THE pirate adventurer, William Dampier, writing in his diary in July, 1687, described a sight that was common enough for sailors at that time. "After 4 o'clock the thunder ceased, and then we saw a corpo Santo at our main top mast head. It is like a star, but when it appears upon the deck it resembles more a glow worm. I have heard some ignorant seamen discouraging how they have seen it creep or move about in the scuppers, but I never did see anyone stir out of the place where it was first fixed except on deck where every sea washeth it about. Neither did I ever see one but when we have had hard weather."
The phenomenon concerned is more commonly known as "St Elmo's fire". It is named, for reasons quite unknown, after St Erasmus, a third century Italian martyr who, as patron saint of Mediterranean sailors, had his name affectionately shortened to "Sant Ermo". Through a local variant, "St Elmo", he gave his name to this maritime will o' the wisp described by Dampier.
St Elmo's fire or Corpo Santo is a luminous brush like glow with flame like streamers, which in stormy weather was often seen to play around the masts and rigging of the old sailing ships. It is electrical in origin. It occurs in thundery conditions when the electrical tension between the clouds and the earth below is such that there is a strong tendency for an electrical current to flow from one to the other sometimes, rather than bursting forth as a flash of lightning, the charge leaks upwards in a more gradual way, and this flow of electricity causes the surrounding air to widely documented down the ages. Some say that the burning bush encountered by Moses on Mount Sinai was in reality this kind of glow. The Roman writer, Pliny, described it as "resembling lightning, leaping to and fro and shifting its place, just as birds do when they fly from bough to bough". Legend also has it that Columbus, having trouble with morale when sailing west wards for what seemed forever, raised the spirits of his crew during a violent tempest by pointing to the "holy fire" as a sign that their troubles were about to end. And the cowboys of the old American west were sometimes scared by the weird effect produced when St Elmo's fire made "a devil with flaming horns" of every steer.
Even today, St Elmo's fire can be seen if times are right. It flows occasionally from lightning conductors on tall buildings or from weather station wind vanes, or now and then it even streams from the loose ends of human hair.