﻿Trowbridge 
  — 
  X-rays 
  by 
  a 
  Battery 
  Current. 
  439 
  

  

  Aet. 
  XLYI. 
  — 
  The 
  Production 
  of 
  the 
  X-Rays 
  by 
  a 
  Battery 
  

   Current; 
  by 
  John 
  Trowbridge. 
  

  

  I 
  have 
  lately 
  completed 
  the 
  installation 
  of 
  a 
  plant 
  of 
  twenty 
  

   thousand 
  storage 
  cells 
  in 
  the 
  Jefferson 
  Physical 
  Laboratory. 
  

   This 
  gives 
  me 
  over 
  forty 
  thousand 
  volts 
  and 
  a 
  comparatively 
  

   steady 
  current 
  through 
  a 
  large 
  resistance. 
  One 
  of 
  the 
  most 
  

   interesting 
  questions 
  in 
  relation 
  to 
  this 
  battery 
  was 
  the 
  possi- 
  

   bility 
  or 
  impossibility 
  of 
  producing 
  the 
  X-rays 
  in 
  an 
  efficient 
  

   manner 
  by 
  means 
  of 
  it. 
  This 
  question 
  has 
  been 
  answered 
  in 
  

   the 
  affirmative, 
  for 
  the 
  rays 
  are 
  produced 
  with 
  the 
  greatest 
  

   brilliancy 
  ; 
  and 
  it 
  is 
  possible 
  to 
  take 
  photographs 
  of 
  the 
  usual 
  

   subjects 
  which 
  lend 
  themselves 
  to 
  this 
  method 
  of 
  study. 
  The 
  

   negatives 
  show 
  great 
  contrasts 
  and 
  there 
  are 
  traces 
  of 
  shadows 
  

   of 
  the 
  ligaments 
  and 
  the 
  muscles. 
  

  

  The 
  great 
  advantage 
  of 
  this 
  new 
  method 
  of 
  generating 
  the 
  

   rays 
  is 
  in 
  the 
  possibility 
  of 
  regulating 
  the 
  current 
  and 
  the 
  dif- 
  

   ference 
  of 
  potential 
  which 
  is 
  necessary 
  to 
  excite 
  the 
  rays 
  ; 
  this 
  

   is 
  not 
  possible 
  by 
  any 
  of 
  the 
  other 
  methods 
  in 
  present 
  use. 
  

   When 
  the 
  X-ray 
  tube 
  is 
  first 
  connected 
  to 
  the 
  battery 
  termi- 
  

   nals 
  no 
  current 
  flows 
  ; 
  it 
  is 
  necessary 
  to 
  heat 
  the 
  tube 
  with 
  a 
  

   Bunsen 
  burner. 
  At 
  a 
  certain 
  critical 
  temperature 
  the 
  tube 
  

   suddenly 
  lights 
  with 
  a 
  vivid 
  fluorescence 
  and 
  when 
  the 
  anti- 
  

   cathode 
  glows 
  with 
  a 
  cherry 
  red 
  the 
  rays 
  are 
  given 
  off 
  with 
  

   great 
  intensity. 
  I 
  employed 
  a 
  distilled 
  water 
  resistance 
  of 
  

   approximately 
  four 
  million 
  ohms 
  in 
  direct 
  circuit 
  with 
  the 
  tube. 
  

   The 
  current, 
  therefore, 
  was 
  not 
  more 
  than 
  three 
  or 
  four 
  

   milliamperes. 
  It 
  is 
  an 
  interesting 
  spectacle 
  to 
  see 
  the 
  tube 
  

   glowing 
  in 
  such 
  a 
  brilliant 
  and 
  noiseless 
  fashion. 
  

  

  Since 
  such 
  a 
  large 
  resistance 
  was 
  necessary 
  with 
  the 
  use 
  of 
  

   forty 
  thousand 
  volts, 
  it 
  seemed 
  possible 
  to 
  produce 
  the 
  rays 
  

   with 
  fewer 
  cells. 
  Indeed 
  there 
  is 
  no 
  difficulty 
  in 
  exciting 
  

   them 
  brilliantly 
  with 
  twenty 
  thousand 
  cells; 
  and 
  I 
  see 
  no 
  

   reason 
  why 
  they 
  cannot 
  be 
  generated 
  by 
  a 
  much 
  smaller 
  num- 
  

   ber 
  if 
  a 
  suitable 
  tube 
  is 
  obtained. 
  

  

  Since 
  I 
  employed 
  four 
  million 
  ohms 
  in 
  circuit 
  with 
  the 
  

   X-ray 
  tube, 
  it 
  is 
  evident 
  that 
  there 
  were 
  no 
  electrical 
  oscilla- 
  

   tions 
  through 
  this 
  circuit. 
  What 
  is 
  needed 
  for 
  the 
  efficient 
  

   production 
  of 
  the 
  rays 
  is 
  evidently 
  a 
  current 
  in 
  one 
  direction 
  ; 
  

   a 
  current 
  moreover 
  of 
  sufficient 
  strength 
  to 
  raise 
  the 
  anti- 
  

   cathode 
  to 
  a 
  cherry 
  red. 
  When 
  the 
  anticathode 
  rises 
  to 
  a 
  

   white 
  heat 
  the 
  resistance 
  of 
  the 
  tube 
  falls 
  to 
  such 
  degree 
  from 
  

   the 
  gases 
  which 
  are 
  set 
  free 
  from 
  the 
  terminals 
  and 
  the 
  walls 
  

   of 
  the 
  tube 
  that 
  the 
  rays 
  are 
  enfeebled. 
  This 
  change 
  of 
  resist- 
  

   ance 
  in 
  the 
  tube 
  is 
  a 
  most 
  important 
  phenomenon. 
  It 
  is 
  evi- 
  

  

  