368 



Results of the Makerstoun Observations, 1844. 



The following are the differences of the hourly means for the 120-day series and for the 60-day series, 

 or means for 120 days minus means for 60 days : — 



Those differences follow nearly the same law as those already considered. The maximum of the positive 

 effect occurs about 3'' p.m., and of the negative effect immetliately after midnight, while there is also a 

 secondary positive ma.Kiraura about 6'^ x.u., and minimum about lO*" a.m. ; whence, as in the analogous 

 discussion for the magnetic declination, we may conclude, that the smallest disturbances obey the same diurnal 

 law as the larger disturbances. 



Differences of the Individual Observations from the Monthly Means for the corresponding hours. — 

 Adopting the process already indicated, p. 346, for the magnetic declination, we obtain the following Table : — 



TABLE XXXIV. — Mean Difference of a Single Observation of the Bifilar Magnetometer from the 

 Monthly Mean, at the corresponding hour, for each Civil Day and Week in 1844. 



Annual Variation of the mean difference for the Horizontal Component. — The foUomng are the average 

 differences, for each month, of an observation from the monthly mean at the corresponding hour in parts 

 of the horizontal component : — 



Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. 



0-000 I 350 533 823 770 568 400 469 645 587 689 591 521 



