NOTES 



325 



thunder and lightning, divides the phenomena into three kinds 

 lightning -flashes, thunderbolts, and thunderings (62). After 

 citing and commenting on the opinions of various philosophers 

 he proceeds to give his own views regarding these appearances. 

 The lightning flash (fulgiiratio) he looks upon as fire widely 

 spread out, the thunderbolt (fulmen) as fire condensed and 

 hurled with violence (66). The difference between the two is in 

 force rather than character; a flash is a bolt without strength 

 enough to reach the earth, while a thunderbolt is lightning in its 

 most intense form (69). With regard to the origin of the fire 

 he points out that fire may be artificially produced in two ways : 

 either by percussion, as when stones are struck ; or by friction, 

 as when two bits of wood are rubbed against each other. He 

 thinks that probably in both of these ways clouds may emit fire, 

 and that in the violence of storms a source of energy is supplied 

 whereby the warm or smoky exhalations from the earth may be 

 kindled and fall with a fierce glow to the earth (70, 101). These 

 exhalations contain dry and moist bodies, to which heavier ele- 

 ments may be added. A combination of such materials will 

 form a thicker and more solid cloud than one of pure air, and 

 such a cloud may burst with a loud report (78). There can be 

 no peal of thunder unless the hollow clouds are broken up with 

 great violence (76). The characteristic path of the thunderbolt 

 is determined by the oblique current of air in which, while the 

 natural tendency of the fire is upward, the violence of its dis- 

 charge presses it downwards and compels it to take up a zig-zag 

 course. The peculiar ozone odour noticed during thunderstorms, 

 and long popularly known as the smell of sulphur, is alluded 

 to by Seneca (69, 97) and by Lucretius. 1 



The discussion of these subjects leads on to a disquisition on 

 the portents that may be drawn from different kinds of thunder 

 and various forms of lightning. Seneca infers from the effects 

 produced by it that lightning possesses an inherent divine power. 

 Among these effects he enumerates some in which he seems to 

 have thoroughly believed, such, for instance, as the smashing of a 

 wine jar already quoted, and the freezing of the wine for the 

 space of three days thereafter. He is thus disposed to attach 

 credit to the opinion that future events are foretold by both 



1 Similar views on thunder and lightning are expressed in the De Rerum 

 Natura : 



semina quod nubes ipsas permulta necessust 



ignis habere. vi. 206. 



post ubi conminuit vis eius et impetus acer, 



turn perterricrepo sonitu dat scissa fragorem. Ibid. 128. 



. . . notaeque gravis halantis sulpuris auras. Ibid. 221. 



