1014 
PROFESSOR J. A. EWING- AND MISS H. G-. KLA.ASSEN 
IX. —Old tests made in JajDan of a Soft Iron Wire. 
Limits of H. 
Limits of B. 
Limits of I. 
jHdI. 
75-2 
15560 
1230 
10040 
26-5 
13700 
1090 
8690 
7-04 
11960 
951 
6590 
G-62 
11480 
913 
6160 
4-96 
10590 
842 
5560 
3'76 
8790 
699 
3990 
3-01 
7180 
571 
2940 
2-56 
5950 
473 
2190 
1-95 
8830 
304 
1160 
1-50 
1970 
157 
410 
None of the specimens tested at this time have given so low values of JHal for the 
higher cycles, though the values in Rings III. and V. are practically identical with 
those in the Japanese iron for cycles in which B is less than 4000. The superior 
magnetic softness of this wire (No. IX.) was further shown by the fact that its 
coercive force after strong magnetization was 1'75, whereas in all the rings now 
tested the coercive force exceeded 2. At least one other specimen of wire used in 
the Japanese experiments was as good. 
The comparison suggests a doubt whether all that is possible has yet been done by 
manufacturers of iron to produce a quality specially suitable for such uses as the con¬ 
struction of transformer cores. The conditions of manufacture which secure low 
hysteresis appear to be imperfectly known, or, at least, to be less generally recognized 
than electricians might wish. It must, however, be admitted that with respect to 
hysteresis losses under the comparatively low intensities of magnetization usual in 
transformers, the sheet iron of Rings III. and V. is very nearly as good as the wire 
tested in Japan. 
This will be apparent from fig. 21, where the values of |H dl are plotted in relation 
to B for all the rings, and also for the wire in question (No. IX.). The figure shows 
in a striking way the extent to which the dissipation of energy in a cyclic magnetizing 
process may vary in different specimens even of soft iron. 
To facilitate comparison, we also give a Table of Numerical Values of JITc/I, measured 
from these curves, for the various specimens of iron. 
