[JACKSON] MAGNETIC OBSERVATIONS IN CANADA 133 
Loaded dip and deflections. 
Log C. 
Needle pair. Short distance. Long distance. 
SS SSS | | 
LP 12 9 - 60462 | 9-52996 
| 
These corrections are obtained by the formulae i 
_ 
K 
CH sec I. sin u. sec I! 
i 
Ca —K,m—H sec I. sin u, 
ee ee sec I dE u sin u, sec I! 
where H —horizontal force at time of observation 
Bip 
I’ —Loaded Dip. 
u —]-I: 
u, —angle of deflection. 
Log C, and log Cg vary with change of temperature, but observations 
are not sufficient to deduce a reliable temperature effect. It appears 
from the observations made at Agincourt to be about -00035 on log 
Ca or log C, per 1° cent, log Cg decreasing with increase of temperature 
and log C; increasing with increase of temperature. 
The sub-joined sample will illustrate the method of work and com- 
putation with this instrument. 
