392 
ASTRONOMY: ADAMS AND PEASE 
those so conspicuous in the spectra of nebulae, the more important in 
order of brightness being X 4686, 5007, 4610, 4364, 4960 and the hydro- 
gen Hnes, Hl3, Hy, Hb and He. 
During the summer the star could not be observed on account of its 
position, but in November another photograph was secured. This 
showed some extraordinary changes. In addition to a great increase 
in the intensity of the continuous spectrum, the plate showed the dis- 
appearance of the chief nebular line at X 5007 and the line so commonly 
associated with it at X 4364, and a marked reduction in the intensity 
of X 4610. The absence of X 5007 is especially remarkable in view of 
the presence, although in reduced intensity, of the nebular line at X 4960. 
These two lines, known as Ni and N2 of the nebular spectrum, without 
exception so far as we know, have always been observed together, and 
vary in intensity together, X 5007 being about twice as strong as X 4960. 
