38 History of Luminescence 



recorded other later displays, one of which, in the third consulate 

 of Marius had the sound of rattling arms and later was compared 

 to two armies rushing against each other from east and west. The 

 last army was defeated. This idea of armies fighting in the sky has 

 persisted and became a common interpretation of the aurora 

 throughout Europe."® 



By far the most detailed accoimt of auroral phenomena is to be 

 found in the Question es Naturales, by Lucius Annaeus Seneca (a. d. 

 3-65) , son of the orator, Seneca the Elder. This work in seven 

 books, written about a. d. 63, presents what was known to the 

 ancient world concerning meteorological phenomena, halos, rain- 

 bows, thunder and lightning, rain, winds, earthquakes and comets. 

 After discussing meteors, rainbows and mock suns, Seneca wrote: "^ 



It is now high time that I ran over the other varieties of celestial fires, 

 whose forms are diverse one from the other. Sometimes there is a shoot- 

 ing star, sometimes there are glowing lights, which are occasionally 

 stationary, sticking to one spot, and at times able to rush through the 

 air. Several species of these may be observed. There are, for example, 

 Bothynae (cave-like meteors) when within an outer circle there is a 

 blazing gulf in the sky like a circular grotto excavated in it. Then there 

 are Pithiae (barrel-shaped meteors) when a vast circular mass of fire 

 like a cask either rushes through the sky, or blazes away in one spot. 

 There are Chasmata (chasms) , too, when there is a subsidence of some 

 portion of the heavens, which sends out hissing flame, as it were, from 

 its hidden recesses. There are also a great number of colours in all these. 

 Some are of brightest red, some of light insubstantial flame, some of 

 white light, some glittering, some with a uniform glow or orange with- 

 out sparks or rays. 



Such appearances are the various forms of the aurora boreal is. 

 Seneca held the streaks of light were like stars moving so rapidly 

 they could not be individually seen and asked how the light could 

 be emitted: 



The answer is, the fire is kindled by the friction of the atmosphere and 

 is urged headlong by the wind. Still, it does not always arise from 

 wind or friction. Sometimes its origin is due to certain peculiar con- 

 ditions in the atmosphere; for on high there are many elements, dry 



!"« Other references are to be found in Livy's (59 b. c.-a. d. 17), History of the 

 Romans (III, cap. 5, 10; XII, 1; XXXI, 12; XLIII, 15) , in Dion Cassius {ca. 155? a. d.) , 

 History of Rome (XLVII, 40; LVI, 24; LXXV, 7) , and in Tacitus (55? A. d.) , De situ, 

 moribus ac populis Germanorum, cap. 45. 



^o' Qiiestiones naturales, Book I. Chap. 14 and 15. The Thomas Lodge translation 

 (London, 1614) is essentially similar, although Lodge speaks of "burning flame" 

 rather than " hissing flame," which implies that a sound might be heard (see Chapter 

 VIII) . Translated as Science in the time of Nero by John Clarke, London, 1910. 



