﻿284 
  

  

  Dr. 
  A. 
  S. 
  Eve 
  on 
  Primary 
  

   Secondary 
  y 
  Hays. 
  

  

  A 
  strong 
  and 
  satisfactory 
  source 
  of 
  secondary 
  7 
  rays 
  was 
  

   obtained 
  by 
  the 
  arrangement 
  shown 
  in 
  fig. 
  4. 
  14 
  milligrams 
  

  

  Fig. 
  4. 
  

  

  of 
  radium 
  bromide, 
  placed 
  in 
  a 
  hollow^ 
  cylinder 
  H, 
  sent 
  

   a 
  cone 
  of 
  rays 
  through 
  the 
  platform 
  P 
  to 
  the 
  secondary 
  

   radiator 
  V. 
  The 
  secondary 
  7 
  rays 
  were 
  measured 
  by 
  the 
  

   electroscope 
  E, 
  after 
  passing 
  through 
  the 
  plates 
  A 
  and 
  B. 
  

   Both 
  electroscope 
  and 
  plates 
  were 
  well 
  screened 
  from 
  the 
  

   radium 
  by 
  much 
  lead. 
  A 
  correction 
  w^as 
  made 
  for 
  natural 
  

   leak 
  and 
  for 
  all 
  rays 
  entering 
  the 
  electroscope 
  otherwise 
  than 
  

   through 
  A 
  and 
  B, 
  and 
  the 
  amount 
  of 
  this 
  deduction 
  could 
  be 
  

   well 
  estimated 
  by 
  placing 
  many 
  thick 
  plates 
  between 
  V 
  and 
  E. 
  

   Three 
  different 
  platforms 
  were 
  tried, 
  of 
  lead, 
  iron, 
  and 
  wood 
  

   respectively, 
  each 
  about 
  6 
  mm. 
  thick. 
  The 
  results 
  obtained 
  

   differed 
  somewhat 
  ; 
  but 
  as 
  the 
  differences 
  were 
  too 
  small 
  to 
  

   measure 
  correctly 
  the 
  mean 
  values 
  were 
  taken. 
  When 
  a 
  

   large 
  lead 
  cylinder 
  served 
  as 
  radiator 
  at 
  V, 
  the 
  secondary 
  

   7 
  rays 
  were 
  feeble, 
  because 
  they 
  were 
  to 
  a 
  large 
  extent 
  

   absorbed 
  in 
  the 
  lead 
  itself. 
  Four 
  bricks 
  placed 
  on 
  end, 
  close 
  

   together, 
  proved 
  a 
  good 
  radiator. 
  A 
  tinned 
  iron 
  pail, 
  17 
  cm. 
  

   high, 
  15 
  cm. 
  in 
  diameter, 
  was 
  also 
  used, 
  and 
  could 
  be 
  

   filled 
  with 
  iron 
  filings, 
  water, 
  sand, 
  or 
  coal. 
  Such 
  different 
  

   radiators 
  did 
  not 
  give 
  well-marked 
  differences 
  in 
  their 
  

   secondary 
  y 
  radiations 
  ; 
  and 
  I 
  worked, 
  therefore, 
  mainly 
  

   with 
  bricks, 
  or 
  with 
  iron 
  filings 
  as 
  radiator, 
  and 
  with 
  a 
  

   wooden 
  platform. 
  

  

  The 
  absorption 
  of 
  the 
  secondary 
  7 
  rays 
  by 
  lead 
  plates 
  is 
  

   shown 
  by 
  the 
  following 
  : 
  — 
  

  

  