RAINBOW 17 



time watch a fuller at work, you will observe the 

 same appearance : when he has filled his mouth 

 with water and spirts it lightly on the clothes 

 stretched on pegs, the air thus besprinkled ex- 

 hibits plainly the various colours that shine in 

 the bow. One cannot doubt that the reason of 3 

 this lies in the moisture. For a rainbow never 

 occurs except when there are clouds about. 



Let us inquire how it is produced. Some 

 authorities say that there are certain drops of 

 water that transmit light, while some are too com- 

 pact to be translucent. Thus the brightness is the 

 effect of the former; the shadow, of the latter; 

 by the intermingling of the two is formed the 

 rainbow, part of which is bright, to wit, that which 

 admits sunlight, part darker, namely, that which 

 has shut out the light and cast a shadow from itself 

 over the objects nearest it. Others again deny that 4 

 this is so. Shade and light, they say, might be the 

 cause if the rainbow had only two colours, and 

 thus was made up of light and shade. 



But now, though there gleam a thousand diverse hues, 

 Their changes withal elude the eyes that behold. 

 The hues that touch seem actually one, yet the edges are quite 

 different. 



In it sight detects something that is red, something 

 that is orange, something that is blue ; and there 

 are other colours too, laid on in finest lines just 

 like a skilful painting, so that, as the poet remarks 

 above, it is impossible to discover whether the 

 colours differ from one another until the last of 

 them is compared with the first. The junction of 5 

 colour with colour deceives the sight : with such 

 marvellous skill does nature starting from what is 

 like end in what is totally unlike. What good, then, 



