XXX 



General Results of the Makeestoun Observations. 



Horizontal Component of Magnetic Force. 



48, The observations in connection with this element are of two classes : — 1st, Observations for the abso- 

 lute value of the component, made by the method of Gauss ; and, 2d, Observations of the bifilar magnetometer for 

 the variations of the component. The observations for the absolute value were made with two different instru- 

 ments ; first, from 1843 till April 1846, with a 15-inch deflecting bar, by Gauss's original method; and 

 second, after April 1846, with 3-65-inch deflecting cylinders, by Dr Lamont's modification of Gauss's method : 

 the whole processes have been already described in the Introductions to the diflerent volumes of Makerstoun 

 Observations. The following Table contains the computed values of (X) the horizontal component corre- 

 sponding to the reading of the bifilar magnetometer at the time of vibration, and also the values reduced to the 

 mean reading of the bifilar for the year of the observations ; to these are affixed approximate weights, depending 

 upon the number and agreement of the partial results, and employed in obtaining the mean in the last column : 



Table 21. — Results of Observations for the Absolute Value of the Horizontal Component of Magnetic 

 Force, made in the Years 1843 — 1849, with the Resulting Mean Value, corresponding to the 

 Mean Reading of the Bifilar Magnetometer for the respective Years in which the Observations 

 were made. 







During Observation. 



X Reduced to 





Mean Value of 





Date. 







the Mean 



Weiglit. 



X for the Mean 





Values of X. 



Mean Bifilar 

 Reading. 



Bifilar for tlie 

 Year. 



Bifilar Reading 

 of each Year. 





( 



1843. 

















August 1 1 



3-3556 



511.5 



3-3512 



1 









August 21 



3-3849 



511-1 



3-3807 



3 









November 8 



3-3773 



510-9 



3-3732 



3 



3-3752 







November 14 



3-3792 



507-6 



3-3757 



2 





u 





December 18 



3-3840 



515-2 



3-3813 



2 









1844. 













60 



a 





February 1 7 



3-3836 



524-6 



3-3851 



1 









March 23 



3-3759 



520-8 



3-3793 



2 





« { 



C 





May 29 



August 5 



3-3853 

 33913 



535-7 

 540-7 



3-3816 

 3-3852 



2 

 2 



3-3801 







December 26 



3-3844 



539-5 



3-3789 



2 





c 





December 30 



3-3760 



534-9 



3-3727 



2 









1845. 

















December 29 



3-3921 



548-9 



3-3870 



2 



3-3832 







December 30 



3-3812 



539-1 



3-3807 



3 







1846. 

















February 16 



3-3929 



553-2 



3-3910 



3 



3-3883 





\ 



AprU 14 



3-3904 



562-3 



3-3843 



2 



, 



, 



1847. 













"5 





May 31 



3-3918 



574-8 



3-3842 



3 









June 1 5 



3-3927 



576-7 



3-3843 



3 



3-3846 





September 1 1 



3-3791 



545-0 



3-3852 



3 





.5 ° 





1849. 













•s" 





June 1 9 



3-3963 



598-0 



3-3873 



3 



3-3917 



t \ 



October 1 1 



3-3913 



568-0 



3-3961 



3 



49 . The results for the large bar indicate an increase of absolute horizontal force fi-om year to year between 

 1843 and 1846 ; those for the small bar exhibit a similar fact, although the considerable difference between the 

 results for June 19 and October 11, 1849, throw some doubt on the amount of increase. 



From these observations the increase of the horizontal component in absolute measure (see No. 53.) 



From 1843 to 1845, = 0-0080 = 0-00400 yearly. 



From 1844 to 1846, = 0-0082 = 0-00410 



From 1847 to 1849, = 0-0071 = 0-00355 



Mean of all, = 0-00388 yearly. 



