MAGNETISATION ON THE THERMOELECTRIC QUALITY OF IRON. 
375 
“demagnetising by reversals” before the magnetisation, whose effects were to be 
observed, was began; whereas in figs. 28-30 the molecular instability to which 
hysteresis in loading has given rise is being overcome by the first magnetisation, and 
this is causing changes of thermoelectric quality which are superposed on what may 
be calfed the normal variation due to magnetism. In the experiments of figs. 23-26 
the process of “ demagnetising by reversals ” was resorted to, after each load was on 
the wire, not for the purpose of removing magnetism (since there was none to remove), 
but in order to produce a molecular commotion by which this state of instability 
should be destroyed, and the reminiscence of previous stresses be dissipated. 
§ 38. To illustrate more fully the effect of the process of “ demagnetising by 
reversals,” an experiment was made whose results are set forth in fig. 31, Plate 23. 
After loading in the usual manner (the wire being free from all residual magnetism, 
and exposed to no magnetic field), up to 2 kilos. (Curve ab, fig. 31), the process of 
demagnetising by reversals was gone through while the load was kept constant. The 
E.M.F. fell in the process from 11*2 to 5'35 microvolts (be, fig. 31). Then loading 
was continued, up to 4 kilos., giving the Curve cd; and at 4 kilos, the process of 
reversals was again performed, causing a fall of E.M.F. from 5'75 to — 0'5 microvolt. 
Further loading (up to 6 kilos.) gave the Curve ef, and the process of reversals gave 
the fall fg: further loading gave the Curve gh, and so on, the process of reversals 
being applied at 8, 10, and 12 kilos. Similarly, at each step of 2 kilos, on the “ off” 
curve, the process of reversals was applied with results which (along with those of the 
intermediate unloadings) are shown in the figure by dotted lines. As the figure is 
somewhat involved, the observed deflections and the values of E.M.F. calculated from 
them are given numerically below :— 
Load. 
Galvanometer 
deflection. 
E.M.F. 
Load. 
Galvanometer 
deflection. 
E.M.F. 
kilos. 
microvolts. 
kilos. 
microvolts. 
0 (after reversals) 
165 
97 
11 
4 
+ 0-25 
1 
191 
11-2 
10 
- 18 
-1-05 
2 
191 
11-2 
After reversals 
- 27 
-1-25 
After reversals 
91 
5-35 
9 
- 55 
-3-25 
3 
109 
6-4 
8 
- 80 
-47 
4 
98 
575 
After reversals 
- 70 
—47 
After reversals 
- 8 
-0-5 
7 
- 83 
-4-85 
5 
+ 15 
+ 0-9 
6 
- 90 
-53 
6 
+ 11 
+ 0-65 
After reversals 
- 56 
-33 
After reversals 
-50 
-2-95 
5 
- 78 
—46 
7 
-28 
-1-65 
4 
- 75 
-4-4 
8 
-32 
-1-9 
After reversals 
- 22 
-1-3 
After reversals 
-80 
-47 
3 
- 17 
-1-0 
9 
-47 
-2-8 
2 
+ 7 
+ 0-4 
10 
-20 
—115 
After reversals 
+ 70 
+ 47 
After reversals 
-34 
-2-0 
1 
+ 61 
+ 3-6 
11 
- 2 
-o-i 
0 
+ 93 
+ 575 
12 
After reversals 
+ 34 
+ 21 
+ 2-0 
+ 1-25 
After reversals 
+ 143 
+ 87 
Temperatures, 144° C. and 17° C. 
