INTRODUCTION. XXV 
If n be the number of scale divisions from the zero or reading for w = 90°, when 
uv =v+f, N the number from the zero, for the same force, if v had its normal 
value, then 1 
sin v’ — sin v Hi ICON v 
Ne =En ; 
& COS U cos v 
or adapting the first constant to logarithmic computation, 
Be 
=i ope (o+§) +n er 
a COS D 2 cos v 
=A+nB. 
6 is considered negative when v is diminished, and m is negative when the reading 
is below the zero. 
The following are the values of 8, A, and B, used in reducing the extra obser- 
vations :— 
TABLE 9.—Constants for the Reduction of Observations after altering the reading 
of the Torsion Circle. 
Periods to which the quantities 
or 
ooocococo . 
+0 
+6 
+4 
+3 
+5 
+3 
+2 
-—0 
or 
I 
to 
bo 
to 
on 
July 2 10 16— 2 13 
ADJUSTMENTS. 
29. The scale of the collimator contains 280 divisions with the graduation at 300. 
Determination of the angular value of 1 scale division :— 
MAG. AND MET. OBS., VOL. I. g 
