Physics. — ‘Discontinutties in the Magnetisation” II. By Dr. Bauru. 
VAN DER Por Jr. (Communicated by Prof. H. A. Lorentz). 
(Communicated at the meeting of Nov. 27, 1920). 
In a previous paper’) under the same title, some preliminary 
experiments were described about the discontinuities in the magnetic 
induction which occur under certain circumstances in ferro magnetic 
bodies, when the magnetic force is varied quite continuously. The 
simplest method to observe these discontinuities is to connect a 
coil surrounding the ferromagnetic substance to be investigated to 
a telephone receiver (through a triode amplifier or even without one) 
in which the discontinuities in the induction can be observed, if one 
brings a permanent magnet slowly near the coil. In our previous 
paper the attention has already been called to the fact that these 
discontinuities can also be made visible galvanometrically and that 
the phenomenon is especially conspicuous with nickelsteel. 
Some further investigations on these discontinuities form the 
contents of the present paper. 
In order to determine on which part of a magnetic cycle the 
discontinuities occur, some hysteresis curves were obtained by means 
of an improvised magnetometer. Figure 1 relates to the above 
mentioned nickelsteel which has the same thermal expansion coefficient 
as glass. The cylindrical wire used has a diameter of 1.98 millimetres 
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1000 
1) These Proceedings Vol. XXIII, N°. 4, page 637 (1920). 
