1911 Encyclopædia Britannica/St Elmo's Fire
ST ELMO'S FIRE, the glow accompanying the slow discharge of electricity to earth from the atmosphere. This discharge, which is identical with the “ brush ” discharge of laboratory experiments, usually appears as a tip of light on the extremities of pointed objects such as church towers, the masts of ships, or even the fingers of the outstretched hand: it is commonly accompanied by a crackling or fizzing noise. St Elmo's fire is most frequently observed at low levels through the winter season during and after snowstorms.
The name St Elmo is an Italian corruption through Sant' Ermo of St Erasmus, a bishop, during the reign of Domitian, of Formiae, Italy, who was broken on the wheel about the 2nd of June 304. He has ever been the patron saint of Mediterranean sailors, who regard St Elmo's fire as the visible sign of his guardianship. The phenomenon was known to the ancient Greeks, and Pliny in his Natural History states that when there were two lights sailors called them Castor and Pollux and invoked them as gods. To English sailors St Elmo's fires were known as “corposants” (Ital. corpo santo).