﻿Emanation 
  in 
  the 
  Atmosphere 
  near 
  Earth's 
  Surface. 
  627 
  

  

  The 
  third 
  column 
  in 
  the 
  table 
  gives 
  the 
  amount 
  of 
  radium 
  

   which 
  would 
  be 
  required 
  to 
  supply 
  the 
  emanation 
  to 
  one 
  cubic 
  

   metre 
  of 
  the 
  atmosphere 
  at 
  the 
  place 
  and 
  during 
  the 
  time 
  of 
  

   the 
  observation 
  on 
  the 
  supposition 
  that 
  the 
  emanation 
  is 
  in 
  

   equilibrium 
  with 
  the 
  amount 
  of 
  radium 
  stated. 
  

  

  I 
  venture 
  to 
  call 
  this 
  the 
  radium 
  equivalent 
  per 
  cubic 
  

   metre. 
  

  

  The 
  remaining 
  columns 
  give 
  the 
  approximate 
  means 
  o£ 
  the 
  

   temperature 
  in 
  degrees 
  Fahrenheit, 
  the 
  barometric 
  pressure 
  

   in 
  inches, 
  and 
  the 
  wind 
  direction, 
  during 
  the 
  time 
  o£ 
  the 
  

   experiments. 
  Remarks 
  have 
  been 
  added 
  to 
  indicate 
  the 
  

   weather 
  conditions, 
  when 
  well 
  defined. 
  The 
  figures 
  and 
  

   remarks 
  are 
  deduced 
  from 
  notes 
  made 
  at 
  the 
  time, 
  from 
  the 
  

   weather 
  reports 
  o£ 
  the 
  McGrill 
  University 
  Observatory, 
  issued 
  

   by 
  Professor 
  C. 
  H. 
  McLeod, 
  and 
  from 
  the 
  weather 
  maps 
  

   issued 
  daily 
  by 
  the 
  United 
  States 
  Department 
  of 
  Agriculture. 
  

  

  Discussion 
  of 
  Results. 
  

  

  In 
  the 
  first 
  place 
  it 
  will 
  be 
  seen 
  that 
  temperature 
  has 
  little 
  

   or 
  no 
  appreciable 
  direct 
  effect 
  on 
  the 
  amount 
  of 
  emanation 
  

   in 
  the 
  atmosphere 
  near 
  the 
  earth's 
  surface. 
  The 
  results 
  for 
  

   July 
  and 
  August 
  with 
  a 
  mean 
  temperature 
  of 
  65° 
  F. 
  are 
  not 
  

   very 
  different 
  from 
  those 
  made 
  in 
  the 
  month 
  of 
  January 
  with 
  

   a 
  mean 
  temperature 
  of 
  12° 
  F. 
  

  

  Again, 
  during 
  the 
  month 
  of 
  March 
  there 
  was, 
  at 
  Montreal, 
  

   an 
  average 
  depth 
  of 
  snow 
  between 
  two 
  and 
  three 
  feet, 
  and 
  

   yet 
  the 
  radium 
  equivalent, 
  45*5 
  X 
  10" 
  12 
  , 
  was 
  but 
  little 
  less 
  

   than 
  that 
  for 
  April, 
  51*5 
  x 
  10 
  — 
  12 
  , 
  after 
  the 
  snow' 
  had 
  melted. 
  

   These 
  results 
  agree 
  with 
  the 
  observations 
  of 
  Rutherford 
  and 
  

   Allen, 
  that 
  the 
  active 
  deposit 
  collected 
  from 
  the 
  atmosphere 
  

   varied 
  little 
  in 
  magnitude 
  between 
  summer 
  and 
  winter, 
  even 
  

   when 
  the 
  wind 
  blew 
  from 
  cold 
  regions 
  deeply 
  covered 
  with 
  

   snow. 
  This 
  fact 
  suggests 
  that 
  the 
  radium 
  emanation 
  escapes 
  

   from 
  considerable 
  depths 
  in 
  the 
  ground. 
  

  

  It 
  may 
  be 
  noted, 
  however, 
  that 
  in 
  the 
  winter 
  1907-8 
  the 
  

   snow 
  preceded 
  any 
  severe 
  frosts 
  and 
  so 
  protected 
  the 
  earth 
  

   that 
  the 
  ground 
  was 
  scarcely 
  frozen. 
  

  

  It 
  may 
  be 
  stated 
  generally 
  that, 
  so 
  far 
  as 
  these 
  experiments 
  

   go, 
  they 
  indicate 
  that 
  a 
  well-defined 
  cyclone, 
  accompanied 
  

   by 
  heavy 
  rain 
  or 
  a 
  quick 
  thaw 
  of 
  snow, 
  gives 
  maximum 
  

   values 
  to 
  the 
  radium 
  equivalent. 
  On 
  the 
  other 
  hand, 
  anti- 
  

   cyclones, 
  with 
  dry 
  weather, 
  and, 
  in 
  winter, 
  very 
  low 
  tempe- 
  

   ratures, 
  give 
  minimum 
  values. 
  

  

  2T2 
  

  

  