300 PHYSICAL SCIENCE BK. vn 



We cannot, Apollonius says, see through the 

 stars what is beyond, but sight passes easily 

 2 through the comets. Well, in the first place, if 

 that is the case, it is not so in the part of the 

 body which consists of dense solid fire, but only 

 where the dispersed glow extends as it breaks up 

 into the appearance of hair. One can see through 

 the gaps in the fire and not through the fire 

 itself. Stars again, it is said, are all round, comets 

 extended ; whence it is plain that they are not true 

 stars. But who, pray, will allow that comets are 

 long ? Their tendency like that of other stars is to 

 a globe shape, only the light from them is prolonged. 

 The sun shoots out his rays far and wide, but has 

 himself a shape different from that of the light that 

 streams from him. So in comets, the body is 

 rounded, but the glow from them presents the 

 appearance of being longer than that of the other 

 stars. 



XXVII 



1 WHY is this so, you ask. Do you tell me first why 

 the light the moon receives is wholly unlike the 

 sun although she receives it from the sun. Why is 

 it now ruddy, now pale ? why is her colour ashen or 

 black when she is cut off from the sun s view ? Or 

 tell me why all the stars have aspects to some extent 

 dissimilar to one another and all as different as 

 possible from the sun. It is no hindrance to their 

 being true stars that they are not all alike ; so there 

 is nothing to prevent comets from being permanent 

 through all time, sharing the same destiny as the 

 other stars, even though they have not an appearance 



2 like theirs. Besides, is not the universe, if you will 



