﻿364 
  Fenner 
  — 
  Stability 
  Relations 
  of 
  Silica 
  Minerals. 
  

  

  by 
  a 
  number 
  of 
  analyses 
  to 
  contain 
  only 
  0*04— 
  0*07 
  per 
  cent 
  

   impurity. 
  The 
  results 
  from 
  these 
  preparations 
  were 
  no 
  more 
  

   concordant 
  than 
  before, 
  and 
  by 
  further 
  investigation 
  it 
  was 
  

   brought 
  out 
  that 
  we 
  had 
  to 
  do 
  with 
  a 
  phenomenon 
  of 
  a 
  rather 
  

   different 
  nature 
  from 
  any 
  which 
  had 
  been 
  encountered 
  in 
  pre- 
  

   vious 
  work 
  in 
  this 
  Laboratory. 
  After 
  considerable 
  preliminary 
  

   experimentation 
  the 
  results 
  began 
  to 
  point 
  in 
  a 
  definite 
  direc- 
  

   tion. 
  A 
  tentative 
  hypothesis 
  was 
  formulated 
  as 
  a 
  working 
  

   basis 
  and 
  investigation 
  was 
  directed 
  along 
  the 
  course 
  indicated 
  

   by 
  this 
  conception 
  and 
  tended 
  to 
  confirm 
  it. 
  As 
  a 
  final 
  result 
  

   it 
  can 
  be 
  said 
  that 
  while 
  absolute 
  proof 
  is 
  lacking, 
  the 
  results 
  

   obtained 
  are 
  perfectly 
  in 
  harmony 
  with 
  the 
  conception 
  and 
  all 
  

   other 
  hypotheses 
  which 
  have 
  presented 
  themselves 
  as 
  possible 
  

   explanations 
  have 
  been 
  pretty 
  well 
  disproved. 
  

  

  Briefly 
  stated 
  the 
  conception 
  is 
  this 
  : 
  that 
  cristobalite 
  con- 
  

   sists 
  not 
  of 
  one 
  but 
  of 
  at 
  least 
  two 
  different 
  molecular 
  species 
  

   in 
  the 
  same 
  crystal. 
  The 
  relative 
  proportions 
  of 
  these 
  depend 
  

   upon 
  the 
  conditions 
  present 
  at 
  the 
  time 
  of 
  crystallization, 
  such 
  

   as 
  the 
  nature 
  of 
  the 
  solution, 
  if 
  formed 
  in 
  a 
  melt, 
  or 
  the 
  tem- 
  

   perature 
  at 
  the 
  time 
  of 
  inversion, 
  if 
  formed 
  in 
  a 
  dry 
  way. 
  The 
  

   relative 
  proportions 
  of 
  the 
  polymeric 
  molecules 
  as 
  fixed 
  by 
  the 
  

   conditions 
  of 
  formation 
  are 
  not 
  affected 
  by 
  cooling 
  quickly 
  to 
  

   room 
  temperatures, 
  but 
  by 
  a 
  second 
  exposure 
  to 
  a 
  high 
  degree 
  

   of 
  heat 
  a 
  variation 
  in 
  the 
  proportions 
  is 
  brought 
  about 
  by 
  a 
  

   transformation 
  of 
  some 
  of 
  the 
  molecules 
  of 
  one 
  kind 
  into 
  the 
  

   other, 
  and 
  upon 
  cooling 
  again 
  the 
  properties 
  are 
  found 
  to 
  have 
  

   become 
  different 
  in 
  accordance. 
  

  

  It 
  will 
  be 
  recognized 
  that 
  this 
  is 
  essentially 
  the 
  theory 
  which 
  

   A. 
  Smits 
  and 
  his 
  co-workers 
  have 
  urged 
  strongly 
  in 
  the 
  last 
  

   three 
  years 
  in 
  a 
  series 
  of 
  papers 
  appearing 
  especially 
  in 
  the 
  

   Zeitschrift 
  fur 
  physikalische 
  Chemie, 
  and 
  the 
  Proceedings 
  of 
  

   the 
  Koninklijke 
  Akademie 
  van 
  Wetenschappen 
  at 
  Amster- 
  

   dam,* 
  and 
  confirmation 
  of 
  this 
  conception 
  has 
  been 
  furnished 
  

   by 
  certain 
  phenomena 
  exhibited 
  by 
  mercuric 
  iodide, 
  sulphur, 
  

   phosphorus, 
  etc. 
  Upon 
  it 
  a 
  theory 
  of 
  allotropy 
  has 
  been 
  

   founded. 
  Smits' 
  theory 
  is 
  a 
  conception 
  of 
  great 
  moment 
  and 
  

   it 
  is 
  important 
  that 
  all 
  possible 
  evidence 
  should 
  be 
  brought 
  to 
  

   bear 
  upon 
  it. 
  In 
  this 
  connection 
  the 
  properties 
  of 
  cristobalite 
  

   appear 
  to 
  have 
  some 
  value. 
  

  

  The 
  point 
  of 
  departure 
  of 
  Smits' 
  theory 
  is 
  that 
  investigation 
  

   has 
  shown 
  that 
  liquids, 
  either 
  pure 
  melts 
  or 
  solutions, 
  contain 
  

   as 
  a 
  rule 
  a 
  given 
  substance 
  in 
  two 
  or 
  more 
  sorts 
  of 
  molecular 
  

   aggregation, 
  each 
  of 
  which 
  is 
  capable 
  of 
  transformation 
  into 
  

   the 
  others 
  by 
  a 
  change 
  in 
  the 
  mode 
  of 
  linkage 
  of 
  the 
  simple 
  

   molecules, 
  but 
  the 
  proportions 
  of 
  the 
  various 
  modifications 
  are 
  

  

  *A. 
  Smits, 
  Zs. 
  phys. 
  Chem., 
  lxxvi, 
  421, 
  1911; 
  lxxxii, 
  657, 
  1913; 
  Kon. 
  

   Akad. 
  v. 
  Wet., 
  Mar. 
  26, 
  1910; 
  Sept. 
  30, 
  1911; 
  Sept, 
  28, 
  1912. 
  A. 
  Smits 
  

   and 
  H. 
  L. 
  DeLeeuw, 
  Kon. 
  Akad. 
  v. 
  Weten., 
  Sept, 
  24, 
  1910; 
  Nov. 
  30, 
  1912. 
  

  

  