamant, Jasper, and Ruby, to Mars; so that it is ruled by two planets. The loadstone moreover is said by him to pertain to the sign Virgo; and he covers many such shameful pieces of folly with a veil of mathematical erudition. Such as that an image of a bear is engraved on a loadstone when the Moon faces towards the north, so that when hung by an iron wire it may conciliate the influence of the celestial Bear, as Gaudentius Merula[40] relates: Or that the loadstone drew iron and directed it to the north, because it is superior in rank to iron, at the Bear, as Ficinus writes, and Merula repeats: Or that by day it has a certain power of attracting iron, but by night the power is feeble, or rather null: Or that when weak and dulled the virtue is renewed by goats' blood, as Ruellius[41] writes: Or that Goats' blood sets a loadstone free from the venom of a diamond, so that the lost power is revived when bathed in goats'

blood by reason of the discord between that blood and the diamond: Or that it removed sorcery from women, and put to flight demons, as Arnaldus de Villanova dreams: Or that it has the power to reconcile husbands to their wives, or to recall brides to their husbands, as Marbodeus Gallus[42], chorus-leader of vanities, teaches: Or that in a loadstone pickled in the salt of a sucking fish[43] there is power to pick up gold which has fallen into the deepest wells, according to the narratives of Caelius Calcagninus.

With such idle tales and trumpery do plebeian philosophers delight themselves and satiate readers greedy for hidden things, and unlearned devourers of absurdities: But after the magnetick nature shall have been disclosed by the discourse that is to follow, and perfected by our labours and experiments, then will the hidden and abstruse causes of so great an effect stand out, sure, proven, displayed and demonstrated; and at the same time all darkness will disappear, and all error will be torn up by the roots and will lie unheeded; and the foundations of a grand magnetick philosophy which have been laid will appear anew, so that high intellects may be no further mocked by idle opinions. Some learned men there are who in the course of long voyages have observed the differences of magnetick variation: the most scholarly Thomas Hariot[44], Robert Hues, Edward Wright, Abraham Kendall, all Englishmen; Others there are who have invented and produced magnetical instruments, and ready methods of observation, indispensable for sailors and to those travelling afar: {8} as William Borough[45] in his little book on the _Variation of the Compass_ or Magneticall Needle, William Barlowe[46] in his _Supply_, Robert Norman in his _Newe Attractive_. And this is that Robert Norman[47] (a skilful seaman and ingenious artificer) who first discovered the declination of the magnetick needle. Many others I omit wittingly; modern Frenchmen, Germans, and Spaniards, who in books written for the most part in their native tongues either misuse the placets of others, and send them forth furbished with new titles and phrases as tricky traders do old wares with meretricious ornaments; or offer something not worthy of mention even: and these lay hands on some work filched from other authors and solicit some one as their patron, or go hunting after renown for themselves among the inexperienced and the young; who in all branches of learning are seen to hand on errors and occasionally add something false of their own.

CHAP. II.

Magnet Stone, of what kind it is, and its _discovery._

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

Hence Lucretius says,

_The Magnet's name the observing Grecians drew_ _From the Magnetick region where it grew._

