Voi,. 7, 1921 
PHYSICS: P. W. BRIDGMAN 
301 
the abscissae are current densities in 10 6 amp. /cm 2 . The specimens varied 
in breadth from 0.06 to 0.22 mm. There was no correlation between 
the results and the breadth, although the microphone effect has a very 
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FIG. 2 
strong connection. The results are scattering, but perhaps not more 
than would be expected when the magnitude of the current densities and 
the fact that different samples of gold leaf may differ in specific resistance 
by a factor of 2 or more is considered. 
The curve drawn through the observed points is taken as the best 
mean of the experimental results. Let us denote the equation of this 
curve by <p(%). Then the departure from Ohm's law is given by the 
expression f <p(x)dx/x. This will be proved in the detailed paper. This 
integral may be calculated graphically from the observed points. 
In figure 3 is given the departure from Ohm's law, calculated in this 
way, for gold of two thicknesses and for silver. The departure is posi- 
tive, that is, the resistance is greater at high density. For thin gold 
and silver the departure rises to something of the order of 1% at a density 
of 5 X 10~ 6 amp. /cm 2 ; for the thicker gold it is greater. It was not possible 
to reach as high current densities in the thick as the thinner gold. The 
accuracy is greatest for thin and least for thick gold. 
