Fig. 199.
a. Powerful electro-magnet supporting a great weight. b. The battery.
Seventh Experiment.
When a piece of soft iron is held sufficiently near one of the poles of a powerful magnet, it becomes by induction endowed with magnetic poles, and will support another bit of soft iron, such as a nail, brought in contact with it. When the magnet is removed, the inductive action ceases, and the soft iron loses its magnetic power. This experiment affords another example of the connexion between the phenomena of electricity and magnetism. It is in consequence of the inductive action of the magnetism of the earth that all masses of iron, especially when they are perpendicular, are found to be endowed with magnetic polarity; hence the reaction of the iron in ships upon the compasses, which have to be corrected and adjusted before a voyage, or else serious errors in steering the vessel would occur, and there is no doubt that many shipwrecks are due to this cause. No other metals beside iron, steel, nickel, cobalt, and possibly manganese, can receive or retain magnetism after contact with a magnet.
The remarkable effect of magnetism upon all matter, so ably investigated by Faraday and others, will be explained in another part of this book—viz., in the article on Dia-Magnetism.
Fig. 200.
Magician and his loadstone-rock.—Vide Fairy Tale.