He considered it probable that the Aurora was essentially an electric discharge between the magnetic poles of the earth, leaving the immediate vicinity of the north magnetic pole in the form of clouds of electrified matter, which floated southward, bright streams of electricity suddenly shooting forth in magnetic curves corresponding to the points from which they originated, and then bending southward and downward until they reached corresponding points in the southern magnetic hemisphere, and forming pathways by which the electric currents passed to their destination; and, further, that the magnetism of the earth caused these currents and electrified matter composing the arch to revolve round the magnetic pole of the earth, giving them their observed motion from east to west or from west to east. [Sidenote: Varley’s observation on a glow-discharge _in vacuo_. Spark surrounded by an aura which could be separated.] Varley showed that when a glow-discharge in a vacuum tube is brought within the field of a powerful magnet, the magnetic curves are illuminated beyond the electrodes between which the discharge is taking place, as well as in the path of the current, and also thought that this illumination was caused by moving particles of matter, as it deflected a balanced plate of talc on which it was caused to infringe. It has also been shown that in electrical discharges in air at ordinary pressure, while the spark itself was unaffected by the magnet, it was surrounded by a luminous cloud or aura which was driven into the magnetic curve, and which might also be separated from the spark by blowing upon it. Most of the foregoing interesting results and experiments will be found repeated and verified in Part III. _Prof. Lemström’s Theory._ [Sidenote: Prof. Lemström’s theory.] Prof. Lemström thinks that terrestrial magnetism plays only a comparatively secondary part in the phenomena of the Polar Light, this part consisting essentially in a direct action upon the rays. That the experiments of M. de la Rive do not all furnish the proof that the rays of the light are really united under this influence. [Sidenote: Character of the Polar Light.] That the Polar Light considered as an electrical discharge gives the following results:— (1) An electric current arising from the discharge itself, which takes place slowly. (2) Rays of light consisting of an infinite number of sparks, each spark giving rise to two induction currents going in opposite directions.