222. St. Elmo's Fire Electrification from the earth is often drawn up through the masts of ships to neutralize that in the clouds (see [§ 220]), and, as it escapes from the points of the masts, light is produced. This may be clearly shown by repeating [Exp. 71] in the dark; the head of the pin ([Fig. 39]) will represent the end of a mast, and the charged electrophorus cover will be the charged cloud.
223. Aurora Borealis, also called Northern Lights, are luminous effects often seen in the north. They often occur at the same time with magnetic storms, at which times telegraph and telephone work may be disturbed. The exact cause of this light is not known, but it is thought by many to be due to disturbances in the earth's magnetism, caused by the action of the sun.