Torsion of Lead Wire beyond the Elastic Limit. 549° 
III. Stretching. Recovering. 
Time zt | Reading. || Time. | t. Reading. 
oe ee EE EEE Ee ol } = ee — 
m h m hi tm “>| he mm 
25 0 0 2°90 LZ | 21 O 16°80 
26 Ort o' 22 He by Ze, | OP 16:57 
27 | 0 2 Foose aod ee oto 16°48 
29 O 4 Seah ODS WW ete 16°41 
31 O 6 3°69 bowel 21 6 16°29 
oo 0 8 381 | 1234 |; 2 9 16:20 
35 O 10 391 ae as 7 O1-12 16°14 
Ok 12 +01 | 12 43 21 18 16°05 
a4 | 018 4:17 1 TAA |) E44 15°98 
a 49 | O 24 4°33 Hic Ze 21 36 15°87 
3 5D 0 30 59 || Jom | 92 0 15°74 
Next day | | 1 46 22 21 1567 
9 36 | 18 11 17'56 ers 7 oF 12, / 15°50 
| i 12 20 47 19°36 
is | 21 0 1950 | | | 
In all three cases the wires were stretched from zero on 
the scale, and the variation in immediate extension (2°70, 
2°74, 2°90) may probably be accounted for by the wires 
being in slightly different states of extension at the beginning 
of the determinations. | 
It will be noticed from the curves:— 
(1) That the immediate or primary recovery is in each case 
practically equal to the immediate or primary stretch. 
ee). 2-645 Li, 2-74,.2°64:> TIL 2:90, 2:70.) 
(2) That after the first hour the curve of extension with 
time is practically a straight line, and points to a purely 
viscous flow. 
(3) That after release the curves in all three cases are of 
the same shape, and practically coincide if superposed. 
It therefore appears that either all the energy is stored 
within the first hour, or that after that time the rate of loss is 
equal to the rate of gain of energy. The immediate or 
primary stretch is apparently purely elastic, since the wire, if 
stretched and released, practically returns to its original 
leneth. This elastic property is retained throughout, since 
the primary recovery is constant and independent of the time. 
Then follows what appears to be a stretch partly elastic and 
partly viscous, and after a certain time the stretch is purely 
a viscous flow, indicated by the curve being a straight line. 
The gradual or secondary recovery which takes place on 
removal of the load is apparently in correspondence with that 
part of the gradual stretch which is non-viscous—the 
secondary strain. : 
