and Energy Distribution of Diffraction Gratings. 



.45 



image, total agreement between this theory ani the observed 

 phenomena is not reasonably to be expected ; but in every 



Fig. 5. 



;, x 













Rttardalcon over a Sinale 



Element 













lA/ood Gmttng #7 





u- 





X 





















c 







X 





















*$ 









> 



K 

















fy„ 













X 



X 













&.. 















». 













^ 



1 



L 



















s 



\ 

























\ 



\. 









C 



r 



f 



„■ f, 



2* 



<? / 



4' / 



t .* 



\ 



case where the effect is at all marked, the agreement is 

 fairly good, as will be seen in the following table : 



Wood Grating No. 7. 



\. 



Order 



in which 



Percentage 

 of the 



Weak 



Retardation Retardation 



energy is 

 concentrated. 



energy in 

 this order. 



orders. 



over in terms (if 



the element. wave4ength. 



1 \6 



9 



57 



5, 7 



3-4 fi, l-2,i 293 X, 103 



147 



7 



60 



3, 5 



4 6/i, 1-9/* 



313 1-29 



171 



C> 



64 



2, 5 



irbfi, 1-8 [i 



321 105 



Abo it 2*30 



5 



68 



4 



22 /, 



110 



„ 230 



4 & 5 



together 71 



1, 3 



6-55 /i, 21 ^ 



2-84, 1-04 



,. 2 (50 



4 & 5 



» 74 



3 



2 - 5 ju 



0-90 



„ 2-1)0 



4 & 5 



„ 79 



2 



3 35/x 



1-15 



„ 3-20 



3 & 4 



„ 81 



1, 2 



5-8/i, 3'3/i 



1-81, 1-03 



„ 3-50 



3 



77 









410 



2, 3 



40, 53 









4 05 



2 



75 









5 60 



2, 1 



60, 30 









Columns 4 and 5 show corresponding orders and retard- 

 ations. The numbers in column 5 are almost exact multiples 

 of the corresponding wave-lengths, as is shown in column 6, 



