6 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
The above statements apply in a greater or less degree to all the metals employed, 
but it will suffice perhaps to give in illustration some experiments with iron and copper 
wires. The pan employed in all these investigations weighed 2 kilogs., and, except 
in one or two instances which will be mentioned, was never detached from the wire. 
In the following experiments a + number will signify an increase, and a — number a 
decrease of length. In all cases the readings are given in half-millims., and the weight 
of the pan is not included in the estimate of the load. 
The following series of experiments was made with an iron wire (+62 millirn. in 
diameter:— 
Experiment I. 
A weight of 12 kilogs. was put upon the pan and had the effect of permanently 
elongating the wire about 1 per cent. The scale and vernier were now fixed to the 
wires and the following readings taken :— 
No. of kilogs. on pan. 
Beading of scale. 
Alteration of length. 
Mean values. 
12 
SOTO 
0 
570 
-24-40 
1 
12 
30-50 
+ 24-80 
V 24-35* 
0 
6-20 
-24-30 
J 
8| 
21-18 
0 
5-08 
-16-10 
1 
8 
21T5 
+ 16-07 
> 16-10 
0 
5-02 
-16-13 
j 
4 
13-00 
+ 7-98 
1 
0 
5-08 
- 7-92 
V 7-95 
4 
13-02 
+ 7-94 
J 
It appears therefore that the first 4 kilogs. would produce an alteration of 7‘95, 
the second four of 8'15, and the third four of 8’25 divisions of the scale. 
* Tlie + numbers are never taken in estimating tbe mean of the values of the alterations produced 
by the largest weight, in order to avoid the effect of permanent set. 
| Scale slightly shifted by accident. 
