1886.] 



Light by Reflection from Iceland Spar. 



181 



Table IV. 



Iceland Spar in Water. 























Difference 



Azimuth 



Azimuth 







Azimuth 



Azimuth 







in the values 



of the 



of the 



Angle of 



of the 



of the 



Angle of 



of the 



principal sec- 

 tion of the 

 crystal. 



plane of 

 polarisation. 



polarisation. 



principal sec- 

 tion of the 

 crystal. 



plane of 

 polarisation. 



polarisation. 



polarising 

 angle at 

 and 























+ 180°. 



o 













o 



37 



o 





-61 



+ 1 



+ 1 



22 



48 



42 



181 



+ 



49 



43 



11 



+ 



50 



49 



10 



191 



+ 4 



02 



49 



25 



-15 



21 



- 



30 



48 



43 



201 - 



+ 7 



17 



49 



52 



-69 



31 



+ 1 



25 



50 



11 



211 



+ 9 



45 



50 



35 



-24 



41 



- 



18 



50 



46 



221 



+ 11 



35 



51 



30 



+ 16 



51 



- 



23 



52 



19 



231 



+ 12 



47 



52 



59 



-40 



61 



- 2 



43 



53 



49 



241 



+ 13 



07 



53 



45 



+ 4 



71 



- 5 



43 



54 



48 



251 



+ 13 



42 



55 



11 



-23 



81 



- 8 







55 



23 



261 



+ 11 



50 



55 



16 



+ 7 



91 



-10 



28 



55 



36 



271 



+ 11 



01 



55 



24 



+ 12 



101 



-12 



30 



55 



05 



281 



+ 8 



25 



55 



25 



-20 



111 



-14 



40 



54 



31 



291 



+ 5 



22 



54 



20 



+ 11 



121 



-12 



40 



53 



43 



301 



+ 3 



20 



53 



29 



+ 14 



131 



-12 



23 



51 



30 



311 



+ 2 







52 



10 



-40 



141 



-12 







51 



33 



321 



+ 1 



37 



51 



48 



-15 



151 



- 7 



23 



50 



15 



331 



- 1 







51 



15 



-60 



161 



- 3 



48 



49 



35 



341 



- 



48 



48 



48 



+ 47 



171 



- 1 



23 



49 



19 



351 



+ 



22 



49 



11 



+ 8 



VOL. XL. 







