﻿I 
  Transmission 
  of 
  X 
  Rays 
  through 
  Metals. 
  713 
  

  

  A 
  medium-hard 
  Cossor 
  tube 
  with 
  an 
  iridium 
  anti-cathode 
  

   and 
  a 
  sharp 
  focus 
  was 
  used 
  throughout 
  the 
  experiments. 
  

   In 
  all 
  cases 
  the 
  photographic 
  plate 
  was 
  enclosed 
  in 
  two 
  

   thicknesses 
  of 
  stout 
  black 
  paper 
  and 
  the 
  exposure 
  given 
  was 
  

   two 
  hours. 
  A 
  narrow 
  cylindrical 
  pencil 
  of 
  X 
  rays 
  (1*5 
  mm. 
  

   diameter) 
  was 
  caused 
  to 
  fall 
  at 
  almost 
  grazing 
  incidence 
  

   upon 
  an 
  excellent 
  optical 
  surface 
  of 
  speculum 
  metal 
  (see 
  

   fig. 
  1). 
  There 
  was 
  no 
  evidence 
  of 
  regular 
  reflexion, 
  but 
  a 
  

  

  *+ 
  

  

  XX 
  = 
  X 
  RAY 
  5£/»M 
  

  

  LUt- 
  - 
  LEAD 
  SCREENS 
  

  

  S 
  = 
  SPECULUty 
  

  

  PP= 
  ?HOro<}f?APnlc 
  PLATE 
  

  

  number 
  of 
  small 
  irregular 
  spots 
  appeared 
  on 
  the 
  plate 
  

   scattered 
  over 
  the 
  region 
  at 
  A. 
  The 
  spots 
  of 
  greatest 
  in- 
  

   tensity 
  were 
  those 
  due 
  to 
  beams 
  which 
  had 
  suffered 
  the 
  least 
  

   deviation. 
  If 
  the 
  metal 
  surface 
  was 
  displaced 
  sideways 
  in 
  

   its 
  own 
  plane, 
  the 
  direction 
  of 
  the 
  primary 
  beam 
  remaining 
  

   unaltered, 
  it 
  was 
  found 
  that 
  the 
  arrangement 
  of 
  the 
  spots 
  

   was 
  no 
  longer 
  the 
  same. 
  Similar 
  results 
  were 
  obtained 
  with 
  

   brass, 
  while 
  silvered 
  glass 
  and 
  liquid 
  mercury 
  surfaces 
  

   merely 
  exhibited 
  a 
  general 
  scattering. 
  The 
  effect 
  is 
  un- 
  

   doubtedly 
  associated 
  with 
  the 
  crystals 
  in 
  the 
  metal. 
  An 
  

   examination 
  of 
  the 
  brass 
  surface 
  under 
  the 
  microscope 
  showed 
  

   a 
  multitude 
  of 
  well-formed 
  crystals 
  ; 
  none 
  were 
  visible 
  on 
  

   the 
  speculum 
  surface, 
  possibly 
  owing 
  to 
  their 
  being 
  covered 
  

   by 
  an 
  amorphous 
  layer 
  produced 
  in 
  the 
  polishing. 
  The 
  

   absence 
  of 
  spots 
  with 
  the 
  silver 
  surface 
  on 
  glass 
  is 
  to 
  be 
  

   attributed 
  to 
  the 
  smallness 
  of 
  the 
  crystals 
  and 
  to 
  the 
  extreme 
  

   thinness 
  of 
  the 
  layer 
  deflecting 
  only 
  a 
  minute 
  fraction 
  of 
  the 
  

   incident 
  radiation 
  ; 
  and 
  in 
  the 
  case 
  of 
  the 
  mercury 
  to 
  the 
  

   absence 
  of 
  crystals. 
  

  

  A 
  study 
  of 
  the 
  " 
  emergent 
  " 
  radiation 
  from 
  thin 
  metal 
  

   sheets 
  gave 
  results 
  differing 
  from 
  those 
  obtained 
  by 
  the 
  

   ionization 
  method. 
  

  

  