POLARISATION OF THE ATMOSPHERE. 



255 



1841, June 15.- 



-Barom. 300 at 9 h , and 29-8 at 10 h a.m. 





Mean Time 







Arago. 



8 h 36 m 







18° 45' 



8 52 



R=25i°at 40° alt. N.E. 





18 32 



9 3 







18 9 



9 15 







18 7 



9 40 







21 16 



9 52 



R = 28|° at 40° alt. N.E. 





21 52 



1841, June 21.- 



-Barom. 294. 







Mean Time 







Babinet. 



7 1 * 42 m 



R=24° at 40° alt.. S. 21J° 



in zenith. 



21° 30' 



7 52 \ 







( 20 44 



8 } 



Clouds passing over the neutral point. 



\ 20 



9 15 1 







1 20 28 



1841, June 2.— Barom. 29*68. 



Mean Time 

 3 h m p.M. R=14|°. A faint whiteness over blue sky. 



8 31 

 R=14|° in horizon, and 25^° in zenith, and 



24£° in alt. 40° S.W. 



9 



9 15 Sky not pure this evening. 



9 30 



8 47 



Arago. 



17° 37' 

 ] 19 58 



18 45 

 18 5 

 18 



1841, June 23.— Barom. 2972. Sky impure. 



Mean Time. Arago. 



8 h 5 m ) (21° 30' 



8 23 ( Clouds below the neutral point. Observations J 17 25 



8 45 r not satisfactory. 1 20 35 



8 52 J ( 20 48 



1841, June 27. — After three days of eastern haur and rain. 



Mean Time. 

 10 h m a.m. R=19J° in zenith plane, the sky being cloudy. 

 1 p.m. R=14i°at20°alt.inE. Barom. 29 6 and rising. 



Arago. 

 7 30 21° 21' 



7 45 R=22&° in zenith plane, and 211° at 30 alt. 22 5 



8 



8 18 



21 42 

 20 12 



When light clouds covered the sky round and over the neutral point, the 

 polarisation was + or vertical from the zenith to the horizon. 



1841, June 28. — After a bad rainy day and the wind east, the sky cleared up 



in the evening and the wind became west. 



Mean Time. 

 8 h 50 m p.m. 

 9 13 



Arago. 



18° 26' 

 18 43 



1841, July 17. — See " Edinburgh Transactions," vol. xxiii. p. 214. 



VOL. XXIV. PART II. 4 A 



