Torsion of Lead Wire beyond the Elastic Limit; 545: 
where W is measured in grams weight and ¢ in minutes. 
The values obtained from this curve are given in the last 
column. 
| | | Val 
ie t | Weight | pee 
| ae in minutes).| re dot / ¥ ge ) 
| | / iquation. | 
h m / | ) 
1450 | 0 Fost gee 7S: >| 
1 46°8 18 | 653 6447 | 642 | 
| 1 493 43 | 1056 | 5944 | 598 
1 521 71 | 1300 | 570-0 567 | 
1 54-7 ai | 148-08) epe0) 549 
| 1 575 i). GIF 588°3 533 
| 2 00 mo | Ie. | 5262 no | 
| 250 | 20 | 1909 | 5091 | 503 | 
| 2100 | 250 | 2056 | 494-4 488 
P2iso0 | sO | 2178 | 4827 476 
moo | 400 | 2368. -|--4682-|- -457- | 
| 2350 | 500 | 2520 | 4480 441 
| 2 45-0 60-0 2650 | 4350 499 | 
| 3 00 | ce |. 2690-1 4150 | 414 
3 150 | 90:0 2986 | 4014 | 401 | 
3 300 100 | 3120 | 3880 391 | 
3450 | 1200 | 3208 | 3792 9. 
4 00 . 1350 3298 | 3712 |. 374 | 
Here the variation from the equation nowhere amounts to 
2 per cent. Owing to reasons given before the first reading 
is again faulty, and with this exception the variation is little 
more than 1 per cent. In this case the curve is exponential 
to an axis = —1 and cuts the axis ¢=0 in the point W=713. 
If the curves had these equations then the couple and the 
stress would vanish after some days, since both the equations, 
represent curves cutting the ¢ axis at a finite distance. 
This experiment was afterwards extended to see w hat 
relation existed between the initial weight a and the constant 
k in the equation 
W =a—khk log (¢+1), 
or in the derived equation 
Bi oN 
GE 0, G41 
Initial weights of 600, 500, and 400 grams were used, and 
in each case an equation of ‘the above form approximately 
fits the experimental curve. In fig. 6 the curv es are those 
plotted from the equations. eae 
Phil. Mag. 8. 6. Vol. 8. No. 46. Oct, 1904, i Ch a 
