In another experiment of Faraday's, where a beam of polarized light was sent through a long glass tube containing water, and introduced as a core _inside_ a powerful electro-magnetic coil, the image of a candle viewed with a proper eye-piece, appeared or disappeared as the battery connexion was made or broken with the coil; but this result is not considered by many philosophers to be conclusive of the action of magnetism on light, but rather as an alteration of the _refracting_ power of the medium through which the light passes. These experiments were the precursors of the other effects of magnetism upon different kinds of matter which Faraday discovered, and he commenced his examination with a small bar of heavy glass suspended by a filament of silk between the poles of an electro-magnet, and when the twisting or effects of torsion had ceased, the battery was connected. Directly the current passed, Faraday's keen eye detected a movement of the glass, and on repeating the experiment, he discovered that the movement was not accidental, but always took place in a certain fixed direction--viz., a direction at right angles to a line drawn across and touching the two poles of a horse-shoe-shaped magnet--_i.e._, supposing the feeder or bit of soft iron usually placed in contact with the poles of the horse-shoe-magnet to represent the "_axial line_," any line drawn across it at right angles would be called the _equatorial line_, whilst the general space included between the poles of the magnet is called "the _magnetic field_." The movement of the heavy glass was therefore _equatorial_, and it pointed east and west instead of north and south, like iron and steel. [Illustration: Fig. 242. A cube of copper suspended between the poles of a powerful electro-magnet.] By the use of the apparatus (Fig. 242) Faraday proved that every [Page 249] substance, whether solid, fluid, or gaseous, was subject to magnetic influences, assuming either the axial or equatorial position. The apparatus consists of a prolongation of the poles of a powerful electro-magnet, between which _the_ cube of copper, weighing from a quarter to half a pound, suspended by a thread, may be set spinning or rotating. If the electro-magnet is connected with the battery, the cube stops immediately, and whilst still in the same position or in the _magnetic field_, with the magnet in full action, it is impossible to set it spinning or twisting round again. (Fig. 242.) A large number of other substances, solid, liquid, and gaseous, were submitted to the action of the magnet, the liquids and gases being hermetically sealed in glass tubes, and some of the results are detailed in the following list: _Bodies that point axially, or are paramagnetic, like a suspended needle._