﻿Absorption 
  of 
  Rontgen 
  Rays 
  by 
  Aqueous 
  Solutions. 
  69 
  

  

  the 
  time 
  of 
  developing 
  and 
  also 
  upon 
  the 
  strength 
  of 
  the 
  

   developing 
  solution. 
  The 
  individual 
  photographic 
  plate 
  and 
  

   also 
  the 
  developing 
  of 
  the 
  photograph 
  are 
  therefore 
  important 
  

   factors, 
  which 
  enter 
  to 
  a 
  great 
  extent 
  into 
  the 
  intensity 
  of 
  the 
  

   impression 
  made 
  on 
  the 
  plate. 
  

  

  Again, 
  after 
  the 
  photographs 
  have 
  been 
  taken, 
  it 
  is 
  a 
  

   somewhat 
  difficult 
  matter 
  to 
  compare 
  the 
  intensities 
  of 
  two 
  

   impressions 
  with 
  any 
  great 
  degree 
  of 
  accuracy, 
  and 
  especially 
  

   to 
  obtain 
  definite 
  numerical 
  comparisons. 
  

  

  In 
  taking 
  a 
  photograph, 
  it 
  is 
  necessary 
  to 
  run 
  the 
  X-ray 
  

   bulb 
  a 
  considerable 
  time 
  ; 
  usually 
  about 
  ten 
  minutes 
  are 
  

   necessary 
  to 
  give 
  an 
  impression 
  of 
  sufficient 
  intensity. 
  In 
  

   order 
  to 
  make 
  a 
  large 
  number 
  of 
  comparisons, 
  the 
  taking 
  of 
  

   photographs 
  for 
  each 
  measurement 
  and 
  developing 
  the 
  plates 
  

   must 
  necessarily 
  involve 
  a 
  great 
  deal 
  of 
  time 
  and 
  labour. 
  It 
  

   is 
  desirable 
  then 
  to 
  obtain 
  a 
  more 
  rapid 
  and 
  also 
  a 
  more 
  

   accurate 
  method 
  for 
  determining 
  these 
  relative 
  absorptions. 
  

  

  Fig. 
  1. 
  

   A 
  

  

  For 
  these 
  reasons 
  the 
  following 
  method 
  was 
  adopted. 
  

   The 
  arrangement 
  of 
  the 
  apparatus 
  used 
  and 
  the 
  connexions 
  

   are 
  shown 
  in 
  fig. 
  1. 
  

  

  