Electroluminescence 265 



We have seen (Chap. Ill) how John Wier (1579) made a plea 

 for a rational explanation of such appearances, rather than to accept 

 the popular belief that they were apparitions or specters, spirits of 

 unrighteous men or ghosts of unbaptized children, generally works 

 of the devil and sometimes omens of death. HoAvever, many writers 

 since his time have applied the supernatural explanation. 



It is interesting to note that 150 years later the question was still 

 alive. Johann Leonard Wolff wrote an Exercitatio Physica entitled. 

 An Ignes Fatui Sint Spectra in 1733 in which he also took the posi- 

 tion that they were not apparitions (even though they did appear 

 in cemeteries and near gallows) because they were material and 

 corporeal and could be explained by physical means. The evidence 

 was 



that putrid wood, the putrid viscera of fish, and the exhalations of cer- 

 tain animals and insects shine at night and emit a splendor very much 

 like that of fire or sparks. . . . But nothing is found in these shining 

 things that could produce the light and splendor except sulphuric, 

 bituminous, oily and viscous effluvia. . . . Hence ignes fatui produced out 

 of these . . . effluvia, which are material, must themselves be material. . . . 



Wolff had to admit that some strange things had been reported 

 in addition to the fact that they follow a person who flees and recede 

 from those who approach at full speed. He wrote: " It has been 

 observed that these ignes fatui recede farther from the vicinity when- 

 ever a man swears recklessly in a loud voice; but when a scrupulous 

 person takes a deep breath out of a pious heart or sends prayers to 

 God, to him they come closer." 



Thus an ignis fatuus was quite generally regarded as " a kind of 

 slight exhalation set on fire in the night-time, which oftimes causes 

 men to wander out of their way," "^ a point nicely expressed by 

 Samuel Butler (1612-1680) in Hudibras (I, 1: 509, 1660) : 



An Ignis Fatuus that bewitches 



and leads Men into Pools and Ditches. 



In more recent times ignis fatuus has been attributed to masses of 

 phosphorescent wood or fimgi, to stray light reflected from wisps of 

 vapor, which frequently condense near low ground and damp places 

 in the early evening, or to marsh gas set afire,-* or to self inflammable 



"Edward Phillips (1630-1696) , in the New worlde of English words (1658) . 



^*' In a letter (Dec. 10, 1776) to Priestley (published in Experiments and observa- 

 tions on different kinds of air, 3: appendix, pp. 381-382, 1777) on "Inflammable Air 

 from Putrefaction of Vegetable substances," A. Volta explained " ignes fatui " over 

 marshy giound by inflammable air set on fire " by the help of the electricity of fogs, 

 and by falling stars which are very probably thought to have an electrical origin." 



