RESEARCHES IN MAGNETISM. 
541 
reading was taken. The following corresponding values of 43 and 93 are reduced from 
the observations ; they are also exhibited graphically in Plate 58, fig. 5. 
Annealed Iron Wire, Plate 58, fig. 5. 
Current in 
magnetising 
solenoid,— 
galvr. reading. 
A 
Magnetometer 
reading. 
SB. 
fi. 
Current in 
magnetising 
solenoid,— 
galvr. reading. 
A 
Magnetometer 
reading. 
SB. 
Current in 
magnetising 
solenoid,— 
galvr. reading. 
A 
Magnetometer 
reading. 
SB. 
0 
0 
0 
0 
9 
0-32 
1 
41 
128 
11-5 
- 0-41 
342 
14,140 
9 
0-32 
-348 
-14,390 
24 
0-85 
4 
165 
194 
23 
- 0-81 
329 
13,600 
19 
067 
-339 
-14,010 
39 
1-38 
10 
413 
299 
31 
- 1-10 
318 
13,150 
29 
102 
-327 
-13,520 
59 
2-18 
28 
1,460 
670 
41 
- 1-45 
295 
12,200 
39 
1-38 
-306 
-12,650 
79 
2-80 
89 
3,680 
1310 
51 
- 1-80 
263 
10,460 
49 
1-73 
-274 
-11,330 
99 
3-50 
175 
7,230 
2070 
62 
- 2 20 
166 
6,860 
59 
209 
-195 
- 8,060 
119 
421 
239 
9,880 
2350 
71 
- 2-51 
70 
2,890 
69 
2-44 
-103 
- 4,260 
139 
4-92 
279 
11,540 
2350 
81 
- 2-87 
- 12 
- 496 
79 
2'80 
+ 4 
165 
159 
5-63 
304 
12,570 
2230 
91 
- 3-22 
- 83 
- 3,430 
86 
304 
58 
2,400 
189 
669 
327 
13,520 
1020 
101 
- 3-50 
-142 
- 5,870 
99 
3-50 
130 
5,370 
239 
8-46 
348 
14,390 
1700 
121 
- 4-28 
-226 
- 9,340 
114 
4-03 
199 
8,230 
289 
10-23 
359 
14,840 
1450 
141 
- 4-99 
-278 
-11,490 
140 
4-96 
279 
11,530 
342 
12-11 
365 
15,090 
1250 
162 
- 5-73 
-306 
-12,650 
190 
6-72 
332 
13,720 
441 
15-61 
373 
15,420 
990 
211 
- 7-47 
-338 
-13,970 
240 
8 50 
351 
14,510 
574 
20-32 
378 
15,630 
770 
261 
- 9-23 
-352 
-14,550 
291 
10-30 
362 
14,970 
629 
22-27 
380 
15,710 
705 
312 
-11-05 
-361 
-14,920 
339 
12-00 
368 
15,210 
464 
16-42 
379 
15,670 
411 
-14-55 
-369 
-15,250 
340 
1204 
374 
15,460 
239 
8-46 
375 
15,500 
511 
—1809 
-373 
-15,420 
579 
20-50 
381 
15,750 
139 
4-92 
372 
15,380 
652 
-23-08 
-376 
-15,550 
630 
22-30 
383 
15,830 
89 
3-15 
369 
15,270 
536 
-18-94 
-376 
-15,550 
0 
0 
353 
14,590 
39 
1-38 
363 
15,010 
411 
-14-55 
-376 
-15,550 
0 
0 
350 
14,470 
311 
-11-01 
-375-5 
-15,530 
211 
- 7-47 
-375 
-15,500 
111 
- 3 93 
-372 
-15,380 
61 
- 2-16 
-368 
-15,210 
23 
- 0-81 
-361 
-14,930 
11-5 
- 0-41 
-358 
-14.800 
0 
0 
-352 
-14,550 
The figures show that the wire of this experiment, although less susceptible than 
the last to low values of the magnetising force, took a greater magnetisation with high 
values of the force. But the most notable feature of this experiment is the enor¬ 
mously great amount of residual magnetism which this wire retained when the 
magnetising force was completely withdrawn. On the positive side the residual was 
92 per cent, of the induced magnetism, and on the negative side 92‘5 per cent. Its 
absolute value is very remarkable. 93=14,500 (the residual value) corresponds to an 
intensity of magnetism (3) of 1150 c.g.s. units of moment per unit of volume. Great 
as this is, it was even slightly exceeded in another experiment with the same wire, in 
which 93 per cent, of the induced magnetism remained after the magnetising force 
was removed, giving a residual intensity of 1200 c.g.s. units of moment per unit of 
volume. So far as I am aware no steel magnet ever holds so much magnetism as this. 
In fact, if by retentiveness we mean simply the faculty of remaining magnetic when 
magnetising force is removed, and in the absence of mechanical or other disturbance, 
soft iron is far more retentive than either hard iron or steel. 
§ 22. One more example may be given of the application of a complete magnetising 
MDCCCLX XXV. 4 A 
