﻿Vol. 
  53.] 
  ORIGIN 
  OF 
  THE 
  RAUENTHAL 
  SERPENTINE. 
  247 
  

  

  I. 
  Investigation 
  in 
  the 
  Field. 
  

  

  The 
  outcrop 
  of 
  the 
  Kauenthal 
  serpentine 
  is 
  marked 
  on 
  the 
  French 
  

   map 
  published 
  in 
  1837 
  * 
  as 
  a 
  somewhat 
  lenticular 
  patch 
  rather 
  more 
  

   than 
  1200 
  metres 
  from 
  S.W. 
  to 
  N.E. 
  by 
  200 
  metres 
  from 
  N.W. 
  to 
  

   S.E., 
  occurring 
  between 
  ' 
  granulitic 
  gneiss 
  ' 
  below 
  and 
  ' 
  granulite 
  ' 
  

   above. 
  A 
  small 
  tributary 
  streamlet 
  2 
  seemed 
  to 
  be 
  fed 
  by 
  springs 
  

   near 
  the 
  upper 
  limit 
  of 
  the 
  serpentine, 
  to 
  fall 
  over 
  a 
  steep 
  rocky 
  

   bed 
  westward 
  in 
  a 
  course 
  roughly 
  determined 
  by 
  the 
  northern 
  

   boundary 
  of 
  the 
  outcrop, 
  although 
  cutting 
  through 
  one 
  corner, 
  then 
  

   to 
  continue 
  to 
  the 
  north 
  and 
  north-west 
  into 
  the 
  Eauenthal 
  stream. 
  

   The 
  steep 
  hillside 
  is 
  often 
  covered 
  with 
  grass 
  or 
  a 
  close 
  growth 
  of 
  

   ferns 
  or 
  flowers, 
  and 
  much 
  of 
  it 
  is 
  richly 
  wooded. 
  Fortunately 
  

   several 
  paths, 
  and, 
  still 
  better, 
  the 
  road 
  leading 
  beyond 
  the 
  Schaaf- 
  

   haus, 
  give 
  easy 
  access 
  to 
  the 
  area 
  which 
  had 
  to 
  be 
  examined. 
  

  

  (1) 
  "Relation 
  of 
  the 
  Gneiss. 
  

  

  In 
  the 
  description 
  given 
  by 
  Herr 
  Weigand 
  he 
  speaks 
  of 
  a 
  passage 
  

   from 
  the 
  gneiss 
  into 
  serpentine. 
  Therefore 
  I 
  first 
  examined, 
  as 
  

   far 
  as 
  possible, 
  the 
  adjacent 
  parts 
  of 
  the 
  former 
  rock. 
  From 
  the 
  

   side 
  of 
  the 
  path 
  near 
  the 
  lower 
  course 
  of 
  the 
  above-mentioned 
  

   streamlet, 
  and 
  from 
  a 
  quarry 
  close 
  by, 
  I 
  took 
  several 
  specimens, 
  one 
  

   being 
  a 
  well-marked 
  hornblendic 
  band, 
  but 
  the 
  outcrop 
  here 
  by 
  

   the 
  path 
  is 
  small, 
  and 
  distant 
  | 
  mile, 
  or 
  perhaps 
  more, 
  from 
  the 
  

   serpentine. 
  3 
  The 
  gneiss 
  is 
  well 
  exhibited 
  on 
  the 
  north 
  of 
  the 
  stream 
  

   along 
  the 
  road 
  (marked 
  o, 
  PI. 
  XYI.) 
  cut 
  by 
  it 
  in 
  small 
  cliffs 
  at 
  

   intervals. 
  This 
  rock 
  is 
  foliated 
  and 
  banded 
  ; 
  it 
  sometimes 
  has 
  layers 
  

   resembling 
  a 
  reddish 
  granitoid 
  rock, 
  and 
  others 
  a 
  foliated 
  diorite 
  ; 
  it 
  

   is 
  usually 
  micaceous, 
  and 
  often 
  has 
  bands 
  especially 
  rich 
  in 
  biotite. 
  

   The 
  general 
  dip 
  here 
  and 
  in 
  other 
  masses 
  is 
  to 
  the 
  west 
  of 
  N". 
  or 
  to 
  

   X. 
  W., 
  often 
  at 
  a 
  considerable 
  angle 
  (45° 
  to 
  60°). 
  The 
  gneiss, 
  of 
  

   perfectly 
  normal 
  type, 
  is 
  seen 
  in 
  a 
  large 
  mass 
  at 
  about 
  240 
  feet 
  4 
  

   north 
  of 
  the 
  stream, 
  and 
  in 
  a 
  small 
  mass, 
  apparently 
  in 
  situ, 
  about 
  

   40 
  feet 
  north 
  of 
  the 
  stream, 
  or 
  120 
  feet 
  north 
  of 
  the 
  serpentine. 
  

   The 
  actual 
  junction 
  south 
  of 
  the 
  stream 
  is 
  obscured, 
  but 
  a 
  sloping 
  

   cliff 
  of 
  muddy 
  talus 
  extending 
  about 
  80 
  feet 
  seems 
  to 
  be 
  full 
  of 
  

   fragments, 
  some 
  of 
  slickensided 
  schistose 
  rock, 
  such 
  as 
  often 
  results 
  

   from 
  disturbance 
  along 
  a 
  junction. 
  Serpentine 
  forms 
  next 
  a 
  mass 
  

   of 
  tumbled 
  big 
  blocks, 
  and 
  then 
  occurs 
  as 
  fragments 
  in 
  the 
  earthy 
  

   bank 
  for 
  about 
  470 
  feet. 
  Beyond 
  this 
  the 
  gneiss 
  apparently 
  extends 
  

  

  1 
  Published 
  by 
  the 
  Depot 
  de 
  la 
  Guerre 
  : 
  scale 
  . 
  This 
  map 
  is 
  rather 
  

  

  later 
  in 
  date 
  than 
  that 
  of 
  Kochlin-Schlumberger 
  to 
  which 
  Weigand 
  refers. 
  

  

  2 
  Marked 
  with 
  more 
  accuracy 
  on 
  the 
  German 
  contour-map 
  of 
  the 
  district, 
  

  

  not 
  coloured 
  geologically 
  (scale 
  2 
  ^ouu)- 
  -^ 
  m8 
  * 
  s 
  ^he 
  streamlet 
  along 
  which 
  

   scattered 
  blocks 
  can 
  be 
  traced, 
  as 
  described 
  by 
  Weigand. 
  

  

  3 
  At 
  this 
  distance, 
  or 
  farther 
  from 
  Uie 
  serpentine, 
  some 
  of 
  the 
  rock 
  is 
  a 
  

   hornblende-schist 
  or 
  foliated 
  diorite. 
  

  

  4 
  All 
  measurements 
  are 
  very 
  rough 
  calculations, 
  made 
  from 
  pacing 
  the 
  

   distances. 
  

  

  