410 Sir W. Orookes. 



both hydrogen and mercury are present, I obtain both mercury and 

 hydrogen strata. 



The following experiments appear to show that the presence of 

 hydrogen* has a considerable influence on the behaviour of mercury 

 vapour in vacuum tubes. A tube with aluminium terminals had been 

 attached to the pump for several days, and consequently mercury had 

 diffused in and condensed on its sides. The tube was exhausted until, 

 under the electric discharge, it phosphoresced of a brilliant green and 

 Avas near the non-conducting point. It was heated very strongly with a 

 Bunsen flame, when a faint pink luminosity was observed between the 

 poles, the spectrum of mercury being absent. The tube was allowed 

 to cool and a little hydrogen was introduced, when the usual pink 

 stratifications appeared. On heating the tube to about the same tem- 

 perature as before blue faces showed on the pink buttons, and the 

 mercury spectrum was seen throughout the tube, especially in the 

 neighbourhood of the negative pole. 



It is known that in a vacuum tube, at an exhaustion approaching 

 the stratification-point, any slight obstruction, such as constriction in 

 the tube, or a series of wires sealed in, will cause luminous strata to 

 hang round the obstruction. In a similar way, the hydrogen strata 

 afford an anchorage, as it were, for the mercury, each hydrogen lumi- 

 nosity having a little blue glow of mercury hanging on to it ; whereas, 

 were there no hydrogen, no mercury stratifications would be seen. 



The pink- and blue luminosities show where the electrons and 

 gaseous atoms meet ; when the speed of the electrons is suddenly 

 diminished, the shock throws the atom into greater vibration, which, 

 being communicated to the ether, produces vibrations of definite wave- 

 lengths, constituting the special spectrum of the atom. The dense 

 mercury atom is not driven back so much as the lighter hydrogen 

 atom hence the blue front to the pink buttons. A very little dif- 

 ference in the exhaustion suffices to break the adhesion between the 

 mercury and the hydrogen ; then the mercury vapour diffusing along 

 the tube meets the electrons from the negative pole and is swept back 

 to the head of the hydrogen strata, and becomes apparent as a single 

 button of blue light. 



Piailiant Matter. Electrons. 



I have spoken of " Radiant Matter " and " Electrons " as if they 

 were identical. Nearly twenty-five years ago I was led by experi- 

 ments in highly rarefied tubes to assume the existence of matter- 

 in an ultra-gaseous state. Later, in a lecture delivered before the 

 British Association at the Sheffield Meeting, 1879,f I first used the 



* Possibly another gas would do as well. Hydrogen was used because in this 

 instance the hydrogen generator was attached to the tube. 

 t ' Chemical News,' vol. 40, pp. 91, 104, 127. 



