CELESTIAL, ATMOSPHEEIC, AND 



ecliptic 23 28 . Clearly, therefore, a secondary rainbow, 

 and still less a primary rainbow, would not be visible about 

 midday. At the autumnal equinox (Sept. 21st) it is evident 



FIG. I. 



Sun at 



midday 



Sept. 2 I 



Sun at 

 any date 

 7 on the horizon 



Dark blue 

 Greenish -ye I low 

 Light red 



L Dark blue 

 -Greenish-yellow 

 1 Light red 



that, at midday, the altitude of the Sun at Athens is 52, 

 and some part of a secondary rainbow might be seen, even 

 at midday, and part also of a primary rainbow could be seen 

 at midday, during the shorter days of the year. It will be 



