PHYSICS NINETEENTH CENT.SPECTROSCOPY. 479 



FIG. 220. WILLIAM WOLLASTON. 



When a very narrow line of the blue light at the lower part of the 

 flame is examined alone, in the same manner, through a prism, the 

 spectrum, instead of appearing a series of lights of different hues con- 

 tiguous, may be seen divided into five images at a distance from each 

 other. The first is broad red, terminated by a bright line of yellow ; 

 the second and third are both green ; the fourth and fifth are blue, 

 the last of which appears to correspond with the divisions of blue and 

 violet in the solar spectrum, or the line D of Fig. 219. 



"When the object viewed is a blue line of electric light, I have 

 found the spectrum to be also separated into several images ; but the 

 phenomena are somewhat different from the preceding. It is, how- 

 ever, needless to describe minutely appearances which vary according 

 to the brilliancy of the light, and which I cannot undertake to explain." 



