POLARISATION OF THE ATMOSPHERE. 275 



1842, December 30.— Boisterous day; thin white clouds. 



Apparent Time. Arago. 



2 h m R = 22|-° maximum polarisation in zenith plane. 



2 24 15° 5' 



1842, December 31.— Windy, and sky cloudy. 



Apparent Time. Arago. 



ll h 53 m R=27-2° maximum polarisation in zen. Sky impure. 16° 40' 



1843, January 4.— Fine day. 



Apparent Time. Arago. 



ll h 32 m R = 27|° maximum polarisation in zenith. 14° 41' 



11 43 14 30 



Babinet. 



11 35 R = 23i° to 18°. Haze coming on. 15° 47' 



1 51 Altitude of Arago's neutral point above hor. 4° 30'. 



R = 24J° to 18-|-°. Haze to east and south. 



1843, January 5. — At Rankeilour M'Gill ; clear and cold. 



Apparent Time. • Arago. 



iih 97m / R = 28 J° maximum polarisation, 18|° in horizon. "1 ., . .,, 

 \ Neutral line convex to sun. J 



1843, January 10. — Barom. 28*5 ; very cold. 



Apparent Time. Arago. 



2 h 3 m R = 29° maximum polarisation in zenith plane. 14° 25' 



2 41 Polarisation of moon 21 J°, 24^° in horizon. 



1843, January 11.— Barom. 28-72. Fine day. 



Apparent Time. Arago. 



1 9 h ^rn / R = 26J-° maximum polarisation. Nebulosity in 1 -. _ , r, 

 \ zenith. J 



1 47 R = 29|° maximum polarisation in zenith. Clear sky. 



2 55 R = 28° maximum polarisation. Slight nebulosity. 19 50 



3 10 Polarisation of moon 15°. 



1843, January 21. — A misty day. 



Apparent Time. Arago. 



2 h 46^ R=19J-°maximumpolarisationin zenith 30° at 14°alt. 16° 40' 



3 18 Misty. 10 6 



The mist increased, and the maximum polarisation everywhere reduced to 

 14|°, and the two neutral points descended to the horizon several degrees. 



1843, January 28.— Barom. 29-45. Very windy. 



Apparent Time. Arago. 



12 h 28 m Neutral point below horizon. 14° 10' 



12 47 „ „ 14 

 1 57 „ „ 11 5 

 3 51 Misty. 22 41 ! 



Babinet. 

 3 54 R = 28J,° maximum polarisation to 20^° in horizon. 



12 28 R = 26|- „ „ to 18| „ 14° 45' 



VOL. XXIV. PART II. 4 F 



