﻿392 
  Prof. 
  McLennan 
  and 
  Mr. 
  Kennedy 
  on 
  tJie 
  

  

  contributed 
  to 
  the 
  conductivity 
  practically 
  as 
  much 
  as 
  the 
  

   combined 
  action 
  o£ 
  the 
  earth's 
  penetrating 
  radiation 
  and 
  that 
  

   emitted 
  by 
  the 
  walls 
  of 
  the 
  cylinder. 
  If 
  then 
  the 
  activity 
  of 
  

   the 
  salt 
  consisted 
  solely 
  of 
  a 
  secondary 
  radiation 
  one 
  should 
  

   expect, 
  with 
  a 
  penetrating 
  radiation 
  gradually 
  increasing 
  in 
  

   intensity, 
  to 
  obtain 
  proportionately 
  greater 
  effects 
  when 
  

   the 
  salt 
  was 
  in 
  the 
  cylinder 
  than 
  when 
  it 
  was 
  removed 
  

   from 
  it. 
  

  

  In 
  order 
  to 
  realize 
  these 
  conditions, 
  a 
  few 
  milligrams 
  of 
  

   radium 
  bromide 
  sealed 
  in 
  a 
  glass 
  tube 
  were 
  enclosed 
  in 
  a 
  

   heavy 
  block 
  of 
  lead, 
  and 
  this 
  was 
  placed 
  at 
  a 
  number 
  of 
  

   different 
  distances 
  from 
  the 
  cylinder 
  and 
  the 
  conductivity 
  of 
  

   the 
  air 
  in 
  the 
  chamber 
  ascertained, 
  with 
  the 
  radium 
  in 
  each 
  

   position. 
  The 
  observations 
  were 
  made 
  first 
  with 
  the 
  salt 
  in 
  

   the 
  cylinder 
  and 
  then 
  repeated 
  for 
  each 
  position 
  of 
  the 
  radium 
  

   after 
  the 
  salt 
  had 
  been 
  removed. 
  

  

  The 
  results 
  of 
  these 
  measurements 
  are 
  given 
  in 
  Table 
  XL, 
  

  

  Table 
  XI. 
  

  

  Position 
  of 
  

   radium 
  bromide. 
  

  

  Saturation 
  current. 
  

   (Arbitrary 
  scale) 
  

   Salt 
  in 
  cylinder. 
  

  

  Saturation 
  current. 
  

  

  (Arbitrary 
  scale) 
  

  

  Salt 
  not 
  in 
  cylinder. 
  

  

  First 
  

  

  6053 
  

  

  2568 
  

  

  907 
  

  

  271 
  

  

  209 
  

  

  6272 
  

  

  2641 
  

  

  945 
  

  

  273 
  

  

  227 
  

  

  Second 
  

  

  Third 
  

  

  Fourth 
  

  

  Fifth 
  

  

  and 
  from 
  the 
  numbers 
  given 
  in 
  the 
  table 
  it 
  will 
  be 
  seen 
  that 
  

   although 
  the 
  ionization 
  currents 
  were 
  increased 
  over 
  thirty- 
  

   fold, 
  the 
  ionization, 
  and 
  consequently 
  the 
  secondary 
  radiation 
  

   produced 
  by 
  the 
  gamma 
  rays 
  from 
  the 
  radium, 
  was 
  invariably 
  

   less 
  when 
  the 
  salt 
  was 
  in 
  the 
  cylinder 
  than 
  before 
  the 
  salt 
  

   was 
  introduced. 
  

  

  Inasmuch 
  as 
  the 
  ordinary 
  or 
  spontaneous 
  ionization 
  in 
  

   the 
  cylinder 
  was 
  found 
  to 
  be 
  increased 
  approximately 
  twofold 
  

   by 
  the 
  introduction 
  of 
  the 
  salt, 
  it 
  is 
  clear, 
  in 
  the 
  light 
  of 
  the 
  

   numbers 
  given 
  above, 
  that 
  this 
  increase 
  in 
  the 
  conductivity 
  

   was 
  due 
  to 
  a 
  primary 
  activity 
  possessed 
  by 
  the 
  salt, 
  and 
  not 
  

   due 
  to 
  a 
  secondary 
  activity 
  imparted 
  to 
  it 
  by 
  the 
  influence 
  

   of 
  external 
  radiations. 
  

  

  