338 Profs. H. da Bois and H. Rubens on Polarization of 



Type IV. (Cu 1, Pt 1, at 52/x ; all the curves for 100 fju) : 

 Q s and Q p both decrease uniformly as the inclination of the 

 grating increases. In addition it is noticed that, up to an 

 inclination of a little over 45°, both Cu 1 and Pt 1 show a 

 practically constant Q p} of nearly the same value, at 100 /x. 



Table VI. 



/3 = 0°' 



Grating. 



d. 



a. 



X. 



a/\. 



Type. 



1 Cu2 



52-5 

 456 

 33-1 

 25-0 

 25 



105-0 

 91-2 

 662 

 50-0 

 500 



24 fx 



>> 



4-36 

 3-80 

 2-76 

 208 

 2-08 



2-02 

 1-76 



1-27 

 0-96 

 096 



1-05! 

 0-91 

 066 

 0-50 

 50 



j „,. 



i 

 i 

 1 



) 



Aff 1 



Au 1 



Cu 1 



Pt 1 





Cu2 



52-5 

 456 

 33-1 

 25-0 

 25-0 



105-0 

 91-2 

 662 

 500 

 50-0 



52 n 



Aff 1 



Aul 



Cu 1 



Pt 1 





Cu2 



52-5 

 45-G 

 331 



25-0 

 250 



105-0 

 91-2 

 662 

 500 

 50-0 



100 ii 



Ag 1 



Au 1 



Cu 1 



Pt 1 





A study of Table VI., in which the order of the gratings 

 for each wave-length is inverted in comparison with the 

 previous tables, may simplify our view of these complications. 

 It contains the ratios of the grating constants to the mean 

 wave-length of our non-homogeneous radiation; these decrease 

 more and more, and the gratings now arrange themselves 

 according to the above types. So far as the elementary 

 equation of diffraction 



X 



sin y = ?n . 



may be considered applicable, the angle of diffraction <y does 

 not become imaginary for integral values of mlSa/\. The 

 digit before the decimal point in the above table consequently 

 gives, when the grating is perpendicularly fixed, the number 

 of diffracted images on each side of the principal image 



