in the Diurnal Motion of the Magnetic Needle. 431 



the single months, as derived from Beaufoy's observations, is as 

 follows : — 



Magnitude of the 

 diurnal motion. 



1813. 



April 



May 



June 



July 



August 



September 



October 



November 



December 



1814. 



January 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



1815. 



January 



February 



March 



11-90 

 8-87 

 9-70 

 8-53 

 7-57 

 6-77 

 7-20 

 2-70 

 2-47 



3-97 

 6-13 

 8-65 



11-00 

 902 

 9-63 



10-25 

 9-58 

 8-73 

 7-62 

 4-28 

 257 



3-43 

 6-67 



8-85 



Magnitude of the 

 diurnal motion. 

 1818. , 



November 8-28 

 December 4-27 



1819. 

 January 

 February 

 March 

 April 

 May 

 June 

 July 

 August 

 September 

 October 

 November 

 December 



1820. 

 January 

 February 

 March 

 April 

 May 

 June 

 July 

 August 

 September 

 October 

 November 

 December 



The yearly and half-yearly averages are as follows -. — 



4-20 

 5-63 

 8-40 



10-55 

 8-67 



10-22 

 9-68 



10-27 

 9-10 

 6-68 

 6-02 

 3-85 



3-80 

 5-80 

 8-77 

 9-85 

 9-43 

 9-43 

 10-32 

 9-58 

 9-22 

 8-55 

 5-25 

 3-52 



