Xxx GENERAL RESULTS OF THE MAKERSTOUN OBSERVATIONS. 
HorizontaAL 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 Lamonv’s modification of Gauss’s method : 
the whole processes have been already described in the Introductions to the different 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. 
Duma ORsE a EBeae X Reduced to Mean Value of 
the Mean X for the Mean 
Bifilar for the Bifilar Reading 
Year. of each Year. 
Mean Bifilar 
Values of X. Reading. 
1843. 
August 11 511.5 
August 21 511-1 
November 8 510-9 
November 14 507-6 
December 18 515-2 
1844. 
February 17 524-6 
March 23 520-8 
May 29 535-7 
August 5 540-7 
December 26 539-5 
December 30 534-9 
1845. 
December 29 | 548-9 
December 30 539-1 
1846. 
February 16 553-2 
April 14 | 562-3 
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1847. 
May 31 574-8 
June 15 576-7 
September 11 545-0 
1849. 
June 19 598-0 
October 11 568-0 
3°'65-inch Deflect- 
49. The results for the large bar indicate an increase of absolute horizontal force from 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 ..... Mean of all, = 0-00388 yearly. 
From 1847 to 1849, = 0:0071 = 
