240 
PROFESSOR J. A. EWING AND MR, W. LOW ON THE 
Table XII.— Hadeield’s Manganese Steel. 
Outside field. 
35 — outside field 
47r 
outside field’ 
1930 
2,620 
55 
1-36 
2380 
3,430 
84 
1-44 
3350 
4,400 
84 
1-31 
5920 
7,310 
111 
1-24 
6620 
8,970 
187 
1-35 
7890 
10,290 
191 
1-30 
8390 
11,690 
263 
1-39 
9810 
14,790 
396 
1-51 
§ 34. The figures in the last two columns of Tables XI. and XIL show as much 
regularity as can be expected, when it is borne in mind that they depend upon the 
small differences between two large quantities which had to be separately measured. 
The two sets of results agree well. They show that the permeability of manganese 
steel is, as nearly as may be judged, constant from fields of 2000 to 10,000 units, 
with a value approximating to 1 ’4 in this sample. It follows from this that, notwith¬ 
standing the excessive resistance which this material opposes to being magnetised, a 
respectably high intensity of magnetisation wall be produced by the application of a 
sufficiently strong force. In the second experiment 3 was raised to nearly 400. It 
is very remarkable that scarcely any of this magnetisation remains wdien the force is 
withdrawn. One might have expected that a material which resists magnetisation so 
strongly would possess much coercive force. In fact, however, the residual magnetism 
(which was determined in the second sample in the usual way, by slipping off one of 
the iron cones along with an induction coil) was so small that it scarcely admitted of 
measurement by the apparatus which served to measure the induced magnetism. After 
applying the strongest field the value of the residual induction 5?*- w^as only about 30. 
It is well kuown that with ordinary iron and steel the magnetisation wholly, or almost 
wholly, disappears when the magnetising force is withdrawn, provided the force is less 
than a certain amount. This elastic stage in the process of magnetisation, the limits 
of which are exceedingly naiTow in soft wrought iron, but somewhat wider in hard 
iron, common steels, and nickel, seems to extend, iu manganese steel, up to the 
strongest force we have been able to apply. 
Nickel. 
§ 35. Two specimens of nickel, supplied by Messrs. Johnson and Matthev, have 
been tested. The first was cut from a bar previously used in examining the perme¬ 
ability of nickel when in a state of compression under the action of ordinarily weak 
