﻿398 
  R. 
  E 
  Call 
  — 
  Silicified 
  Woods 
  of 
  Eastern 
  Arkansas. 
  

  

  Thus 
  far 
  sufficient 
  distributional 
  facts 
  to 
  give 
  a 
  taxonomic 
  

   value 
  to 
  the 
  fossil 
  woods 
  have 
  not 
  been 
  discovered. 
  Until 
  

   extensive 
  collections 
  throughout 
  the 
  whole 
  region 
  of 
  the 
  south- 
  

   ern 
  Tertiary 
  have 
  been 
  made 
  it 
  will 
  not 
  be 
  possible 
  to 
  use 
  these 
  

   forms 
  for 
  purposes 
  of 
  differentiation 
  or 
  of 
  correlation. 
  It 
  is 
  be 
  

   lieved, 
  however, 
  that 
  since 
  in 
  the 
  Tertiary 
  sands 
  of 
  Arkansas, 
  

   Louisiana, 
  Texas 
  and 
  Mississippi 
  the 
  same 
  relations 
  of 
  silici- 
  

   fied 
  woods 
  to 
  lignites 
  have 
  been 
  observed, 
  it 
  may 
  be 
  possible 
  to 
  

   coordinate 
  the 
  divisions 
  recognized 
  in 
  those 
  states 
  by 
  geologists 
  

   and 
  devise 
  a 
  system 
  of 
  nomenclature 
  that 
  will 
  explain 
  the 
  

   relationships 
  of 
  the 
  various 
  beds 
  to 
  each 
  other, 
  though 
  it 
  can- 
  

   not 
  be 
  done 
  at 
  present. 
  

  

  During 
  the 
  progress 
  of 
  the 
  study 
  of 
  the 
  region 
  by 
  the 
  

   writer 
  it 
  became 
  more 
  and 
  more 
  clear 
  that 
  the 
  silicified 
  wood 
  

   had 
  some 
  intimate 
  relation 
  to 
  the 
  pockets 
  or 
  beds 
  of 
  lignite 
  

   which 
  are 
  scattered 
  throughout 
  the 
  ridge. 
  It 
  was 
  early 
  noticed 
  

   that 
  no 
  lignite 
  occurs 
  in 
  the 
  sands 
  or 
  gravels 
  above 
  the 
  clays, 
  

   and 
  that 
  no 
  detached 
  masses 
  of 
  silicified 
  wood 
  occur 
  entirely 
  

   in 
  the 
  clays. 
  As 
  the 
  investigation 
  proceeded 
  it 
  became 
  a 
  favor- 
  

   ite 
  hypothesis 
  that 
  the 
  silicified 
  wood 
  was 
  transformed 
  lignite, 
  

   and 
  that 
  careful 
  microscopic 
  study 
  would 
  probably 
  prove 
  the 
  

   hypothesis 
  to 
  be 
  correct. 
  Professor 
  Knowlton's 
  investigations 
  

   appear 
  to 
  verify 
  the 
  hypothesis. 
  

  

  The 
  opinion 
  that 
  the 
  silicified 
  wood 
  was, 
  in 
  some 
  way, 
  to 
  be 
  

   connected 
  with 
  the 
  lignites 
  of 
  the 
  beds 
  underlying 
  the 
  sands 
  

   was 
  suggested 
  by 
  Hilgard* 
  many 
  years 
  ago. 
  Speaking 
  of 
  the 
  

   occurrence 
  of 
  fossils 
  in 
  the 
  Orange 
  Sands 
  he 
  says 
  :".... 
  

   The 
  closest 
  scrutiny 
  I 
  have 
  bestowed 
  on 
  hundreds 
  of 
  extensive 
  

   exposures, 
  has 
  failed 
  to 
  detect 
  any 
  fossil 
  apparently 
  peculiar 
  to 
  

   the 
  formation 
  as 
  such. 
  This 
  might 
  seem 
  paradoxical 
  enough 
  

   to 
  any 
  one 
  acquainted 
  with 
  the 
  frequent 
  occurrence 
  of 
  silicified 
  

   wood 
  in 
  these 
  strata, 
  but 
  it 
  soon 
  becomes 
  quite 
  obvious 
  to 
  an 
  

   attentive 
  observer 
  that 
  the 
  regions 
  of 
  the 
  frequent 
  occurrence 
  

   of 
  this 
  fossil 
  in 
  the 
  Orange 
  Sand 
  are 
  coextensive 
  with 
  those 
  in 
  

   which 
  fossil 
  wood, 
  either 
  silicified 
  — 
  when 
  imbedded 
  in 
  siliceous 
  

   sands 
  — 
  or 
  lignitized, 
  occurs 
  in 
  the 
  underlying 
  lignitiferous 
  

   Cretaceous 
  or 
  Tertiary 
  strata. 
  It 
  is 
  not 
  unusual 
  to 
  find 
  trunks 
  

   of 
  silicified 
  wood 
  imbedded 
  partly 
  in 
  the 
  unchanged 
  lignitic 
  

   strata, 
  partly 
  in 
  the 
  Orange 
  Sand 
  ; 
  the 
  portion 
  contained 
  in 
  the 
  

   latter 
  being 
  nearly 
  or 
  wholly 
  deprived 
  of 
  carbon, 
  while 
  the 
  

   part 
  imbedded 
  in 
  the 
  lignitic 
  material 
  is, 
  if 
  at 
  all 
  silicified, 
  of 
  

   an 
  ebony 
  tint 
  and 
  often 
  contains 
  pyrites." 
  Again, 
  " 
  I 
  am 
  con- 
  

   vinced 
  that 
  the 
  great 
  part, 
  if 
  not 
  all 
  of 
  this 
  fossil 
  wood 
  is 
  

   derived 
  from 
  the 
  underlying 
  strata 
  and 
  will 
  be 
  represented 
  in 
  

   their 
  flora." 
  

  

  *This 
  Journal, 
  II, 
  vol. 
  xli, 
  p. 
  313, 
  18G6. 
  

  

  