166 O. N. Rood— Nature and Duration of 
_ of 840 per second, was ninety-four billionths of a second 
(000000094) ; still, on experimenting, it was evident that the 
duration of the discharge was less than this quantity, as the 
lines were always plainly to be seen. 
Duration of the first act of the discharge. 
Before finally abandoning the attempt to determine the ac- 
tual duration of the discharge, another effort was made; a 
second lamp-black plate was prepared, in which the breadth of 
the image of a line, black or white, on the observing plate was 
zz Of a millimeter. These lines were viewed with the terres- 
was between forty-one and forty-eight billionths; and when the 
striking distance was increased to ten millimeters, it was be- 
ti 
discharges take place in a given time as with points; hence, the 
: The evidence from 
twenty-six observations, gathered in not less than three hours, _ 
went to show that the duration with a striking distance of five 
millimeters was between forty-eight and fifty-five billionths of 
a second. 
Tt has thus been shown that the duration of the first act of 
the electric discharge is in certain cases only forty billionths of @ 
