1298 
the deflexion of 2,2 em. We may therefore say that there would 
have been a permanent deviation of 0,14 < 2,2 — 0,31 em, if the 
couple with which the residual field acts on the remanent magnetism, 
had existed permanently. 
The angular acceleration which this couple may produce is found 
by multiplication of the permanent deflexion by »,°*). Thus we find 
for the acceleration on the scale 
41 
Na NCI): Ol 
1 
0.31 = 3.3 m/s. 
0 
Now the couple in question gives rise to effect 3a, when it acts 
during sy sec. It therefore causes a sudden change of velocity of 
3, 
oo 
3 —_ 
0 == 0.04 m/s. 
oO | 
As at each impulse the first effect gives rise to a velocity 0,21 °™/scc, 
effect 3a has been about 5 times weaker than effect 1. 
7. It must be remarked that our conclusions are drawn from the 
following phenomenon. By continually regulating compensation II 
the amplitude of the oscillation of the cylinder is made to pass 
through a minimum, while the phase is reversed. If it is O at first, 
it finally becomes + 7, passing through + 7’ when the amplitude is 
at its minimum. 
Now it might be thought, that this could be caused by effect 2 
alone without the intervention of 1 or 3. Let us suppose, that the 
current in the compensating coil is first O and then increases to a 
value far above that which is required for the compensation II. Then 
it might be said, that there is initially a vibration 2, caused by the 
action of the residual field on the horizontal magnetism of the cylinder 
and that gradually a second vibration u of opposite direction, caused 
by the action of the compensating coil on the magnet fixed to the 
cylinder, is added to 4. 
Now if it might be supposed that the vibration u had not exactly 
the opposite phase as 4, but a slightly different one, the value 0, 
would not be reached, but only a certain minimum and at that 
minimum the phase would differ + 7’ from that of 2 or u. 
To this we may object that in reality, whatever be the position 
of the magnet and the axis of the compensating coil with respect 
to the horizontal magnetism of the cylinder and the residual field, 
the actions, which cause the vibrations + and u have exactly opposite 
1) Because if the deflection is «, the elastic couple causes an acceleration 72% 
(see the equation of motion). 
