116 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
Experiment XL V. 
An annealed iron wire, '063 centim. in diameter, permanently twisted. 
Torsion in terms of a 
unit taken as the 
torsion in a wire 
1 centim. long 
when twisted through 
one revolution. 
Percentage of average temporary 
superior increase of resistance 
of twisted wire over untwisted 
for 1° C. between 20° and 100° C. 
+ signifies superior increase of 
twisted wire on rise of 
temperature. 
Percentage of average 
permanent decrease 
of resistance 
of twisted wire for 
1° C. between 
20° and 100° C. 
0-260 
+ -00474 
•00025 
1-090 
+-00421 
•00050 
2-180 
+-00092 
•00100 
The effect of permanent extension, of hammering, and of torsion on the alteration of 
resistance produced by change of temperature in the case of copper, of iron, and of 
other metals is shown in Tables XX., XXI., and XXII. 
Table XX.—Curves showing the effect of permanent extension on the temporary 
alteration of electrical resistance produced by change of temperature. 
In Table XX. the curves have their abscissae representing the average superior 
increase of resistance for a rise of 1° C. of the stretched wire on a scale of '000075 
