﻿Vol. 
  53.] 
  ORIGIN 
  OF 
  THE 
  EAUENTHAL 
  SERPENTINE. 
  267 
  

  

  seems 
  to 
  be 
  due 
  to 
  differentiation 
  of 
  an 
  original 
  magma, 
  in 
  which 
  

   fluxion-structures 
  were 
  developed. 
  

  

  (V) 
  Neighbouring 
  serpentines 
  in 
  the 
  Vosges 
  are 
  found 
  to 
  exhibit 
  

   closer 
  likeness 
  one 
  to 
  another, 
  greater 
  variation 
  in 
  each 
  mass, 
  and 
  

   more 
  marked 
  resemblance 
  to 
  that 
  of 
  the 
  Eauenthal 
  (in 
  mineralogical 
  

   composition 
  and 
  structure) 
  than 
  are 
  described 
  by 
  Herr 
  Weigand. 
  

   Thus 
  it 
  seems 
  impossible 
  to 
  maintain 
  that 
  the 
  Eauenthal 
  serpentine 
  

   is 
  distinct 
  in 
  its 
  origin 
  from 
  these 
  adjacent 
  masses. 
  Yet 
  they 
  are 
  

   claimed 
  by 
  him 
  as 
  derived 
  from 
  peridotites 
  (olivine- 
  or 
  enstatite- 
  

   rock). 
  

  

  (VI) 
  By 
  comparison 
  with 
  serpentines 
  from 
  many 
  other 
  localities 
  

   beyond 
  the 
  Vosges, 
  such 
  a 
  likeness 
  is 
  found 
  that 
  it 
  does 
  not 
  seem 
  

   possible 
  to 
  attribute 
  a 
  different 
  origin 
  to 
  the 
  Eauenthal 
  mass. 
  As 
  

   Prof. 
  Bonney 
  has 
  said, 
  possibly 
  ' 
  the 
  white 
  hornblende 
  is 
  rather 
  

   exceptionally 
  abundant 
  ' 
  * 
  and 
  ' 
  (as 
  sometimes 
  occurs 
  elsewhere) 
  a 
  

   peculiar 
  variety 
  of 
  chlorite 
  is 
  locally 
  developed.' 
  2 
  Otherwise, 
  the 
  

   Eauenthal 
  rock 
  resembles 
  in 
  structure, 
  in 
  chemical 
  composition, 
  in 
  

   mineral 
  constitution, 
  and 
  even 
  in 
  the 
  variations 
  of 
  its 
  minerals, 
  

   certain 
  serpentines 
  from 
  Cornwall, 
  Scotland, 
  and 
  the 
  Continent. 
  

  

  Thus 
  the 
  serpentine 
  of 
  the 
  Eauenthal 
  would 
  be 
  but 
  one 
  of 
  the 
  

   varied 
  forms 
  in 
  which 
  that 
  rock 
  occurs 
  in 
  the 
  neighbourhood 
  of 
  the 
  

   Bressoir. 
  It 
  seems 
  to 
  have 
  developed 
  there 
  from 
  a 
  not 
  very 
  pure 
  

   or 
  an 
  ill-mixed 
  magma, 
  which 
  was 
  sometimes 
  an 
  olivine-rock 
  (a 
  

   dunite), 
  sometimes 
  either 
  an 
  olivine-enstatite 
  rock 
  (saxonite) 
  or 
  an 
  

   augite- 
  olivine 
  or 
  a 
  hornblende-olivine, 
  or, 
  as 
  I 
  believe, 
  a 
  mica- 
  

   peridotite. 
  These 
  variations 
  may 
  extend 
  over 
  fairly 
  large 
  areas 
  or 
  

   may 
  be 
  closely 
  associated 
  as 
  thin, 
  probably 
  fluxional 
  bands, 
  within 
  

   the 
  same 
  mass. 
  As, 
  then, 
  I 
  cannot 
  admit 
  the 
  Eauenthal 
  serpentine 
  

   to 
  be 
  anything 
  but 
  an 
  altered 
  peridotite, 
  I 
  should 
  not 
  expect 
  that 
  

   serpentines 
  in 
  other 
  gneissic 
  regions 
  3 
  were 
  unusual 
  in 
  their 
  origin. 
  

  

  EXPLANATION 
  OF 
  PLATES. 
  

   Plate 
  XVI. 
  (Map). 
  

  

  The 
  serpentine-bosses 
  are 
  marked 
  diagrammatically, 
  but 
  the 
  patches 
  give 
  a 
  

   rough 
  idea 
  of 
  the 
  relative 
  size 
  of 
  the 
  different 
  crags. 
  The 
  boundary 
  of 
  the 
  

   outcrop 
  cannot 
  be 
  traced 
  with 
  exactness, 
  but 
  indications 
  are 
  given 
  by 
  fragments 
  

   of 
  rock 
  and 
  by 
  the 
  contour 
  of 
  the 
  ground 
  ; 
  thus 
  the 
  curving 
  line 
  at 
  the 
  south-west 
  

   is 
  drawn 
  roughly 
  along 
  the 
  direction 
  where 
  a 
  rather 
  sudden 
  steepening 
  in 
  the 
  

   slope 
  seemed 
  to 
  imply 
  a 
  change 
  of 
  rock. 
  The 
  minerals 
  (chlorite, 
  enstatite, 
  

   hornblende) 
  are 
  indicated 
  in 
  the 
  serpentine 
  at 
  places 
  on 
  the 
  plan, 
  as 
  examples 
  

   of 
  the 
  variation 
  in 
  its 
  composition 
  ; 
  but 
  no 
  attempt 
  has 
  been 
  made 
  to 
  show 
  

   exhaustively 
  where 
  these 
  minerals 
  occur. 
  

  

  The 
  blocks 
  and 
  fragments 
  of 
  rocks 
  are 
  intended 
  only 
  to 
  show 
  general 
  

   position. 
  

  

  Paths 
  and 
  roads 
  are 
  mapped 
  from 
  examination 
  of 
  the 
  area 
  by 
  the 
  Author. 
  

  

  1 
  Not 
  without 
  parallels 
  for 
  comparison 
  : 
  for 
  example, 
  Zoblitz, 
  Portsoy. 
  

  

  2 
  Geol. 
  Mag. 
  1887, 
  p. 
  69. 
  

  

  8 
  B. 
  Weigand, 
  op. 
  cit. 
  p. 
  203 
  ' 
  Es 
  steht 
  mit 
  Sicherheit 
  zu 
  erwarten, 
  dass 
  

   Serpentine 
  ahnlicher 
  Entstehung 
  sich 
  in 
  Gneissgebieten 
  in 
  Menge 
  finden 
  

   werden.' 
  

  

  T2 
  

  

  