617 
1907-8.] Sensitive State in Magnetic Materials. 
of the test rods, they were dropped on either end alternately, so as to affect 
the material as uniformly as possible throughout its entire mass. 
A large number of similar specimens of thick steel wire were employed 
in the experiments. All were annealed at 900° C. Six were tested without 
further treatment. A further six were given one fall each in the manner 
described above, and like numbers were subjected to 3, 5, 10, 25, and 50 
falls respectively. The rods were thereafter tested by the magnetometer, 
complete hysteresis cycles being taken. It was found that the enhancement 
of the intensity of magnetisation, the retentivity, and the coercive force, 
induced by the heating had been reduced by the jarring, the magnitude 
of the reduction increasing with the amount of vibration applied. Table 
III. shows the general nature of the results obtained for the six bars. 
Table III. — Effect of Vibration. 
Number of Falls. 
0 
1 
3 
5 
10 
25 
50 
35-4 
264 
20-9 
18-0 
13-8 
12-5 
10-2 
32-9 
22-4 
17-5 
154 
134 
13-8 
12-0 
Percentage 
41*8 
24-9 
20T 
16’5 
14-6 
10-8 
11-3 
“ Sensitive State.” 
39-5 
26-7 
20-8 
18-5 
15-9 
10T 
9T 
42T 
22-5 
16-7 
16-0 
16-0 
16-3 
9*7 
35*5 
21 '4 
193 
16-2 
13-7 
12T 
10-2 
Mean 
37-9 
24-0 
19-2 
16-7 
14’5 
12-6 
10-4 
The figures given correspond to a magnetising field of 10 C.G.S. units. The 
n sensitive state ” is expressed by the percentage by which the enhanced 
values of I exceed the normal magnetic intensities — that is, the intensities 
obtained in tests after the specimen has been subjected to an alternating 
magnetic field gradually diminishing from a large value to zero. The mean 
values show a steady reduction of the “ sensitive state ” with continued 
jarring of the specimens. The variation of the individual values from the 
means is not larger than one would expect considering the sensitiveness of 
the specimens to vibration, and the unavoidable shaking they must experi- 
ence in being removed from the gas furnace in which they were annealed, 
and in being placed within the coil of the magnetometer. 
Similar figures were obtained for other values of the magnetising held, 
and for the residual magnetism and coercive force. In the latter cases, as 
the quantities to be measured were small, the experimental error caused a 
somewhat greater variation of the results from the mean, but their general 
character was the same. 
