598 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
§ 81. To examine further the state of instability which is reached by annealing in 
the magnetic field, the wire was again annealed with no load on it; then on cooling— 
Load. 
Magnetometer. 
0 
295 
1 
311 
0 
309 
1 kilo, on and off 
five times, then 
0 
309 
1 
311 
In this instance, perhaps because of slower cooling, the initial magnetism was much 
nearer its full normal value than in the last case, and a cyclic state was reached after 
a single application of the load. 
The wire was again annealed, by being heated to redness and allowed to cool very 
slowly. The reading was then 316, and the application of 1 kilo, raised it only to 
317. 
Finally the wire was again heated to redness, and cooled as quickly as possible (in 
air). The magnetometer reading was then exceptionally low, and the first application 
of load caused a great rise. 
Then, as before, successive applications and removals of 
1 kilo, gave on +, off — 
2 kilos, gave doubtful, scarcely visible effects, 
3 kilos, gave on —, off + 
4 kilos, gave on —, off 
§82. The same wire was again annealed, and the cycle 0 — 4 kilos. —0 was per¬ 
formed several times, until the changes of magnetism became cyclic. Observations 
were then taken during the cycle 0 — 4 — 0 which gave the curves a b c d a of Plate 62, 
fig. 38. Then the same cycle was repeated, with vibration of the wire before each 
observation, and the curves ef g h e were obtained. Finally, starting at e, the cycle 
0 — 4 — 0 was again performed twice without vibration. This gave the curves 
eij Icl m n o. 
These observations confirm what has been already said as to the existence of a 
maximum point near the zero of stress in the effects of stress on the magnetism of 
annealed iron. The maximum, which had been obliterated by hysteresis in the cycle 
abccl a appears again in the vibration curves, and is again seen to disappear when 
the process of loading and unloading is resumed, without vibration. The curves 
ijklmno show the manner of this disappearance very plainly, and support the 
conclusions of § 78. A few more repetitions of the cycle would restore completely a 
