C. HORIZONTAL INTENSITY. 
As already mentioned in the introduction, the magnetic apparatus 
EK. A. Zscuau No. 289 was arranged for the taking of both deflection obser- 
vations at two different distances, and observations of the deflectors’ time 
of vibration, whereby the absolute value of the horizontal intensity may be 
determined when the constants of the instrument are known. 
If the following signs are employed: 
H = absolute horizontal intensity 
gy = angle of deflection 
e = distance of the deflector 
k 
I 
a constant depending upon the distribution of magnetism in 
the deflecting and deflected magnets 
= induction coefficient 
moment of inertia of the magnet 
Ry 
| 
= time of vibration, corrected for rate of chronometer, are of 
vibration and torsion force of the suspending thread. 
a = temperature coefficient 
8 = coefficient of dilatation for brass (0:000180) 
6’ = coefficient of dilatation for steel (0000124) 
t 
= temperature of magnet during the vibrations 
’ = temperature of magnet during the deflections, 
we have 
H = po [1+ etter 4 at—o, (1) 
T ysin p 
