(lave) 
ADDENDUM. 
117. The process of making and reducing the observations for the absolute hori- 
zontal intensity made according to the method of Gauss with a 15-inch deflecting 
bar, has been already described (Introduction, Unijilar Magnetometer), and the ob- 
servations of deflection and vibration will be found, p. 133-4, 347-8. The results 
are as follows :— 
TABLE 12.—Results of the Observations for the Absolute Horizontal Intensity, 
made with the 15-inch deflecting bar, in 1845 and 1846. 
™ 
Pairs of Distances. Log. xX 
0-454094 
0-456497 
0:455291 
0-455826 
0-455640 
0-455766 
0-456009 
0:455309 
0-454785 
0.454664 
0.455078 
0-455281 
0-453826 
0-453431 
0.454274 
Log. m X. 
1-515975 
1-513839 
1.516163 
1.514334 
118. The value of m X, for December 30, is deduced from the 2d series of vibra- 
tions made upon that day, as there was obviously some error involved in the Ist 
series ; for a similar reason, the deflection at the distance of 8 feet has not been 
employed. 
The mean value of X from the previous Table reduced to the mean 
bifilar reading: for sl 8450052... See f oy ck .s ccesnedsareesserevssesusosmat chests o- = 3'38355 
The mean value of X from the observations for 1844, reduced to the mean 
bifilar resdinpstor gl S44 an cca one ote \ecectuces tose thes wo-becee ae eee dso = 3:38005 
Whence the secular change from 1844 to 1845 in parts of X, ........ ...... = 0:00104 
From the readings of the bifilar magnetometer the secular change 1844 
to 1845, ..... SE tere osu den inc dnace daca sable anti talacisialc guanidino eset = 0:00142 
MAG. AND MET, OBS. 1845 anpD 1846. r 
