619 
1907-8.] Sensitive State in Magnetic Materials. 
marked, succeeding falls are of rapidly diminishing influence. Thus the 
curve lies considerably above the axis for any moderate number of falls of 
the specimen, and possibly does not meet the axis even when the number of 
falls is increased indefinitely. 
Fatigue Effect . — In carrying out the foregoing investigation of the effect 
of vibration on material in the sensitive condition, it was at first intended 
to use only seven specimens. These were to be employed in the following 
manner. Having been annealed at 900° C., they were to be given 0, 1, 3, 5, 
10, 25, and 50 falls respectively, and then tested by the magnetometer. 
Afterwards they were to be reannealed at the same temperature, and 
— taken in the same order — to be given 50, 0, 1, 3, 5, 10, and 25 falls 
respectively and tested. This procedure was to be repeated until all the 
specimens had been subjected to each of the various numbers of falls. It 
was found, however, that the percentage “ sensitive states ” for each treat- 
ment showed a general tendency to diminish ; that is to say, the second and 
subsequent annealings had not restored the initial conditions. In fact, the 
specimens showed a fatigue effect. This gradual narrowing of the limits 
between magnetic intensities corresponding to the “ sensitive ” and “normal ” 
conditions of the steels was made the subject of a separate examination. 
Seven specimens of the thick steel wire were annealed, tested, demagnetised, 
retested, and then reannealed, and the procedure repeated. This was con- 
tinued until the specimens had undergone seventeen successive heatings. 
Table V. gives the mean values obtained. 
Table V. — Fatigue Effect. 
Annealing. 
i 
“ Sensitive State.” 
Actual Percentage. 
Relative Percentage. 
1st 
38-0 
100- 
2nd 
33 T 
87- 
3rd 
29-3 
77- 
4th 
25-8 
68- 
5 th 
22*8 
60- 
6th 
20-5 
54- 
7th 
18*2 
48* 
8th 
16-7 
44- 
9th 
15-2 
40- 
10th 
14T 
37- 
11th 
12-5 
33* 
12 th 
11-4 
30’ 
13th 
10-3 
27- 
14 th 
9-5 
25- 
15th 
8-7 
23* 
16th 
8-0 
21* 
17th 
7-2 
19- 
