Page:Popular Science Monthly Volume 53.djvu/496

more active as causes than the Edlund currents. It is natural to suppose that any variation of the earth's electrical equilibrium or potential would tend to draw down the atmospheric currents. Here would come in the action of the electrical currents which coincide

Fig. 5.—Melbourne. Aurora with Arcs and Corona Australis.

with sun spots, and which undoubtedly produce electric storms in summer and auroras in winter. Magnetic disturbances and telluric currents have a known relation to sun spots; so also must the aurora in its secondary widespread form.