507 
from a glowing lime cathode in mercury vapour. 
spectrum of mercury which are of nearly the same wave-length 
as two of the orange lines measured by the author. They are 
A = 6125 and \=6074‘5, each of intensity 1. It is possible that 
more accurate measurements would show that my lines coincide 
with these. 
The wave-lengths of the five lines with the oscillation 
frequencies deduced therefrom are : 
X 
10 8 /\ 
6912 
14468. 
y difference = 424 
6715 
14892/ 
6232 
16046. 
6121 
16337 / difference = 428 
6070 
16474 X 
From the equality of the differences between the oscillation 
frequencies of the first and second, and of the third and fifth 
of these lines, it is probable that these four lines form a pair of 
doublets, and are due to the same substance. If more accurate 
measurement should show that the lines \ = 6121 and A, = 6070 
coincide with the faint lines observed by Stark in the vacuum 
tube spectrum of mercury, it would follow that all five are mercury 
lines. 
