588 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
the cycle (12-66 kilos.) and at a steep part of the off curve (2 kilos.). The results 
were as follows :— 
Load. 
Magnetometer. 
11 
188 
1178 
186 
12-22 
184-7 
12-66 
183 
12-57 
183 
12-46 
183 
12-22 
183-1 
11-78 
184 
11 
185 
10 
186-7 
9 
188-5 
8 
190 
Load. 
Magnetometer. 
7 
191 
6 
192 
5 
189 
4 
183-6 
3 
172-6 
2 
155-7 
2-09 
155-7 
2-20 
155-8 
2-44 
156-1 
2-87 
157-8 
&c. 
&c. 
These three observations are plotted in Plate 62, fig. 35. The results render the 
conclusion very probable that, if we call 3 the magnetism and P the stress, is 
initially zero when the change of stress is altered in sign (from loading to unloading, 
or vice versa), provided the operation be performed without mechanical disturbance. 
§ 76. In all the above experiments on the effects of stress (§ 71 to § 75) the same 
wire was used—a wire which had been previously stretched beyond its limit of 
elasticity. To examine the effects of stress within the limit of elasticity on the 
magnetism of iron in the annealed state, and to trace the changes which occur during 
the passage from the annealed to the hardened state when the stress is carried up 
to and beyond the limit of elasticity, the following series of observations were made 
(March 3-4, 1882) with another piece of iron wire cut from the same bundle as the 
last. As before, the magnetising field 0‘34 was in operation throughout. 
The wire, after being hung in the vertical position behind the magnetometer which 
it was to occupy during the experiment, was annealed twice,—once with a small 
amount of weight hanging from it, which served to straighten the wire when it 
was heated to redness, and a second time after this weight had been removed. A 
weight of 1 kilo, was then applied and removed several times, during which the 
magnetisation rose somewhat. When the effects became cyclic the following readings 
were taken. As before, the magnetometer readings are proportional on an arbitrary 
scale to the total magnetism of the piece. 
Load. 
Magnetometer. 
0 
291 
1 
292 
0 
291 
1 
292 
