

Lesson xxvi.] RAINBOW. 169 



for concluding, that the appearance is occasioned 

 by the rays of the sun shining upon the falling 

 drops of rain. 



There is also often seen a fainter coloured bow, 

 commonly called a water-gall, above the Rainbow; 

 and here it will be found, that the colours are in a 

 contrary position to what they are in the bow it- 

 self : hence it is evident that this is a kind of re- 

 flection from the Rainbow, or a double reflection 

 from the drops of rain ; and as a considerable 

 quantity of light is lost at each reflection, it 

 is plain that the colours in the superior bow 

 will be more dilute and faint than those in the 

 lower. 



The nature of the Rainbow, as here explained, 

 may be illustrated and confirmed by experiment in 

 several different ways. Thus, for example, hang 

 up a glass globe, full of water, in the sun-shine, 

 and view it in such a posture, that the rays which 

 come from the globe to the eye may make an 

 angle of about 42- with the sun's direct rays, and 

 you will see a full red colour in that side of the 

 globe opposite to the sun : and by varying the 

 position so as to make that angle gradually less, 

 the other colours, yellow, green, and blue, will 

 appear very distinctly, in succession, on the same 

 side of the globe. But if, by raising the globe, 

 the angle be made about 50 , there will appear a 

 red colour in that side of the globe which is toward 

 the sun, though somewhat faint ; and if, by raising 

 the globe still higher, the angle be made greater, 

 x this 



