﻿212 
  J. 
  J. 
  Stevenson 
  — 
  Origin 
  of 
  Formkohle. 
  

  

  Drifted 
  fuel 
  materials 
  necessarily 
  take 
  up 
  mineral 
  substances, 
  

   which 
  accompany 
  them 
  in 
  the 
  water, 
  and 
  this 
  inorganic 
  matter 
  

   may 
  be 
  in 
  excess. 
  He 
  has 
  instances 
  from 
  the 
  lower 
  Rhine 
  

   region, 
  where 
  clay 
  beds 
  intervene 
  in 
  secondarily-allochthonous 
  

   coal 
  and 
  contain 
  scattered 
  fragments 
  of 
  coal. 
  Similar 
  scattered 
  

   bits 
  of 
  coal 
  occur 
  in 
  rocks 
  between 
  beds 
  of 
  brown 
  coal 
  in 
  

   southern 
  Sachsen 
  and 
  in 
  Anhalt, 
  as 
  well 
  as 
  in 
  the 
  underclay 
  at 
  

   the 
  Emma 
  mine. 
  

  

  Drying-cracks 
  indicate 
  secondarily-allochthonous 
  origin, 
  

   since 
  autochthonous 
  coals 
  must 
  be 
  compared 
  with 
  moors, 
  which 
  

   develop 
  under 
  constant 
  cover 
  of 
  water. 
  If 
  a 
  dry 
  period 
  come 
  

   to 
  these, 
  the 
  humus 
  masses 
  sink 
  together 
  in 
  consequence 
  of 
  

   their 
  water 
  content, 
  so 
  that 
  extreme 
  drying 
  would 
  be 
  needed 
  

   to 
  produce 
  the 
  shrinkage 
  cracks. 
  It 
  is 
  very 
  different 
  with 
  

   unstratitied 
  humus, 
  transported 
  by 
  high 
  water 
  and 
  therefore 
  

   easily 
  carried 
  to 
  areas 
  with 
  only 
  a 
  slight 
  cover 
  of 
  water. 
  So, 
  

   he 
  knows 
  of 
  drying- 
  cracks, 
  up 
  to 
  this 
  time, 
  only 
  in 
  secondarily- 
  

   allochthonous 
  coals. 
  It 
  must 
  be 
  recognized 
  also 
  that 
  certain 
  

   features, 
  which 
  elsewhere 
  indicate 
  autochthonous 
  origin, 
  may 
  

   occur 
  also 
  in 
  secondarily-allochthonous 
  coals. 
  In 
  study 
  of 
  a 
  

   particular 
  area, 
  one 
  must 
  not 
  forget 
  that 
  a 
  deposit 
  of 
  trans- 
  

   ported 
  material, 
  organic 
  or 
  inorganic, 
  can 
  produce 
  in 
  times 
  of 
  

   quiet 
  an 
  autochthonous 
  vegetation 
  — 
  trees, 
  reed-banks 
  and 
  the 
  

   rest 
  — 
  and 
  that 
  this 
  in 
  turn 
  may 
  be 
  covered 
  by 
  an 
  allochthonous 
  

   fuel-material. 
  In 
  illustration, 
  be 
  cites 
  conditions 
  observed 
  by 
  

   Zimmermann, 
  who 
  stated 
  that 
  in 
  the 
  Culm 
  near 
  Landeshut, 
  

   between 
  the 
  many 
  meters 
  thick 
  layers 
  of 
  cemented 
  gravel 
  and 
  

   conglomerate 
  (allochthonous) 
  there 
  occur 
  thinly-layered 
  clay 
  

   beds 
  (allochthonous) 
  with 
  Stigmaria 
  spreading 
  in 
  all 
  direc- 
  

   tions, 
  therefore 
  the 
  foundation 
  of 
  a 
  coal 
  bed 
  and 
  autochthonous. 
  

   Zimmermann 
  saw 
  this 
  condition 
  repeated 
  thrice 
  in 
  a 
  single 
  

   quarry 
  — 
  but 
  the 
  coal 
  beds 
  there 
  are 
  few 
  and 
  thin. 
  Potonie 
  

   adds 
  that 
  this 
  is 
  a 
  familiar 
  occurrence 
  in 
  all 
  productive 
  coal 
  

   areas. 
  Erect 
  trees 
  and 
  reed-beds 
  are 
  not 
  always 
  evidence 
  that 
  

   the 
  coal 
  is 
  autochthonous. 
  The 
  belief 
  that 
  the 
  secondarily- 
  

   allochthonous 
  coal 
  of 
  Coin 
  must 
  be 
  autochthonous, 
  because 
  

   trees 
  grow 
  on 
  it, 
  is 
  absurd. 
  Logically, 
  on 
  the 
  same 
  basis, 
  the 
  

   North 
  German 
  sands 
  must 
  be 
  autochthonous 
  because 
  firs 
  grow 
  

   on 
  them. 
  He 
  is 
  inclined 
  to 
  regard 
  bursting 
  bogs 
  as 
  a 
  by 
  no 
  

   means 
  unimportant 
  agent 
  is 
  causing 
  distribution 
  of 
  the 
  organic 
  

   material. 
  The 
  great 
  Sumatran 
  bog, 
  described 
  by 
  Koorders, 
  is 
  

   pulp-like 
  ; 
  it 
  could 
  be 
  torn 
  away 
  by 
  high 
  water 
  and 
  redis- 
  

   tributed. 
  

  

  The 
  manner 
  in 
  which 
  pyropissite 
  occurs 
  affords 
  additional 
  

   evidence 
  to 
  Potonie. 
  He 
  uses 
  this 
  term 
  to 
  designate 
  the 
  clean 
  

   material, 
  composed 
  essentially 
  of 
  resinous 
  and 
  waxy 
  sub- 
  

   stances 
  ; 
  pyropissite-brown 
  coal 
  is 
  a 
  mixture 
  with 
  fuel 
  coal 
  and 
  

  

  