170 RAINBOW. [Lesson xxvi. 



this red will change successively to the other co- 

 lours, yellow, green, ajid blue. 



Or, the appearances of the Rainbow may be 

 exhibited, in a very natural and beautiful manner, 

 any day when the sun shine?, with the assistance 

 of an artificial fountain, or jet d'eau, which is an 

 instrument expressly intended to throw up streams 

 of water to a great height. These streams, spreading 

 very wide in their upper part, when falling, form 

 a delightful shower of artificial rain. When the 

 fountain is playing, move between it and the sun, 

 at a proper distance from the fountain, until your 

 shadow points directly towards it : then looking at 

 the shower, you will observe the colours of the 

 Rainbow, very vivid and strong those of the 

 water-gall very languid and faint the gradations 

 of the colours of each in an inverted order : and, 

 what forcibly shews the deceitfulness of vision, the 

 bows appear, notwithstanding the nearness of the 

 artificial shower, to be as far off, and as large, as 

 those which we really see in a natural shower of 

 rain. 



A similar bow is often observed among the 

 waves of the sea, the upper parts of the waves 

 being blown about by the wind and so falling down 

 in drops : this is called the Marine Rainbow. This 

 appearance is also sometimes seen by moon-light, 

 though it is seldom vivid enough to render the 

 difFert-nt colours distinguishable: it is then called 

 the Lunar Rainbow. Rainbows are even sometimes 

 seen on the ground, when the sun shines on a very 



thick 