It is called Heraclean from the city Heraclea, or from the invincible Hercules, on account of the great strength and domination and power which there is in iron of subduing all things: it is also called _siderite_, as being of iron; being not unknown to the most ancient writers, to the Greeks, Hippocrates, and others, as also (I believe) to Jewish and Egyptian writers; For in the oldest mines of iron, the most famous in Asia, the loadstone was often dug out with its uterine brother, iron. And if the tales be true which are told of the people of the Chinas, they were not unacquainted in primitive times with magnetical experiments, for even amongst {9} them the finest magnets of all are still found. The Egyptians, as Manetho relates, gave it the name Os Ori: calling the power which governs the turning of the sun Orus, as the Greeks call it Apollo. But later by Euripides, as narrated by Plato, it was designated under the name of Magnet. By Plato in the _Io_, Nicander of Colophon, Theophrastus, Dioscorides, Pliny, Solinus, Ptolemy, Galen, and other investigators of nature it was recognized and commended; such, however, is the variety of magnets and their points of unlikeness in hardness, softness, heaviness, lightness, density, firmness, and friability of substance: so great and manifold are the differences in colour and other qualities, that they have not handed down any adequate account of it, which therefore was laid aside or left imperfect by reason of the unfavourable character of the time; for in those times varieties of specimens and foreign products never before seen were not brought from such distant regions by traders and mariners as they have been lately, and now that all over the globe all kinds of merchandise, stones, woods, spices, herbs, metals, and ore in abundance are greedily sought after: neither was metallurgy so generally cultivated in a former age. There is a difference in vigour; as whether it is male or female: for it was thus that the ancients used often to distinguish many individuals of the same species. Pliny quotes from Sotacus five kinds; those from aethiopia, Macedonia, Boeotia, the Troad, and Asia, which were especially known to the ancients: but we have posited as many kinds of loadstones as there are in the whole of nature regions of different kinds of soil. For in all climates, in every province, on every soil, the loadstone is either found, or else lies unknown on account of its rather deep site and inaccesible position; or by reason of its weaker and less obvious strength it is not recognized by us while we see and handle it. To the ancients the differences were those of colour[49], how they are red and black in Magnesia and Macedonia, in Boeotia red rather than black, in the Troad black, without strength: While in Magnesia in Asia they are white, not attracting iron, and resemble pumice-stone. A strong loadstone of the kind celebrated so often nowadays in experiments presents the appearance of unpolished iron, and is mostly found in iron mines: it is even wont to be discovered in an unbroken lode by itself: Loadstones of this sort are brought from East India, China, and Bengal, of the colour of iron, or of a dark blood or liver colour; and these are the finest, and are sometimes of great size, as though broken off a great rock, and of considerable weight; sometimes single stones, as it were, and entire: some of these, though of only one pound weight, can lift on high four ounces of iron or a half-pound or even a whole pound. Red ones are found in Arabia, as broad as a tile, not equal in weight to those brought from China, but strong and good: they are a little darker in the island of Elba in the Tuscan sea, and together with {10} these also grow white ones, like some in Spain in the mines of Caravaca: but these are of lesser power. Black ones also are found, of lower strength, such as those of the iron mines in Norway and in sea-coast places near the strait of Denmark. Amongst the blue-black or dusky blue also some are strong and highly commended. Other loadstones are of a leaden colour, fissile and not-fissile, capable of being split like slates in layers. I have also some like gray marble of an ashen colour, and some speckled like gray marble, and these take the finest polish. In Germany there are some perforated like honeycombs, lighter than any others, and yet strong. Those are metallick which smelt into the best iron; others are not easily smelted, but are burned up. There are loadstones that are very heavy, as also others very light; some are very powerful in catching up pieces of iron, while others are weaker and of less capacity, others so feeble and barren that they with difficulty attract ever so tiny a piece of iron and cannot repel an opposite magnetick. Others are firm and tough, and do not readily yield to the artificer. Others are friable. Again, there are some dense and hard as emery, or loose-textured and soft as pumice; porous or solid; entire and uniform, or varied and corroded; now like iron for hardness, yea, sometimes harder than iron to cut or to file; others are as soft as clay. Not all magnets can be properly called stones; some rather represent rocks; while others exist rather as metallick lodes; others as clods and lumps of earth. Thus varied and unlike each other, they are all endowed, some more, some less, with the peculiar virtue. For they vary according to the nature of the soil, the different admixture of clods and humours, having respect to the nature of the region and to their subsidence in this last-formed crust of the earth, resulting from the confluence of many causes, and the perpetual alternations of growth and decline, and the mutations of bodies. Nor is this stone of such potency rare; and there is no region wherein it is not to be found in some sort. But if men were to search for it more diligently and at greater outlay, or were able, where difficulties are present, to mine it, it would come to hand everywhere, as we shall hereafter prove. In many countries have been found and opened mines of efficacious loadstones unknown to the ancient writers, as for instance in Germany, where none of them has ever asserted that loadstones were mined. Yet since the time when, within the memory of our fathers, metallurgy began to flourish there, loadstones strong and efficacious in power have been dug out in numerous places; as in the Black Forest beyond Helceburg; in Mount Misena not far from Schwartzenberg[50]; a fairly strong kind between Schneeberg and Annaberg in Joachimsthal, as was noticed by Cordus: also near the village of Pela in Franconia. In Bohemia it occurs in iron mines in the Lessa district and other places, as Georgious Agricola and several other men learned in metallurgy {11} witness. In like manner in other countries in our time it is brought to light; for as the stone remarkable for its virtues is now famous throughout the whole world, so also everywhere every land produces it, and it is, so to speak, indigenous in all lands. In East India, in China, in Bengal near the river Indus it is common, and in certain maritime rocks: in Persia, Arabia, and the islands of the Red Sea; in many places in aethiopia, as was formerly Zimiri, of which Pliny makes mention. In Asia Minor around Alexandria and the Troad; in Macedonia, Boeotia, in Italy, the island of Elba, Barbary; in Spain still in many mines as aforetime. In England quite lately a huge power of it was discovered in a mine belonging to Adrian Gilbert, gentleman[51]; also in Devonshire and the Forest of Dean; in Ireland, too, Norway, Denmark, Sweden, Lapland, Livonia, Prussia, Poland, Hungary. For although the terrestrial globe, owing to the varied humours and natures of the soil arising from the continual succession of growth and decay, is in the lapse of time efflorescing through all its ambit deeper into its surface, and is girt about with a varied and perishable covering, as it were with a veil; yet out of her womb ariseth in many places an offspring nigher to the more perfect body and makes its way to the light of day. But the weak and less vigorous loadstones, enfeebled by the flow of humours, are visible in every region, in every strath. It is easy to discover a vast quantity of them everywhere without penetrating mountains or great depths, or encountering the difficulties and hardships of miners; as we shall prove in the sequel.

