of the Atmosphere. 295 



1841, May 14. — The sky in the forenoon has very little blue 

 in it, being in its colour a French grey. R less than 14 J°. 



Mean time. ' 



h m o 



3 30 R=14|, and 



R=18^ in a bluer part of the sky. 



According as the thin white haze which masked the blue 

 colour of the sky was removed or returned, the places of the 

 neutral points constantly varied in their position. 



In the evening the sky became clear, and R became 24^° 

 and 26J°. 



1841, May 16.— See Phil. Mag. vol. xxx. p. 162. 



1841, May 16. — Barom. 29*4 in. Windy. Considerably above 

 the horizon R varied from 17J° to 14|°, as the blue sky was 

 more or less distant from the white moving clouds. 



At 7 h , when the blue was purer, R = 22J° at 45° of altitude 

 in the S. 



At 7 h 42 m R=24i° at 20° altitude in the N. 



1841, May 17.— Barom. 29'5 in. 



o 



1 20 R=*t7fj the maximum polarization at 99° from sun 



in the plane of zenith and sun. 



2 R=17^, and 15^° at lower altitudes. 



The following observations from May 24 to June 3 were made 

 in Edinburgh : — 



1841, May 24. 



11 10 R=17| maximum in plane of zenith and sun. 



R=14.t in horizon. 



After a cloud had passed the polarization was diminished. 



o 



3 15 R=22} maximum in plane of zenith and sun. 



R= 14 1- elsewhere. 



5 R=26^ maximum in plane of zenith and sun. 



R=24^ in horizon. 



Babinet's neutral point near the sun. 



7 R=22i 7 in zenith and horizon. 



. 7 o 



8 



9 



R= 22^ in horizon. 



1841, May 25. 



6 Arago's neutral point in horizon, and the hyperbolic 



neutral line distinct. 



* The height of Arago's neutral point is to be understood as above the 

 antisolar point, and that of Babinet as above the sun. 



Height. ; 



o / 



Arago's neutral point * . . 



22 5 



Do. do. 



17 48 



Do. do. 



15 50 



