On the Magnet, by William Gilbert

Chap. vi.

Loadstone attracts the ore of iron, as well as iron proper, smelted and wrought.

P rincipal and manifest among the virtues of the * magnet, so much and so anciently commended, is the attraction of iron; for Plato states that the magnet, so named by Euripides, allures iron, and that it not only draws iron rings but also indues the rings with power to do the same as the stone; to wit, draw other rings, so that sometimes a long chain of iron objects, nails or rings is formed, some hanging from others. The best iron (like that which is called acies from its use, or chalybs from the country of the Chalybes) is best and strongly drawn by a powerful loadstone; whereas the less good sort, which is impure, rusty, and not thoroughly purged from dross, and not wrought in second furnaces, is more feebly drawn; and yet more weakly when covered and defiled with thick, greasy, and sluggish humours. It also draws ores of iron, those that are rich and of iron colour; the poorer and not so productive ores it does not attract, except they be prepared with some art. A loadstone loses some attractive virtue, and, as it were, pines away with age, if exposed too long to the open air instead of being laid in a case with filings or scales of iron. Whence it should be buried in such materials; for there is nothing that plainly resists this exhaustless virtue which does not destroy the form of the body, or corrode it; not even if a thousand adamants were conjoined. Nor do I consider that there is any such thing as the Theamedes69, or that it has a power opposite to that of the loadstone. Although Pliny, that eminent man and prince of compilers (for it is what others had seen and discovered, not always or mainly his own observations, that he has handed down to posterity) has copied from others the fable now made familiar by repetition: That in India there are two mountains near the river Indus; the nature of one being to hold fast all that is iron, for it consists of loadstone; the other's nature being to repel it, for it consists of the Theamedes. Thus if one had iron nails in one's boots, one could not tear away one's foot on the one mountain, nor stand still on the other. Albertus Magnus writes that a loadstone had been found in his day which with one part drew to itself iron, and repelled it with its other end; but Albertus observed the facts badly; for every loadstone attracts with one end iron that has been touched with a loadstone, and drives it away with the other; and draws iron that been touched with a loadstone more powerfully than iron that has not been so touched.

69 Page 18, line 24. Page 18, line 27. Theamedem.— For the myth about the alleged Theamedes, or repelling magnet, see Cardan, De Subtilitate (folio ed., 1550, lib. vii., p. 186).

Pliny's account, in the English version of 1601 (p. 587), runs:

"To conclude, there is another mountaine in the same Æthyopia, and not farre from the said Zimiris, which breedeth the stone Theamedes that will abide no yron, but rejecteth and driveth the same from it."

Martin Cortes, in his Arte de Nauegar (Seville, 1556), wrote:

"And true it is that Tanxeades writeth, that in Ethiope is found another kinde of this stone, that putteth yron from it" (Eden's translation, London, 1609).

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