MASTER KEY OF SCIENCE RUSSELL 139 



water. The problematical white dwarf stars, like the companion of 

 Sirius, show conclusive evidence of being in this state, while the 

 shift toward the red of the lines in their spectra (coming from 

 the outer atmosphere) affords an important confirmation of general 

 relativity. At the other extreme, the gaseous nebulae — which from 

 gravitational considerations must be of extreme tenuity — show spec- 

 tral lines which were long a tantalizing problem. Modern spec- 

 troscopy revealed the existence of metastable atomic states, from 

 which light-producing transitions would not occur unless the in- 

 dividual atoms were left undisturbed much longer than they would 

 be except in an exceedingly rarefied gas. Bowen thus identified 

 the nebular lines as " forbidden " lines of the sort produced by the 

 most familiar elements, oxygen and nitrogen above all. The hypo- 

 thetical unknown element nebulium thus very literally vanished into 

 thin air. 



