628 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
Load =14‘8 kilos., or 36 T kilos, per sq. mm. 
•e. 
3 induced. 
3 residual. 
Batio. 
0 
0 
0 
_ 
0-54 
19 
9 
0-47 
1-08 
53 
29 
0 - 55 
1*62 
104 
62 
0-60 
2-16 
176 
110 
0-63 
2-70 
258 
172 
0-67 
3-78 
419 
289 
0-69 
4-86 
530 
371 
0-70 
5-99 
619 
432 
0-70 
7-02 
679 
471 
0-69 
8T0 
731 
489 
0-68 
9-45 
790 
524 
0-66 
10-80 
835 
546 
0-65 
12-26 
874 
559 
0-64 
13-50 
910 
570 
0-62 
16-20 
966 
581 
0-60 
18-90 
1011 
590 
0-58 
21-60 
1040 
595 
0-57 
24-30 
1067 
598 
0-56 
28-08 
1093 
598 
0-55 
29-16 
1108 
598 
0-54 
Here the results are somewhat different from those of the last paragraph. A 
distinct maximum occurs in the value of the ratio of residual to induced magnetism 
in each of the curves with load, as well as in the curve taken without load, and it 
occurs at earlier values of -§ in the loaded curves than in the unloaded. The effect of 
stress on retentiveness is again very great, especially with weak magnetisations : thus 
for <§=1 the ratio of residual to induced magnetism is nearly zero when there is no 
load, but ranges from *55 to ’64 in the curves taken with load. It is to be noticed, 
however, that the curves of ratio and <§, corresponding to 5, 10, and 14*8 kilos, of load, 
perhaps cross each other at a value of £> lower than that at which the observations can 
be said to begin. On the other hand, the curve of ratio and & corresponding to no 
load may perhaps cross the others at a value of <§ much greater than that to which 
the experiment extends. 
The greatest ratio of residual to induced magnetism, throughout the whole group, 
occurs at the maximum point of the 5-kilo, curve, when its value is (P83. This is a 
much greater value than is reached at any point under no load, where the maximum 
is only 0 - 6. Moreover, the presence of a moderate load increases, in a still greater 
proportion, the retentiveness of stretched iron under strong values of «§. At the 
highest value of *§ which was reached in this experiment the 5 and 10-kilo, curves of 
residual magnetism, and also of the ratio, lie much higher than the no-load curve. 
§ 111. To illustrate this last point more fully the following additional observations 
were made. The same piece of wire was successively tested under loads of 0, 2, 4, 6, 
8, 10, 12, and 14*8 kilos., by first demagnetising it in each case, then applying a force 
