272 Dr. G. J. Stoney on the Resolution of Light 



illumination on all the dotted lines of fig. 1, i. e. on all the 

 lines dotted or imdotted of fig. 4, except the central one. 



Fig. 0. 



j 1 

 1 1 



i 



! 



i i 



i 

 i 



! ■ 



t 

 i 



& ill 

 /Li i 



i 1 i ! i 



t 



i 

 i 



8 



i 



\ \ \ J 



: i ! 



! ! 



i 

 i 



i 



y 



1 



vc ! 



i 





k \ 



Each strip is the same part of plane K as in fig. 4. 



Fig-. 



Fisr. 8. 



o 



I I I I 



' I i 

 i i i 



t 



i i 



1 l i i ! I I J i 



Li : : : i : : ! : 



L_i-_'_ LJ.J. L_!_-L_L _i__J 



The same part of plane K. 

 By similarly dividing the rectangular macula into 2, 4, 8, 

 16, &c. equal parts by lines parallel to b, we find a second 

 set of dotted lines along which the illumination is cipher, as 



in fig. 8. 



The results we thus arrive at may be summarized as 



follows : — 



Theorem VIII. 

 If the sheaf of u'-f vPs represented by a rectangular macula 

 on the indicator-diagram are of the same wave-length, similarly 

 polarized, and of equal intensity ; and if they cdl reach the 

 point k in the same phase : then, if a flat screen parallel to the 

 indicator-diagram pass through the point k, the illumination 

 produced on it by the ufw's of this sheaf is such that there is 

 maximum illumination at k, where the phases are identical : 

 considerable brightness close to it, where the phases do not 

 differ much ; cipher illumination along all the dotted lines of 

 fig. 8 ; and probably glimmers of illumination in the interspaces 

 between them. 



