AND STRAIN ON THE ACTION OF PHYSICAL FORCES. 
11 
part is evidently due to the influence of mere rest; this is best shown by taking the 
differences between consecutive + or — alterations for the different times. 
It will also be observed that the fl- and — values both here and in the experiments 
on iron gradually become equal under the influence of rest and loading and unloading. 
Cases of aluminium and zinc. 
With these metals"' both the maximum temporary increase of length, caused by 
putting on weight, and the recovery on the removal of stress, are attained slowly in 
comparison with most metals. An illustration of this is afforded in the next experi¬ 
ment, which was made on an aluminium wire. 
Experiment VII. 
No. of kilogs.f 
Reading of scale. 
No. of minutes after 
putting on or taking off 
load. 
Alteration of length 
in kalf-millims. 
0 
1-4 
6 
18-9 
P7 
+ 17-5 
19-2 
3-0 
+ 17-8 
19-5 
5-0 
+ 18-1 
19-8 
87 
+ 18-4 
20-1 
12-0 
+ 18-7 
20-4 
18-0 
+ 19-0 
207 
26-3 
+ 19-3 
20-8 
30-0 
+ 19-4 
0 
4-4 
•5 
-16-4 
37 
1-5 
— 17 1 
3-4 
6-0 
-17-4 
3-0 
25-0 
-17-8 
1-9 
1440-0 
-18-9 
6 
19-0 
1-0 
+ 17-1 
19-3 
3-0 
+ 17-4 
19-6 
5-0 
+ 17-7 
19-9 
10-5 
+ 18-0 
20-2 
18-0 
+ 18-3 
20-5 
26-0 
+ 18-6 
20-8 
40-0 
+ 18-9 
21-1 
52-0 
+ 19-2 
21-15 
60-0 
+ 19-25 
0 
4-35 
1-0 
-16-80 
3-00 
30-0 
-18-15 
2-20 
1440-0 
-18-95 
It must be observed that during the whole of this time the comparison-ware was 
loaded with a permanent weight equal to that on the wire which was being tested, 
* Probably tin and lead if they had been loaded sufficiently would have also behaved in this manner; 
it was impossible, however, to use any but very light weights in determining their elasticity, as otherwise 
permanent set would always have been produced. 
t A weight of 4 kilogs. was kept permanently on the scale-pan. 
C 2 
