168 Transactions of the American Institute. 



appeared uppermost upon the screen, being a minute cup, into which 

 he placed Euccessively lithium and thallium, to show the color of 

 their light as they were vaporized. He then projected upon the 

 screen a representation of the multitudinous lines of the solar spec- 

 trum, calling special attention to the sodium line, which was double, 

 with a faint line between the two. He finally exhibited a circle or 

 wheel divided into sectors colored with brilliant prismatic colors, 

 and the wheel being rapidly revolved, the colors were so blended as 

 to produce almost a pure white circle. 



