﻿Penetrating 
  Radiation 
  from 
  the 
  Earth. 
  609 
  

  

  or 
  other 
  structures 
  have 
  a 
  doubtful 
  value 
  both 
  on 
  account 
  of 
  

   the 
  unknown 
  radium 
  content 
  of 
  the 
  building 
  material 
  and 
  

   the 
  probability 
  of 
  a 
  contribution 
  to 
  the 
  penetrating 
  radiation 
  

   being 
  due 
  to 
  a 
  distribution 
  of 
  active 
  deposit 
  from 
  the 
  atmo- 
  

   sphere. 
  On 
  the 
  other 
  hand, 
  the 
  results 
  obtained 
  from 
  balloon 
  

   ascensions 
  have 
  not 
  revealed 
  the 
  required 
  gradient, 
  and 
  as 
  no 
  

   explanation 
  of 
  the 
  failure 
  has 
  been 
  forthcoming, 
  the 
  writer 
  

   has 
  ventured 
  to 
  bring 
  forward 
  evidence 
  to 
  show 
  that 
  the 
  

   results 
  may 
  be 
  vitiated 
  by 
  ionization 
  contributed 
  by 
  radiations 
  

   from 
  an 
  active 
  deposit 
  on 
  the 
  car 
  of 
  the 
  balloon 
  or 
  even 
  on 
  

   the 
  electroscope 
  itself. 
  This 
  explanation 
  has 
  already 
  been 
  

   suggested 
  to 
  explain 
  the 
  variation 
  of 
  Wulf's 
  observations 
  on 
  

   the 
  Eiffel 
  Tower 
  from 
  the 
  requirements 
  of 
  theory 
  *. 
  

  

  It 
  is 
  well 
  known 
  that 
  balloons 
  may 
  become 
  very 
  highly 
  

   charged 
  relatively 
  to 
  the 
  surrounding 
  air. 
  An 
  account 
  of 
  

   the 
  subject 
  is 
  to 
  be 
  found 
  in 
  the 
  Report 
  of 
  the 
  Advisory 
  

   Committee 
  of 
  Aeronautics, 
  1909-1910 
  f. 
  According 
  to 
  

   evidence 
  there 
  collected 
  (p. 
  119), 
  and 
  also 
  to 
  experiments 
  and 
  

   calculations 
  described 
  by 
  G. 
  W. 
  Walker 
  (p. 
  112), 
  it 
  seems 
  

   probable 
  that 
  a 
  balloon 
  takes 
  a 
  considerable 
  length 
  of 
  time 
  

   to 
  attain 
  the 
  potential 
  of 
  the 
  surrounding 
  air. 
  It 
  is 
  probable 
  

   that 
  in 
  the 
  course 
  of 
  an 
  ascent 
  the 
  balloon 
  may 
  be 
  at 
  a 
  

   potential 
  differing 
  by 
  several 
  thousand 
  volts 
  from 
  that 
  of 
  the 
  

   air 
  in 
  its 
  neighbourhood: 
  definite 
  measurements 
  on 
  this 
  point 
  

   were 
  made 
  by 
  Dieckmann 
  in 
  1911 
  during 
  two 
  voyages 
  of 
  a 
  

   Zeppelin 
  airship 
  %. 
  

  

  If 
  this 
  difference 
  of 
  potential 
  should 
  happen 
  to 
  be 
  negative 
  

   (as 
  in 
  the 
  case 
  of 
  a 
  balloon 
  rising 
  rapidly 
  from 
  a 
  normal 
  

   negative 
  earth) 
  enough 
  active 
  deposit 
  might 
  be 
  collected 
  on 
  

   the 
  balloon, 
  its 
  car, 
  and 
  fixtures, 
  and 
  perhaps 
  even 
  on 
  the 
  

   electroscope 
  itself, 
  to 
  give 
  rise 
  to 
  a 
  penetrating 
  radiation 
  of 
  

   sufficient 
  intensity 
  to 
  mask 
  that 
  coming 
  from 
  the 
  earth. 
  

   Flemming§ 
  found 
  from 
  balloon 
  observations 
  that 
  at 
  an 
  

   altitude 
  of 
  3000 
  metres 
  about 
  the 
  same 
  amount 
  of 
  active 
  

   deposit 
  could 
  be 
  collected 
  as 
  at 
  the 
  surface, 
  while 
  Saake 
  || 
  

   and 
  GockellF 
  found 
  the 
  amount 
  collected 
  at 
  high 
  altitudes 
  

   greater 
  than 
  at 
  sea-level. 
  

  

  The 
  explanation 
  just 
  put 
  forward 
  agrees 
  with 
  the 
  trend 
  of 
  

  

  * 
  Chauveau, 
  loc. 
  cit. 
  p. 
  73 
  ; 
  Rutherford, 
  ' 
  Radio 
  -activity/ 
  1913, 
  p. 
  636 
  

  

  t 
  Published 
  by 
  Wyman 
  & 
  Sons, 
  London, 
  1910 
  ; 
  see 
  also 
  Abstracts, 
  24, 
  

   p. 
  159, 
  and 
  54, 
  p. 
  180. 
  

  

  | 
  Dieckmann, 
  M., 
  Zeit. 
  fur 
  Flugtechnik 
  mid 
  Motorhtftschiffahrt, 
  

   Jan. 
  14, 
  1911. 
  Abstracted 
  in 
  Report 
  of 
  the 
  Advisory 
  Committee 
  for 
  

   Aeronautics, 
  1910-11, 
  p. 
  124. 
  

  

  § 
  Flemming, 
  Phijs. 
  Zeit. 
  ix. 
  p. 
  801 
  (1908). 
  

  

  || 
  Saake, 
  Phijs. 
  Zeit. 
  iv. 
  p. 
  626 
  (1903). 
  

  

  % 
  Gockel, 
  Phys. 
  Zeit. 
  viii. 
  p. 
  701 
  (1907). 
  

  

  