410 
MK. W. R. CARR ON THE LAWS GOVERNING 
For example, the pressures at which discharge took place with an applied potential 
ol 1800 volts were, for the ditferent distances between the electrodes, approximately; 
Distance between electrodes 
in millims. 
1 
•7 
3 
5 
10 
Discharge pressures in millims. 
of mercury. 
1-05 
•536 
•351 
•216 
•105 
and it will be seen that the numbers in Column II. are almost exactly in inverse 
proportion to the numbers in Column I. 
Again, with an applied potential of 500 volts (say), the approximate j^ressures at 
which discharge occurred were : 
Distance between electrodes 
in millims. 
1 
2 
3 
5 
10 
Discharge pressures in millims. 
of mercury. 
2-35 
1-30 
•804 
•517 
•259 
where the pressures are in the ratio COO : -55 : -34 : -22 : ’ll, numbers which are 
again very nearly Inversely proportional to the distance between the electrodes. 
Furthei, we notice that the sjjark potential corresponding to the critical pressure 
in all cases was practically the same, 350 volts, and the values of the critical pressures 
for the different spark lengths were, from Table I. ; 
Distance between electrodes 
in millims. 
1 
•) 
3 
5 
10 
Discharge pressures in millims. 
of mercury. 
4-98 
2-71 
C89 
C34 
•679 
and these numbers, while not exactly in the ratio 10:5:3:2:1 are still very close 
to it. 
In finding the values for portions of the curves around the critical pressures the 
lesults given in Table I. show that a small variation in potential difference was 
associated with a relatively very large change in the pressures, so that a very small 
