I adijfr acted Lony-waved Heat Rays by Wire Gratinq; 



339 



this 



which can appear when the grating is inclined. In 

 sense corresponds 



Type I. to two or more diffracted images. 



Type TI. to two diffracted images. 



Type III. to one diffracted image. 



Type IV. to no diffracted image. 

 § 13. In the arrangement for the waves of 100 jj, wave- 

 length, the inclination of the grating could be increased even 

 up to 60°, whereby b' = finally, so that any grating ceases 

 to be transparent for light waves at this angle. In fact the 

 corrected Q s disappear with the exception of a few permilles, 

 which are probably due to slight irregularities. The Hertzian 

 polarization is, accordingly, as good as complete. It is re- 

 markable that the values of Q p remain quite considerable. 



In addition the values of Q s at 24 /.i and 52 /n seem to 

 converge towards zero in such a way that, conjecturally, 

 they would vanish at 60°; our rotating support (see fig. 1) 

 did not, however, allow a greater inclination than 45°*6. 



The gratings Pt 1 and Cu 1 — the only two possessing equal 

 diameters of wire — behave almost similarly throughout. It 

 is difficult to tell whether the slight divero-ence between the 

 two is due to difference of material or of geometrical con- 

 figuration. 



In the previous investigation with two copper gratings 

 Cu 1 and Cu 2 of different wire diameters, it was shown that 

 the transmissibility ratio depended only on the apparent 

 width of aperture, and not perceptibly on the radius of cur- 

 vature of both the contiguous metal wires. Table VII. 



Table VII. 



1 











It 2 . 







j Grating. 



fr 



b'. 













1-5 fi. 



4"5/*. 



24 /(. 



1 52 /*. 



100 ii. 





( 0° 



52o /* 



1-04 



0-92 



0-86 



0-80 



0-45 





30 



38-5 



105 



091 



072 



019 



0-20 



Cu2...< 



40 



27-9 



109 



0-87 



043 



0-14 







45 



21-7 



1-13 



0-84 



0-32 



011 



09 





k 60 









... 





... 



001 





f 0° 



25-0/i 



1-13 



0-87 



073 



041 



0-05 





15 



233 







0-39 



0-37 



0025 



Cul...< 



30 



18-3 



1-17 



082 



0-32 



029 



0010 





45 



10-4 



1-41 



0-59 



014 



0-15 



0-005 





, 60 







i 











0006 



Z2 



