32 



Sir J. Conroy. 

 Table III. 



[Feb. 15, 



Angle of 

 Incidence. 



Percentage amount of Light reflected by Tin Mirror. 







A. 



B. 



C. 



Mean. 



10 



39 -54 



40-34 



39 39 



39-76 



20 



39 -69 



41-01 



40 -14 



40 -28 



30 



42-65 



45-48 



45 -02 



44-38 



40 



43 -19 



43-23 



45-91 



44-11 



50 



46-25 



45 -31 



50-80 



47-48 



60 



49 -63 



49 -77 



52-40 



50-60 



65 



51 -24 



51 -47 



54 -25 



52-32 



70 



52-79 



54-95 



57-17 



54 -97 



75 



57 -89 



58 -92 



59-73 



58 -85 



80 



65 -86 



63 80 



65-57 



65 -08 



Table IV. 



Angle of 

 Incidence. 



Percentage amount of Light reflected bj Speculum 

 Metal Mirror. 





A. 



B. 



C. 



Mean. 



10 



63 83 



67-11 



67 -45 



66 -13 



20 



65 -51 



67-29 



67 -84 



66 -88 



30 



65-77 



67-96 



66-87 



66-87 



40 



66 -93 



68 -49 



66-35 



67 -26 



50 



67-35 



67-37 



67 -07 



67-26 



60 



66-97 



66-99 



66-98 



66-32 



65 



65 71 



66 -49 



67-39 



66 53 



70 



66-70 



67-64 



68-60 



67 -65 



75 



65-68 



68 -80 



67 -82 



67 -43 



80 



71 72 



69 -86 



68 -94 



70 -17 



The principal incidences and azimuths for the four mirrors were 

 determined in the manner described in the paper on metallic reflection 

 which has already been referred to (" Proc. Roy. Soc," vol. 31, 

 p. 486), a soda flame being used as the source of light. Four observa- 

 tions were made in each position of the retarding plate, two with the 

 principal section of the polarising Nicol on the right, and two with it 

 on the left of the plane of incidence. The means of several sets of 

 eight observations each are given in Table V. 



