On the Magnet, by William Gilbert

Chap. xxxviii.

On Cases of Attraction in other Bodies.

V ery often the herd of philosophizers and plagiarists repeat from the records of others in natural philosophy opinions and errors about the attractions of various bodies; as that Diamond attracts iron, and snatches it away from a magnet; that there are various kinds or magnets, some which attract gold, others silver, brass, lead; even some which attract flesh, water, fishes. The flame of sulphur is said to seek iron and stones; so white naphtha is said to attract fire. I have said above that inanimate natural bodies do not attract, and are not attracted by, others on the earth, excepting magnetically or electrically. Wherefore it is not true that there are magnets which attract gold or other metals; because a magnetick substance draws nothing but magnetick substances. Though Fracastorio says that he has shown a magnet drawing silver; if this were true, it must have happened on account of iron skilfully mixed with that silver or concealed in it, or else because nature (as she does sometimes, but rarely) had mixed iron with the silver; iron indeed is rarely mixed with silver by nature; silver with iron very rarely or never. Iron is mixed with silver by forgers of false coin or from the avarice of princes in the coining of money, as was the case with the denarius of Antony189, provided that Pliny is recording a true incident. So Cardan (perhaps deceived by others) says that there is a certain kind of loadstone which draws silver; he adds a most foolish test of this: "If therefore" (he says) "a slender rod of silver be steeped in that in which a versatory needle has stood, it will turn toward silver (especially toward a large quantity) although it be buried; by this means anyone will be able easily to dig up concealed treasures." He adds that "it should be very good stone, such as he has not yet seen." Nor indeed will either he or anyone else ever see such a stone or such an experiment. Cardan brings forward an attraction of flesh, wrongly so named and very dissimilar from that of the loadstone; for his magnes creagus or flesh-magnet, from the experiment that it sticks to the lips, must be hooted out from the assembly of loadstones, or by all means from the family of things attractive. Lemnian earth, ruddle, and very many minerals do this, and yet they are fatuously said to attract. He will have it that there is another loadstone, as it were, a third species, into which, if a needle is driven and afterwards stuck into the body, it is not felt. But what has attraction to do with stupefaction, or stupor with a Philosopher's intellect, when he is discoursing about attraction? There are many stones, both found in nature and made by art, which have the power of stupefying. Sulphur flame is said by some to attract, because it consumes certain metals by its power of penetration. So white naphtha attracts flame, because it gives off and exhales an inflammable vapour, on which account it is kindled at some distance, just as the smoke of a recently extinguished candle takes fire again from another flame; for fire creeps to fire through an inflammable medium. Why the sucking fish Echineis or the Remora should stay ships has been variously treated by Philosophers, who are often accustomed to fit this fable (as many others) to their theories, before they find out whether the thing is so in nature. Therefore, in order that they may support and agree with the fatuities of the ancients, they put forward even the most fatuous ratiocinations and ridiculous problems, cliffs that attract, where the sucking fish tarry, and the necessity of some vacuum, I know not what, or how produced. Pliny and Julius Solinus make mention of a stone Chatochitis190. They say that it attracts flesh, and keeps hold of the hands, just as a loadstone does iron, and amber chaff. But that happens only from a stickiness and from glue contained in it, since it sticks more easily to the hands when they are warm. Sagda or Sagdo191, of the colour of a sard, is a precious stone mentioned by Pliny, Solinus, Albertus, and Evax192; they describe its nature and relate, on the authority of others, that it specially attracts wood to itself. Some even babble that woods cannot be wrenched away except they are cut off. Some also narrate that a stone is found which grows pertinaciously into ships, in the same way as certain testacea on long voyages. But a stone does not draw because it sticks; and if it drew, it would certainly draw shreds electrically, Encelius saw in the hands of a sailor such a stone of feeble virtue, which would hardly attract even the smallest twigs; and in truth, not of the colour of the sard. So Diamond, Carbuncle, Crystal, and others do attract. I pass over other fabulous stones; Pantarbe, about which Philostratus writes that it draws other stones to itself; Amphitane also, which attracts gold. Pliny in his origin of glass will have it that a loadstone is an attractor of glass, as well as of iron. For in his method of preparing glass, when he has indicated its nature, he subjoins this about loadstone. "Soon (such is the astute and resourceful craft) it was not content to have mixed natron; loadstone also began to be added, since it was thought to attract to itself the liquor of glass (as it does iron)." Georgius Agricola writes that to the material of glass (sand and natron) one part also of loadstone is added. "Because that force is believed, in our times just as in former times, to attract the liquor of glass to itself, as it attracts iron to itself, purges it when drawn, and makes clear glass from green or muddy; but the fire afterwards burns up the loadstone." It is true indeed that some sort of magnes (as the magnesia of the glass-makers imbued with no magnetick virtues) is sometimes put in and mixed with the material of the glass; not, however, because it attracts glass. But when a loadstone is burnt, it does not lay hold of iron at all, nor is iron when red-hot allured by any loadstone; and loadstone also is burnt up by more powerful fires and loses its attractive potency. Nor is this a function of loadstone alone in the glass furnaces; but also of certain pyrites and of some easily combustible iron ores, which are the only ones used by our glass-makers, who make clear, bright glass. They are mixed with the sand, ashes, and natron (just as they are accustomed to make additions in the case of metallick ores whilst they are smelted), so that when the material slows down into glass, the green and muddy colour of the glass may be purged by the penetrating heat. For no other material becomes so hot, or bears the fire for such a convenient time, until the material of the glass is perfectly fluid, and is at the same time burnt up by that ardent fire. It happens, however, sometimes, that on account of the magnetick stone, the magnesia, or the ore, or the pyrites, the glass has a dusky colour, when they resist the fire too much and are not burnt up, or are put in in too great quantity. Wherefore manufacturers are seeking for a stone suitable for them, and are observing also more diligently the proportion of the mixture. Badly therefore did the unskilful philosophy of Pliny impose upon Georgius Agricola and the more recent writers, so that they thought the loadstone was wanted by glass-makers on account of its magnetick strength and attraction. But Scaliger in De Subtilitate ad Cardanum, in making diamond attract iron, when he is discussing magneticks, wanders far from the truth, unless it be that diamond attracts iron electrically, as it attracts wood, straws, and all other minute bodies when it is rubbed. Fallopius reckons that quicksilver draws metals by reason of an occult property, just as a loadstone iron, amber chaff. But when quicksilver enters metals, it is wrongly called attraction. For metals imbibe quicksilver, just as clay water; nor do they do this unless they are touching, for quicksilver does not allure gold or lead to itself from afar, but they remain motionless in their places.

