344 Professor Liveing, On Differences 



orange and green, due, I suppose, to chlorine ; and the anode shews 

 this continuous spectrum. 



Striae of a reddish tint, very faint and thin, are formed in 

 succession close to the kathode and move slowly away from it, 

 becoming more developed as they cross what would be the dark 

 space if the head of the positive column were stationary. They 

 were not bright enough to allow of my making sure that they 

 shewed the second spectrum of hydrogen, but from their red tint 

 I conclude that they are due to hydrogen. If so their gradual 

 formation probably arises from decomposition of hydrochloric acid 

 at the kathode. They move up to the anode and then disappear. 

 This continuous movement implies some sort of circulation such 

 as we may suppose to occur if the ions of hydrochloric acid are 

 dissociated in a strong electric field and are reassociated in a weak 

 one. The continuous movement of the striae, if we except a 

 little flickering now and then, does not, so far as I have observed, 

 occur except when there is reason to suppose that chemical 

 change attends the discharge. For example, striae are formed and 

 move from kathode to anode in a mixture of cadmium vapour 

 with carbonic acid gas, where probably the latter gas gives up 

 half its oxygen to the metal in one part of the field, and the 

 reverse reaction occurs in another part of the field. 



The behaviour of water vapour was analogous to that of 

 hydrochloric acid. When the carbonic acid gas had been 

 thoroughly pumped out, and the pressure of the residual water 

 vapour reduced to about one and a half millimeters by cooling a 

 prolongation of the tube to — 15° C, there was a bright crimson 

 kathode glow, a red capillary, and hardly any light on the anode. 

 Platinum electrodes were used in this case. The kathode glow 

 gave the first spectrum of hydrogen very bright, and much less 

 brightly four lines in the blue, which by comparison with 

 an oxygen tube I identified as oxygen lines. They were not 

 easily seen at first, more easily after a little sparking. I looked 

 for the orange and green lines of Schuster's compound line 

 spectrum, but failed to detect them. Nor could I see the two 

 broad green bands. The blue lines were, however, observed and 

 compared with the oxygen lines several times. At the anode 

 there was no bright spot, nor a trace of the second spectrum of 

 hydrogen. There was a faint flickering striation, of the same 

 colour and appearance as that in hydrochloric acid, too faint to 

 shew a spectrum. The capillary gave the first spectrum of 

 hydrogen without the second spectrum, but no oxygen lines. 



That some decomposition of the vapour was produced by the 

 discharge was shewn by a little increase of pressure, and the fact 

 that after sparking for a few minutes a little permanent gas could 

 always be pumped out of the tube. 



