269 



new experiment the phenomena became less distinct than they were 

 before.] 



I think it most probable that, properly speaking, electric light 

 does not exist ; the light which we see belongs to the gas, rendered 

 incandescent by the thermal action of the current. Accordingly, in 

 our case, the colour of the appearing light depends upon the nature 

 of the gas and the concentration of the current. This opinion is 

 strongly supported by the observed fact, that the temperature of the 

 capillary tube increases considerably in some instances. Considering 

 that this increase of temperature has its source in the heat of the 

 residual gas, which is too small in amount to be indicated by the 

 balance, this heat being produced by the electric current, and com- 

 municated to the heavy substance of the tube ; we have scarcely an 

 idea of the enormous temperature of the gaseous electrode included 

 in the capillary channel*. 



II. " On the Interruption of the Voltaic Discharge in Vacuo by 

 Magnetic Force." By J. P. GASSIOT, Esq., F.R.S. Re- 

 ceived December 6, 1859. 



The late Professor Daniell, in his Fifth Letter on Voltaic Combina- 

 tions (Phil. Trans. 1839, part 1), describes some experiments made with 

 seventy series of his constant battery, and states (page 93) " that the 

 arc of flame between the electrodes was found to be attracted and 

 repelled by the poles of a magnet, according as one or the other pole 

 was held over or below it, as was first ascertained by Sir H. Davy ; 

 and the repulsion was at times so great as to extinguish the flame." 



In the Philosophical Magazine of July 1858, Mr. Grove has de- 

 scribed an experiment made by him with one of my vacuum-tubes, 

 2 feet 9 inches long, in which he ascertained that the discharge of a 

 Ruhmkorff s induction coil could be stopped by bringing a magnet 

 near the positive terminal wire, but that this effect was not obtained 

 when the magnet was made to approach the negative. The mercurial 

 vacuum-tube in which Mr. Grove observed this phenomenon was 



* In some peculiar cases my primitive theoretical views were modified, reformed, 

 or extended by subsequent experiments. The abstract now given refers only to 

 what I think at present to be the state of the question. 



u 2 



