﻿508 
  Prof. 
  A. 
  Roiti 
  on 
  the 
  K-JRays 
  and 
  the 
  Cathodic 
  Beam. 
  

  

  platinocyanide 
  of 
  potassium 
  and 
  turned 
  towards 
  the 
  centre 
  of 
  

   the 
  anticathode 
  disk. 
  Under 
  the 
  influence 
  of 
  moderate 
  rare- 
  

   faction 
  this 
  face, 
  at 
  first 
  extremely 
  brilliant, 
  became 
  perfectly 
  

   dark 
  ; 
  but 
  when 
  the 
  rarefaction 
  was 
  great, 
  it 
  still 
  showed 
  

   4/100 
  of 
  its 
  original 
  brightness, 
  showing 
  that 
  the 
  anticathode, 
  

   notwithstanding 
  the 
  deflexion, 
  was 
  still 
  giving 
  olF 
  ^-rays. 
  

   This 
  small 
  residuum 
  might, 
  however, 
  have 
  been 
  formed, 
  so 
  to 
  

   speak, 
  by 
  second 
  intention 
  — 
  by 
  the 
  cathode-rays 
  reflected 
  on 
  

   the 
  lateral 
  wall 
  F. 
  

  

  To 
  decide 
  this 
  question 
  I 
  introduced 
  into 
  the 
  tube 
  a 
  leaden 
  

   tube, 
  supported 
  against 
  the 
  aluminium 
  bottom 
  as 
  is 
  seen 
  in 
  

   the 
  figure 
  ; 
  and 
  by 
  means 
  of 
  this 
  screen 
  the 
  brightness, 
  even 
  

   with 
  extreme 
  rarefaction, 
  was 
  reduced 
  to 
  1/1000 
  under 
  the 
  

   action 
  of 
  the 
  magnet. 
  

  

  On 
  replacing 
  the 
  permanent 
  magnet 
  by 
  an 
  electromagnet 
  

   separated 
  from 
  the 
  tube 
  by 
  plates 
  of 
  ebonite 
  to 
  prevent 
  the 
  

   discharge 
  taking 
  place, 
  at 
  that 
  extreme 
  rarefaction, 
  on 
  the 
  

   outside, 
  every 
  excitement 
  of 
  the 
  electromagnet 
  was 
  observed 
  

   to 
  occasion 
  the 
  sudden 
  passage 
  of 
  the 
  actinometer 
  from 
  

   extreme 
  brilliancy 
  to 
  perfect 
  darkness. 
  

  

  The 
  coil 
  with 
  the 
  interruptor, 
  which 
  I 
  have 
  described 
  in 
  

   L'Elettricista 
  for 
  November 
  1897, 
  gave 
  a 
  spark 
  of 
  15 
  centim. 
  

   between 
  balls 
  of 
  2 
  centim. 
  in 
  diameter, 
  and 
  the 
  magnetizing 
  

   current 
  of 
  the 
  electromagnet 
  was 
  less 
  than 
  half 
  an 
  ampere. 
  

  

  Hence 
  it 
  is 
  clear 
  that 
  non-deflect 
  ible 
  cathodic 
  rays 
  probably 
  

   do 
  not 
  exist, 
  or 
  if 
  they 
  exist 
  they 
  are 
  not 
  transformable 
  into 
  

   t 
  i'-rays. 
  

  

  III. 
  

  

  As 
  an 
  appendix 
  to 
  this 
  communication 
  I 
  will 
  speak 
  of 
  one 
  

   of 
  my 
  former 
  experiments*, 
  which 
  also 
  shows 
  that 
  A'-rays 
  

   cannot 
  be 
  considered 
  as 
  simply 
  diffused 
  cathodic 
  rays. 
  Two 
  

   tubes, 
  of 
  the 
  form 
  represented 
  in 
  fig. 
  1, 
  alike 
  in 
  all 
  respects 
  

   except 
  that 
  in 
  one 
  the 
  disk 
  was 
  of 
  aluminium, 
  in 
  the 
  other 
  of 
  

   copper, 
  were 
  both 
  applied 
  to 
  the 
  same 
  air-pump 
  and 
  connected 
  

   with 
  the 
  two 
  poles 
  of 
  a 
  Ruhmkorff 
  coil. 
  On 
  covering 
  the 
  

   aluminium 
  disk 
  with 
  a 
  copper 
  plate 
  and 
  the 
  copper 
  disk 
  with 
  

   an 
  aluminium 
  plate 
  in 
  such 
  a 
  manner 
  that 
  the 
  ar-rays 
  issuing 
  

   from 
  the 
  two 
  tubes 
  were 
  forced 
  to 
  traverse 
  equal 
  thicknesses 
  

   of 
  the 
  two 
  metals, 
  I 
  found 
  the 
  power 
  of 
  emission 
  of 
  the 
  second 
  

   tube 
  considerably 
  greater 
  than 
  that 
  of 
  the 
  first. 
  

  

  Since 
  Prof, 
  Battelli 
  has 
  arrived 
  at 
  a 
  different 
  conclusion 
  f, 
  

   finding 
  that 
  glass, 
  aluminium, 
  and 
  magnesium 
  experimented 
  

  

  * 
  Rend, 
  della 
  R. 
  Ace. 
  dei 
  Lincei, 
  vol. 
  vi. 
  p. 
  355. 
  Experiment 
  of 
  August 
  

   26th, 
  1896. 
  

  

  t 
  N. 
  Cimento, 
  ser. 
  4, 
  voL 
  v. 
  May 
  1897. 
  Experiment 
  15.. 
  

  

  