62 PHYSICAL SCIENCE BK. n 



directs the year, whose solstices determine winter 

 2 and summer. Next in importance is the moon's 

 influence. But even the other stars produce an 

 effect alike on the earth and on the air that rests 

 upon the face of the earth. Their rising or their 

 corresponding setting and their disturbances cause 

 now cold, now rain, now other damage such as 

 earth is subject to. 



It was necessary for me to make these preliminary 

 remarks before going on to speak of thunder and 

 thunderbolts and lightnings. For as these pheno- 

 mena occur in the atmosphere, I had to explain the 

 nature of the latter, that it might more readily appear 

 what active or passive capacities it possessed. 



XII 



1 THERE are, I have just said, three phenomena 

 lightnings, thunderbolts, thunderings : the last is 

 simultaneous in occurrence with the others, but its 

 sound reaches us subsequently. Lightning (i.e. 

 sheet) merely reveals fire, the thunderbolt (forked 

 lightning) actually despatches it on its mission. 

 The former is, so to speak, a threatening and feint 

 without a blow, the latter a stroke and a blow. 

 There are some of the facts connected with the 

 phenomena of thunder and lightning on which 

 there is general agreement, others on which there 



2 is much diversity of opinion. For example, there 

 is agreement that they occur in the clouds and 

 issue from the clouds ; further, it is agreed that 

 lightning of both kinds is either composed of fire 

 or at any rate presents the appearance of fire. 

 But to pass on to the points which are disputed 



