﻿724 
  Prof. 
  E. 
  Rutherford 
  and 
  Mr. 
  H. 
  Robinson 
  on 
  the 
  

  

  the 
  intensities 
  of 
  the 
  different 
  groups. 
  On 
  account 
  of 
  the 
  

   great 
  penetrating 
  power 
  of 
  the 
  high 
  velocity 
  (3 
  particles, 
  the 
  

   photographic 
  effect 
  for 
  equal 
  numbers 
  of 
  particles 
  is 
  relatively 
  

   much 
  weaker 
  than 
  that 
  for 
  the 
  slower 
  rays. 
  In 
  consequence 
  

   of 
  this, 
  three 
  or 
  four 
  times 
  the 
  length 
  of 
  exposure 
  was 
  required 
  

   to 
  bring 
  out 
  clearly 
  the 
  groups 
  of 
  high 
  velocity 
  j3 
  rays. 
  In 
  

   the 
  absence 
  of 
  definite 
  knowledge 
  of 
  the 
  relative 
  photographic 
  

   effects 
  of 
  j3 
  rays 
  of 
  different 
  velocities, 
  it 
  is 
  desirable 
  to 
  

   classify 
  the 
  intensity 
  of 
  a 
  given 
  group 
  by 
  the 
  strength 
  with 
  

   which 
  it 
  stands 
  out 
  above 
  the 
  general 
  photographic 
  fog 
  due 
  

   to 
  scattered 
  radiation 
  &c. 
  The 
  following 
  symbols, 
  in 
  order 
  

   of 
  decreasing 
  intensity, 
  have 
  been 
  used 
  : 
  — 
  

  

  v.s., 
  very 
  strong 
  ; 
  s., 
  strong 
  ; 
  m.s., 
  moderately 
  strong 
  ; 
  

   m., 
  mean 
  intensity; 
  m.f., 
  medium 
  faint 
  ; 
  f., 
  faint 
  ; 
  v.f., 
  very 
  

   faint. 
  

  

  In 
  addition, 
  it 
  is 
  convenient 
  for 
  reference 
  to 
  mark 
  the 
  

   strong 
  lines 
  by 
  a 
  letter. 
  

  

  It 
  is 
  evident 
  from 
  the 
  nature 
  of 
  the 
  problem 
  and 
  the 
  large 
  

   number 
  of 
  lines 
  examined 
  that 
  this 
  classification 
  must 
  be 
  

   somewhat 
  arbitrary, 
  but 
  it 
  suffices 
  for 
  a 
  general 
  indication 
  of 
  

   the 
  variation 
  of 
  intensity 
  among 
  the 
  groups. 
  

  

  In 
  the 
  following 
  table 
  column 
  I. 
  gives 
  the 
  distinctive 
  

   number 
  of 
  the 
  line, 
  II. 
  the 
  intensity; 
  column 
  III. 
  the 
  value 
  

   of 
  Hp 
  where 
  H 
  is 
  the 
  magnetic 
  field 
  in 
  gauss 
  and 
  p 
  the 
  radius 
  

   of 
  curvature 
  in 
  cm. 
  Column 
  IY. 
  gives 
  the 
  value 
  of 
  j3, 
  the 
  

  

  Table 
  I. 
  

   Groups 
  of 
  rays 
  from 
  Radium 
  B. 
  

  

  I. 
  

  

  II. 
  

  

  III. 
  

  

  IV. 
  

  

  V. 
  

  

  Energy 
  

   -^10 
  13 
  e. 
  

  

  No. 
  

  

  IntJ. 
  

  

  1 
  

  

  2 
  

  

  f. 
  

   m.s. 
  

  

  s. 
  

  

  v.f. 
  

   m.s. 
  

  

  v.s. 
  

  

  m. 
  

   m.s. 
  

  

  v.s. 
  

  

  1U.S. 
  

  

  v.s. 
  

  

  m. 
  

  

  m. 
  

  

  m.s. 
  

  

  s. 
  

   v.s. 
  

  

  2450 
  

   2295 
  

   2235 
  

   2140 
  

   1990 
  

   1925 
  

   1815 
  

   1752 
  

   1660 
  

   1470 
  

   1392 
  

  

  Groups. 
  

   950-914 
  

   861-836 
  

  

  798 
  

  

  770 
  

  

  663 
  

  

  •823 
  

   •805 
  

   •797 
  

   •787 
  

   •762 
  

   •751 
  

   •731 
  

   •719 
  

   •700 
  

   •656 
  

   •635 
  

  

  •426 
  

   •414 
  

   •365 
  

  

  3-852 
  

   3-480 
  

   3-332 
  

   3-160 
  

   2-758 
  

   2 
  ■610 
  

   2-366 
  

   2-228 
  

   2039 
  

   1-650 
  

   1-519 
  

  

  •539 
  

   •503 
  

   •376 
  

  

  3A 
  

  

  4 
  

  

  5 
  

  

  6B 
  

  

  7 
  

  

  8 
  

  

  9C 
  

  

  10 
  

  

  11D 
  

  

  12 
  

  

  13 
  

  

  14 
  

  

  15E 
  

  

  16F 
  

  

  

  