APPENDIX, 629 



variation ; and which had a motion concentric with the 

 graduated arcs, rendering it unnecessary to approach 

 the instrument too closely, and thus obviating many 

 inconveniences. 



The instrument was placed on the solid stand in the 

 observatory described before. The observations of the 

 direction of the needle were made for seven succes- 

 sive days, in October 1833, from the 22d to the 28th of 

 the month, at every hour from 8 a.m. until midnight; 

 and similar observations were made in April 1834, from 

 the 23d of the month to the 29th, both days inclusive; 

 and again in October 1834, from the 22d to the 28th 

 inclusive. 



The mean results of these observations are given in 

 Tables II., III., and IV. 



From November 1833 to April 1834, both months in- 

 clusive, and again, from November 1834 to March 1835, 

 the direction of the needle was observed and registered 

 each day, at the hours of 8 and 9 in the morning, noon, 

 1, 2, 3, 4, 7, 10, 12, afternoon. 



The means of all the observations for each month (with- 

 out attributing any of the deviations to, or making any 

 correction for the appearance of, the Aurora Borealis) 

 are contained in Table V.; and Table VI. shows the num- 

 ber of times, during each month, that the needle was in 

 motion, whether tremulous or vibrating, at the several 

 hours of registering its direction ; together with the 

 number of times that the aurora was visible. 



ss S 



