the Discharge of a Leyden Jar. 373 
Striking distance 1 millimeter.—The form varied considerably, 
three or four different kinds being mingled. e simplest 
. form consisted of ten or twelve instantaneous sparks following 
each other at a pretty regular interval, which increased some- 
what toward the close of the act. This kind of discharge pro- 
duced a short hissing sound like that obtained by thrusting a 
red hot wire in cold water, and its presence could be detected 
by the ear alone. The total duration of this form was subject 
to considerable variation; below I gi 
The greatest, 0099 sec. 
M ‘0037 
tc 
“ medium, 0068 “ 
The last quantity was not obtained as the mean of the other 
two, but is the average of eleven distinct experiments with the 
disc and mirror. These I give as a sample of the variation in 
the results sometimes obtained in these experiments, the discord- 
ance being mainly due, not to the methods, but to the pheno- 
menon itself. 
sec, 
0047 mirror and compass. 
“0099 “ “ “ 
006 4 © &e “ 
70047 “  “ mercury tube. 
6c “ce “ 
Average 0068 
If we take the average number of sparks as ten, we shall 
lave for the average interval separating them ‘0007 sec., that 
8, these sparks were generated at the rate of 1428 per second. 
Suppose that a combination of ten or fifteen of them would 
be sufficient to render the ear sensible of the tone produced ; 
but Owing to the irregularity of their position, instead of fur- 
Nishing an approximation to a musical tone, the sound resem- 
bled rather that of the combination of the consonants, sr. 
hap drawing a card or piece of thin sheet brass over the 
e of an irregularly notched plate of brass, this sound could 
be imitated. 
. Other forms.—Quite often the discharge was like that given 
m fig. 7, with a total duration of ‘017 sec. More rarely the 
form in fig. 5 was produced, but I could obtain no good 
_ Me€asurement of it. In one case its average duration was 
doubtfully estimated to be sec. 
