﻿386 
  Scientific 
  Intelligence, 
  

  

  bands 
  were 
  not 
  produced 
  bj^ 
  refraction. 
  Haga 
  and 
  Wind 
  set 
  

   themselves 
  to 
  determine 
  what 
  causes 
  the 
  Forara 
  bands 
  and 
  

   whether 
  there 
  are 
  refraction 
  phenomena 
  in 
  the 
  case 
  of 
  the 
  X-rays. 
  

   The 
  Fomni 
  bands 
  or 
  lines 
  are 
  maxima 
  produced 
  by 
  a 
  difference 
  

   of 
  illumination 
  on 
  a 
  surface 
  lighted 
  through 
  a 
  slit, 
  and 
  the 
  phe- 
  

   nomenon 
  was 
  studied 
  as 
  early 
  as 
  1866 
  by 
  E. 
  Mach, 
  and 
  the 
  results 
  

   were 
  published 
  in 
  the 
  Proceedings 
  of 
  the 
  Vienna 
  Academy 
  of 
  

   Sciences 
  under 
  the 
  title 
  " 
  Ueber 
  die 
  Physiologische 
  Wirkung 
  

   raumlich-vertheilter 
  Lichtreize." 
  A 
  study 
  of 
  this 
  pseudo 
  dif- 
  

   fraction 
  effect 
  showed 
  the 
  authors 
  that 
  their 
  earlier 
  work 
  on 
  the 
  

   wave 
  nature 
  of 
  the 
  Rontgen 
  rays 
  fell 
  to 
  the 
  ground, 
  and 
  that 
  

   previous 
  investigations 
  in 
  which 
  the 
  distance 
  between 
  the 
  Crookes 
  

   tube 
  and 
  the 
  sensitive 
  plate 
  was 
  as 
  much 
  as 
  24 
  meters 
  and 
  the 
  

   time 
  of 
  exposure 
  80 
  hours, 
  and 
  in 
  which 
  double-flowed 
  plates 
  and 
  

   strengthening 
  screens 
  were 
  used, 
  are 
  worthless. 
  The 
  authors, 
  

   moreover, 
  are 
  convinced 
  that 
  the 
  eventual 
  wave 
  length 
  of 
  the 
  

   X-rays 
  must 
  be 
  of 
  far 
  smaller 
  value 
  than 
  has 
  been 
  supposed. 
  

   New 
  experiments 
  were 
  then 
  undertaken 
  to 
  test 
  the 
  question 
  

   whether 
  there 
  are 
  true 
  refraction 
  effects 
  with 
  X-rays. 
  The 
  

   authors 
  believe 
  that 
  such 
  effects 
  will 
  be 
  found 
  and 
  that 
  the 
  wave 
  

   length 
  of 
  the 
  rays 
  lies 
  under 
  a 
  tenth 
  of 
  /x/x. 
  

  

  C. 
  H. 
  Wind 
  also 
  discusses 
  the 
  question 
  whether 
  the 
  refraction 
  

   phenomena 
  studied 
  by 
  Haga 
  and 
  himself 
  are 
  due 
  to 
  certain 
  vibra- 
  

   tions 
  of 
  the 
  source 
  of 
  light 
  3000 
  times 
  smaller 
  than 
  the 
  time 
  of 
  

   vibration 
  of 
  yellow 
  light, 
  and 
  that 
  the 
  emission 
  of 
  the 
  X-ray 
  sys- 
  

   tem 
  must 
  be 
  ascribed 
  to 
  a 
  nature 
  of 
  vibration 
  entirely 
  different 
  

   from 
  that 
  of 
  ordinary 
  light. 
  He 
  comes 
  after 
  an 
  analytical 
  discus- 
  

   sion 
  of 
  this 
  question 
  to 
  the 
  conclusion 
  that 
  this 
  conclusion 
  is 
  not 
  

   justified 
  (Wied. 
  Ann., 
  No. 
  8, 
  1899, 
  pp. 
  884-901). 
  

  

  M. 
  Maier 
  has 
  also 
  investigated 
  the 
  question 
  of 
  the 
  refraction 
  of 
  

   the 
  X-rays 
  and 
  states 
  that 
  he 
  has 
  discovered 
  interference 
  phe- 
  

   nomena 
  which 
  indicate 
  the 
  wave 
  nature 
  of 
  these 
  rays. 
  He 
  finds 
  

   wave 
  lengths 
  0*000015'"™ 
  in 
  length. 
  His 
  experiments 
  do 
  not 
  

   decide 
  the 
  question 
  of 
  the 
  transversality 
  of 
  these 
  waves, 
  for 
  no 
  

   polarization 
  phenomena 
  were 
  in 
  evidence. 
  — 
  Wied. 
  Ann.^ 
  No. 
  8, 
  

   1899, 
  pp. 
  903-916. 
  ^ 
  J. 
  T. 
  

  

  9. 
  Radio-actme 
  substances. 
  — 
  E. 
  de 
  Haen- 
  has 
  discovered 
  two 
  

   preparations 
  of 
  uranium 
  earth 
  which 
  possess 
  the 
  property 
  of 
  

   exciting 
  X-rays 
  in 
  a 
  remarkable 
  degree. 
  Preparation 
  A 
  shows 
  

   the 
  phenomenon 
  of 
  the 
  Becquerel 
  rays 
  ; 
  excites 
  fluorescence 
  of 
  

   barium 
  platinum-cyanide 
  screens, 
  even 
  through 
  substances 
  opaque 
  

   to 
  light 
  ; 
  acts 
  upon 
  photographic 
  plates 
  ; 
  makes 
  air 
  conducting 
  

   for 
  electricity, 
  and 
  has, 
  moreover, 
  the 
  hitherto 
  undiscovered 
  prop- 
  

   erty 
  of 
  being 
  self-luminous. 
  Preparation 
  B 
  proves 
  to 
  have 
  in 
  

   general 
  the 
  peculiarities 
  of 
  preparation 
  A. 
  The 
  excitation 
  of 
  a 
  

   screen 
  is 
  more 
  intense, 
  the 
  self-lighting 
  is 
  much 
  weaker. 
  — 
  Wied. 
  

   Ann., 
  No. 
  8, 
  p. 
  902. 
  J. 
  T. 
  

  

  10. 
  F/iysikalische 
  Zeitschrift, 
  No. 
  1-2, 
  pp. 
  1-38, 
  Leipzig 
  (S. 
  

   Hi 
  rzel).— 
  Physicists 
  will 
  be 
  interested 
  in 
  the 
  appearance 
  of 
  the 
  

   Fhysikalische 
  Zeitschrift, 
  of 
  which 
  the 
  first 
  number 
  (1 
  and 
  2) 
  was 
  

  

  