558 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
Induced and Residual Mao-netism in Soft Iron, Plate 60, fig. 17. 
O ' ' O 
■6. 
SB 
induced. 
S3 
residual. 
Ratio of 
33 residual 
to 
SB induced. 
1-34 
413 
165 
0-400 
3-33 
6,690 
5,660 
0-846 
4-88 
11,910 
10,790 
0-906 
6-80 
14,060 
13,060 
0-921 
8-43 
14,800 
13,640 
0-922 
13-74 
15,670 
14,550 
0-926 
22-37 
16,080 
15,010 
0-933 
The ratio in this example is slightly greater than I ever observed it in other cases, 
though values of 0‘87 and even O^O were not uncommon, and in one other example 
0'92 was exceeded. It appears to be approaching a maximum. In many other 
instances, which will be cited below, this maximum was actually passed, by using 
sufficiently great magnetising forces. 
§ 38. The series of double loops described in § 35, and shown in fig. 15, give another 
set of values of residual and temporary magnetism corresponding to a greater set 
of values of <§, in an annealed iron wire (length =29 centims., diameter = 0'078 centim.). 
The following are the values they yield of <§, 3 (induced) and the ratio of the residual 
to the induced value of 3- The figures given refer to the positive side of the 
diagram. 
Induced and Residual Magnetism in Soft Iron, Plate 60, fig. 15. 
A 
3 
induced. 
Ratio of 
residual to 
induced. 
1-50 
157 
0-651 
1-95 
304 
0-781 
2-56 
473 
0-824 
3-01. 
571 
0-842 
3-76 
699 
0-837 
4-96 
842 
0-836 
6-62 
913 
0-825 
7-04 
951 
0-805 
26-5 
1090 
0-753 
75-2 
1230 
0-683 
Here a distinct maximum is passed, when the ratio is about 0'84, after which it falls 
very considerably as the magnetising force is strengthened. 
§ 39. As an example of the ballistic method the case may be cited of a ring of iron 
wire 0'248 centim. in diameter, the diameter of the ring being 8’3 centims. The 
following values were obtained :— 
