﻿176 
  

  

  Dr. 
  J. 
  Knnz 
  on 
  Catliode 
  and 
  

  

  positive 
  rays. 
  In 
  hydrogen 
  the 
  phenomena 
  at 
  low 
  pressure 
  

   coincide 
  with 
  those 
  observed 
  in 
  air. 
  

  

  Experiment 
  5. 
  — 
  In 
  place 
  of 
  the 
  sphere 
  used 
  in 
  the 
  last 
  expe- 
  

   riment, 
  the 
  cathode 
  consists 
  of 
  two 
  parallel 
  triangular 
  plates 
  

   3 
  or 
  1 
  mm. 
  apart 
  held 
  together 
  by 
  means 
  of 
  three 
  thin 
  pins 
  

   and 
  supported 
  by 
  a 
  bar 
  of 
  brass 
  entering 
  into 
  the 
  middle 
  of 
  

   the 
  plane 
  of 
  one 
  of 
  the 
  plates. 
  The 
  triangular 
  hollow 
  space 
  

   between 
  the 
  two 
  plates 
  lies 
  in 
  the 
  same 
  horizontal 
  plane 
  

   as 
  the 
  anode 
  towards 
  which 
  a 
  corner 
  of 
  the 
  triangle 
  is 
  

   directed. 
  At 
  a 
  comparatively 
  high 
  pressure 
  we 
  observe 
  a 
  

   narrow 
  dark 
  space 
  surrounding 
  each 
  plate. 
  Beyond 
  this 
  is 
  

   the 
  negative 
  glow, 
  and 
  this 
  is 
  exceedingly 
  bright 
  between 
  the 
  

   two 
  triangles. 
  Three 
  blue 
  beams 
  start 
  from 
  this 
  central 
  light, 
  

   in 
  a 
  direction 
  perpendicular 
  to 
  the 
  sides 
  of 
  the 
  triangle, 
  

   giving 
  the 
  aspect 
  shown 
  in 
  fig. 
  16 
  when 
  looked 
  at 
  in 
  a 
  

  

  Fig. 
  16. 
  

  

  direction 
  perpendicular 
  to 
  the 
  plates. 
  As 
  the 
  air 
  is 
  pumped 
  

   out, 
  the 
  velvet 
  glow 
  appears, 
  Crookes's 
  dark 
  space 
  gets 
  wider, 
  

   the 
  light 
  between 
  the 
  plates 
  disappears, 
  the 
  blue 
  beams 
  from 
  

   the 
  sides 
  of 
  the 
  triangular 
  hollow 
  space 
  contract 
  into 
  sharper 
  

   I 
  teams 
  spreading 
  out 
  over 
  a 
  longer 
  distance 
  than 
  before, 
  as 
  

   will 
  be 
  seen 
  from 
  tig. 
  17. 
  

  

  At 
  a 
  still 
  lower 
  pressure 
  the 
  blue 
  cathode 
  rays 
  A 
  get 
  very 
  

   bright 
  and 
  distinct, 
  causing 
  quite 
  distinct 
  patches 
  of 
  phos- 
  

   phorescence, 
  while 
  from 
  the 
  corners 
  of 
  the 
  triangle 
  short 
  red 
  

   beams 
  start 
  into 
  existence. 
  The 
  difference 
  of 
  colour 
  between 
  

   the 
  two 
  kinds 
  of 
  beams 
  LS 
  mosi 
  remarkable 
  in 
  hydrogen 
  and 
  

  

  