166 



M. G. Quincke on the Optical Properties 



Before the eye was placed a red glass that specially transmitted 

 the rays of the spectrum between the Fraunhofer's lines B and D. 



Table II. 





«=45°. a = 7>-603. 







Transmitted light. 



Reflected light. 



I. 



Po- 



PlSO' 



9- 



L 



ft. 



Pl80* 



|3. 



fe 



P- 



8. 



|3. 







r 

 



r 

 



r 

 







45° 20 



46° 44 



46° 2 



45° 20 







O i 



10 



0054 



0058 



0056 



00074 



46 5 



45 20 



45 42 



46 5 









20 



0224 



176 



0-200 



00263 



46 20 



46 47 



46 33 



46 7 



0-430 00566 



45 32 



30 



0-466 



0-496 



0-481 



00632 



46 53 



47 53 



47 23 



46 33 



1 060. 01394 



40 58 



40 



0858 



0-858 



0-858 



01128 



49 3 



49 57 



49 30 



47 30 



2102 0-2765 



39 9 



50 



1-466 



1-514 



1-490 



0-1960 



52 12 



51 15 



51 43 



48 8 



2-556 0-4677 



34 55 



60 



2044 



1-712 



1-878 



0-2470 



55 18 



54 36 



54 57 



50 12 



5-700 



0-7498 



31 51 



70 



2-912 



2-484 



2-698 



0-3550 



62 20 



59 25 



60 52 



56 18 



8-860 



1 086 



29 45 



80 



3784 



3146 



3-465 



0-4557 



66 55 



64 31 



65 43 



60 47 



11-938 



1-570 



33 28 



85 



3-968 





3-968 



0-5219 67 25 





67 25 



63 39 



13-498 



1-775 



38 23 



From these numbers it appears that the difference of phase 

 and the azimuth are the same, whether the light goes first 

 through metal and then through glass, or first through glass and 

 then through metal. The difference of phase is, however, much 

 smaller than when the metal has both its surfaces in contact 

 with the air. The reason of this diversity is partly that, owing 

 to refraction at the surface of the glass, the 'angle of incidence 

 under which the rays going through the glass meet the metallic 

 plate is smaller than the corresponding value under I, which ex- 

 presses the angle of incidence under which the rays in air fall 

 upon the glass plate bearing the metallic plate. 



The following Table contains the observations upon a film of 

 silver of a blue-grey colour, and of a thickness determined 

 according to the method of Fizeau* to be 0*000076 millim. 

 Fizeau's method depends upon the colours which are produced 

 by the action of a minute portion of iodine on the silver film. 

 The silver film was obtained on parallel glass by the method of 

 Petitjeanf. From the angle of polarization 56° 58', it follows 

 that the index of refraction of the glass plate was n= 1*538. 



A red glass was placed before the eye. The letters have the 

 same meaning as in the former Tables. 



* Comptes Rendus, vol. lii. 1. 1861, p. 274. 

 t Pogg- Ann. vol. ci. p. 313. 



