186 



CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Sek. 



4- 



Fig. 3. Diagrams contrasting the inversions of the rays in a beam 

 of light rays on passing through their foci. (A) According to 

 Sturm's theory, (B) according to observed changes (See fig. 2), (I-VIII) 

 successive hypothetical phases, (a-1) successive actual phases, (1-9 rays> 

 whose positions are traced through each plane. 



