REFRACTION AND REFLECTION IN THE DROPS. 223 



the sun has just come into view, breaking through the 

 clouds in the west. 



In the shower-cloud in the east the rain is still falling ; 

 the sky in that quarter is full, in fact, of falling drops. As 

 the rays of the sun enter these drops, they are at first re- 

 fracted at the surface where they enter, and are partially 

 separated into their component portions. When they reach 

 the back side of the drop, some of them strike it at such an 

 angle that they are reflected by the inner side of that sur- 

 face, just as the light is reflected from the under side of the 

 upper surface of water in a tumbler, as has already been 

 explained. The reflected light, then passing out on the 

 front part of the drop that is, on the side toward the sun, 

 the same by which it entered is there refracted more, and 

 the rays then come back toward the west again, those char- 

 acteristic of the various colors being separated from each 

 other, and diverging more and more widely as they pass 

 through the air. 



Now one would suppose that, this being the state of 

 the case, the whole air Avould be filled with these radiating 

 colors, or, rather, with the different radiations capable of 

 producing these different colors, and that is the fact. But 

 it is proved by the most exact and profound mathematical 

 calculations that any individual drop must be in a certain 

 precise and determinate position in reference to the ob- 

 server in order to send the rays of any particular color 

 the green, for example to his eye ; and that all the drops 

 which are in the same relative position will send the same 

 rays to him ; and those which are in the same relative po- 

 sition are those which come in the range of a circle of 

 which the point opposite to his eye, in relation to the sun, 

 is the centre that is, the point determined by a line drawn 

 from the sun, through the position of his eye, to the cloud. 

 Thus, if a drop at a certain distance above that point sends 



