560 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
as described in that paragraph. The influence of stretching in reducing the reten¬ 
tiveness as well as the magnetic susceptibility of the iron is very remarkable. Here, 
again, the method was the direct magnetometric one. 
Soft Iron Wire, Annealed and Hardened by Stretching, Plate 59, fig. 18. 
Before stretching. 
After stretching. 
A 
3 
induced. 
3 
residual. 
Ratio of 
residual to 
induced. 
A 
cv 
3 
induced. 
3 
residual. 
Ratio of 
residual to 
induced. 
0-42 
16 
3-9 
0-24 
0-42 
3-6 
0 
0 
0-58 
24 
6-6 
0-27 
0-99 
13-1 
2-9 
0-22 
070 
33 
9-9 
0-30 
1-44 
2P1 
6-5 
0-31 
0-99 
62 
24 
0-40 
1-73 
26-9 
11-8 
0-38 
1-16 
91 
46 
0-50 
2-14 
41 
15-3 
0-38 
1-30 
140 
85 
0-61 
2-88 
72 
32-7 
0"46 
1-44 
195 
133 
0-68 
3-58 
116 
61-7 
0-53 
1-58 
280 
209 
0-74 
4-20 
167 
98 
0-59 
1-76 
364 
283 
0-78 
4-90 
218 
132 
0-61 
2-02 
468 
380 
0-81 
5-76 
265 
167 
0-63 
2-14 
507 
418 
0-82 
7-20 
359 
225 
0-625 
2-28 
549 
455 
0-83 
10-78 
566 
327 
0-58 
2-51 
614 
513 
0-84 
11-90 
613 
348 
0-57 
2-74 
673 
568 
0-85 
15-20 
751 
381 
0-51 
2-88 
702 
598 
0-85 
17-50 
817 
399 
0-49 
3T6 
764 
650 
0-85 
23-61 
947 
414 
0-44 
3'58 
842 
711 
0"85 
29-81 
1017 
417 
0-41 
4-20 
926 
783 
0-85 
35-71 
1078 
419 
0-39 
5-02 
984 
832 
0-84 
41-90 
1114 
419 
0-38 
5-76 
1020 
848 
0-83 
GAG 
1050 
864 
0-82 
7-20 
1070 
877 
0-82 
8-64 
1110 
897 
0-81 
10-26 
1130 
910 
0-80 
11-91 
1150 
913 
0-80 
17-50 
1190 
929 
0-79 
23-61 
1195 
929 
0-78 
3571 
1230 
933 
0-76 
45-51 
1230 
933 
0-76 
These results are also shown in Plate 59, fig. 18, where the full lines exjDress in terms 
of $ the values of the induced and residual magnetism, and their ratio, before 
stretching, and the dotted lines show the corresponding quantities after stretching. 
The maximum which the ratio of residual to temporary magnetism passes is even 
more distinctly marked in the hardened than in the annealed condition. The curves 
of fig. 18 show very clearly that the residual magnetism approaches saturation much 
sooner than the induced magnetism does, as <§ is increased. In the region of strong 
force, while the curves of induced magnetism are still rising considerably, the curves 
of residual magnetism are running very nearly parallel to the axis of <§, and it is to 
this that the maximum in the ratio is due. 
