﻿586 
  Messrs. 
  Cameron 
  and 
  Oettino-er 
  on 
  Electromotive 
  

  

  & 
  

  

  this 
  case 
  the 
  contributory 
  thermal 
  effects 
  o£ 
  the 
  radioactive 
  

   substances 
  has, 
  probably, 
  been 
  small, 
  however 
  long 
  a 
  time 
  we 
  

   are 
  willing 
  to 
  assign 
  to 
  the 
  genesis 
  o£ 
  heat. 
  

  

  An 
  estimate 
  of 
  the 
  intrinsic 
  heating-effect 
  of 
  the 
  radioactive 
  

   lavas 
  we 
  have 
  been 
  considering 
  is 
  of 
  interest. 
  The 
  mean 
  

   radium-content 
  of 
  the 
  lavas 
  ejected 
  since 
  1631 
  is 
  12'3 
  x 
  10"^^ 
  

   gram 
  per 
  gram. 
  Assuming 
  that 
  the 
  presence 
  of 
  one 
  gram 
  

   of 
  elemental 
  radium 
  in 
  equilibrium 
  involves 
  the 
  generation 
  

   of 
  201*6 
  gram-degrees 
  per 
  hour, 
  the 
  heating-effect 
  in 
  the 
  

   lava 
  is 
  about 
  25 
  x 
  10"^^ 
  calorie 
  per 
  hour. 
  The 
  mean 
  quantity 
  

   of 
  thorium 
  is 
  2*3 
  x 
  10~^ 
  gram 
  per 
  gram. 
  Pegram 
  and 
  

   Webb's 
  result, 
  obtained 
  by 
  a 
  direct 
  thermal 
  measurement 
  

   applied 
  to 
  thorium 
  oxide, 
  gives 
  the 
  heat 
  per 
  gram 
  of 
  elemental 
  

   thorium 
  in 
  equilibrium 
  as 
  2*38 
  x 
  10~^ 
  calorie. 
  Hence 
  the 
  

   thorium 
  present 
  would 
  produce 
  5'5x 
  10~^° 
  calorie 
  per 
  hour. 
  

   The 
  added 
  results 
  of 
  these 
  quantities 
  of 
  heat 
  works 
  out 
  as 
  

   giving 
  a 
  rise 
  of 
  temperature 
  of 
  about 
  150° 
  C. 
  in 
  one 
  million 
  

   years 
  ; 
  assuming 
  no 
  loss 
  by 
  conduction. 
  

  

  Those 
  who 
  look 
  to 
  radioactive 
  heating 
  as 
  affording 
  an 
  

   explanation 
  of 
  volcanic 
  periodicity 
  would 
  do 
  well 
  to 
  reflect 
  

   upon 
  the 
  slowness 
  with 
  which 
  beat 
  is 
  supplied, 
  even 
  in 
  

   exceptionally 
  rich 
  radioactive 
  materials. 
  

  

  In 
  the 
  case 
  of 
  the 
  Yesuvian 
  lavas 
  the 
  abnormally 
  large 
  

   amount 
  of 
  radium 
  present 
  renders 
  the 
  heating-effect 
  of 
  the 
  

   thorium 
  relatively 
  small. 
  The 
  mean 
  thorium-content 
  of 
  the 
  

   other 
  lavas 
  examined 
  is 
  2'6 
  x 
  10~^, 
  and 
  the 
  mean 
  radium- 
  

   content 
  of 
  these 
  rocks 
  is 
  4*0 
  x 
  10~^^ 
  gram 
  per 
  gram. 
  The 
  

   heating-effects 
  are 
  respectively 
  6-2x10-^^ 
  and 
  8*1x10-^^ 
  

   gram-degree 
  per 
  hour. 
  Here 
  there 
  is 
  nearly 
  equality 
  in 
  

   the 
  thermal 
  values. 
  Blanc 
  [Rend. 
  d. 
  R. 
  Accad. 
  d. 
  Lincei, 
  xviii. 
  

   ser. 
  5, 
  p. 
  289) 
  has 
  concluded 
  that 
  the 
  thermal 
  effect 
  of 
  

   thorium 
  in 
  rocks 
  may 
  amount 
  to 
  about 
  double 
  that 
  due 
  to 
  

   the 
  radium 
  series, 
  but 
  his 
  figures 
  are 
  based 
  on 
  a 
  somewhat 
  

   larger 
  thorium- 
  and 
  smaller 
  radium-content 
  than 
  has 
  prevailed 
  

   in 
  the 
  rocks 
  which 
  I 
  have, 
  so 
  far, 
  examined. 
  

  

  LXIII. 
  On 
  the 
  Electromotive 
  Forces 
  produced 
  hy 
  Acid 
  and 
  

   Alkcdine 
  Solutions 
  streaming 
  through 
  Glass 
  Capillary 
  Tubes, 
  

   By 
  Alexander 
  T. 
  Cameron 
  and 
  Erich 
  Oettinger*. 
  

  

  THE 
  electromotive 
  forces 
  existing 
  between 
  glass 
  or 
  other 
  

   insulating 
  material 
  and 
  aqueous 
  solutions, 
  and 
  the 
  con- 
  

   sequences 
  resulting 
  therefrom 
  when 
  these 
  solutions 
  are 
  

   moving 
  over 
  the 
  insulating 
  surface, 
  as, 
  e. 
  g.^ 
  when 
  they 
  are 
  

  

  * 
  Communicated 
  by 
  the 
  A.utliors. 
  

  

  