1895.] On the Electrolysis of Gases. 255 



of the plate is due to the spark being BO intense that the hydro-carbon 

 which is supposed to be the origin of this spectrum cannot exist, then 

 we ought to see the spectra of the substances which result from the 

 decomposition of the hydro-carbon, i.e., we ought to see the hydrogen 

 spe'ctrum at the negative electrode. The view which seems most in 

 accordance with the results of observations on the discharge through 

 these vapours is that the " candle spectrum " is the spectrum of 

 carbon when the atom is charged with negative electricity, or of some 

 compound of carbon in which its atom is negatively charged, while the 

 " carbonic oxide " spectrum is the spectrum of carbon when the atom 

 is charged with positive electricity, or of some compound in which 

 the carbon atom is positively charged. 



Discharge through an Elementary Gas. It has long been known 

 that when the discharge passes through some elementary gases, the 

 spectra at the two electrodes are different. This was first shown to 

 be the case for nitrogen, then Dr. Schuster showed that the same 

 thing occurred with oxygen, and recently Mr. Crookes has shown 

 that it is also true in the case of argon. I have observed a very 

 striking change in the relative brilliancy of the red and green 

 hydrogen lines at the two electrodes. When the tube with the 

 plate across it was filled with hydrogen at a low pressure, then on 

 the positive side of the plate the red line tends to be brighter than 

 the green, while on the negative side the green line tends to be 

 brighter than the red ; in some tubes this was so marked that on 

 the positive side of the plate the red line was bright, and the green 

 invisible, while on the negative side of the plate the green line was 

 bright, and the red invisible. The spectroscope I was using 

 weakened the red rays much more than the green, so that I 

 cannot be sure that the red rays were really altogether obliterated 

 on the negative side of the plate ; the above experiment is, however, 

 sufficient to show that on the positive side of the plate the red rays 

 are more easily excited than the green, while on the negative side 

 the green line is more easily excited than the red. On the negative 

 side of the plate we have an excess of positively charged hydrogen 

 atoms, while on the positive side of the plate there is an excess of 

 negatively charged hydrogen atoms, and I am inclined to attribute 

 the difference in the spectra partly at any rate to the difference in 

 properties between a positively and a negatively charged hydrogen 

 atom. The reason I do not attribute it wholly to the difference in 

 the potential gradient on the two sides of the plate is that the effect 

 is not reversed immediately, but only gradually on reversing the 

 coil, the former spectra clinging for some time to the sides of the 

 plate. 



Chlorine. I have made a great many experiments to see if there 

 is any difference between the spectra given by chlorine on the two 



VOL. LVIII. T 



