MAGNET (Magnes), the LOADSTONE: a sort of ferruginous stone, in weight and colour resembling iron ore, though somewhat harder and more heavy; endowed with various extraordinary properties, attractive, directive, inclinatory, &c. See MAGNETISM.
The magnet is also called Lapis Heracleus, from Heraclea, a city of Magnesia, a port of the ancient Lydia, where it is said to have been first found, and from which it is usually supposed to have taken its name. Though others derive the word from a shepherd named Magnes, who first discovered it with the iron of his crook on mount Ida. It is also called Lapis Nauticus, by reason of its use in navigation; and fiderites, from its attracting iron, which the Greeks call dyq.
The magnet is usually found in iron mines, and sometimes in very large pieces half magnet half iron. Its colour is different according to the different countries it is brought from. Norman observes, that the best are those brought from China and Bengal, which are of an iron or sanguine colour; those of Arabia are reddish; those of Macedonia blackish; and those of Hungary, Germany, England, &c. the colour of unwrought iron. Neither its figure nor bulk is determinate, it is found of all forms and sizes.
The ancients reckoned five kinds of magnets, different in colour and virtue; the Ethiopic, Magnesian, Boetic, Alexandrian, and Natolian. They also took it to be male and female: but the chief use they made of it was in medicine; especially for the cure of burns and defluxions on the eyes.—The moderns, more happy, employ it to conduct them in their voyages. See NAVIGATION.
The most distinguishing properties of the magnet are, That it attracts iron, and that it points to the poles of the world; and in other circumstances also dips or inclines to a point beneath the horizon, directly under the pole; and that it communicates these properties, by touch, to iron. On which foundation are built the mariner's needles, both horizontal and inclinatory.
Attractive Power of the Magnet was known to the ancients; and is mentioned even by Plato and Euripides, who call it the Heracleian stone, because it commands iron, which subdues every thing else: but the knowledge of its directive power, whereby it disposes its poles along the meridian of every place, and occasions needles, pieces of iron, &c. touched with it, to point nearly north and south, is of a much later date; though the exact time of its discovery, and the discoverer himself, are yet in the dark. The first tidings we hear of it is in 1260, when Marco Polo the Venetian is said by some to have introduced the mariner's compass; tho' not as an invention of his own, but as derived
Magnet. ved from the Chinese, who are said to have had the use of it long before; though some imagine that the Chinese rather borrowed it from the Europeans.
Flavio de Gioia, a Neapolitan, who lived in the 13th century, is the person usually supposed to have the best title to the discovery; and yet Sir G. Wheeler mentions, that he had seen a book of astronomy much older, which supposed the use of the needle; though not as applied to the uses of navigation, but of astronomy. And in Guyot de Provins, an old French poet, who wrote about the year 1180, there is an express mention made of the loadstone and the com-
passe; and their use in navigation obliquely hinted at. Magnet.
The Variation of the MAGNET, or its declination from the pole, was first discovered by Seb. Cabot, a Venetian, in 1500; and the variation of that variation, by Mr Gellibrand, an Englishman, about the year 1625. See VARIATION.
Lastly, the dip or inclination of the needle, when at liberty to play vertically, to a point beneath the horizon, was first discovered by another of our countrymen, Mr R. Norman, about the year 1576. See the article Dipping-NEEDLE.