34<5 On tialos. 



The apparent femidiameter of this ring is 

 meafured by the angle GOMorHDB =to the 

 angle BCG or 2 the angle BCE j and if the 

 radii CB, CE, remain the fame, the greater the 

 angle EBG the greater will be the angle BCE; 

 and therefore the greater the femidiameter of the 

 ring; confequently, the red rays will be refrafled to 

 the eye from the outermoft drops, and the violet 

 from the innermoft, and rays of an intermediate 

 degree of refrangibility from the intermediate 

 ones. 



The/ays which do not pafs out of the water at 

 G (fig. 4.) will be reflected converging to the 

 middle of the chord G L or I N (Lem. III. Cor. 2.) 

 and as before, will be refle6led at I, diverging 

 from the middle of the chord Ip or KP, and 

 thofe which pafs out at K will be refrafted in the 

 diredion of the tang. KO, parallel to each other. 

 Thus a fecond ring may be formed, and becaufc 

 the angle BCK is double of the angle BCG, the 

 apparent femidiameter of this ring will be double 

 that of the former, which being true of every 

 other ring of a given colour, the order of the 

 colours in the fecond halo muft be the fame as 

 in the firft. In the fame manner may a third 

 and fourth be formed at equal difiances from the 

 preceding ones, in which th^ order of the colours 

 will be the fame, but the brightnefs lefs. 



Having given the proportion of the radii CB, 

 CE (fig. 3.) the diameter of the halo may be 



found : 



