34 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
Experiment XX V. 
Iron wire about 8 feet in length and ‘13 centim. in diameter. 
Observations. 
Time of 
vibration. 
Current. 
Total 
percentage of 
diminution 
of rigidity 
caused by the 
current. 
Percentage of 
diminution 
of rigidity 
produced by 
heating effect 
of current. 
Percentage of 
diminution 
of rigidity 
produced by 
the current 
proper. 
Seconds. 
4T53 
0° 
4197 
65°-8 
2-10 
1-30 
•80 
4-155 
0° 
2-00 
1-30 
•70 
4-207 
68°-2 
2-48 
1-60 
•88 
After three days’ rest . . . 
4-180 
0° 
4-177 
28°-5 
•14- 
•05 
T9- 
4-191 
46° 
•52 
•25 
•27 
After three days’ further rest . 
4-161 
0° 
4-252 
71° 
4-34 
2-05 
2-19 
After three days’ further rest . 
4-164 
0° 
4-164 
16°-3 
0 
Experiment XXVI. 
A piece of the same kind of iron wire as that used in the last experiment, about 
35 centims. in length, was placed in the axis of a magnetizing helix, 30 centims. in 
length; the helix consisted of 1,200 turns of copper wire - 2 \th of an inch in diameter, 
wound round a glass tube of 3 centims. inner diameter and 3 centims. thickness. 
Time 
of vibration. 
Temperature 
of wire. 
Current. 
Total percentage 
of diminution 
of rigidity caused 
by the magnetizing 
current. 
Percentage 
decrease due to 
heating effect of 
the current. 
Percentage 
decrease of rigidity 
due simply to 
magnetization. 
Seconds. 
° C. 
1-739 
10 
0 
1-743 
16 
80 
•46 
•28 
•18 
1-722 
14 
0 
2-42 
•07 
2-35 
Several other experiments of the same kind as the last were made with different 
magnetizing helices and current strengths, and all seemed to show that slight temporary 
diminution of rigidity is produced by high magnetizing force; but that magnetizing 
forces small in comparison with that indicated in the last table, and yet sufficient to 
cause very sensible magnetization, produced no sensible effect. The vibrations were 
counted for at least half an hour in each determination, and an initial arc of 10° of 
torsion was employed in all cases. The percentage decrease of rigidity produced by 
