of the Metals. 

 Table I. 



165 



«=-45°. a = 6'-944. 





Transmitted light. 



Reflected light. 



I. 



Po- 



Pl80- 



P- 



8. 



Po- 



PlSO' 



P- 



P- 



8. 



0- 



o r 

 ' 



r 

 



r 

 







46° 32 



44° 30 



45° 31 







O 4 



10 ! 0038 





0-038 



00054 



44 34 



45 48 



45 11 









20 



0-222 



0-236 



0-229 



00330 



48 35 



46 6 



47 20 



0-656 



0-0945 



45 50 



30 



0548 



0-664 



0-606 



0-0873 



49 31 



49 52 



49 41 



1-438 



0-2070 1 46 45 



40 



1-444 



1-218 



1-331 



0*1917 



54 15 



54 24 54 19 



2124 



0-3059 



43 15 



50 



2-382 



2-400 



2-391 



0-3443 



59 40 



58 5759 18 



3140 



0-4522 



42 37 



60 



3-230 



4144 



3-687 



0-5309 



63 17 



65 22 64 19 



5-576 



0-8024 



40 23 



70 



5-562 



5-324 



5-442 



0-7838 



68 37 



67 36 68 6 



6-800 



0-9792 



41 11 



75 



6-840 



6-783 



6 811 



0-9808 



70 27 



66 39 68 33 



8124 



1-1700 



43 2 



80 



















10-226 



1-4730 



42 21 



85 



















11-622 



1-6740 43 27 



That in perpendicular incidence (S was not exactly equal to 45°, 

 arose from the circumstance that the gold plate was not quite 

 even, but slightly cylindrical, inasmuch as it hung in the frame 

 like a cloth suspended by the corners. Owing to this the angle 

 of incidence was therefore not 0°, but greater, and indeed situ- 

 ated in a plane of incidence which, parallel to the axis of the 

 goniometer, stood at right angles to the plane of incidence for 

 which the angles of incidence are given under I. 



With other gold- leaves similar values were obtained. Warren 

 De la Rue and Faraday* have found the thickness of a gold-leaf 

 to be about O000091 millim. 



The values of the difference of phase, or accordingly of p, turn 

 out much less when the gold has one of its surfaces in contact 

 with glass and the other with the air. The following Table 

 contains the observations made upon a film of gold spread upon 

 a plane-parallel glass according to the method of Liebigf. The 

 gold film was thinner than gold-leaf, and transparent, and of a 

 green-blue colour. The angle of polarization of the glass was 

 57° 35', corresponding to an index of refraction of 1*575. 



The values of p are given under p and p ]80 , in the one case 

 the glass, and in the other the metal being turned towards the 

 heliostat; under /3 and /3 i80 are given the corresponding values 

 of ft; under /3 g the azimuth of the light is given when the light 

 has passed only through the glass plate and not through metal. 



* Experimental Researches, vol. iv. p. 393. 

 t Liebig's Annalen, April 1856, p. 132. 

 vol. cxi. p. 199 et seq. 



Dingler's Journal, 1856, 



