638 
In order to try this two solenoids were wound, the first one fitting 
narrowly round the iron (1.104 windings of 0,1 m.m. copper wire, 
the second one with an inner diameter of 24 m.m. (1.7 . 104 windings 
of the same copper wire). The diameter of the soft-iron core was 
1,00 mm. Therefore the wider solenoid had an inner diameter 24 
times that of the core. 
The rod was magnetised longitudinally by means of a small 
permanent magnet that was slowly brought near the core with the 
hand. Using then the narrow solenoid we could hear some increase 
in the intensity of the rustling, but not to such a degree as might 
be expected from the conception that principally the number of 
lines of force in the immediate neighbourhood of the iron is changed 
discontinuously. 
This experiment leads therefore to the view that the magnetisation 
of long filaments of molecule-groups are reversed as a whole, and in 
such a way that the direction of such a group coincides with the 
external magnetomotive force. For only then induction-pulses are 
possible of the same order of magnitude in two solenoids one of which 
fits narrowly round the core, while the second has a diameter 
more than 20 times that of the iron core. The distance between the 
poles of the permanent magnet we used was 60 m.m. At both sides 
of the solenoids, the core could be touched by the poles. 
Generally an annealed soft-iron wire shows the discontinuities very 
well. Even an iron wire thick 0,1 m.m. (annealed beforehand in 
a hydrogen atmosphere) showed the phenomenon distinctly, only 
over a shorter distance of the movable magnet, which can be simply 
explained by the iron being sooner saturated. This is also in good 
agreement with the hypothesis of the existence of long iron filaments, 
which are discontinuously magnetised each as a whole. 
As still other ferro-magnetic substances than iron were investi- 
gated, we may already here compare the characteristic iron-noise 
with a long-stretched french “ch”, viz. a sound that consists of a 
very great number (for the present not yet to be estimated numeri- 
cally) of soft ticks of nearly equal intensity; only with a greater 
amplification some sharply defined crashes are audible. 
When now a soft-iron wire (diameter e.g. 1 m.m.) has been 
magnetised first by bringing the magnet within a small distance 
from it, and when afterwards this magnet is taken away again, the 
characteristic iron-sound is heard during both operations. A rema- 
nent magnetism will however still be in the wire. When thereupon, 
we draw with short pulls at the iron-wire, we hear in the telephone 
at each pull again the characteristic iron-sound. With short pulls this 
