﻿40 
  W. 
  P. 
  White 
  — 
  Silicate 
  Specific 
  Heats. 
  

  

  pseudo-wollastonite 
  is 
  less 
  than 
  that 
  of 
  the 
  lower 
  tem- 
  

   perature 
  form, 
  wollastonite. 
  

  

  The 
  inversions 
  of 
  silica, 
  on 
  the 
  other 
  hand, 
  seem 
  

   capable 
  of 
  challenging 
  much 
  that 
  is 
  now 
  accepted. 
  

   Bridgman, 
  52 
  for 
  instance, 
  speaks 
  of 
  the 
  formation 
  of 
  

   crystals 
  as 
  always 
  a 
  process 
  of 
  building 
  up 
  from 
  nuclei. 
  

   But 
  it 
  seems 
  incredible 
  that 
  in 
  quartz, 
  a 
  substance 
  whose 
  

   very 
  melting 
  is 
  extraordinarily 
  sluggish, 
  a 
  rearrange- 
  

   ment 
  of 
  this 
  sort 
  could, 
  at 
  relatively 
  low 
  temperatures, 
  

   take 
  place 
  with 
  almost 
  instantaneous 
  promptness. 
  A 
  

   further 
  objection 
  to 
  the 
  idea 
  of 
  growth 
  from 
  nuclei 
  is 
  

   found 
  in 
  the 
  extension 
  in 
  temperature 
  of 
  the 
  phenomenon. 
  

   I 
  have 
  hitherto 
  spoken 
  of 
  the 
  phenomena 
  preceding 
  the 
  

   inversion, 
  but 
  the 
  evidence 
  at 
  present 
  is 
  very 
  uncer- 
  

   tain 
  that 
  the 
  " 
  inversion' 
  ' 
  is 
  anything 
  more 
  than 
  the 
  

   final 
  increment 
  of 
  these 
  preceding 
  phenomena, 
  which 
  

   extend 
  over 
  a 
  temperature-range 
  of 
  at 
  least 
  400°. 
  

   Wright, 
  in 
  commenting 
  upon 
  the 
  progress 
  of 
  these 
  

   changes, 
  speaks 
  of 
  a 
  constantly 
  increasing 
  disorienting 
  

   force 
  which 
  at 
  last 
  "the 
  crystal 
  forces 
  can 
  no 
  longer 
  

   withstand'' 
  (italics 
  mine). 
  Alongside 
  of 
  this 
  view 
  it 
  

   seems 
  desirable 
  to 
  put 
  that 
  of 
  a 
  gradual 
  change, 
  which 
  

   while 
  rapidly 
  accelerated 
  is 
  nowhere 
  sudden 
  nor 
  discon- 
  

   tinuous. 
  The 
  question 
  may 
  perhaps 
  be 
  left 
  open 
  till 
  

   more 
  data 
  are 
  available. 
  

  

  The 
  discrepancy 
  between 
  the 
  expansion 
  of 
  quartz 
  dur- 
  

   ing 
  the 
  inversion 
  interval, 
  and 
  the 
  energy 
  required 
  to 
  

   produce 
  it 
  (Table 
  IX) 
  is 
  not 
  at 
  all 
  disconcerting. 
  The 
  

   phenomena, 
  accompanying 
  the 
  melting 
  of 
  ice 
  show 
  that 
  

   in 
  a 
  change 
  of 
  state 
  there 
  is 
  no 
  fixed 
  relation 
  between 
  the 
  

   volume 
  changes 
  and 
  the 
  work 
  done 
  by 
  the 
  attractive 
  

   forces. 
  Bridgman 
  has 
  shown 
  that 
  this 
  fact 
  is 
  abundantly 
  

   illustrated 
  in 
  inversions, 
  and 
  has 
  accounted 
  for 
  it 
  by 
  

   pointing 
  out 
  that 
  bringing 
  the 
  centers 
  of 
  force 
  of 
  atoms 
  

   nearer 
  together 
  is 
  a 
  very 
  different 
  thing 
  from 
  bringing 
  

   their 
  centers 
  of 
  figure 
  nearer 
  together. 
  But 
  the 
  dis- 
  

   crepancy 
  in 
  quartz 
  is, 
  of 
  course, 
  another 
  reason, 
  and 
  a 
  

   very 
  strong 
  one, 
  for 
  considering 
  the 
  phenomena 
  over 
  a 
  

   wide 
  temperature 
  range 
  below 
  575° 
  as 
  belonging 
  to 
  a 
  

   change 
  of 
  state. 
  Even 
  if 
  there 
  is 
  a 
  sudden 
  change 
  in 
  

   quartz 
  at 
  the 
  upper 
  end 
  of 
  the 
  long 
  region, 
  a 
  change 
  

   which 
  would 
  be 
  the 
  only 
  "inversion" 
  if 
  an 
  infinite 
  rate 
  

   of 
  change 
  with 
  temperature 
  is 
  essential 
  in 
  our 
  definition 
  

  

  82 
  Ibid., 
  p. 
  75. 
  

  

  