﻿Radioactivity 
  of 
  certain 
  Lavas. 
  583 
  

  

  vulcanicitj 
  is 
  so 
  natural 
  an 
  association 
  o£ 
  ideas 
  that 
  even 
  

   before 
  the 
  general 
  prevalence 
  o£ 
  radium 
  in 
  rocks 
  had 
  been 
  

   demonstrated 
  by 
  Strutt, 
  a 
  suggestion 
  to 
  that 
  effect 
  had 
  been 
  

   made. 
  Major 
  Button 
  (Journal 
  of 
  Geology, 
  xiv. 
  May-June 
  

   1906, 
  p. 
  259) 
  in 
  1906 
  put 
  forward 
  the 
  view 
  that 
  radioactive 
  

   materials 
  might 
  give 
  rise 
  to 
  fusion 
  temperatures 
  at 
  points 
  

   within 
  3 
  or 
  4 
  miles 
  of 
  the 
  surface 
  : 
  indeed, 
  his 
  appeal 
  to 
  

   radioactive 
  energy 
  was 
  mainly 
  based 
  on 
  the 
  necessity 
  which, 
  

   according 
  to 
  Major 
  Dutton's 
  views, 
  exists 
  of 
  locating 
  volcanic 
  

   foci 
  at 
  these 
  short 
  distances 
  beneath 
  the 
  surface 
  of 
  the 
  Earth. 
  

   The 
  repetitive 
  character 
  of 
  the 
  phenomena 
  was 
  also 
  regarded 
  

   as 
  more 
  readily 
  accounted 
  for 
  on 
  the 
  theory 
  of 
  the 
  accumu- 
  

   l-ition 
  of 
  radioactive 
  energy 
  than 
  in 
  any 
  other 
  manner. 
  

   Major 
  Dutton''s 
  ideas 
  were 
  criticised 
  by 
  Gr. 
  D. 
  Lauderback 
  

   {ihid. 
  p. 
  748) 
  more 
  especially 
  as 
  to 
  the 
  necessity 
  of 
  assuming 
  

   a 
  position 
  so 
  superficial 
  for 
  volcanic 
  foci 
  and 
  of 
  appealing 
  to 
  

   radium 
  to 
  explain 
  the 
  repetitive 
  phenomena. 
  Moreover, 
  it 
  

   was 
  pointed 
  out 
  by 
  more 
  than 
  one 
  critic 
  at 
  the 
  time 
  that 
  any 
  

   theory 
  involving 
  haphazard 
  pockets 
  of 
  radioactive 
  materials 
  

   was 
  not 
  in 
  accord 
  with 
  the 
  fact 
  that 
  the 
  location 
  of 
  volcanoes 
  

   w^as 
  by 
  no 
  means 
  haphazard, 
  but 
  was 
  determined 
  according 
  

   to 
  certain 
  great 
  surface 
  features 
  of 
  the 
  Globe 
  ; 
  the 
  geo- 
  

   synclines, 
  wherein 
  sediments 
  collect 
  and 
  crust-flexure 
  occurs. 
  

   When 
  recently 
  dealing 
  with 
  the 
  latter 
  subject 
  — 
  the 
  very 
  

   probable 
  connexion 
  between 
  radioactive 
  beating 
  and 
  the 
  

   instability 
  of 
  the 
  sediment-laden 
  part 
  of 
  the 
  crust 
  (Address 
  

   Sect. 
  C. 
  Brit. 
  Assoc. 
  1908), 
  it 
  appeared 
  to 
  me 
  that 
  a 
  

   x3onnexion 
  between 
  vulcanicity 
  and 
  radioactivity 
  was, 
  in 
  

   point 
  of 
  fact, 
  involved 
  in 
  the 
  conditions 
  determining 
  the 
  rise 
  

   of 
  the 
  geotherms 
  under 
  a 
  superficial 
  covering 
  of 
  some 
  kilo- 
  

   metres 
  of 
  radioactive 
  sediments. 
  While 
  we 
  are 
  not 
  entitled 
  

   to 
  assume 
  upon 
  our 
  present 
  knowledge 
  the 
  existence 
  of 
  

   radioactive 
  magmas 
  in 
  pockets 
  close 
  to 
  the 
  surface 
  and 
  

   possessed 
  of 
  sufficient 
  radioactivity 
  to 
  establish 
  a 
  local 
  

   volcanic 
  focus, 
  some 
  miles 
  down 
  high 
  temperatures 
  might 
  

   be 
  ascribed 
  to 
  the 
  great 
  sedimentary 
  accumulations 
  which 
  

   have 
  been 
  sufficiently 
  long 
  in 
  situ 
  for 
  the 
  accumulation 
  of 
  

   radioactive 
  heat. 
  The 
  crust 
  buried 
  beneath 
  the 
  covering 
  of 
  

   sediment 
  is, 
  in 
  fact, 
  heated 
  both 
  from 
  above 
  and 
  from 
  

   beneath, 
  and 
  the 
  quantities 
  involved, 
  as 
  regards 
  depths 
  of 
  

   sedimentary 
  deposit 
  and 
  average 
  radioactivity 
  of 
  such 
  

   materials, 
  are 
  such 
  as 
  to 
  justify 
  the 
  view 
  that 
  in 
  the 
  geo- 
  

   synclines 
  vulcanicity 
  would 
  be 
  specially 
  favoured. 
  If 
  this 
  

   hypothesis 
  is 
  correct, 
  not 
  only 
  the 
  flexure 
  and 
  distortion 
  

   affecting 
  these 
  areas, 
  but 
  the 
  chains 
  of 
  volcanoes 
  breaking 
  

   out 
  along 
  the 
  great 
  mountain 
  ranges, 
  may 
  be 
  logically 
  

  

  