And these we shall take pains so to prepare by an easy operation that their languid and dormant virtue shall be made manifest. It is called by the Greeks[52] [Greek: heraklios], as by Theophrastus, and [Greek: magnetis]; and [Greek: magnes], as by Euripides, as quoted by Plato in the _Io_: by Orpheus[53] too [Greek: magneosa], and [Greek: siderites] as though of iron: by the Latins _magnes_, _Herculeus_; by the French _aimant_[54], corruptly from _adamant_; by the Spaniards _piedramant_: by the Italians _calamita_[55]; by the English LOADSTONE and ADAMANT STONE[56], by the Germans _magness_[57] and _siegelstein_: Among English, French, and Spaniards it has its common name from adamant; perhaps because they were at one time misled by the name _sideritis_ being common to both: the magnet is called [Greek: siderites] from its virtue of attracting iron: the adamant is called [Greek: siderites] from the brilliancy of polished iron.

Aristotle designates it merely by the name of _the stone_:[58] [Greek: Eoike de kai thales ex hon apomnemoneuousi, kinetikon ti ten psuchen hupolabein, eiper ton lithon ephe psuchen echein, hoti ton sideron kinei]: _De Anima_, Lib. I. The name of magnet is also applied to another stone differing from siderite, having the appearance of silver; it is like Amianth in its nature; and since it consists of laminae (like specular stone)[59], it differs in form: in German _Katzensilber_ and _Talke_[60].

{12} CHAP. III.

