86 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
planes ; for not only is it difficult to keep the latter absolutely parallel, but also there 
is a tendency to discharge near the peripheries of the discs, notwithstanding that they 
are 0'125 inch thick, and are bounded by carefully rounded edges. 
inch 
By connecting the battery with a condenser a much more dense spark passes, giving 
rise to a greater or less explosion as the capacity of the condenser is greater or less. 
The length of the spark is not affected in the case of spherical terminals being used, 
but is considerably shortened in that of a point and plate : thus with 8040 cells — 
Without condenser. 
Length of spark, 
inch. 
Two spherical surfaces 1*5 inch diameter and 3 inches radius 0082 
Point positive and disc negative 0 - 340 
With condenser. 
Length of spark, 
inch. 
0-082 
0-268 
The condenser E, page 99, used in the above experiment, has a capacity of OH 48 
microfarad. 
