POLARISATION OF THE ATMOSPHERE. 269 



1842, April 22.— Fine day. 



Apparent Time. 

 ll h 10 m A.M. R=17|°; maximum polarisation in zenith 90° from sun. 



Brewster. 



2 R= 27° at 90° from sun in zenith plane. 12° 10' 



3 R=29 at 88 from sun in zenith plane. 11 10 



4 10 R= 29 £° at 90° from sun. 



Arago. 

 6 55 20° 25' 



Babinet. 

 6 58 Thin clouds. 22° 15' 



1842, April 24.— Barom. 2984, rising. 



Apparent Time. 



{A haze. Babinet's neutral point 70° high ; Brewster's 

 not yet risen. After the haze had increased the sky 

 cleared. 

 6 21 Altitude of Arago' s neutral point above horizon. 8° 40' 



6 10 „ „ „ 13 



6 10 Secondary neutral point exactly in horizon. 



1842, April 25, 26, 27, 28, 29.— See " Edinburgh Transactions, 1 ' vol. xxiii. pp. 

 218, 230. 



1842, May 2.— Barom. 29-93 ; wind east. 



Apparent Time. Arago. 



6 h 18 m 23° 45' 



7 1 R=22|° zenith to 18|° in horizon. 24 45 

 7 45 20 15 



Babinet. 

 6 21 Ii= 28 1° maximum in zenith plane. 16° 30' 



1842, May 3* — China-ink sky; wind east. 



Apparent Time. 



9 h m a.m. R = 19|° maximum polarisation in zenith to 14 J° in horizon. 

 11 R= 19£° maximum polarisation in zenith to 14 J° in horizon ; 



bands ragged. 



Arago. 



11 29 R=20°; maximum at 89° from sun. 10° 15' 



12 15 R = 20°. 9 25 



1842, May 4. 



Apparent Time. Arago. 



5 h 56 m 



fi _ f The — bands of secondary neutral point distinct, 1 ,_ <>,, 



\ and this point commenced. J 



6 13 '20 46 



6 16 The secondary neutral point distinctly formed. 21 1 



* See Edin. Trans., vol. xxiii. p. 230. 



