562 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
Pianoforte Steel Wire, Normal Temper, Plate 61, fig. 20. 
3. 
Magnetomet 
Induced. 
er readings. 
Residual. 
Ratio of residual 
to induced. 
9'4 
5'0 
0-6 
0-120 
10-9 
71 
1-5 
0-211 
12-5 
101 
3-3 
0-327 
14-0 
13-8 
6-0 
0-435 
15-6 
17-8 
9-0 
0-505 
172 
24-3 
141 
0-580 
18-9 
30-6 
19-7 
0-644 
20-3 
37-5 
26-4 
0-704 
23-4 
54-9 
41-0 
0-747 
25'0 
64-0 
48-8 
0-762 
26A 
72 - 2 
56-9 
0-788 
28-2 
82-9 
66-0 
0-796 
29-6 
90-3 
73-0 
0-808 
31-2 
98-2 
80-3 
0-818 
32-8 
106-4 
87-8 
0-825 
34-3 
113-5 
94-4 
0-832 
35-9 
120-2 
100-5 
0-836 
37-4 
126-2 
106-0 
0-840 
42-1 
140-5 
1202 
0856 
46-9 
150-4 
127-5 
0-848 
54-6 
1611 
135-7 
0-842 
62-4 
167-5 
140-9 
0-841 
70-2 
172-6 
143-9 
0-830 
78-0 
176-0 
146-0 
0-829 
90-9 
182-1 
1490 
0-818 
This experiment is shown graphically in fig. 20, where, as in the former cases, 
curves are given showing the relation of 2> induced, 3 residual, and their ratio, to §. 
§ 45. Plate 61, fig. 21, gives in the same way the corresponding results for a piece of 
the same pianoforte steel wire, annealed. Here the ratio of residual to temporary 
magnetism touches a maximum of 0'805 with ,§ = 23, and falls to 071 with § = 97. 
§ 46. Finally, Plate 61, fig. 22, gives corresponding results for a piece of the same 
steel wire, glass-hardened. Here even the strongest magnetising force used did not 
saturate the wire sufficiently to allow the maximum in the ratio of residual to induced 
magnetism to be very distinctly passed. It appears, however, to have been reached, 
and its value was 0'69. 
§ 47. Summary of Conclusions as to the Ratio of Residual to Induced Magnetism 
in Iron and Steel. —The results of this section of the experiments may be summarised 
as follows :— 
(1) When the induced magnetisation of iron or steel is very weak it almost all 
disappears on the removal of the inducing field. 
(2) When it is increased its capability of being retained also increases, very 
rapidly, and the ratio of residual to induced magnetism reaches a maximum. 
