53 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
Moderately soft iron ring, Plate 57, fig. 1. 
Battery 
galvanometer 
reading. 
Ballistic 
throw. 
Sum of throws. 
SB. 
3. 
K. 
5*3 
013 
IT 
IT 
26 
2-1 
10-2 
0-26 
PI 
2-2 
53 
4-2 
12-0 
0-30 
0-5 
27 
65 
5-1 
160 
0-40 
0-8 
35 
84 
6-7 
21 
0-53 
1-0 
4-5 
107 
8-6 
28 
071 
2T 
6-6 
158 
12-5 
37 
0-93 
2-9 
9-5 
227 
18-0 
52 
1-31 
3-9 
13-4 
320 
25-4 
19 
67 
1-69 
9-2 
22-6 
540 
42-9 
25 
75 
1-89 
6-9 
29-5 
705 
56-0 
30 
110 
2-78 
77-5 
107-0 
2,560 
203 
73 
133 
3-36 
78-7 
185-7 
4,440 
353 
105 
159 
4-01 
82 
267-7 
6,400 
509 
127 
196 
4-95 
91-5 
359-2 
8,580 
683 
138 
232 
5-86 
57 
416-2 
9,940 
791 
135 
285 
7'20 
57 
473-2 
11,300 
899 
125 
321 
840 
23-5 
496-7 
11,870 
944 
116 
362 
914 
24 
520-7 
12,440 
989 
108 
310 
7'83 
- 4-4 
516-3 
12,330 
981 
246 
6-21 
- 6-7 
509-6 
12,170 
968 
188 
4-75 
- 7T 
502-5 
12,000 
955 
107 
2-70 
-14-0 
488-5 
11,670 
929 
0 
0 
-33-2 
455-3 
10,880 
866 
110 
2-78 
15 
470-3 
11,240 
894 
196 
4-95 
14'2 
484-5 
11,570 
921 
246 
6-21 
11-9 
496-4 
11,860 
943 
317 
8-00 
14-5 
510-9 
12,170 
971 
362 
9T4 
10 
520-9 
12,440 
990 
§ 11. Plate 57, fig. 2, shows the changes of magnetism of another ring, of very soft 
iron wire, when the magnetising force was (1) raised to 7*07, (2) reversed to — 7'07, 
(3) restored to +7'07, (4) reduced to 0, (5) restored again to fi-7'07, all by a series 
of numerous sudden steps. Also, during the second operation two small loops were 
formed by reducing the force by steps to zero, reapplying it, and continuing the 
operation. In the curve of first magnetisation the greatest value of k is 180, corre¬ 
sponding to <§ = 3. During the reversal, as soon as the magnetising force changes 
its sign a very rapid demagnetisation begins, and a force of about —1'9 suffices to 
remove completely the residual magnetism. The reversal curves are steepest when 
the magnetisation is zero : at that point the value of is about 14,500. That is to 
say, for every line of force (per sq. centim.) which is then entering or leaving the 
field, 14,500 lines of induction are entering or leaving the substance of the metal. 
Complete double reversal has the effect of slightly reducing 03 below the value 
reached in the first application of <§, but removal and reapplication of the force 
raises 03 slightly above its primitive value. Every loop in the diagram shows that 
