Scientific Lectures. 139 



will burn with a peculiar light, containing but one color, which we 

 therefore call a monochromatic light. Now that they have been 

 lighted, I ask you to mark its effect upon these silken flags of various 

 colors. In this flame there is no red light, and the consequence is 

 that all these colors are lost excepting a yellowish tinge. The red 

 has departed from our lips, and the consequence is that we present a 

 ghastly, cadaverous appearance. Don't look at me, please look at 

 each other. As this gradually dies away, let me call your attention 

 to anotlier triumph of modern science in regard to electricity as a 

 means of producing light. At the capitoi at Washington, if a 

 committee is engaged in a private conference when the sun is setting, 

 and they wish to continue in session, the gas is turned on and in an 

 instant, by electricity, the room is lighted. So here, a spark lights 

 the gas, and thus we recei\''e the light which changes the hues of our 

 faces and of all these pieces of silk to their natural colors. [The 

 sudden lighting of two chandeliers at the top of the room by electricity 

 was received with applause. The gas was again turned ofl:', and 

 relighted in an instant by the same means.] 



Let me now take the liberty of presenting to you one -of the most 

 beautiful applications of modern science to the production of light. 

 About three years since, M. Tessie du Motay, a French chemist, of 

 great distinction and originality, conceived the possibility of produ- 

 cing oxygen by decomposing the alkaline manganates, with super- 

 heated steam. M. Schwartz wehee, Professor of Chemistry at Metz, 

 was requested to test the truth of his conception. This he did, and 

 found to his delight that manganate of soda was decomposed in the 

 presence of superheated steam. Perhaps it would be a violation of 

 confidence if I were to tell you how these French gentlemen expressed 

 their delight at such a discovery. The result was the erection of 

 works on a grand scale at four different places, each successively 

 triumphant, a fifth near Paris, and the sixth will be in the city of 

 New York, where oxygen will be made at such a rate that it can be 

 disposed of not only for theoretical purposes, but to be employed in 

 practical use. Messrs. Ball & Black have adjusted these two candela- 

 bras for the oxygen and hydrogen light. Here we have nine covered 

 jets, by the side of twenty-five jets of common gas, and on the oppo- 

 site side of the platform you have nine uncovered jets by the side of 

 twenty-five uncovered lights. You can judge of the brilliancy by 

 comparing them, [The new lights filled the hall with a light resemb- 

 ling noonday, and by their side the gas flames appeai'ed pale and 



