

POLARISATION OF THE ATMOSPHERE. 261 



1842, January 7. — Very fine day, with haze. 



Apparent Time. 

 9 h 18 m A.M. 



12 



11 52 



12 4 p.m. 



12 9 R = 22|° in zenith. 



Babinet. 



15° 



51' 



13 



53 



Arago. 



20° 



34' 



22 







22 



37 



20 



40 



19 



49 



3 25 



4 17 



At 9 h 18 m . R = 24 , a maximum in horizon. The neutral line was convex to 

 the sun. Sky clear, without clouds. 



1842, January 16. — Ground everywhere covered with snow. 



Apparent Time. Babinet. 



4 h 12 m 19° 25' 



1842, January 17. — Fine clear day ; therm. 36. 



Apparent Time. Babinet. 



8 h 37 m a.m. R = 24|° at 35° alt. 201° in horizon. 16° 55' 



3 47 p.m. R= 25° in zenith; 24 J° in horizon. Neutral 

 line concave towards the sun. 



1842, January 21. — Barom. 29.77 ; dry, frosty day. 



Apparent Time. Arago. 



•jh c>4.m JR=27|° maximum polarisation in zenith) 1f . 4f) , 



\ plane, and 24|° near horizon. J 



Babinet. 



3 31 19° 3' 



1842, January 25. — Snow covers the ground. Barom. 294. 



Arago. 

 Arago' s neutral point in horizon. 

 R= 17i° in zenith plane, and + 15° in horizon. 



16° 45' 

 R=:18|° in zenith, and 15° in horizon. 19 21 



R=18|° in zenith, and at 50° altitude, 15°.16 20 



Babinet. 



17° 20' 



18 30 



1842, January 27.— Barom. 29-2 ; therm. 36° at 8 b 30 m . 



Apparent Time. Arago. 



oh oA-m ( R=24A° near horizon ; neutral line concave 



8 n 34 m a.m J. • , 2 ' 



( to sun. 



2 20 p.m. 11° 50' 



4 37 20 40 

 2 32 R=25° in zenith plane and S. horizon. 

 . nr f Thin clouds, almost invisible everywhere but \ , o° n ±A> 



\ above the sun J 



Apparent Time. 



l h 



12 m P.M 



2 



15 



2 



12 



3 



40 



2 



15 



3 



36 



