ON THE POLARISATION OF THE ATMOSPHERE. 



223 



and nearly as high in the atmosphere as the neutral point of Arago. " I after- 

 wards,"* he says, " determined, a great number of times, the position of this 

 new neutral point which appeared in the west, even when the sun was just on 

 the horizon before setting, and in the east when he had risen only a few degrees. 

 A very imperfect estimate made me sometimes believe, that this new neutral 

 point was a little less high than that of Arago." 



The following observations on this neutral point were made generally on the 

 same day, and even in the same hour, as those on Arago's neutral point, and 

 therefore under the same atmospherical influences. 



1841, May 12. — Wind west in the evening. 



Mean Time. 



8*^ 10™ P.M. 



1841, May 16.— Barom. 2924. Windy. 



Mean Time. 



Height of Neutral Point above 

 the Antisolar Point. 



16° 4' 



Height of Neutral Point above 

 the Antisolar Point. 



M 



san Time. 



10'' 10«> 



A.M 



7 



17 



P.M. 



7 



35 



>) 



7 



52 



5) 



8 



8 



J! 



8 



21 



)) 



8 



39 



)) 



8 



52 



!) 



7^ O'" P.M. 



1841, June 10.— Barom. 29-27. Very fine sky. 



Sun's altitude about 50°. 



Sun sets. 



9 3 „ 

 9 15 „ 



1841, September 6.— Barom. 29-55. 



Mean Time. 



6^ 30ni 

 6 45 



6 58 



7 6 



1841, September 12.— Barom. 29-75. Sky clear. 



Mean T;me. 

 gh 54m 

 7 



1841, September 29. — Barom. 2873. After rain sky clear. 



H" 



Height of Neutral Point above 

 the Antisolar Point. 



2° 



or 



3° 



13° 





15' 



14 





55 



14 





5 



16 





37 



15 





27 



17 





15 



16 





25 



16 





42 



16 





20 



Height of Neutral Point above 



the Antisolar Point. 



16° 



15 



/ 



14 



45 





12 



55 





13 



8 





Height of Ne 



utral Point above 



the Antisolar Point. 



18° 



53 



f 



18 



20 





Mean Time. 

 5h46m 



5 57 



6 7 



Height of Neutral Point above 

 the Antisolar Point. 



12° 53' 

 14 55 

 16 15 



* Comptes Rendus, &c., 1840, torn. xi. p. 619. 

 VOL. XXIII. PART II. 



3 Q 



