330 Profs. H. du Bois and H. Rubens on Polarization of 



Auer-mantle itself emits partially polarized rays, were not 

 equal. Q s and Q^, the transmissibility of polarized rays 1 1 and 

 J_ to the wires, as well as the transmissibility ratio n 2 = Q s /Q P , 

 could then be calculated corresponding to a given inclination 

 to the wave-front. 



§ 9. In our previous paper we gave an account of our 

 investigations with eight wire gratings, which included very 

 thin platinum, copper, iron, gold, and silver wires of French 

 manufacture. Out of these eight we felt compelled for 

 certain reasons to limit ourselves to five ; the iron gratings 

 had suffered too much damage in the meantime. One of 

 them, however, in addition to the coarser platinum grating, 

 served well for control investigations. In all these gratings 

 the true slit-width b was exactly equal to the diameter of 

 the wire d; the true "grating constant," i. e. the periodic 

 interval from one wire axis to the next, is a = 2b = 2d. If 

 now the plane of the grating is inclined at an angle /3 to the 

 wave-front in such a way that the wires remain parallel to 

 the section of both planes, then the apparent grating constant 

 a' is evidently given by a' = a cos /3, and the apparent 

 aperture b' by 



b r =d (2 cos £-1). 



With the above-mentioned maximum inclination of the plate 

 Q to the axis of the tube (4.4°-4, fig. 1) we have 



cos45°-6 = sin'44°-4 = 0-700, 



so that by fixing the finest grating (d = 25 fi) to that plate, 

 the apparent slit-width was exactly 10 /jl. 











Table I. 

















Pt 1 ! Cu 1 !! 



Au 1 !!! 



Ag 1! 



Cu2! 



0. 



0° 



2cos/3-l. 



! 









a' 



b' 

 25-0 



a' 

 50 



b' 

 25-0 



a ' 

 66-2 



b' 



a' 



V 



a! 



V 



1000 



50 



33-1 



91-2 



45 6 



105-0 



52-5 



5 



0-992 



49-8 



24-8 



49-8 



24-8 



65 9 32-8 



90-9 



453 



1046 



52-1 



10 



0-970 



49-3 



24-3 



49-3 



24-3 



65-4 32-3 



90-0 



44-4 



103-5 



510 



15 



0932 



48-3 



233 



48-3 



23 3 



641 310 



88-2 



42-6 



101-5 



49 



20 



0-879 



47 



22-0 



47 



220 



62-3 29-2 



85-7 



40-1 



98-6 



461 



25 



0812 



45-3 



203 



45-3 



■iO-3 



60-1 



27-0 



82-7 



371 



95-1 



42-6 



30 



0-732 



43-3 



183 



43-3 



18-3 



57-5 



244 



79-0 



33-4 



91-0 



38-5 



35 



0-638 



410 



16-0 



410 



160 



54-2 



21-1 



74-7 



29-1 



86-0 



33-5 



40 



0-532 



38-3 



13 3 



38-3 



13-3 



50-8 



17-7 



70-0 



24-4 



804 



27-9 



45 



0414 



35-4 



10-4 



35-4 



10 4 



46-8 



13-7 



64-5 



189 



742 



21-7 



50 



0-286 



322 



7-2 



32-2 



7-2 



426 



9-5 



58-6 



13-0 



67 5 



150 



55 



0148 



28-7 



3-7 



28-7 



3-7 



38-0 



4-9 52-3 



6-7 



603 



7-8 



60 







250 







250 







33-1 







45-6 







52-5 







We give in Table I. the dimensions of the gratings 



