346 



Results of Makeestoun Observations, 1844. 



TABLE XIV. — Mean difference of a Single Observation from the Monthly Mean at the 

 corresponding hour, for each Civil Day in 1844. 



Annual Variation of the Difference/: for the Magnetic Declination. — The fuilowinfi; are the mean differences 

 for each month ; — 



Jan. Feb. March. April. May. June. July. -^ng- Sept. Oct. Nov. Dec. 



l'-34 l'-40 2'-22 l'-87 l'-60 1'12 l'-43 l'-71 l'-93 2'-26 2'-30 l'-40 



There are here two ma.xinia and two minima ; the principal minimum occurs in .fune, and tlie principal 

 ma.\imum in Octoher and November; the mean for the three months, May, June, and July, is T'SS, whicli is 

 also the mean for the three months, December, January and February. The law of the variations may be stated 

 as follows : — The mean difference of hourly observations from their corresponding monthly means is a minimum 

 near the solstices, and a ma.ximum near the equinoxes. This result is in accordance with that already obtained 

 in the discussion for the diurnal range. 



