of Metallic Vapours in Electric Sparks. 351 



On reversing the spark, thus making the globule of lithium 

 compound the kathode, a bright red colour developed in the 

 flame near the kathode, but it did not pass the whole way across 

 to the anode unless the electrodes were brought nearer together. 



RED 



! GREENISH 



Lithium 

 Carbonate. 



The appearance of the spark and flame is shown in the figure. 

 There were observed in the spectrum of the red portion, viewed 

 through a vertical slit, the red lithium line as a long line, the 

 orange line as a short line of feeble intensity, and the sodium 

 lines as lines of medium length. The orange line is the sti-ongest 

 line in the subordinate series of lithium, and it is only seen near 

 the central axis of the spark. An exceedingly bright spot of 

 white light was always observed on the salt where the spark 

 touched it, and in the spectrum of this spot the red lithium line 

 and the yellow sodium lines were somewhat brighter than they 

 were in the red portion of the flame, but the lines of the two 

 subordinate series of lithium were exceedingly bright. It was 

 this spot, and possibly the vapour very close to it, which gave 

 the broadened lines in the diffuse series which were described 

 in the above-mentioned paper. The salt on the kathode becomes 

 hot and sometimes it fuses; if the current is then reversed the 

 flame becomes coloured throughout its whole length but the 

 colour fades away as the temperature of the bead falls. A single 

 spark passing to the kathode produces both the bright spot and 

 the red flame. 



The electrodes were next placed vertically in a line, the bead 

 of salt being first placed on the lower end of the upper electrode. 

 When this was made the kathode, the red colour appeared, but it 

 only extended for about one-half the distance from the electrode 

 that it did when these were horizontal ; the upward current of hot 

 air from the spark evidently opposed its motion downwards. The 

 bead and electrodes were allowed to cool and the sparks were then 

 passed in the opposite direction, but no red colour appeared until 

 the bead became heated by the upward current of hot air and 

 then the red colour appeared and extended down to the clean 

 kathode. 



The bead was next put on the upper end of the lower electrode. 

 When it formed the kathode the red colour extended up to the 

 anode but it was deepest near the kathode. When the electrodes 



