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Definition: will-o'-the-wisp from The Columbia Encyclopedia

phenomenon known also as ignis fatuus and jack-o'-lantern. It is seen at night as a pale, flickering light over marshland. There is no generally accepted explanation for it; it may result from the spontaneous ignition of gases (e.g., methane) produced by the disintegration of dead plant or animal matter, or it may be a form of phosphorescence. The eerie lights have given rise to many superstitions.

Summary Article: will-o’-the-wisp
from Chambers Dictionary of the Unexplained

An elusive moving light sometimes seen over marshes or bogs at night, thought in folklore to be a mischievous fairy or a restless spirit.

The will-o’-the-wisp is a natural phenomenon which occurs all over the world, and every region has its own name for this mysterious moving light which is sometimes seen hovering over marshes or bogs at night. Scientists generally agree that the light is caused by the spontaneous ignition, by traces of hydrogen phosphide, of the methane produced by the decaying organic matter found in marshes. It has also been suggested that the little-understood phenomenon of ball lightning may be the cause. However, in folklore, the will-o’-the-wisp is feared as an ill omen which foretells the death of the person who sees it, or of someone close to them. When seen near a graveyard it may be called a corpse light or corpse candle, and is believed to light the way from the victim’s house to the grave, and in Ireland, it is often thought to lead a spectral funeral procession. It is also popularly believed to be a wandering soul rejected by both heaven and hell, or in some places, the spirit of an unbaptized child. In Northern Europe it is sometimes seen hovering over burial mounds, when it is said to be the souls of the dead, guarding the treasure buried in their graves. In German and Swedish folklore it may also be the soul of a person who, in life, disregarded boundary markers and stole a neighbour’s land.

When approached, the will-o’-the-wisp vanishes, often reappearing just out of reach, so that in many parts of the world it is seen as a mischievous spirit which delights in leading travellers astray, a fairy which either appears as a ball of light or carries a lantern to lure the unwary over cliff-tops or into a bog. However, these spirits have occasionally been known to help rather than hinder, showing travellers the way to safety.

The will-o’-the-wisp is known by many other names, such as ignis fatuus (‘foolish light’), jack o’lantern, friar’s light, fairy light and fox fire, and the word is also used figuratively to refer to any elusive or deceptive person or idea which leads people astray.

© Chambers Harrap Publishers Ltd 2007

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