﻿222 
  J. 
  J. 
  Stevenson 
  — 
  Origin 
  of 
  Formkohle. 
  

  

  below 
  it. 
  Potonid 
  recognizes 
  the 
  efficiency 
  of 
  weathering 
  upon 
  

   peat 
  and 
  explains 
  by 
  it 
  the 
  nests 
  and 
  streaks 
  of 
  pyropissite 
  in 
  

   lump 
  coal, 
  though 
  he 
  does 
  not 
  apply 
  the 
  same 
  explanation 
  to 
  

   the 
  similar 
  nests 
  and 
  streaks 
  in 
  Formkohle. 
  

  

  The 
  cementing 
  substance 
  of 
  brown 
  coal, 
  related 
  to 
  the 
  dop- 
  

   plerite 
  of 
  peat, 
  can 
  be 
  removed 
  by 
  solution, 
  as 
  Pishel* 
  has 
  

   shown. 
  In 
  describing 
  the 
  conditions 
  on 
  an 
  Indian 
  reservation 
  

   in 
  J^orth 
  Dakota, 
  he 
  says 
  that 
  much 
  u 
  hydrocarbon 
  " 
  can 
  be 
  

   removed 
  during 
  the 
  lignite 
  stage 
  and 
  that 
  a 
  great 
  quantity 
  is 
  

   carried 
  out 
  from 
  lignite 
  beds 
  by 
  springs. 
  The 
  larger 
  springs 
  

   are 
  but 
  slightly 
  discolored 
  but 
  those 
  of 
  less 
  size 
  are 
  decidedly 
  

   dark. 
  The 
  substance 
  is 
  dissolved, 
  it 
  is 
  not 
  in 
  suspension, 
  for 
  

   water 
  in 
  pools 
  becomes 
  darker 
  on 
  evaporation 
  and 
  leaves 
  no 
  

   precipitate 
  until 
  wholly 
  removed, 
  when 
  some 
  dry 
  scales 
  remain. 
  

   The 
  water 
  of 
  this 
  region 
  contains 
  some 
  alkaline 
  matter. 
  

   Wilderf 
  states 
  that 
  sometimes 
  the 
  upper 
  part 
  of 
  a 
  lignite 
  bed 
  

   is 
  " 
  slacked 
  " 
  and 
  does 
  not 
  improve 
  away 
  from 
  the 
  outcrop. 
  

   The 
  condition 
  is 
  such 
  as 
  would 
  result 
  from 
  exposure 
  of 
  the 
  

   upper 
  portion 
  while 
  the 
  lower 
  portion 
  was 
  protected. 
  At 
  

   times 
  the 
  whole 
  bed 
  has 
  been 
  reduced 
  to 
  " 
  slack 
  " 
  or 
  pulveru- 
  

   lent 
  coal. 
  The 
  change 
  in 
  structure, 
  judging 
  from 
  Wilder's 
  

   descriptions, 
  may 
  have 
  begun 
  before 
  the 
  deposit 
  was 
  covered. 
  

  

  While 
  in 
  some 
  districts 
  weathering 
  appears 
  to 
  have 
  been 
  the 
  

   cause 
  of 
  change, 
  still 
  there 
  are 
  others 
  in 
  which 
  there 
  is 
  no 
  

   proof 
  that 
  it 
  was 
  the 
  sole 
  or 
  even 
  the 
  dominant 
  cause. 
  But 
  

   whatever 
  the 
  cause 
  may 
  have 
  been, 
  the 
  hypothesis 
  of 
  origin 
  

   by 
  transport 
  fails 
  to 
  offer 
  an 
  adequate 
  explanation. 
  As 
  pre- 
  

   sented, 
  the 
  supporting 
  arguments 
  are 
  contradictory, 
  while 
  the 
  

   basal 
  postulates 
  are 
  inconsistent 
  with 
  all 
  known 
  existing 
  condi- 
  

   tions. 
  

  

  * 
  M. 
  A. 
  Pishel, 
  " 
  Lignite 
  in 
  the 
  Fort 
  Berthold 
  Indian 
  Keservation," 
  U. 
  S. 
  

   G. 
  S. 
  Bull. 
  471-C, 
  1912, 
  pp. 
  9-11. 
  

  

  f 
  F. 
  A. 
  Wilder, 
  " 
  The 
  Lignite 
  Coals 
  of 
  North 
  Dakota," 
  Econ. 
  Geol. 
  vol. 
  i, 
  

   1906, 
  pp. 
  676, 
  677. 
  

  

  