224 ILLUSIONS EXPLAINED. 



a green ray or, more strictly, a green-producing ray to 

 his eye, all the other drops in the range of a great circle 

 drawn at the same distance from the central point above 

 'named will do the same. But, as the sun is above the ho- 

 rizon, the central point of this circle, which is the point ex- 

 actly opposite to the sun, must be below it, and, of course, 

 less than half the circle will come upon the sky; but all 

 the drops which come at the same distance from the centre 

 in that portion of the circle which has rain-drops in it will 

 send green rays to the eye. 



Now it is evident that if an eye in any given position is 

 in the range of the green rays from any drop in the cloud, 

 it would be out of the range of its yellow or its blue rays, 

 and that the drops which would send these rays to his eye 

 would be for the one color above, and for the other below 

 the one which sent him green-producing light. Each of 

 these, too, would have its circular band of drops formed 

 of all those that were at the same distance from the cen- 

 tral point with themselves, all of which w r ould take effect 

 in sending those component parts of the solar ray to the 

 eye, which would produce there the sensations of their 

 color. Thus, while the whole sky is filled with falling 

 drops, each of which is sending the same diversified radia- 

 tions in precisely the same manner, only those radiations 

 of any particular color would reach the eye of an observer 

 in any one place which came from drops within the range 

 of a circle drawn at a certain distance from the point op- 

 posite to his eye, and thus would be produced the appear- 

 ance of concentric colored bands. 



Of course, if he moves his position, he brings himself 

 into a corresponding range of radiation from a new set of 

 drops, and so changes the position of the rainbow in the 

 cloud. In other words, he forms the rainbow for himself, 

 wherever he stands, out of the light coming from the drops 



