184 



Sir J. Conroy. On the Polarisation of [Feb. 4 y 



Table VII. 



Iceland Spar in Tetrachloride of Carbon. 



Azimuth 

 of the 

 principal sec- 

 tion of the 

 crystal. 



Azimuth 



of the 

 plane of 



Angle of 

 polarisation. 



Azimuth 

 of the 

 principal sec- 

 tion of the 

 crystal. 



Azimuth 



of the 

 plane of 

 polarisation. 



1 Angle of 

 ' polarisation. 



Difference 

 in the values 



of the 

 polarising 

 angle at 6 



and 

 0+180°. 



o 



o / 



o / 



o 



o / 



o / 







— 10 



O / 



T -LOU 



T KJ OKJ 



44 44 



4. 99 



T AO 



o 



4. ft ^ 

 t o oo 



4^ 98 



^tO ^JO 



1 8^ 

 loo 



i O QO 

 T £ Oil 



ax. ne 



tkO KJO 



+ AO 



XW 



4- ft 4^ 



V 'iO 





1 QO 



JLVKJ 



T OX/ 



ax j.7 



4- 8 



XO 



+ 55 



46 52 





4- ft 9*7 



HT O All 



AX 4,1 



4- 71 



-r /X 



20 



+ 2 22 



46 36 



200 



a- n ak 



4R 



rcu Ov/ 



T O 



9^ 

 ^o 



-u 1 9ft 



T X ^O 



47 06 



205 



-ul A 49 





9A 

 — A\J 



oo 



i OX/ 



48 06 



210 



i 1 K C7 

 T lO O / 



47 4o 



+ 21 



oo 



10 



48 38 



215 



■ 17 17 



T X / X 4 



48 13 



+ 25 



4ft 



— O — O 



49 41 



220 



4- 91 ^7 



17 



OKJ J. I 



— oo 



A^ 

 "*0 



_ 9 ft 

 — .i O 



50 37 



225 



-u 9A *>9 



T O.^ 



^9 17 



JL / 



— 100 



OKJ 



— O £iO 



52 14 



230 



4- 9fi ft7 

 i .-u O/ 



OO JL«7 



— 65 



OO 



— 5 *i8 



— o oo 



53 41 



235 



+ 26 45 



54 12 



— 31 



fift 



oo 



— O OO 



54 30 



240 



4- 91 9A 

 T OX ^O 



57 26 



1 7« 



— x / o 



oo 



14, AO 



— X^r *±0 



58 23 



245 



-u 99 A7 



T OO O/ 



OO Oil 



- 9 1 



iKJ 



— 1 *t A*\ 



— xo *±o 



60 08 1 250 



■ 3Q 45 



59 48 



_j_ 20 



rx 



1 O 



on 



— AKJ OO 



60 18 



255 



4. 9Q 9ft 



T £a OKJ 



91 



Ot7 OX 



4- 47 



OO 



22 28 



60 43 



260 



4- ^4 1 ^ 

 T Ot lO 



fi^ 43 



OO rlO 



— 300 



8^ 

 oo 



— 26 25 



62 13 



265 



+ 32 32 



63 24 



— 71 



Qft 



VKJ 



— 9K 98 



— ~0 ^o 



59 42 



270 



+ 29 05 



63 18 



— 216 



95 



29 42 



61 05 



275 



+ 25 52 



61 52 



— 47 



inn 



— OX 1U 



61 58 



280 



4. 9R 47 

 -t- ^<o t 1 / 



(\A A*7 

 o* *±/ 



— 169 



XOO 



— 99 19 



— OA XO 



61 24 



285 



-f 22 07 



60 32 



+ 52 



no 



— 28 19 



58 07 



290 



+ 17 15 



58 57 



— 50 



XXO 



98 Oft 



56 47 



295 



tic: a.9 



T XO 



OO KJi 



— 80 



1 9ft 



X^O 



9ft ^ft 



— OO OKJ 



57 17 



300 



4- in 99 



+ 1U O^i 



57 04 



+ 13 



125 



-27 50 



56 13 



305 



+- 9 47 



55 47 



+ 26 



130 



-22 53 



51 59 



310 



+ 7 05 



54 09 



-130 



135 



-21 30 



51 04 



315 



+ 3 32 



51 09 



— 5 



140 



-21 40 



49 23 



320 



+ 1 42 



50 38 



— 75 



145 



-18 58 



49 15 



325 



+ 25 



48 40 



+ 35 | 



150 



-15 15 



47 08 



330 



- 05 



48 12 



- 64 i 



155 



-12 35 



47 30 



335 



- 1 03 



47 11 



+ 19 



160 



-10 43 



46 15 



340 



- 05 



47 25 



- 70 



165 



- 8 18 



46 12 



345 



- 10 



45 48 



+ 24 



170 



- 4 58 



45 16 



350 



+ 05 



46 02 



- 46 | 



175 



- 2 30 



45 11 



355 



+ 10 



45 06 



+ 5 • 



It bad been intended to make similar measurements witb artificial 

 surfaces cut perpendicular and parallel to the axis of the crystal, and 

 three pieces of Iceland spar cut respectively parallel to a natural face, 

 and perpendicular and parallel to the axis, and all polished with 

 " whiting " were obtained. 



Seebeck states (" Pogg. Ann.," vol. xxi, 290) that Iceland spar 

 polished with rouge or putty powder differs in its optical properties 



