﻿

  Emanation 
  in 
  the 
  Atmosphere 
  near 
  Earth's 
  Surface. 
  631 
  

  

  to 
  make 
  fairly 
  good 
  forecasts 
  o£ 
  the 
  radium 
  equivalent, 
  when 
  

   weather 
  of 
  a 
  pronounced 
  type 
  prevailed. 
  The 
  gradual 
  thaw 
  

   of 
  March 
  and 
  April 
  produced 
  fairly 
  steady 
  values, 
  until 
  the 
  

   well-defined 
  cyclone 
  of 
  27th 
  April 
  arrived 
  from 
  the 
  westward 
  

   with 
  a 
  south 
  wind 
  and 
  an 
  inch 
  of 
  rainfall, 
  and 
  then 
  there 
  

   was 
  a 
  considerable 
  increase. 
  

  

  The 
  month 
  of 
  February 
  was 
  spent 
  in 
  calibrating 
  instru- 
  

   ments, 
  and 
  in 
  vain 
  endeavours 
  to 
  obtain 
  daily 
  measurements. 
  

   The 
  quantity 
  of 
  emanation 
  collected 
  between 
  5 
  p.m. 
  and 
  9 
  a.m. 
  

   proved 
  too 
  small 
  for 
  measurement 
  with 
  any 
  approach 
  to 
  

   accuracy. 
  

  

  The 
  mean 
  of 
  the 
  results 
  is 
  59*7 
  x 
  10~ 
  12 
  grm. 
  of 
  radium 
  as 
  

   the 
  amount 
  in 
  equilibrium 
  with 
  the 
  emanation 
  present 
  in 
  a 
  

   cubic 
  metre 
  of 
  air. 
  This 
  is 
  in 
  fair 
  agreement 
  with 
  the 
  

   determination 
  82 
  x 
  10 
  -12 
  described 
  in 
  a 
  previous 
  paper 
  (Phil. 
  

   Mag. 
  July 
  1905). 
  In 
  the 
  latter 
  case, 
  the 
  active 
  deposit 
  on 
  a 
  

   negatively 
  charged 
  wire 
  was 
  measured 
  and 
  compared 
  with 
  

   similar 
  deposits 
  from 
  the 
  emanation 
  arising 
  from 
  a 
  standard 
  

   solution. 
  

  

  I 
  regret 
  that 
  pressure 
  of 
  other 
  work 
  prevented 
  me 
  from 
  

   making 
  simultaneous 
  observations 
  on 
  the 
  active 
  deposit, 
  

   ionization 
  and 
  potential 
  gradient. 
  At 
  present 
  there 
  is 
  much 
  

   waste 
  of 
  labour 
  in 
  the 
  incomplete 
  work 
  of 
  many 
  observers 
  

   who 
  have 
  not 
  time 
  or 
  opportunity 
  to 
  make 
  more 
  thorough 
  

   investigations. 
  The 
  time 
  has 
  certainly 
  come 
  for 
  a 
  complete 
  

   radioactive 
  survey 
  at 
  a 
  well-equipped 
  laboratory 
  with 
  a 
  

   sufficient 
  staff 
  of 
  skilled 
  observers. 
  Simultaneous 
  and 
  con- 
  

   tinuous 
  experiments 
  are 
  needed 
  on 
  the 
  meteorological 
  con- 
  

   ditions, 
  amount 
  of 
  radium 
  emanation 
  in 
  the 
  atmosphere, 
  

   active 
  deposit 
  obtainable, 
  potential 
  gradient, 
  penetrating- 
  

   radiation, 
  and 
  ionization 
  (Ebert's 
  and 
  Langevin's 
  methods). 
  

   In 
  the 
  measurement 
  of 
  penetrating 
  radiation 
  too 
  much 
  

   reliance 
  has 
  sometimes 
  been 
  placed 
  on 
  the 
  readings 
  of 
  a 
  

   single 
  instrument. 
  It 
  is 
  desirable 
  to 
  observe 
  the 
  fluctuations 
  

   with 
  both 
  electroscope 
  and 
  electrometer, 
  and 
  to 
  ascertain 
  if 
  

   the 
  variations 
  agree 
  with 
  different 
  types 
  and 
  arrangements 
  

   of 
  apparatus. 
  

  

  Those 
  engaged 
  in 
  balloon, 
  or 
  kite, 
  experiments 
  might 
  

   obtain 
  useful 
  information 
  on 
  the 
  penetrating 
  radiation 
  at 
  

   high 
  altitudes, 
  by 
  observations 
  on 
  the 
  rate 
  of 
  discharge 
  of 
  

   electroscopes 
  at 
  the 
  earth's 
  surface 
  and 
  at 
  considerable 
  

   elevation. 
  The 
  active 
  deposit 
  on 
  the 
  wires 
  employed 
  should 
  

   also 
  be 
  measured. 
  

  

  The 
  ionization 
  of 
  the 
  atmosphere 
  near 
  the 
  ground 
  appears 
  

   to 
  be 
  largely 
  due 
  to 
  radioactive 
  matter, 
  and 
  meteorological 
  

   conditions 
  are 
  dependent 
  on 
  ionization 
  to 
  a 
  large 
  and 
  unknown 
  

  

  