﻿Vol. 
  53-] 
  OEIGIN 
  OE 
  THE 
  EAUENTHAL 
  SEEPENTINE. 
  263 
  

  

  Thus 
  the 
  most 
  noticeable 
  peculiarity 
  in 
  the 
  Rauenthal 
  serpentine 
  

   may 
  be 
  connected 
  with 
  conditions 
  characteristic 
  of 
  other 
  peridotites. 
  

   Lastly, 
  in 
  both 
  the 
  Starkenbach 
  and 
  Bonhomme 
  masses, 
  a 
  banding 
  

   is 
  well 
  exhibited, 
  being 
  apparently 
  the 
  effect 
  of 
  a 
  flow-structure 
  

   similar 
  to 
  that 
  which 
  has 
  developed 
  some 
  characters 
  of 
  the 
  Rauenthal 
  

   rock. 
  

  

  V. 
  COMPAEISON 
  WITH 
  SeEPENTIJJES 
  FEOM 
  OTHEE 
  LOCALITIES. 
  

  

  Other 
  serpentines 
  afford 
  a 
  valuable 
  means 
  of 
  comparison 
  on 
  many 
  

   points, 
  and 
  I 
  have 
  to 
  thank 
  Prof. 
  Bonney 
  for 
  the 
  opportunity 
  of 
  

   studying 
  the 
  large 
  collection 
  of 
  slides 
  of 
  this 
  rock 
  made 
  by 
  him 
  

   during 
  so 
  many 
  years 
  of 
  his 
  work. 
  1 
  

  

  First, 
  as 
  to 
  the 
  accessory 
  minerals 
  : 
  while 
  in 
  some 
  of 
  the 
  Lizard 
  

   rocks 
  picotite 
  is 
  well 
  developed, 
  many 
  of 
  them 
  do 
  not 
  contain 
  ii: 
  : 
  

   and 
  even 
  in 
  outcrops 
  of 
  the 
  Vosges 
  (as 
  Herr 
  Weigand 
  shows) 
  it 
  is 
  

   found 
  at 
  some 
  parts, 
  while 
  absent 
  at 
  others 
  of 
  the 
  same 
  massif. 
  

   It 
  is 
  thus 
  by 
  no 
  means 
  universal 
  as 
  a 
  constituent. 
  Further, 
  the 
  

   occurrence 
  in 
  the 
  Rauenthal 
  rock 
  of 
  perofskite 
  and 
  of 
  rutile, 
  similar 
  

   in 
  character 
  to 
  that 
  in 
  other 
  serpentines, 
  has 
  now 
  been 
  shown. 
  2 
  

  

  The 
  iron 
  oxide 
  visible 
  in 
  the 
  slides 
  in 
  most 
  of 
  the 
  Rauenthal 
  

   specimens 
  is 
  small 
  in 
  amount, 
  and 
  this 
  fact 
  is 
  associated 
  with 
  the 
  

   character 
  of 
  the 
  serpentine 
  next 
  to 
  be 
  considered, 
  but 
  the 
  chemical 
  

   analyses 
  prove 
  that 
  a 
  fair 
  quantity 
  of 
  iron 
  oxide 
  is 
  present. 
  Much 
  

   of 
  it 
  is 
  connected 
  with 
  the 
  chlorite, 
  although 
  some 
  occurs 
  in 
  minute 
  

   form 
  in 
  the 
  serpentine. 
  

  

  The 
  meshwork-structure 
  of 
  serpentine, 
  now 
  so 
  well 
  known, 
  is 
  not 
  

   always 
  universal 
  (even 
  in 
  the 
  rocks 
  of 
  one 
  area) 
  ; 
  although 
  no 
  doubt 
  

   would 
  be 
  entertained 
  as 
  to 
  their 
  origin 
  from 
  peridotites. 
  The 
  valu- 
  

   able 
  article 
  of 
  F. 
  Becke 
  on 
  the 
  Stubachthal 
  has 
  recently 
  expressed 
  

   this 
  conclusion. 
  3 
  In 
  the 
  Rauenthal 
  rock, 
  however, 
  a 
  serpentinous 
  

   network 
  can 
  be 
  recognized 
  generally, 
  and, 
  although 
  it 
  is 
  usually 
  

   somewhat 
  regular 
  in 
  form, 
  a 
  similar 
  rectangular 
  net 
  was 
  traceable 
  

   in 
  the 
  great 
  majority 
  of 
  the 
  slices 
  from 
  the 
  Lizard 
  rocks. 
  No 
  

   argument 
  seemed 
  more 
  impressive 
  than 
  this 
  likeness 
  in 
  the 
  essential 
  

   structure 
  4 
  shown 
  throughout 
  so 
  large 
  a 
  collection 
  of 
  specimens, 
  

  

  1 
  The 
  collections 
  of 
  slides 
  which 
  I 
  examined 
  included 
  43 
  specimens 
  from 
  18 
  

   localities 
  at 
  the 
  Lizard 
  ; 
  others 
  from 
  Portsoy, 
  Zoblitz, 
  the 
  Rauenthal, 
  the 
  

   Harz, 
  Aberdeenshire, 
  and 
  New 
  Brunswick. 
  

  

  2 
  It 
  is 
  interesting 
  to 
  recall 
  the 
  fact 
  that 
  the 
  mica-peridotite 
  dyke 
  of 
  Kentucky 
  

   is 
  described 
  by 
  J. 
  S. 
  Diller 
  as 
  composed 
  ' 
  essentially 
  of 
  biotite, 
  serpentine, 
  and 
  

   perofskite,' 
  with 
  small 
  amounts 
  of 
  secondary 
  minerals 
  : 
  Am. 
  Journ. 
  Sci. 
  ser. 
  3 
  

   vol. 
  xliv. 
  (1892) 
  p. 
  287. 
  

  

  3 
  ' 
  A 
  distinct 
  serpentine 
  occurs 
  which 
  is 
  derived 
  from 
  a 
  typical 
  olivine-rock, 
  

   and 
  in 
  which 
  nevertheless 
  the 
  meshwork-structure 
  is 
  completely 
  wanting 
  in 
  

   the 
  changed 
  parts,' 
  Olivinfels 
  & 
  Antigorit-Serpentin, 
  Min. 
  & 
  Petr. 
  Mitth. 
  1894, 
  

   p. 
  271. 
  

  

  Of 
  the 
  three 
  types 
  of 
  serpentine 
  enumerated 
  by 
  Mr. 
  Teall 
  (' 
  Brit. 
  Petrogr.' 
  

   1888, 
  p. 
  115) 
  the 
  study 
  of 
  the 
  Rauenthal 
  rock 
  seems 
  to 
  take 
  away 
  one 
  chief 
  

   example 
  of 
  the 
  second, 
  and 
  the 
  work 
  of 
  Herr 
  Becke 
  to 
  lead 
  to 
  an 
  important 
  

   subtraction 
  from 
  the 
  third. 
  

  

  4 
  A 
  likeness 
  which 
  was 
  pre\iously 
  indicated 
  by 
  Prof. 
  Bonney, 
  Geo!. 
  Mag 
  

   1887, 
  p. 
  68. 
  

  

  