296 Sir David Brewster on the Polarization 



1841, May 27. -Slightly hazy. 



Mean time, 

 h m 



4 45 R = 2(H in zenith. 



R = 19|° in horizon. 



Babinet's neutral point not seen. 



1841, May 28. 



11 R = 15^°. . Hazy bands, ill-defined and ragged. 



Observations resumed at St. Andrews. 



1841, June 3.— In the morning, R = 14i° and 18J . 



6 p.m. R=25|° in zenith and horizon. 

 6 27 „ Arago's neutral point not above horizon. 

 6 36 „ Do. do. very near the horizon. 



6 43 „ Do. do. above and close to horizon. 



See Phil. Mag. vol. xxx. p. 121 for the height of Arago's neutral point. 



1841, June 6.— Barom. 29'9 in. 



4 45 p.m. R=14^° through zenith. 



R=23f° 45° above S. horizon. 

 R = 22|° in S. horizon. 



In and near the horizon the white bands of the polariscope 

 are bluish on the side of the neutral line from the sun. Maxi- 

 mum polarization more than 90° from sun, and diminished by 

 clouds coming on. 



Arago*. 



j 18 36 

 Sky very clear . . . . < 19 28 



(21 20 

 Sun set. Haze in S.E. 



R=28£° through zenith, and 26^° in horizon. 

 R = 28° through zenith, and in 3. (17 20 

 and N. horizon. -j 21 39 



Haze continued. ( 22 12 



1841, June 8. — Barom. 30 in. Fine day. 



11 40 R=2U° through zenith. R = 19° in W. horizon. 



1 5 R = 29j° through zenith. 



4 10 R=26*° through zenith. R = 2/° 30' from N.E. 



horizon. 

 4 30 R=28£° 45° above N.E. horizon. 



4 45 Babinet's neutral point and the neutral hyperbolic line 



clearly seen. 



5 50 f R=20° to 24° as the sky was more or less clear. 



* The numbers under Arago and Babinet are the heights of their neutral 

 points above the antisolar point and the sun. 

 f See Edinb. Trans, vol. xxiii. p. 221. 



