540 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
to —17*26, reversed again to + 17*26, reduced to 0, and restored to +17*26, all by 
steps. At the beginning of the operation the wire had a small amount of initial 
magnetism, which was determined by sliding off the induction coil. 
Very Soft Annealed Iron Wire, Plate 57, fig. 4. 
A 
SB. 
A 
SB. 
>5. 
SB. 
A 
SB. 
0 
166 
(initial) 
0-05 
166 
- 0-05 
10,970 
0-05 
-10,795 
0-05 
10,845 
019 
183 
- 019 
10,790 
0-19 
-10,620 
0-19 
10,850 
0-37 
216 
- 0-37 
10,460 
0-37 
-10,268 
0-57 
10,860 
0-71 
393 
- 0-71 
9,530 
0-71 
- 9,270 
0-71 
10,890 
1-08 
941 
- 1-08 
7,360 
1-08 
- 6,780 
1-08 
10,930 
1-84 
4,088 
- 1-84 
20 
1-84 
- 642 
1-84 
11,040 
3-30 
8,684 
- 3-30 
- 7,840 
3-30 
8,190 
3-30 
11,480 
5-62 
11,380 
- 5-62 
-11,100 
5-62 
11,270 
5-62 
12,210 
7-63 
12,320 
- 7-63 
-12,080 
7-63 
12,170 
7-63 
12,650 
10-54 
12,950 
-10-54 
-12,690 
10-54 
12,770 
10-54 
13,040 
14-19 
13,280 
-1419 
-13,030 
14-19 
13,110 
14-19 
13,300 
17-26 
13,450 
-17-26 
-13,190 
17-26 
13,280 
17-26 
13,440 
14-19 
13,370 
-14-19 
-13,110 
14-19 
13,220 
10-54 
13,250 
-10-54 
-13,000 
10-54 
13,100 
7-63 
13,100 
- 7-63 
-12,900 
7-63 
12,940 
5-62 
12,970 
- 5-62 
-12,800 
5-62 
12,830 
3-30 
12,680 
- 3-30 
-12,520 
3-30 
12,570 
1-84 
12,240 
- 1-84 
-12,080 
1-84 
12,150 
1-08 
11,850' 
- 1-08 
-11,700 
1-08 
11,790 
0-71 
11,590 
- 0-71 
-11,430 
0-71 
11,510 
0-37 
11,277 
- 0-37 
-11,130 
0-37 
11,200 
0-19 
11,100 
- 0-19 
-10,970 
0-19 
11,030 
0-05 
11,000 
- 0-05 
-10,820 
0-05 
10,880 
0 
10,980 
0 
-10,800 
0 
10,840 
Here the residual magnetism is 82 per cent, of the induced magnetism, both on the 
positive and on the negative side. An opposite force of about —1*9 serves to remove 
it completely. The general form of the curves in fig. 4 should be noted, since, as 
many other experiments have shown, this is a thoroughly typical example of the 
behaviour of annealed iron. 
§ 21. In the next example the method of experiment was different. The magne¬ 
tising force was varied continuously and very slowly by means of the liquid slide 
described in § 18, occasional pauses being made to allow current and magnetometer 
observations to be taken. The magnetisation was measured by the direct magneto¬ 
metric method of § 18. The wire was a piece of moderately soft iron, well annealed, 
of 0*077 centim. diameter, and 30*5 centims. or 400 diameters in length. The 
magnetising force was raised to 22*3, reversed to —23, and restored to +22‘3, all very 
gradually. Whenever, as was frequently the case, the magnetometer deflection 
appeared to be creeping up or down after the alteration of magnetising force had 
ceased, time was given to allow the magnetisation to become sensibly steady before a 
