﻿506 
  Prof. 
  A. 
  Roiti 
  on 
  the 
  iL-Rays 
  and 
  the 
  Cathodic 
  Beam. 
  

  

  diffusion, 
  since 
  these 
  are 
  so 
  various 
  and 
  not 
  yet 
  firmly 
  

   established. 
  Hence 
  it 
  will 
  be 
  better, 
  until 
  further 
  proof, 
  to 
  

   assume 
  that 
  they 
  do 
  undergo 
  diffusion. 
  

  

  8. 
  The 
  emission 
  of 
  the 
  ,^-rays 
  is 
  not 
  confined 
  to 
  the 
  surface 
  

   of 
  the 
  object 
  struck, 
  but 
  takes 
  place 
  within 
  a 
  stratum 
  of 
  

   perceptible 
  thickness 
  ; 
  and 
  this 
  follows 
  as 
  a 
  consequence 
  * 
  

   from 
  the 
  fact 
  that 
  it 
  does 
  not 
  follow 
  Lambert's 
  law 
  of 
  cosines, 
  

   but 
  is 
  constant 
  in 
  all 
  directions. 
  For 
  this 
  reason, 
  as 
  Hertz 
  

   and 
  Lenard 
  have 
  shown, 
  very 
  thin 
  strata 
  are 
  transparent 
  for 
  

   cathode-rays 
  which 
  are 
  there 
  transformed 
  to 
  a 
  certain 
  extent 
  ; 
  

   but 
  when 
  the 
  thickness 
  is 
  increased 
  the 
  intensity 
  of 
  the 
  trans- 
  

   mitted 
  rays 
  sinks 
  to 
  zero 
  ; 
  while, 
  on 
  the 
  other 
  hand, 
  the 
  

   intensit}' 
  of 
  the 
  #-rays 
  emanating 
  from 
  these 
  strata 
  increases 
  

   to 
  a 
  maximum, 
  so 
  that 
  photographs 
  taken 
  in 
  the 
  interior 
  of 
  

   the 
  tubes 
  upon 
  films 
  protected 
  by 
  not 
  very 
  thin 
  wrappers 
  are 
  

   due 
  rather 
  to 
  the 
  x- 
  than 
  to 
  the 
  cathode-rays. 
  

  

  9. 
  Lenard 
  certainly 
  had 
  under 
  his 
  hands 
  the 
  rays 
  afterwards 
  

   detected 
  by 
  Rontgen; 
  but 
  they 
  escaped 
  him 
  perhaps 
  because 
  

   the 
  keton-screen 
  with 
  which 
  he 
  made 
  his 
  observations, 
  although 
  

   it 
  fluoresces 
  under 
  the 
  action 
  of 
  cathode-rays, 
  does 
  not 
  do 
  

   so 
  under 
  that 
  of 
  «r-rays|, 
  but 
  more 
  probably 
  because 
  his 
  

   windows 
  of 
  aluminium-leaf 
  were 
  too 
  thin 
  to 
  emit 
  ^-rays 
  of 
  

   sufficient 
  intensity; 
  and 
  for 
  this 
  reason 
  all 
  the 
  rays 
  issuing 
  

   from 
  the 
  tube 
  through 
  these 
  windows 
  appeared 
  to 
  him 
  more 
  

   or 
  less 
  deflected 
  under 
  the 
  action 
  of 
  the 
  magnet. 
  

  

  10. 
  On 
  the 
  invention 
  of 
  the 
  focus-tubes 
  in 
  which 
  a 
  small 
  

   plate 
  of 
  platinum 
  inclined 
  at 
  an 
  angle 
  of 
  45° 
  acts 
  as 
  an 
  anti- 
  

   cathode, 
  photographs 
  were 
  obtained 
  with 
  outlines 
  so 
  clear 
  as 
  

   to 
  indicate 
  that 
  the 
  place 
  from 
  which 
  the 
  ^-rays 
  emanated 
  

   was 
  confined 
  to 
  the 
  points 
  of 
  the 
  platinum 
  struck 
  by 
  the 
  

   cathodic 
  pencil. 
  But 
  it 
  was 
  soon 
  observed 
  that 
  at 
  the 
  discharge 
  

   the 
  whole 
  of 
  the 
  wall 
  in 
  front 
  of 
  the 
  platinum 
  plate 
  shines 
  

   with 
  a 
  fluorescent 
  light, 
  while 
  that 
  behind 
  it 
  remains 
  almost 
  

   dark 
  unless 
  the 
  little 
  plate 
  of 
  platinum 
  be 
  replaced 
  by 
  a 
  leaf. 
  

   And 
  an 
  object 
  placed 
  within 
  the 
  tube 
  before 
  the 
  anticathode 
  

   plate 
  throws 
  a 
  shadow 
  both 
  on 
  the 
  wall 
  and 
  on 
  an 
  external 
  

   fluorescent 
  screen 
  : 
  the 
  first 
  shadow 
  is 
  displaced 
  by 
  magnetic 
  

   action, 
  but 
  not 
  the 
  second 
  J. 
  

  

  There 
  can 
  be, 
  therefore, 
  no 
  doubt 
  that 
  there 
  spring 
  from 
  

   the 
  platinum 
  anticathode 
  not 
  only 
  <#-rays, 
  but 
  also 
  rays 
  of 
  a 
  

   different 
  kind 
  which 
  were 
  called 
  internal 
  rays, 
  and 
  were 
  con- 
  

   sidered 
  different 
  from 
  the 
  cathode-rays 
  because 
  they 
  were 
  

  

  * 
  Ch.-Ed. 
  G 
  uillaiime, 
  u 
  Sur 
  l'Emission 
  des 
  Rayons 
  x? 
  Compt. 
  Rend. 
  

   vol. 
  cxxiii. 
  p. 
  450. 
  

  

  t 
  J. 
  Precht, 
  Wied. 
  Ann. 
  Bd. 
  lxi. 
  p. 
  345. 
  

  

  % 
  S. 
  Thompson, 
  'The 
  Electrician/ 
  Jan. 
  8, 
  1897. 
  

  

  