104 
ON THE MEASUREMENT OF MAGNETIC HYSTERESIS. 
II. 
B. 
h. 
Pole. 
H. 
B. 
h. 
Pole. ' 
10-67 
9850 
•00839 
N. 
- 0-59 
4250 
■ 00587 
N. 
9-44 
9675 
•00810 
N. 
- 1-13 
3800 
-00610 
N. ! 
8-30 
9465 
•00757 
N. 
i - 2-36 
1900 
•00590 
N. 1 
7-12 
9204 
•00676 
N. 
- 2-88 
730 
•00460 
N. i 
5 • 95 
8800 
•00575 
N. 
- 3-52 
- 850 
•00238 
S. ! 
4 • 65 
8320 
•00446 
N. 
- 4-05 
-2200 
•00120 
s. 
3-52 
7590 
•00344 
N. 
- 4-65 
- 3480 
•00023 
s. 
2-88 
7190 
•00323 
N. 
- 5-95 
-5370 
- -00119 
s. 
2-36 
6820 
•00338 
N. 
- 7-12 
-6680 
- -00276 
s. 
1-13 
5900 
•00440 
N. 
- 8-30 
-7950 
- -00450 
s. 
0-59 
5450 
•00486 
N. 
- 9-44 
-8900 
- -00630 
s. 
0 
4900 
•00559 
N. 
-10-67 
- 9850 
- -00839 
s. 
As B diminishes from 9850, h diminishes to a minimum at B = 7200, and then 
increases to a maximum at B = 3000 ; after this it passes to its greatest negative 
value corresponding to B = —9850 without jDassing through a maximum or minimum. 
As B increases again to 9850, h goes through a similar set of changes, its values from 
B = 7000 to 9850 differing’ hut little from those which it had when B was diminishing. 
From B = 9850 to 4700, h is less than 2BA/47rF, and from B = 0 to B = — 3800, 
h has the opposite sign to B. Both these cases require that there should he “ poles ” 
on the wire between the centre and the ends, with signs opposite to those of the 
poles at the ends of the wire. Our arrangement of apparatus was not well adapted 
for detecting these subsidiary poles, since the magnetic force due to a uniformly 
distriljuted pole would be at right angles to the wire, and therefore parallel to the 
magnetic meridian, thus producing no deflexion of the search compass. Still we were 
able to verify the conclusion when B was —3480, for though the corresponding 
S-magnetism appeared at the eastern portion of the wire, being most concentrated at 
a point about 7 centims. from the end, yet we found a weak N-pole at 9 centims. from 
the same end. 
From the areas of the curves we found 
J’HdB = 102100, j/nZB = 72’3, J/n/H = MIS. 
These experiments add empliasis to Mr. Lamb’s remark that “ the magnetometric 
method [of determining I—H curves], although extremely useful for comparative 
work, must he used with much caution in determinations of an absolute character.” 
\_Dece 7 y 1 her 23, 1901.—C. Benedicks (‘Annalen der Physik,’ 1901, vol. 6, p. 726) 
compared the B—H curve for a cylinder of steel with the curve for au ellipsoid formed 
out of the same piece of metal, and deduces that, as B increases, li rises to a maximum 
and then rapidly decreases, as in our fig. 18. From Ewixg’s experiments (‘Phil. Trans.,’ 
1885, pp. 532, 535) on (1) a ring, (2) straight pieces of iron wire, Ite deduces the same 
result. Neither experimenter, however, reached the minimum of /u] 
