﻿250 
  MISS 
  C. 
  A. 
  RAISIN 
  ON 
  THE 
  NATUEE 
  AND 
  [May 
  1 
  897, 
  

  

  Here 
  angular 
  and 
  irregular 
  patches 
  of 
  serpentine 
  and 
  amphibolite 
  

   are 
  intermingled, 
  giving 
  the 
  appearance 
  of 
  a 
  breccia. 
  

  

  This 
  occurrence 
  of 
  hornblendic 
  bands 
  and 
  patches 
  presumably 
  

   represents 
  the 
  passage 
  of 
  the 
  amphibolite 
  into 
  the 
  serpentine 
  

   described 
  by 
  Weigand. 
  In 
  these 
  separate 
  bands 
  or 
  streaks, 
  as 
  also 
  

   in 
  the 
  chlorite-bearing 
  serpentine, 
  a 
  parallelism 
  and 
  orientation 
  of 
  

   the 
  minerals 
  is 
  usually 
  found, 
  and 
  Herr 
  Weigand 
  speaks 
  of 
  this 
  as 
  if 
  

   only 
  one 
  cause 
  could 
  bring 
  it 
  about. 
  He 
  states 
  that 
  the 
  serpentine 
  

   ' 
  lies 
  in 
  the 
  amphibolite 
  and 
  in 
  the 
  strike 
  of 
  the 
  gneiss 
  ; 
  it 
  is 
  thus 
  

   a 
  metamorphosed 
  banded 
  complex 
  of 
  hornblende-rock.' 
  1 
  As 
  will 
  

   be 
  seen 
  from 
  my 
  description, 
  the 
  fact 
  is 
  rather 
  that 
  the 
  amphibolite 
  

   lies 
  in 
  the 
  serpentine. 
  A 
  parallelism, 
  however, 
  with 
  the 
  foliation 
  

   of 
  the 
  gneiss 
  could 
  be 
  explained 
  on 
  the 
  theory 
  of 
  the 
  igneous 
  nature 
  

   of 
  the 
  serpentine 
  and 
  amphibolite. 
  If 
  a 
  magma 
  were 
  intruded 
  into 
  

   a 
  mass 
  of 
  gneiss, 
  the 
  intrusion 
  would 
  be 
  likely 
  to 
  follow 
  the 
  

   structure-planes 
  of 
  that 
  rock 
  and 
  to 
  show 
  a 
  general 
  parallelism 
  

   with 
  them. 
  

  

  (3) 
  General 
  Character 
  of 
  the 
  Gneiss. 
  

  

  Finally, 
  we 
  must 
  notice 
  one 
  general 
  difficulty. 
  The 
  gneiss 
  near 
  

   the 
  Eauenthal, 
  as 
  I 
  have 
  stated, 
  is 
  exposed, 
  and 
  exhibits 
  a 
  normal 
  

   character 
  over 
  a 
  large 
  area. 
  Occasionally 
  (I 
  should 
  say 
  rarely) 
  it 
  

   has 
  bands 
  rich 
  in 
  hornblende 
  or 
  composed 
  of 
  that 
  mineral. 
  In 
  

   these, 
  the 
  hornblende, 
  as 
  Weigand 
  describes 
  it, 
  is 
  the 
  dark 
  greenish 
  

   variety 
  usually 
  found 
  in 
  the 
  gneiss. 
  The 
  rock 
  shows 
  the 
  usual 
  

   alternations 
  of 
  layers 
  : 
  quartz 
  and 
  felspar, 
  biotite 
  and 
  felspar, 
  or 
  

   quartz, 
  felspar 
  and 
  mica. 
  Yet, 
  on 
  Weigand's 
  hypothesis, 
  the 
  

   gneiss 
  becomes 
  in 
  one 
  isolated 
  locality 
  a 
  mass 
  of 
  almost 
  pure 
  

   hornblende. 
  Nowhere 
  else 
  in 
  the 
  neighbourhood 
  is 
  this 
  repre- 
  

   sentation 
  found. 
  2 
  The 
  only 
  evidence 
  for 
  it 
  here 
  consists, 
  first, 
  in 
  a 
  

   comparatively 
  few 
  isolated 
  layers 
  of 
  the 
  peculiar 
  pale 
  amphibolite 
  

   (and 
  no 
  hypothesis 
  is 
  put 
  forward 
  to 
  explain 
  the 
  supposed 
  bleaching 
  

   and 
  modification 
  of 
  the 
  dark 
  mineral 
  of 
  the 
  gneiss), 
  and 
  secondly, 
  

   in 
  a 
  mass 
  of 
  serpentine 
  into 
  which 
  the 
  hornblende-rock 
  is 
  supposed 
  

   to 
  be 
  changed. 
  Of 
  the 
  latter 
  alteration 
  we 
  may 
  at 
  least 
  say 
  that 
  it 
  

   is 
  neither 
  usual 
  nor 
  easily 
  explained. 
  Even 
  if 
  there 
  were 
  a 
  passage, 
  

   of 
  which 
  I 
  can 
  see 
  no 
  evidence, 
  this 
  general 
  difficulty 
  should 
  have 
  

   been 
  discussed. 
  

  

  On 
  Herr 
  Weigand's 
  measurements, 
  the 
  serpentine-outcrop 
  is 
  

   30 
  paces 
  broad, 
  3 
  and 
  the 
  occurrence 
  of 
  hornblendic 
  bands 
  a 
  few 
  

   inches 
  in 
  thickness 
  would 
  not 
  afford 
  much 
  material 
  for 
  so 
  massive 
  

   a 
  development. 
  

  

  1 
  ' 
  Er 
  liegt 
  im 
  Amphibolit 
  und 
  im 
  Streichen 
  des 
  Gneisses 
  ; 
  er 
  ist 
  also 
  ein 
  

   uragewandelter 
  Schichtencomplex 
  yon 
  Hornblendefels.' 
  (Op. 
  tit. 
  p. 
  203.) 
  

  

  2 
  As 
  Prof. 
  Bonney 
  points 
  out, 
  a 
  large 
  mass 
  of 
  either 
  pure 
  hornblende 
  or 
  

   pure 
  pyroxene 
  is 
  certainly 
  very 
  rare. 
  (G-eol. 
  Mag. 
  1887, 
  p. 
  66.) 
  

  

  3 
  'Die 
  grosste 
  Breite 
  des 
  Serpentinanstehenden 
  ist 
  ungefahr 
  30 
  Schritte' 
  

   (op. 
  cit. 
  p. 
  197). 
  My 
  own 
  very 
  rough 
  measurements 
  up 
  the 
  steep, 
  covered, 
  

   boulder-strewn 
  slope 
  gave 
  the 
  outcrop 
  as 
  about 
  260 
  yards 
  broad. 
  This 
  agrees 
  

   better 
  with 
  the 
  map, 
  but 
  would 
  increase 
  the 
  difficulty 
  discussed 
  above. 
  

  

  