, in consequence of its tendency to rotate as a whole round the pole of the magnet.
When narrow bands of tin foil wrapped round the glass tube near the platinum wires were put in communication with the poles of the induction battery, brilliant stratifications filled the whole tube between the tin coatings every time the electric circuit was broken or renewed; and when the tube was placed horizontally on the pole of a magnet, the stratifications no longer showed a tendency to rotate as a whole, they were divided into two parts tending to rotate in opposite directions; when the tube was placed between the poles of a powerful electro-magnet, one half of the stratifications were repelled and the other half attracted. When the tube was placed on the north pole, the divided stratifications arranged themselves on each side of the tube, changing their respective positions when placed on the south pole, but in every case each half was concave in opposite directions.
[Fig. 2] (p. 81) represents the form which the induced stratified discharges assume when the vacuum tube is placed on or between the poles of a powerful electro-magnet—the tin foil coatings C+ C- being attached by wires to the terminals of an induction coil.
Fig. 2.
If a vacuum tube with or without wires or tin coatings be laid upon the induction coil of a battery, or upon the prime conductor of an electrifying machine, stratifications are produced by induction which are divided by a magnet. Thus there are two distinct forms of the stratified discharge, one direct, the other induced.
When Professor Plücker of Bonn sent an induced current of electricity from Ruhmkorff’s coil through a vacuum tube having a platinum wire fused into each extremity, and extending a little way into the interior of the tube, electric light radiated from every point of the negative wire, and when exposed to the action of an electro-magnet the whole tube was filled with a luminous atmosphere. But when all the negative platinum wire except its extreme point was insulated by a coating of glass, the rays of electric light which radiated from the point were united into one single and perfectly regular magnetic curve, upon the approach of an electro-magnet; when the negative platinum wire was partially insulated by glass coating, electric light emanated from every exposed part, and assumed the form of magnetic curves under electro-magnetic action. Whence Professor Plücker concluded that the luminous atmosphere in the first experiment was the locus of an infinite number of magnetic curves, and consequently that magnetic light emanates from the negative or warmth pole, and electric light from the positive or light pole. These magnetic curves of light are precisely similar to those assumed by iron filings from magnetic action.
The most remarkable of these experiments is the absolute extinction of a powerful electric discharge by magnetic action. Mr. Gassiot sent a discharge from a voltaic water battery, containing 3,520 insulated cells, into a tube filled with attenuated carbonic acid gas. The discharge was so strong that it was capable of passing through more than six inches of the gas, yet, on the approach of a very powerful electro-magnet, the stratifications were arrested as soon as they appeared, as if blown out, and finally extinguished. A stratified discharge, in vacuo, from 400 insulated cells of a nitric acid battery, was extinguished by the large electro-magnet of the Royal Institution; the luminous strata rushed from the positive pole of the battery, but under the magnetic force they retreated; cloud followed after cloud with deliberate motion, appearing as if swallowed up by the positive terminal. The amount of electricity that passed through the tube appeared to be materially increased by exciting the electro-magnet; the discharge was so intense on one occasion as to fuse half an inch of the positive terminal. A very powerful magnet is also capable of extinguishing a stratified discharge. In fact, according to the law of the reciprocal action of magnetism, the forces are equal in intensity and opposite in direction.
The electric discharge from an induction coil is discontinuous, or eruptive sparks of high tension are given out producing stratified discharges.