The Resonance Spectra of Iodine, 

 Table VI. 



261 



Substance. 



Eeflectiug power, observed for 



residual ravs from ' focal isolation 

 KJBr\ = 8fy. X = 108/*. 



X. 



RqO- 



24-0 

 18-1 ! 

 )8T) 



14-3 



19-7 



19 5 

 64 

 44-5 

 139 



Iceland spar 



Marble 



per cent. 



25-8 

 30 

 82-G 

 296 



19-7 



* "9(5 



per cent. 

 471 

 43-8 

 203 

 193 

 311 

 35-5 

 202 

 19-2 

 1J-6 

 1-6 

 43 



8-5 



614 



6-29 



494 



6-8 



81 

 25 

 4-78 



Eoc-k-salt 



KBr 



KI 



Fluorite 





Water ,. 



Alcohol 



Castor oil ......... 



value calculated for A, = x> than the value previously found 

 with 82 fju radiation. Iceland spar and the fluids examined 

 showed no such agreement however. The refractive indices 

 of water, alcohol, and castor oil are of the same order of 

 magnitude in this region as in the visible spectrum. The 

 high reflecting power of water probably results from the 

 presence of one or more absorption bands in the region under 

 investigation. 



XXVIII. The Resonance Spectra of Iodine. By R. W. Wood, 

 Professor of Experimental Physics, Johns Hopkins Uni- 

 versity *. 



AS I have shown in previous papers, the complicated 

 channeled (band) absorption spectrum and the corre- 

 sponding banded emission-spectrum of sodium vapour, ren- 

 dered fluorescent by white light, can be analysed into many 

 simple series of (nearly) equidistant lines, by exciting the 

 fluorescence with monochromatic light of various wave- 

 lengths obtained from metallic arcs or vacuum-tubes. Such 

 spectra I have named resonance spectra. I have also shown 

 that the fluorescent spectrum of iodine resembles that of 

 sodium, and have now found that it can be excited by mono- 

 chromatic light and made to yield resonance spectra in the 

 same manner. Thus far but a single source of light has been 



* Communicated by the Author. 



