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.
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.
(3) A galvanic current going in an opposite direction to that of the discharge, and having its origin in the electromotive force discovered by M. Edlund in the electric spark. That these currents require a closed circuit; but this is not necessary in the case of the Aurora, as the earth and rarefied air of the upper regions are immense reservoirs of electricity producing the same effect as if the circuit were closed. That permanent moisture in the air, a good conductor of electricity, is the cause of a slow and continuous discharge assuming the form of an Aurora, instead of suddenly producing lightning as in equatorial regions and mean latitudes.
Polar Light due to electric discharges only.
He sums up, that the electric discharges which take place in the Polar regions between the positive electricity of the atmosphere and the negative electricity of the earth are the essential and unique cause of the formation of the Polar Light, light the existence of which is independent of terrestrial magnetism, which contributes only to give to the Polar Light a certain direction, and in some cases to give it motion.