988 
The other terms 
en e—2a(t—t,) 
every time disappear very soon after each discontinuity and produce 
a small bend at the upper part of each jump. See e.g. fig. 4. The 
more the galvanometer is damped, the greater therefore «, the smaller 
these bends are and the quicker the galvanometer is able to follow 
the sudden changes of the flux. 
If we disregard these small bends the deflection of the greatly 
damped galvanometer is simply given by 
U 
i 
Ae Sn ie 
2a 2a 
and the galvanometer deflections are at any moment proportioual 
to the flux going through the induction solenoid‘). If the H there- 
fore increases proportionally to the time, the deflection of a greatly 
damped galvanometer accurately describes a hysteresis curve. This 
extreme case can be better approximated with a moving coil 
galvanometer than with a string instrument. The curve described 
by the image of the string galvanometer representing the solution 
of (1) from which the function N has to be found back, does not 
lead to such a simple interpretation. 
Haarlem. Physical Laboratory, Teruem’s Institute. 
1) This relation is obtained at once from (1) by neglecting the first and third 
term of the left hand member. 
