XXXVl 



Intkodtjction, 



42. Vibration of the balance magnet in the vertical plane. 



The needle being in its usual position on the supports, the moveable wire of 

 the left micrometer is made to bisect the spider cross ; the needle is then vibrated, 

 by means of a small piece of iron, through an angle, varying from 10' to 5', and the 

 periods of the cross passing the wire estimated. 



Table 16. — Values of T, the Time of Vibration of the Balance Needle in a Vertical Plane. 









Time of one 



Vibration. 







Date. 





Number 

 of 







Adopted 

 Mean. 



Remarks. 











Vibrations. 



Observed. 



Adopted. 







<J. 

 1841. 



h. 





6. 



s. 



s. 





July 6 







10 



10-72 



10-60 



10-6 



Adjustment, &c., after July 23*. 



Aug. 3 



4 



48 



10-25) 

 10-17/ 



10-04 



10-0 



Aug. 3 



4 



54 







/August 30*. Agate planes adjusted, and 

 {spider's lines inserted in stead of silver wires. 

















Sept. 4 



5 



36 



10-83) 

 10-69^ 

 10-6l) 







Sept. 4 



5 



84 



10-63 







Sept. 4 



5 



96 





10-6 





Sept. 27 



5 



44 



10-69) 

 10-66/ 



lO-fi.T 







Sept. 27 



5 



66 



L\J \J<J 







Oct. 2 



4 



42 



1107) 

 11-09/ 



11-06 





(Oct. 2" 2^. Needle reversed to determine 

 \the deviation of the crosses. 





Oct. 2 



4 



54 







Oct. 16 



4 



56 



11-081 

 11-03/ 



1105 







Oct. 16 



4 



34 



110 





Oct. 29 



4 



50 



11-03 



11-00 







Nov. 20 



3 



80 



10-99 



10-97 







Dec. 3 



4 



18 



11-00) 

 1101/ 



10-98 







Dec. 3 



1842. 



4 



60 





















J Jan. l"*, &c. Needle removed in order to 

 (determine its temperature correction. 



Jan. 15 

 Jan. 29 



5 

 5 



38 

 46 



10-70 

 10-32 



10-66 

 10-30 



10-6 





Feb. 12 



5 



30 



10 15\ 



10-04 







Feb. 12 



5 



57 



10-19/ 







Mar. 5 



6 



63 



10-34 



10-32 



10-1 





Mar. 19 



5 



48 



10-15) 

 10-12/ 



1002 







Mar. 19 



H 



42 







Apr. 2 



6 



68 



11-02 



10-96 





(March 22*. Needle vibrated excessively 

 (by iron brought near it by visitors. 





Apr. 9 



5 



56 



10-94 



10-94 



U-O 





Apr. 16 

 Apr. 23 





 



60 

 36 



11-02 

 10-77) 



10-96 









Apr 23 







36 



10-72V 



10-64 







Apr. 23 







30 



10-82) 









June 20 

 June 20 



6 

 6 



50 

 40 



10-65) 

 10-65/ 



10-60 







June 25 

 June 25 



8 

 8 



30 

 50 



10-58) 

 10-59/ 



10-56 







July 16 



6 



50 



10-46 



10-42 



10-5 





