54  Stellar  Evolution

observations  on  the  spectra  of  stars,  and  soon  established  a
system  of  types,  based  upon  the  examination  of  the  spectra
of  several  thousand  objects.  This  work  has  since  been  greatly
extended  through  the  application  of  photographic  methods,
introduced  by  Huggins,  and  applied  with  marked  success  by
Draper  and  many  others.  In  1868  the  spectroscope  was
used  for  the  first  time  to  analyze  the  red  flames  seen  during
total  eclipses  of  the  Sun.  Not  only  did  it  demonstrate  their
gaseous  nature,  but  a  short  time  later,  through  the  efforts  of
Janssen,  Lockyer,  and  Huggins,  it  was  found  possible  to  em-
ploy the  spectroscope  to  observe  the  forms  of  the  prominences
in  full  sunlight.
These  and  other  applications  of  the  spectroscope  will  be
more  fully  described  in  subsequent  chapters.  Our  present
purpose  is  to  explain  how  the  new  method,  in  the  hands  of
Huggins  (Plate  XXIII),  finally  proved  beyond  doubt  that
certain  nebulae  are  to  be  sharply  distinguished  from  star
clusters.
