1012 
PROFESSOR J. A. EWING AND MISS H. G. KLAASSEN 
Fig. 20 has been drawn in further illustration of the magnetic qualities of this 
ring (Ring VIII. after special annealing). The curves in it show the whole induced 
magnetism and the residual magnetism (for each cycle) in relation to H. Taking the 
inclination of a tangent to the former curve drawn through the origin to measure the 
maximum permeability we find its value to be 2420. 
In the same diagram (fig. 20) the curve drawn in broken line shows, in relation 
to H, the ratios of the residual to the induced value of B in each cycle. This curve 
rises with a rapid, nearly uniform, gradient (from a point'to the right of the origin, 
since a finite amount of magnetising force may be applied without causing the iron 
to acquire any residual magnetism). It bends over fast when H is about 2'5, passes a 
maximum which is not sharply defined, and slowly falls as the magnetism is pushed 
into the region of saturation. Throughout the steep part of the magnetization curve 
the difference between the residual and induced magnetisms scarcely increases at aU, 
while B is increasing tenfold. The relation of the residual to the induced magnetism 
presents, in this and other respects, just those characteristics which the molecular 
theory (referred to below) would anticipate. In the present instance when the ratio 
is a maximum the residual induction is 93 per cent, of the induced. 
The values of |II(iI and the coercive force for Ring VIII. in its second (annealed) 
state are as follows :— 
Ring VIII.—Second state. Soft iron wire of “ Hedgehog ” Transformer after 
special annealing. Values of |H dl and coercive force. 
No. of cycle. 
Limits of H. 
Limits of B. 
Limits of I. 
Coercive force. 
1 
23-60 
16170 
1285 
17380 
2-98 
2 
15-25 
15490 
1231 
15790 
2-95 
3 
11-24 
14870 
1183 
14800 
2-89 
4 
8-05 
13840 
1101 
12990 
2-85 
5 
6-15 
12640 
1005 
10770 
2-73 
6 
4-66 
10940 
871 
8780 
2-56 
7 
3-63 
8640 
688 
6120 
2-44 
8 
2-50 
4000 
318 
1770 
1-71 
9 
1-92 
1390 
111 
310 
1-00 
10 
1-41 
660 
53 
70 
0-70 
It will be seen from these figures that the special annealing had hardly any 
influence on the value of jll(il and of the coercive force, notwithstanding its very 
considerable effect in changing the form of the cyclic curves and in improving the 
permeability. The curve from Ring VIII. in fig. 21 gives the relation of JH(iI to B 
in this final state. The corresponding curve for the ring in its previous state would, 
if drawn, be nearly coincident with this one. 
