300 Sir David Brewster on the Polarization 



1841, July 28. — Barom. 29'37 in. A clear blue sky; cloudy. 



Arago. 



R= 26i° to 28;-° 



1841 , July 31. — Cloudy. Neutral point covered with minute 

 cirri. 



8 .. .. .. .. 16 45 



8 14 .. .. .. .. 17 25 



1841, August 6. — After two days of rain. 



8 5 p.m. R=29|°. A cloud had passed. 16 28 

 18-11, August 8. — Morning rainy; splendid evening. 



6 50 R=29|° 16 17 



7 5 R=28|° . . . . . . 18 20 



7 35 Clouds came on . . , . 1 7 53 



1841, August 10. — After rain. 



7 45 . . . . . . . . 18 15 



1841, August 17. — Clear and windy. 



9 a.m. R=21|° in zenith, and 15^° near horizon. 



The blue of the sky, though very clear, was whitish, which 

 always reduces the polarization. Same day at Perth. 



7 1 5 R=24i° in zenith, and 20±° in horizon 20 38 



7 30 . . . . . . . . 19 24 



During the whole day the blue sky became whiter and whiter, 

 and the polarization fell below 14J° out of the scale of the polari- 

 meter. Small black clouds appeared on the white sky. 



The observations from the 6th to the 17th of August were 

 made at the Bridge of Earn. 



1841, August 31, September 6 and 12. See Philosophical 

 Magazine, vol. xxx. p. 121. 



1841, September 6. — See Philosophical Magazine, vol. xxx. 

 pp. 122, 162. 



1841, September 12. — See Philosophical Magazine, vol. xxx. 

 pp. 122, 162. 



1841, September 13. 



5 55 a.m. R = 25r zenith ; 23*° horizon. 19 10 



5 58 „ . . . . . . . . 20 



6 32 p.m. R=25i° zenith .. .. 18 16 



6 38 „ .. " .. .. .. 18 



6 42 „ .. 17 27 



