132 Transactions of the American Institute. 



itself to single lines, but diffuses in a cloud-like form through the 

 space generally. It moreover seems prelim manly to induce a strati- 

 fication of the residual gas, and then the areas of varying density are 

 variously illuminated by the flash, so causing a very beautiful appear- 

 ance. (See figs. 10 and 11.) 



As you might naturally expect from analogy, with previous experi- 

 ments in sound, a change in the nature of the gas, or even in the 

 degree of its rarefaction, will make a great difference in the color of 

 the light produced, just as a change in the weight or elasticity of a 

 string, plate, or tuning-fork will produce a change in their note. To 

 illustrate this fact, I have arranged here on this framework a number 

 of glass tubes containing traces of various gases variously exhausted. 

 By means of the two large induction coils which are placed in connec- 

 tion with them, these will be illuminated by the electric discharge ; 

 and when you read the name which they will there display, I think 

 you will recognize one who, by his own labors and by his munificent 

 patronage to science, well deserves to have his name recorded in let- 

 ters of electric light. (See fig. 12.) 



If now, in this very imperfect and brief sketch of a vast subject, 

 I have at all succeeded in my object, I shall have shown you that 

 light, like sound, is a vibratory force ; that every little flame and glow- 

 ing fire is sending out its voice in light rays, while our grand sun and 

 every other star in the countless hosts of the heavens is part of a vast 

 chorus which, in such tones of light and color as no words can ade- 

 quately express, chants in inarticulate but most expressive harmonies 

 the power and goodness of their Creator, and realize in a very true 

 and real sense that poetical expression of Plato, " The music of the 

 spheres." 



