AND STRAIN ON TITE ACTION OF PHYSICAL FORCES. 
25 
Experiment XV. 
A copper wire was elongated by 10 per cent., and when vibrated gave the following 
results :— 
Number of minutes 
after stretching. 
Time of vibration. 
Seconds. 
1 
4-348 
11 
4-337 
120 
4-330 
1440 
4-316 
Experiment XVI. 
An iron wire about 4-| feet long received 50 turns of permanent twist and was then 
tested :— 
Number of minutes 
after toreion. 
Time of vibration. 
Seconds. 
1 
3-0415 
180 
3-0200 
1440 
3-0000 
Experiment XVII. 
A copper wire about 4|- feet long received 50 turns of permanent twist and gave 
the following results :— 
Number of minutes 
after torsion. 
Time of vibration. 
Seconds. 
1 
4-615 
2 
4-500 
5 
4-488 
1440 
4"444 
Experiment XVIII. 
The time of vibration of a copper wire which had suffered no permanent torsion 
was, when vibrated through a small arc, 6*242 seconds, and when started with a twist 
of three revolutions* 6*316 seconds, there being thus a difference of *074 second. 
The wire was now subjected to 100 turns of permanent torsion, and in a few minutes 
* Only 19 vibrations were counted in eacb trial, so that the amplitude of vibration might not be 
diminished too much. 
MDCCCLXXXIII. 
E 
