264 



SIR DAVID BREWSTER ON THE 



At 3 b 10 m the weak polarisation at m n now extends down to H H. R = 22£ 

 in zenith, and in horizon at 25° alt. 



_l_ At 3 h 44 m the two neutral points are developed, as in 



the annexed figure, the — hands x x being just dial 

 ■ I i.f.j tinctly visible. 



1842, February 18.— See "Edinburgh Transactions," 



x : 



H- 



-H 



vol. xxiii. pp. 217, 229. 



1842, February 19. — Fine day, with wind. 



Arago. 



Fig. 5. 

 Apparent Time. 



2 h 58 m R = 26i° in S.E. horizon, alt. 20°. 



3 7 Neutral point 2° alt. 13 Q 38' 



3 20 Secondary neutral point seen. 14 42 



4 15 Fleecy clouds over neut. point. R = 24±° S. hor. 20 

 4 40 R=24i° in zenith plane. 19 28 



1842, February 21.— From 4 h 52 m to 4 h 57 m , a secondary neutral point to that 

 of Arago was gradually but imperfectly developed.* 



1842, February 22. — Dull, cold morning, which cleared up about l h 25 m , when 

 R = 21i° in clear sky, from which clouds had passed. 



Apparent Time. 



Arago. 



3 h 24 m R = 25f° in zenith, 22£° near W. and E. horizon. 15° 40' 

 3 38 17 29 



( Negative bands do not touch the sea horizon. | .. 



\ Secondary neutral point in the horizon. j 



4 2 



4 28 



5 8 



4 6 



4 24 



5 6 



Pol. of moon, R = 3°; R = 27£° in zenith. 



20 50 

 23 8 

 19 2 



Babinet. 



17° 15' 

 16 19 

 19 5 



1842, February 24.— Barom. 290. 



Apparent Time. Arago. 



3 h 47 m 17° 20' 



2 32 R=26|° in zenith, 27£° in S.E. horizon. 



3 51 R = 23| in zenith, and 25|° at 35° alt. N.W. horizon. 



1842, February 25. — Dull day ; frost in morning ; cleared up at 4 b 2 m . 



Apparent Time. 



Babinet. 



5 h 9 m R = 28° in zenith, 26£° in E. and W. horizon 17° 50' 



5 12 



Arago. 

 18° 5' 



* See Edin. Trans., vol. xxiii. pp. 217, 224, 228. 



