POLARISATION OF THE ATMOSPHERE. 



263 



1842, February 11.— Rain in the forenoon till 2 h 30 E 



Apparent Time. 

 3 h lfl m 



3 55 R = 29|- in zenith. Sky quite clear. 



R = 29| in zenith. Sky quite clear. 



R = 24i° 30° above S.E. horizon. 



4 20 

 4 38 



3 22 



3 53 



4 23 

 4 36 



R = 28i° in zenith, and in N. horizon. 



R = 29J-° in zenith. Neutral line convex to 

 sun." R = 28-i-° 15° alt. 



Arago. 



17° 



33' 



21 



8 



19 



45 



20 



Bab 



5 



inet. 



16° 



19' 



17 







19 



34 



18 36 



1842, February 12. — Barom. 29"3. Rainy, with wind. Cleared up at 4 h . 



Apparent Time. 

 4 h 18 ra 



4 20 

 3 55 



Arago. 



Clouds passed away. 



R = 24J°, but reduced to 20 J° when watery 

 clouds passed over the sky from W. to S. 



r 17° 28' 



< Babinet. 

 I 17° 12' 



1842, February 15.— Rain in morning, then fine day. Wind west.* 



R= 27|° in zenith to 221° in S.E. horizon. 



Apparent Time. 



4 44 

 4 55 



Babinet. 

 21° 58' 

 20 24 

 Barom. 3005, therm. 43° ; wind west. 20 30 



Seco 



Clouds came into S. horizon at 4 h 55 m , and the whole of the N. and N.E. horizon, 

 especially above the sea, was covered 6° or 8° high with a dark band of distant 

 haze. 



N.B. — At 3 h 48 m , when the neutral point was 

 1° 57' high, there was just above the sea horizon, H H, 



a portion mn of + bands, a continuation of those m — v^tp|$j1fc[^ — " 

 on the sea, so that there were two neutral points 

 here. These were more fully developed at 3 b 58 m , as Hj 

 shown in a former paper.f 



1842, February 16.— Barom. 30-164 



At noon, sun's alt. 21°, there is clearly a faint 

 neutral point a little above the horizon, and 19° below 

 the sun. 



At 2 h 48 m , though the bands at Arago's neutral 

 point are all +, as in fig. 4, they are most weak- 

 ened at m n, which is the effect of the secondary 

 cause. R = 19^° in zenith, and in both horizons at 

 25^ alt. 



Fig. 4. 



* See Edin. Trans., vol. xxiii. pp. 216, 224. 



f Ibid., vol. xxiii. p. 222. + Ibid., vol. xxiii. pp. 217, 228. 



VOL. XXIV. PART II. 4 C 



Fig. 3, 



