Electroluminescence 255 



this fascinating type of light; then ignis lambens and ignis fatuus 

 will be considered. 



The Aurora Borealis or Polaris 



SEVENTEENTH AND EIGHTEENTH CENTURY VIEWS 



Although observation of flames in the sky, popularly called the 

 northern lights," has been made throughout recorded history, and 

 they have regularly been considered omens of war, death, pestilence, 

 or famine— signs of the wrath of God— few of the early reports con- 

 tain more than records ^^ of particularly brilliant displays. They 

 might have the appearance of a monk's hood or an eagle with ex- 

 tended wings. A number of such ancient and medieval examples 

 has already been given in Chapters I, II, and III. 



The name " aurora borealis " is usually attributed to Pierre Gas- 

 sendi (1592-1655) , used in his Diogenes Laerce (1649) , while aurora 

 australis designates the similar phenomena at the south pole. These 

 aurorae may exhibit every possible luminous effect, from a mere 

 glow in the sky, or columns and shafts of light pointing upward, 

 or a crown, to waving curtains of a brilliant red color. 



Most early treatises on cosmic phenomena mention the aurora. 

 Francis Bacon thought they were signs of heat and Rene Descartes 

 intimated that they might result from the light of the sun below 

 the horizon, but a more common view regarded them as vapors 

 from the earth set on fire, as suggested in the previously quoted 

 book on meteors (1560) by William Fulke (see Chapter III) . 



The seventeenth-century view of the northern lights is well ex- 

 pressed by John Swan in Speculum Miindi (Cambridge, 1635) , at 

 a time when the phrase " aurora borealis " had not been coined, 

 and many of the types of meteors were not known to be essentially 

 the same. After the listing of various meteors, Swan proceeded to 

 explain how all these kinds of fiery meteors might arise. For 

 example: 



Burning Streams, Spears, or Darts, is that Meteor which is called Bolis 

 or Jaculum, and is an Exhalation hot and drie, meanly long, whose 

 thick and thinner parts are equally mixt: and thereupon being fired 

 in the highest Region, it flameth on the thin or subtil part; which 

 nevertheless, because the matter is well mixed, doth also send fire to 

 the other parts, insomuch that it seems to run like a dart from the one 

 unto the other. 



^'Nororljds (northern lights), is said to have been applied to the aurora borealis 

 by the Icelandic settlers of Greenland. 



^^A list of records from 503 B.C. to 1873 will be found in H. Fritz, Verzeichniss 

 beobachteter Polarlichten, Wien, 1873. 



