Mr. Christie on the Aurora Borealis. 



275 



affected. In order, however, to determine how far any effects 

 were manifest in the direction of the needle, we will analyse the 

 abstract of the observations made by Capt. Foster, at Port 

 Bowen, in the months of January and February, 1825, during 

 which" months it happens that, in each, the aurora was visible 

 and invisible during the same number of nights as nearly as 

 possible. 



Aurora visible. 



Aurora invisible. 



Means 



February 6 

 11 

 12 

 13 

 14 

 15 

 16 

 19 

 20 

 21 

 22 

 23 

 24 

 25 



1 47 



1 27 



3 53 



2 46 

 2 25 

 5 00 



4 25 

 1 41 

 1 55 

 1 41 



1 53$ 



2 10$ 

 1 46$ 

 19$ 

 45 



Means . . . . 2 17.5 

 Means, Jan. and Feb. 2 02.7 



Means, Jan. and Feb. 1 13.7 



