What is an Ignis Fatuus?

   Ignis Fatuus is a flame or light which on summer and autumn nights is seen sometimes to hover over swamps, stagnant waters, or graveyards. Many explanations have been given for these marsh lights, and it is quite possible that several different causes result in the quite varied appearance of the phenomena. Luminous insects, or phosphorescence of decaying vegetable matter may account in some cases for the light. Another theory is that phosphoretted hydrogen, a gas which is spontaneously inflammable, is produced where there is decaying animal matter and that its ignition causes the flames.
   Ignis fatuus is known sometimes as Will-o'-the-wisp or Jack-o'-lantern. It was regarded formerly with awe by the superstitious who had many stories to tell of travelers decoyed to danger and death by evil spirits whose torches made these strange lights.
   The words ignis fatuus are Latin and mean foolish fires. Figuratively the term is used to designate the foolish impulses and light motives which lead many people astray by their resemblance to something worth while.

ignis fatuus

Ignis fatuus