of Magnesium in Stellar Spectra, 325 
It would appear then that either (1) the laboratory line 
and the stellar line are not identical, or (2) the wave-length 
of the laboratory line as recorded by Fowler is from 01 to 0:2 
tenth-metre too high. In stating these alternatives, it is as- 
sumed that the two outside stellar lines are identical with the 
solar lines mentioned, but there is practically no doubt on this 
oint. 
The 4481 line of magnesium, which is a very strong line 
in Fowler’s spectrum giving the magnesium lines under discussion, 
is, in stellar spectra, about at its maximum in such stars as 
a Cygni and a Canis Majoris, in which these other magnesium 
lines appear to exist. 
