﻿94 
  Mack 
  and 
  Hulett 
  — 
  Water 
  Content 
  of 
  Coal. 
  

  

  portions 
  that 
  there 
  was 
  a 
  continuous 
  diminution 
  in 
  the 
  per- 
  

   centage 
  of 
  oxygen 
  present 
  in 
  the 
  substances 
  which 
  make 
  up 
  

   the 
  coal. 
  

  

  It 
  must, 
  however, 
  be 
  noted 
  that 
  water 
  cannot 
  be 
  removed 
  

   from 
  peat 
  or 
  coal 
  to 
  any 
  great 
  extent 
  by 
  pressure, 
  but 
  as 
  a 
  

   result 
  of 
  the 
  chemical 
  reaction 
  involved 
  in 
  the 
  transformation 
  

   of 
  peat 
  to 
  coal 
  the 
  physical 
  properties 
  of 
  the 
  mass 
  changed 
  

   so 
  that 
  it 
  was 
  possible 
  for 
  the 
  water 
  partially 
  to 
  escape. 
  We 
  

   may 
  question 
  whether 
  too 
  much 
  importance 
  has 
  not 
  been 
  

   assigned 
  to 
  the 
  influence 
  of 
  pressure 
  as 
  a 
  factor 
  in 
  the 
  change 
  

   from 
  peat 
  to 
  coal 
  ; 
  for 
  pressure 
  plays 
  little, 
  if 
  any, 
  role 
  in 
  the 
  

   chemical 
  reactions 
  which 
  take 
  place 
  in 
  a 
  condensed 
  system, 
  

   either 
  as 
  regards 
  the 
  kind 
  of 
  the 
  reaction 
  or 
  the 
  rate. 
  How- 
  

   ever 
  if 
  the 
  pressure 
  causes 
  a 
  rise 
  in 
  temperature 
  then 
  the 
  rates 
  

   of 
  the 
  chemical 
  reactions 
  taking 
  place 
  are 
  markedly 
  accel- 
  

   erated. 
  Pressure 
  has 
  undoubtedly 
  aided 
  somewhat 
  in 
  the 
  

   mechanical 
  elimination 
  of 
  the 
  more 
  volatile 
  and 
  liquid 
  pro- 
  

   ducts 
  of 
  the 
  chemical 
  reactions, 
  and 
  has 
  been 
  a 
  factor 
  in 
  giv- 
  

   ing 
  coal 
  its 
  firm, 
  compact 
  qualities. 
  

  

  The 
  possibility 
  that 
  pressure 
  may 
  have 
  caused 
  a 
  rise 
  in 
  the 
  

   temperature 
  of 
  the 
  peat-like 
  substance 
  has 
  been 
  suggested. 
  It 
  

   is, 
  however, 
  to 
  be 
  remembered 
  that 
  the 
  mere 
  subjection 
  of 
  a 
  

   body 
  to 
  a 
  pressure 
  strain 
  will 
  not 
  generate 
  heat 
  unless 
  there 
  is 
  

   an 
  actual 
  decrease 
  in 
  the 
  volume 
  Of 
  the 
  substance 
  compressed, 
  

   in 
  accordance 
  with 
  'the 
  energy 
  equation 
  : 
  

  

  P 
  X 
  V 
  = 
  2T 
  calories. 
  

  

  Heat 
  is 
  produced 
  by 
  the 
  action 
  of 
  pressure 
  through 
  a 
  distance, 
  

   represented 
  here 
  by 
  a 
  volume 
  change. 
  And 
  in 
  the 
  case 
  of 
  

   peat, 
  coal 
  and 
  the 
  intermediate 
  substances, 
  the 
  deposit 
  (from 
  

   the 
  old 
  swamp) 
  either 
  yielded 
  suddenly 
  to 
  an 
  enormous 
  pres- 
  

   sure, 
  breaking 
  or 
  crumpling, 
  in 
  which 
  case 
  the 
  heat 
  produced 
  

   would 
  be 
  dissipated 
  or 
  conducted 
  off 
  fairly 
  rapidly 
  by 
  sur- 
  

   rounding 
  rock 
  ; 
  or 
  the 
  deposit 
  and 
  the 
  rock 
  above 
  and 
  below 
  

   it 
  were 
  pressed 
  in 
  such 
  a 
  way 
  that 
  they 
  were 
  not 
  forced 
  to 
  

   yield 
  suddenly, 
  but 
  remained 
  under 
  the 
  strain 
  for 
  a 
  long 
  time.* 
  

   For 
  this 
  latter 
  case 
  we 
  may 
  make 
  an 
  approximate 
  calculation. 
  

  

  Assume 
  that 
  we 
  have 
  a 
  deposit 
  of 
  dense 
  peat 
  5 
  meters 
  thick 
  

   and 
  that 
  it 
  is 
  compressed 
  at 
  the 
  rate 
  of 
  about 
  one-half 
  a 
  

   meter 
  a 
  century, 
  i. 
  e. 
  one-tenth 
  of 
  its 
  volume 
  the 
  first 
  hundred 
  

   years. 
  Suppose 
  the 
  peat 
  layer 
  to 
  be 
  buried 
  one 
  kilometer 
  

   beneath 
  the 
  surface, 
  under 
  a 
  mass 
  of 
  debris, 
  which 
  had 
  an 
  

   average 
  specific 
  gravity 
  of 
  3*0. 
  Then 
  the 
  pressure 
  on 
  the 
  peat 
  

   per 
  square 
  centimeter 
  would 
  have 
  been, 
  

  

  1000 
  (m) 
  X 
  100 
  (cm) 
  X 
  3 
  grams 
  

  

  ',„ 
  , 
  —^ 
  = 
  300 
  kilograms 
  

  

  1000 
  (grams) 
  b 
  

  

  * 
  White 
  and 
  Thiessen, 
  The 
  Origin 
  of 
  Coal, 
  pages 
  106 
  and 
  128 
  of 
  the 
  chap- 
  

   ter 
  " 
  Regional 
  Metamorphism 
  of 
  Coal." 
  

  

  