MAGNET, NATURAL. One of the numerous oxides of iron ; possessed, however, of properties peculiar to itself, if we except the metals nickel and co balt, which possess it also in a very slight degree. The magnet consists chiefly of two oxides, together with a small portion of quartz and alumine. Its color varies in different specimens, according to mi nute differences in the ratios of the two oxides, and the nature of the foreign substances with which they are found united ; but it is usually of a dark-gray hue, and has a dull metallic lustre. It is found in considerable masses in the iron mines of Sweden and Norway ; in the Isle of Elba; in different parts of Arabia, China, Siam, and the Philippine Islands. Small magnets are also occasionally, though rarely, met with among the iron ores of this country. The properties are ; 1. It attracts iron in all its states ex cept the oxides.
2. If formed into a bar, and suspended freely by a hair, or on a pivot passing through its centre, it will turn itself round, and, after a few pendulous vibra tions, settle into some one position ; which it will retain if left undisturbed, or if disturbed will, after a few similar vibrations, return to it again as before.
3. By rubbing on a bar of steel it will give the bar the same properties ; and a bar of soft iron will, while contiguous to it, even when not touched by it, obtain the same properties, which, however, the iron does not, like the steel, retain upon removal.
4. The position of rest is different at different places, and different at the same place at distant periods of time.
A great number of amusing toys have been formed of this substance, and the phenomena are often at first sight very surprising ; but its application to the purposes of navigation renders it one of the most important discoveries ever made. The earlier navigators believed that it pointed always to the north pole of the world ; and that, therefore, by means of it they could always at once tell the di rection of their meridian, and conse quently in what direction they were sail ing. It was hence called the loadstone, or leading stone.
The employment of the loadstone itself for the purposes of navigation has long been laid aside • as artificial magnets can be constructed having a much greater in tensity of directive power.