PRECONTACT CONDUCTION CURRENTS. 
L. E. DODD. 
During some work 1 in which capacity measurements were 
made of plane conducting plates (silver films) in air at very 
short distances, the writer was able to take some incidental read- 
ings of small currents that passed between the plates when they 
apparently lacked several wave lengths of being in contact. 
Three sets of measurements were taken in one evening. Figure 
1 of figure 38 shows the electrometer deflection plotted with the 
time. The characteristic shape of the curves suggests an ex- 
ponential relation. This view is supported by the curves of 
figure 2 of figure 38 which give linear relations expressed by the 
equation, 
log D = k 2 t + b. 
(i) 
From (1), 
D=e b • e k 2 t = Do e k 2 t • 
(2) 
For the current, 
i = d t Q = C d t V = Cki d t D . 
(3) 
where k x is the electrometer constant. 
From (2) 
d t D = Do k 2 e k 2 t . 
(4) 
. Substitute (4) in (3), 
i = kik 2 CDo e k 2 t . 
(5) 
The potential gradient between the plates is 
p. g. = k,D/ d, 
where d is the distance of separation. 
In the curves of figure 3 of figure 38 the relation between i and 
p.g. appears to be linear. The straight lines as drawn include 
fhe origin. Since d was constant, within the reading limits of 
the apparatus, for the three cases, the x-values are proportional 
to Y, and thus Ohm’s Law seems to hold consistently. The 
slopes decrease in the order in which the sets of data were taken, 
showing that the resistance increases in that order. A factor 
known to be changing continually in one direction was the room 
temperature, but temperature readings were not taken at the 
Physical Review, Vol. V, No. 1, p. 78, Jan., 1915. 