189 Page 110, line 11. Page 110, line 12. qualis fuit Antonij denarius.— The Elizabethan version of Pliny (book xxxiii., ch. ix., p. 479) runs thus: "To come now unto those that counterfeit money. Antonius whiles hee was one of the three usurping Triumvirs, mixed yron with the Romane silver denier. He tempered it also with the brasen coine, and so sent abroad false and counterfeit money."

Georgius Agricola (De Natura Fossilium, p. 646) says:

"Sed ea fraus capitalis est, non aliter ac eorum qui adulterinas monetas cudunt, argento miscentes multam plumbi candidi portionem, aut etiam ferri, qualis fuit Antonii denarius, ut Plinius memoriæ tradidit. Nunc dicam de candido plumbo, nam majoris pretii est quàm aes. In quod plumbum album, inquit Plinius, addita aeris tertia portione candidi adulteratur stannum."

190 Page 111, line 3. Page 111, line 3. Meminerunt Chatochitis lapis Plinius, atque Iulius Solinus.— The passage in Pliny (English version of 1601, book xxxvii., ch. x., p. 625) runs:

"Catochitis is a stone proper unto the Island Corsica: in bignesse it exceedeth ordinarie pretious stones: a wonderfull stone, if all be true that is reported thereof, and namely, That if a man lay his hand thereon, it will hold it fast in manner of a glewie gum."

191 Page 111, line 7. Page 111, line 7. Sagda vel Sagdo.— Albertus Magnus in De Mineralibus (Venet., 1542, p. 202) says:

"Sarda quem alij dicunt Sardo lapis est qui se habet ad tabulas ligni sicut magnes ad ferrū, et ideo adhæret ita fortiter tabulis nauium quòd euelli nō possit, nisi abscindatur cum ipso ea pars tabulæ cui inhæserit, est autē in colore purissimus nitens."

And Pliny (op. citat., p. 629):

"Sagda is a stone, which the Chaldeans find sticking to ships, and they say it is greene as Porrets or Leekes."

192 Page 111, line 8. Page 111, line 8. Euace.— Evax, king of the Arabs, is said to have written to Nero a treatise on the names, colours, and properties of stones. See the note on Marbodæus, p. 7, line 20.

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Last updated Friday, March 14, 2014 at 22:17