420 
Mk W. li. CAKii ON THE LAATS GOA^EEXING 
law is most accurately expressed by saying, “ that, with a given applied potential 
difference, discharge in a uniform field, in any gas, is dependent solelv on the 
constancy of the quantity of matter per unit cross section between the electrodes.” 
VII. Minimum Sjyarh Potentials. 
An interesting result in connection with these exijeriments is the almost constant 
value obtained for the minimum spark j^otential with the diflerent electrode distances 
in each of the gases. 
Peace,'''' in the paper already referred to, was able to point to the probable 
existence of such a condition, but his results were not sufficiently regular to allow 
him to speak with certainty from the evidence at that time in his possession. This 
is seen from the following table of results taken from his paper, which ap])ear to be 
the readings upon which he based his conclusions ;— 
Peace’s Tid^le of Minimum Spark Potentials. 
Spark length in 
millims. 
Minininm discharge 
potential in volts. 
•01 
326 
•02.5 
330 
•05 
333 
•1 
354 
. •> 
370 
, •> 
O 
390 
•5 
400 
•7 
428 
1 
458 
2 
475 
While these results are of the same order, it will be noticed that the spark 
potential rapidly increases with the distance l)etween the electrodes, and that the 
smallest value differs from the greatest by nearly 150 volts. 
In the results recorded in the present experiments, however, it cannot be said 
that there is any indication of an increase in spark potential for an increasing spark 
length. 
The minimum spark potentials observed in these experiments, for the three 
different gases, are given in the following table :—- 
I’e.WE, ‘Eoy. Sue. I’roc.,’ vol. 52, pp. 107, 112. 