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

The stone itself manifests many qualities which, though known afore this, yet, not having been well investigated, are to be briefly indicated in the first place so that students may understand the powers of loadstone and iron, and not be troubled at the outset through ignorance of reasonings and proofs. In the heaven astronomers assign a pair of poles for each moving sphere: so also do we find in the terrestrial globe natural poles preeminent in virtue, being the points that remain constant in their position in respect to the diurnal rotation, one tending to the Bears and the seven stars; the other to the opposite quarter of the heaven. In like manner the loadstone has its poles, by nature northern and southern, being definite and determined points set in the stone, the primary boundaries of motions and effects, the limits and governors of the many actions and virtues. However, it must be understood that the strength of the stone does not emanate from a mathematical point, but from the parts themselves, and that while all those parts in the whole belong to the whole, the nearer they are to the poles of the stone the stronger are the forces they acquire and shed into other bodies: these poles are observant of the earth's poles, move toward them, and wait upon them. Magnetick poles can be found in every magnet, in the powerful and mighty (which Antiquity used to call the masculine) as well as in the weak, feeble and feminine; whether its figure is due to art or to chance, whether long, flat, square, three-cornered, polished; whether rough, broken, or unpolished; always the loadstone contains and shows its poles. * But since the spherical form, which is also the most perfect, agrees best with the earth, being a globe, and is most suitable for use and experiment, we accordingly wish our principal demonstrations by the stone to be made with a globe-shaped magnet as being more perfect and adapted for the purpose. Take, then, a powerful loadstone, solid, of a just size, uniform, hard, without flaw[61]; make of it a globe upon the turning tool used for rounding crystals and some other stones, or with other tools as the material and firmness of the stone requires, for sometimes it is difficult to be worked. The stone thus perpared is a true, homogeneous offspring of the earth and of the same shape with it: artificially possessed of the orbicular form which nature granted from the beginning to the common mother earth: and it is a physical corpuscle imbued with many virtues, by {13} means of which many abstruse and neglected truths in philosophy buried in piteous darkness may more readily become known to men. This round stone is called by us a [Greek: mikroge] or _Terrella_[62]. To find, then, the poles conformable to the earth's, take the round stone in hand, and place upon the stone a needle or wire of iron: the ends of the iron move upon their own centre and suddenly stand still.

Mark the stone with ochre or with chalk where the wire lies and sticks: move the middle or centre of the wire to another place, and so on to a third and a fourth, always marking on the stone along the length of the iron where it remains at rest: those lines show the meridian circles, or the circles like meridians on the stone, or terrella, all of which meet as will be manifest at the poles of the stone. By the circles thus continued the poles are made out, the Boreal as well as the southern, and in the middle space betwixt these a great circle may be drawn for an aequator, just as Astronomers describe them in the heavens and on their own globes, or as Geographers do on the terrestrial globe: for that line so drawn on this our terrella is of various uses in our demonstrations and experiments magnetical. Poles are also found in a round stone by a versorium, a piece of iron touched with a loadstone, and placed upon a needle or point firmly fixed on a foot so as to turn freely about in the following way:[63]

[Illustration]

On the stone A B the versorium is placed in such a way that the versorium may remain in equilibrium: you will mark with chalk the course of the iron when at rest: Move the instrument to another spot, and again make note of the direction and aspect: do the same thing in several places, and from the concurrence of the lines of direction you will find one pole at the point A, the other at B. A versorium placed near the stone also indicates the true pole; when at right angles it eagerly beholds the stone and seeks the pole itself directly, and is turned in a straight line through the axis to the {14} centre of the stone. For instance, the versorium D faces toward A and F, the pole and centre, whereas E does not exactly respect * either the pole A or the centre F[64]. A bit of rather fine iron wire, of the length of a barley-corn, is placed on the stone, and is moved over the regions and surface of the stone, until it rises to the perpendicular[65]: for it stands erect at the actual pole, whether Boreal or austral; the further from the pole, the more it inclines from the vertical. The poles thus found you shall mark with a sharp file or gimlet.