272 PHYSICAL SCIENCE BK. vn 



room to the nights ; he occults the planets ; though 

 so much larger than the earth he does not burn it up, 

 but cheers it by his heat, which he so regulates as to 

 make it alternately more intense and more subdued. 

 He never fills up with light, nor yet obscures, the 



4 moon, except when she is right opposite to him. All 

 this we allow to pass unnoticed as long as the usual 

 order is preserved. But if there is any disturbance 

 or any extraordinary light displayed in the sky, we 

 gaze at it, ask questions, and point it out to our 

 neighbours. So natural is it to admire what is 

 strange rather than what is great. 



The same thing holds in regard to comets. If 

 one of these infrequent fires of unusual shape have 

 made its appearance, everybody is eager to know 

 what it is. Blind to all the other celestial bodies, 

 each asks about the newcomer ; one is not quite sure 



5 whether to admire or to fear it. Persons there are 

 who seek to inspire terror by forecasting its grave 

 import. And so people keep asking and wishing to 

 know whether it is a portent or a star. But, by my 

 honour, no one could embark on a more exalted 

 study, or master a more useful branch of knowledge 

 than that which treats of the nature of the stars and 

 planets. Are they a concentration of flame as our 

 vision avers, and as the very light that streams from 

 them, 1 and the heat that descends from them suggest ? 



6 Or are their orbs not of flame, but, as it were, solid 

 bodies of earth that glide through tracts of fire, 

 and having no light of their own draw thence 

 their brightness and heat ? That is an opinion that 

 has been held by great men who have believed 

 the stars to be compact of hard material, and to be 

 nourished by fire that is not their own. Flame 



1 The common reading, aliis=. others, seems an error for z7/r = 



