[JACKSON] MAGNETIC OBSERVATIONS IN CANADA 131 
court observatory and its instrumental constants, as determined at 
Kew, are as follows:— 
Apparent dist. ro True dist. r, at O°C 
0.3 metre 0.299925 
OREMNT 0.399942 
True distances at t°c are given by formula 
rr, (1+0.000017 (t—0°C) ) 
Induction co-efficient y—0 -00000549 
Log r°K at O°C—9- 43076 
Angular value 1 scale division of deflection apparatus =1’ 30-1”. 
Angular value 1 scale division magnet marked 48 A=1’-815. 
Temperature correction to magnet marked 48 A. = 0-000325 
X (t—O°C) + 0-00000128 (t—O°C)? 
The formulge used for determination of Hotizontal Intensity are— 
1 
re, (al pene ey ) 
86400 16 
2 : H Se H 
TT? (ro FCO “9h O20) ) 
F M, 
ee rk 
RZ 
den (: +7# 44 (t-0°C) +q, (t-O°C à 
Ho a, i, re q ( as cha ) 
Mat M, ( TA PF ) 
Jae tet re 
where T,— observed time of one vibration. 
S = rate of chronometer per day. 
a and a!— semi arcs at beginning and end of vibration series. 
= — ratio of torsion couple to magnet direction couple 
qand q, = temperature correction coefficients 
mw = induction coefficient. 
m — Magnetic moment of magnet. 
H = Horizontal Intensity. 
u = Angle of deflection. 
r, = apparent distance. 
and P = distribution coefficient and'is determined from formula:— 
Pa at ey ea 
: a, | 
where A and A! are values of — at distances r, and r!, 
1 
