POLARISATION OF THE ATMOSPHERE. 267 



1842, April 2. 



Apparent Time. Arago. 



6 h 5 m 19° 15' 



7 4 19 42 



Babinet. 

 6 36 18° 5' 



6 38 19 8 



7 4 20 18 



1842, April 3. — Fine clear sky ; hail in the afternoon. 



Apparent Time. 



1 1>, ACrr, f Brewster's neutral point most distinctly seen. 1 1o0 •. 



ll n 4o m I tv . * > lo 



I Distance trom sun, J 



1842, April 5, 6, 8.— See "Edinburgh Transactions," vol. xxiii. pp. 217, 225, 

 and 229. 



1842, April 9.— Barom. 30-16. Wind east; bitterly cold. 



Apparent Time. Arago. 



3 h 25 m R= 221° in zenith plane. The sky clear. 



5 46 22° 7' 



6 651 M , ,, f 15 20 



7 o) Effectoff °g- I 1 6 2 



Babinet. 



5 49 R=15i° in horizon. 17° 10' 



6 57 19 30 



Between 5 h 49 m and 6 h 57 m a fog came on, and there were no neutral points. 

 1842, April 10. 



Apparent Time. 



4 h 5 m R=18J° in zenith, and 14£° in horizon. 



4 22 R=27 in zenith, and 14J in horizon. 



Babinet's neutral point very near the sun, and no neutral point seen below 

 the sun. 



1842, April 13.— Barom. 30-12. Fine day* 



Apparent Time Arago. 



5 h 48 m 16° 20' 



6 20 17 55 



6 54 19 40 



7 10 19 45 

 7 19 R=30£° in zenith. 19 4 

 7 29 R=32|° in zenith. 22 10 



R increased from 25° at 4 h to 32£° at 7 h 29 m . 



1842, April 15. — See " Edinburgh Transactions," vol. xxiii. p. 230. Haze 

 from west. 



Apparent Time. 

 5 h 40 



5 48 



5 57 R= 14£°, in zenith 18i°, 20° ahove N. horizon. 



6 28 White nebulosity. 



7 



5 50 



* See Edin. Trans., vol. xxiii. p. 225. 

 VOL. XXIV. PART II. 4 D 



Arago. 



16° 



25' 



18 



40 



18 



21 



18 



50 



Babinet. 



28° 



20' 



