AND STRAIN ON THE ACTION OF PHYSICAL FORCES. 
105 
twisting a wire beyond the limits of elasticity would at all resemble the effect 
produced on the specific resistance by strain set up by the two former processes, a 
few experiments were made in which the wires having been secured at one end and 
stretched sufficiently to make them tight, were twisted more and more until they broke. 
Experiment XXXV. 
A wire of annealed zinc, 8 feet in length and “095 centim in diameter, twisted. 
Amount of torsion; 
the torsion of a complete 
revolution in a length 
of 1 centim. taken as 
unit =A. 
Total increase of 
specific resistance per 
cent, produced 
by the torsion =B. 
Ratio of B : A. 
•083 
+ •269 
3'24 
•167 
+ •546 
3-27 
•250 
+ •376 
1-27 
Experiment XXXVI. 
A wire of annealed iron, 8 feet in length and “092 centim. in diameter, twisted. 
Amount of torsion; 
the torsion of a complete 
revolution in a length 
of 1 centim. taken as 
uDit =A. 
Total increase of 
specific resistance per 
cent, produced 
by the torsion = B. 
— signifies decrease of 
specific resistance. 
Ratio of B : A. 
•080 
+ -394 
+ 4-93 
T60 
+ -195 
+ 1-22 
•240 
- -053 
-0-22 
•320 
- '076 
-0-24 
•800 
+ -413 
-0-52 
1-200 
+ '928 
-0-73 
1-600 
+ 1-454 
-0-91 
In Table XVII. are drawn a series of curves showing the changes produced by 
permanent torsion in the specific resistance of zinc, iron, copper, and platinum-silver. 
The abscissae in these curves represent the percentage alteration of resistance on a 
scale of “0125 to 1 millim., and the ordinates representing the torsion in terms of the 
torsion of a complete revolution in a length of 1 centim. of the wire taken as unit on 
a scale of '015 to 1 millim. 
MDCCCLXXXIII. 
P 
