28 PHYSICAL SCIENCE BK. i 



a cloud by which a defective appearance of the sun 

 should be presented ? 



VI 



1 AMONG the other arguments it must be mentioned 

 that a rainbow never is seen greater than a semi- 

 circle : the higher the sun is, too, the smaller is the 

 bow. As our countryman Virgil says : 



And deep drinks 

 The mighty bow, 



when rain is brewing. But the threat the bow con- 

 veys is not the same whatever the quarter it has 



2 shown itself in. If it rises toward the south, it will 

 bring a heavy fall. The rain in that quarter, such is 

 its force, cannot be mastered by the strongest midday 

 sun. If it shine toward the west, there will be only 

 a dew or a light rain. If it rise in the east or there- 

 abouts, it prognosticates fine weather. If, 

 however, the bow is the sun's reflection, why does 

 it appear of far larger size than the sun himself? 

 Just because there is a kind of mirror that exhibits 

 objects on a far larger scale than that on which 

 they are presented to it, increasing their form to a 

 portentous magnitude : and in turn there is another 

 kind that reduces the size. And tell me this again, 

 why does an image assume the form of a circle if 



3 it does not answer to a circle ? You may, perhaps, 

 tell me why the colour of the bow is varied : why 

 its shape is what it is, you will not be able to tell 

 me except by citing some model after which it is 

 formed. Now, other model there is none save that 

 of the sun ; when you admit that the rainbow 

 receives its colour from him, it follows that it 



