xiv OTHER CELESTIAL FIRES 39 



it may be asked, do they issue forth ? 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. Some- 

 times its origin is due to certain peculiar conditions 

 in the atmosphere ; for on high there are many 

 elements, dry and hot and earthy, among which fire 

 is generated. It then streams down in pursuit of 

 fuel to sustain it, and therefore is hurried rapidly 

 along. The reason for the differences of colour it 6 

 presents lies in the nature of the material set on 

 fire and in the degree of violence of the conflagra- 

 tion. A falling body of this kind betokens wind, 

 which may be looked for in the quarter in which 

 the meteor has burst out. 



XV 



How, some one further inquires, are those bright i 

 gleams of light which the Greeks call Sela (lumin- 

 osities) produced ? In many ways, people say. 

 They may arise from the violence of the winds, 

 or from the fervent heat of the upper heavens. 

 Fire is a very widely diffused element there, and 

 sometimes catches the lower regions if they are 

 combustible. The mere motion of the stars in 

 their courses may kindle fire, and convey it 

 to all that lies beneath them. Nay, is it not 

 quite possible that the atmosphere should drive up 

 even to the ether the germs of fire, from which may 

 arise a glow or burning or darting resembling a 

 star ? Some of these gleams rush headlong like 2 

 shooting stars, some remain fixed in their place, 

 emitting light sufficient to dispel darkness and re- 



