﻿Analysis 
  of 
  (3 
  Rays 
  from 
  Radium 
  B 
  and 
  Radium 
  C. 
  721 
  

  

  whether 
  a 
  continuous 
  spectrum 
  of 
  j3 
  rays 
  is 
  superimposed 
  on 
  

   the 
  line 
  spectrum, 
  rays 
  are 
  excited 
  in 
  all 
  parts 
  of 
  the 
  

   vessel 
  on 
  which 
  the 
  y 
  rays 
  fall 
  ; 
  in 
  addition, 
  the 
  rays 
  falling 
  

   on 
  the 
  photographic 
  plate 
  are 
  partially 
  scattered 
  in 
  all 
  

   directions. 
  These 
  disturbing 
  effects 
  were 
  reduced 
  to 
  a 
  

   minimum 
  by 
  lining 
  the 
  vessel 
  with 
  thick 
  cardboard, 
  and 
  

   placing 
  cardboard 
  screens 
  CC 
  in 
  the 
  positions 
  shown 
  in 
  the 
  

   figure. 
  It 
  is 
  also 
  clear 
  from 
  the 
  figure 
  that 
  the 
  direct 
  effect 
  

   of 
  the 
  7 
  rays 
  on 
  the 
  photographic 
  plate 
  was 
  greatly 
  reduced 
  

   by 
  their 
  passage 
  through 
  the 
  lead 
  block. 
  

  

  The 
  essential 
  conditions 
  for 
  bringing 
  out 
  lines 
  of 
  feeble 
  

   intensity 
  depend 
  mainly 
  on 
  the 
  conditions 
  : 
  (1) 
  narrow 
  

   source, 
  (2) 
  a 
  uniform 
  magnetic 
  field 
  over 
  the 
  whole 
  path 
  of 
  

   the 
  yS 
  particles, 
  (3) 
  a 
  comparatively 
  wide 
  slit 
  ; 
  the 
  width 
  

   of 
  slit 
  employed 
  in 
  most 
  of 
  the 
  experiments 
  varied 
  from 
  

   1-3 
  mm. 
  The 
  lines 
  were 
  comparatively 
  sharp 
  even 
  with 
  

   the 
  widest 
  slits 
  used 
  ; 
  and 
  photographs 
  could 
  be 
  obtained 
  

   with 
  exposures 
  so 
  short 
  that 
  the 
  effect 
  of 
  the 
  scattered 
  

   radiations 
  was 
  relatively 
  much 
  reduced. 
  

  

  Under 
  the 
  experimental 
  conditions, 
  the 
  outside 
  edges 
  of 
  

   the 
  lines 
  were 
  very 
  sharply 
  defined, 
  but 
  there 
  was 
  a 
  distinct 
  

   shading 
  off 
  towards 
  the 
  slit. 
  This 
  was 
  especially 
  marked 
  in 
  

   the 
  strong 
  groups 
  of 
  /3 
  rays 
  from 
  radium 
  B, 
  using 
  the 
  a-ray 
  

   tube 
  as 
  a 
  source. 
  

  

  The 
  measurements 
  were 
  always 
  made 
  on 
  the 
  sharp 
  outside 
  

   edge 
  of 
  the 
  line, 
  and 
  the 
  radius 
  p 
  of 
  the 
  circular 
  path 
  could 
  

   be 
  readily 
  determined 
  for 
  the 
  rays 
  forming 
  this 
  part 
  of 
  the 
  

   trace. 
  To 
  a 
  first 
  approximation, 
  it 
  is 
  given 
  by 
  /? 
  = 
  v 
  /D 
  2 
  + 
  a 
  2 
  

   where 
  2D 
  is 
  the 
  distance 
  of 
  the 
  outside 
  of 
  the 
  line 
  from 
  the 
  

   centre 
  of 
  the 
  slit, 
  and 
  2a 
  the 
  distance 
  of 
  the 
  source 
  from 
  

   the 
  slit. 
  The 
  position 
  of 
  the 
  source 
  relative 
  to 
  the 
  slit 
  was 
  

   accurately 
  measured 
  in 
  each 
  experiment 
  with 
  the 
  aid 
  of 
  

   a 
  travelling 
  microscope 
  provided 
  with 
  a 
  horizontal 
  and 
  

   vertical 
  movement. 
  

  

  The 
  positions 
  of 
  the 
  strong 
  lines 
  on 
  the 
  plates 
  were 
  deter- 
  

   mined 
  with 
  the 
  aid 
  of 
  a 
  travelling 
  microscope. 
  The 
  weak 
  

   lines, 
  however, 
  were 
  too 
  faint 
  to 
  be 
  seen 
  in 
  the 
  microscope. 
  

   It 
  was 
  consequently 
  necessary 
  to 
  mark 
  their 
  positions 
  on 
  the 
  

   plate 
  with 
  a 
  fine 
  pen. 
  Each 
  plate 
  was 
  marked 
  several 
  times, 
  

   and 
  the 
  measurements 
  of 
  a 
  given 
  line 
  in 
  most 
  cases 
  were 
  

   found 
  to 
  be 
  in 
  close 
  agreement. 
  It 
  is 
  obvious, 
  however, 
  

   that 
  the 
  position 
  of 
  weak 
  lines 
  could 
  not 
  be 
  determined 
  by 
  

   this 
  method 
  with 
  the 
  same 
  accuracy 
  as 
  for 
  the 
  stronger 
  lines. 
  

  

  In 
  order 
  to 
  examine 
  the 
  whole 
  extent 
  of 
  the 
  /3-ray 
  

   spectrum, 
  photographs 
  were 
  taken 
  in 
  ten 
  different 
  magnetic 
  

   fields, 
  increasing 
  with 
  approximately 
  constant 
  ratio 
  from 
  

  

  