a e 
Torsion of Lead Wire beyond the Elastic Limit. 541 
taken 3°3 minutes later. The amount of the twist was 360°, 
and the couple was measured as the mean of the two de- 
flexions on AA. The curve obtained is shown in fig. 2, and 
to it was fitted the equation 
(4¥=28°3—12°9 log ¢, 
where ¢ is measured in hours and G in divisions of scale. 
The values obtained from this equation are given in the last 
column. 
. DEFLEXIONS. | . 
| dS Sra ue — Value 
t / e & | from 
Time. (in hours). | I. (zero= +09). IT. (zero= + 0°5). Mean. | Equa- 
| Re. eisai : Fe | tion. 
Reading. Corrected. | Reading. Corrected. 
h m | 
115 UV 
1 18:3 0:055 45°0 44-5 44-0 43°5 44:0 | 448 
1235 | 0125 41-2 40:7 40:0 39°5 40°1 40:0 
1 26-4 0-190 dk | 386 377 372 379 | 376 
1 31-0 0:267 302 36°7 360 30°D 36°1 30°7 
1 367 0°361 39°6 30°1 34°2 33°T 34°4 34-2 
1 41°1 0435 | 344 33°9 33'0 325 33°22 33'0 
1 465 0°525 33°2 32°7 31°8 313 3270 | 31°9 
olf 0-611 32-2 31-7 31:0 30°5 31-1 31-1 
1565 |' 0691 314 | 309 30°2 29°7 303 30°5 
2 56 0°843 30°3 298 | 293 28°8 29°3 29;2 
2 16°8 1:03 29-2 | 28°7 28:0 27°5 28°1 28°1 
2 29°7 1-24 28°0 27°5 26°8 26°3 269 | 27-1 
2 39°8 141 272 26°7 260 25°5 26:1 26°4 
a 1:6 1-78 25°7 25°2 24°7 242 | 247 | 251 
3 18-2 2°05 24-9 24-4 23°5 23°0 23°7 24°3 
3 46°7 2°53 23°5 230 | 223 21°8 pepe 23°1 
4 20°5 3°09 225 22:0 21°3 20°8 214 |) 220 
Next day 
9 44 20°48 97 9°2 85 8-0 8°6 
1 53 24°6 tie |) (109. 100 9°5 10-2 jy) 104 
4 6 26°8 Mis |. 102 Fos, | 9:0 96 98 
With the exception of the reading at 9-44 all these points 
lie very approximately on the curve of the equation given. 
This particular reading is faulty owing to the fact that over- 
night the wire was left under the action of a couple 21-4, 
and became twisted some eight or nine degrees more than 
360° in consequence. On the sudden release to 360° the 
restoring couple appears to be less than would be the case at 
the same time had the twist been kept constant throughout 
the night. The two further readings on the second day, 
during which the wire was again kept at constant twist, are 
