AND STRAIN ON THE ACTION OE PHYSICAL FORCES. 
117 
percentage of superior increase for each millimetre, and in Table XXI. the curves are 
drawn with their abscissae representing the average superior increase of resistance of 
the hammered wire for a rise of 1° C. on a scale of ’000025 percentage of superior 
increase for each millimetre. In both sets of curves the ordinates represent the 
percentage of permanent increase of length on a scale of ’25 percentage of increase of 
length for 1 millim. 
Table XXI.—Curves showing the effect of hammering on the temporary alteration 
of electrical resistance produced by change of temperature. 
For zinc the abscissae represent 10 times as much alteration of resistance as they do for the other metals. 
In Table XXII. the abscissae of the curves represent the superior increase of resis¬ 
tance of the twisted wire on a scale of "0005 percentage of superior increase for each 
millimetre, and the ordinates the amount of permanent torsion in terms of a unit taken 
as the torsion of a complete revolution in a length of 1 centim. on a scale of '025 unit 
for 1 millim. In all the tables a -f- sign before an abscissa signifies that the strained 
wire increases most on rise of temperature, and the values of these abscissae were deter- 
mined as follows Let — and — represent the ratios of the wire to be tested, and 
the comparison-wire at any two temperatures t and t f ; then the average percentage 
