﻿248 
  MISS 
  C. 
  A. 
  RAISIN 
  ON 
  THE 
  NATURE 
  AND 
  [May 
  1 
  89 
  7, 
  

  

  until 
  we 
  reach 
  the 
  granite 
  rather 
  north 
  of 
  the 
  next 
  tributary 
  

   streamlet. 
  

  

  Here, 
  then, 
  was 
  the 
  first 
  result 
  which 
  I 
  had 
  not 
  anticipated. 
  No 
  

   clean 
  continuous 
  sections 
  were 
  found, 
  showing 
  a 
  passage 
  from 
  gneiss 
  

   to 
  serpentine, 
  nor 
  even 
  from 
  gneiss 
  to 
  an 
  almost 
  pure 
  amphibolite, 
  

   and 
  the 
  gneiss 
  seemed 
  to 
  be 
  everywhere 
  of 
  normal 
  type. 
  Herr 
  

   Weigand 
  states 
  in 
  regard 
  to 
  this 
  rock 
  that 
  the 
  hornblende 
  ' 
  gradually 
  

   gains 
  the 
  upper 
  hand, 
  and 
  thus 
  the 
  rock 
  passes 
  through 
  amphi- 
  

   bole-gneiss 
  to 
  a 
  pure 
  hornblende-rock, 
  which, 
  however, 
  retains 
  the 
  

   stratified 
  aspect 
  of 
  the 
  gneiss.' 
  x 
  Whatever 
  changes 
  have 
  occurred 
  

   in 
  the 
  local 
  exposures 
  (and 
  it 
  would 
  have 
  been 
  perhaps 
  a 
  help 
  if 
  

   Herr 
  Weigand 
  had 
  given 
  a 
  more 
  detailed 
  description 
  of 
  the 
  parts 
  

   which 
  he 
  examined 
  in 
  the 
  field), 
  it 
  is 
  difficult 
  to 
  see 
  where 
  the 
  

   sections 
  can 
  have 
  been 
  which 
  showed 
  the 
  passage 
  stated. 
  2 
  As 
  just 
  

   previously 
  recorded, 
  in 
  the 
  gneiss 
  almost 
  adjacent 
  to 
  the 
  serpentine 
  

   (along 
  the 
  strike 
  of 
  the 
  foliation) 
  hornblende 
  can 
  hardly 
  be 
  found, 
  

   all 
  the 
  dark 
  layers 
  which 
  have 
  been 
  cut 
  for 
  the 
  microscope 
  proving 
  

   to 
  be 
  micaceous 
  ; 
  and 
  although 
  the 
  mineral 
  occurs 
  in 
  the 
  valley 
  

   below 
  3 
  and 
  in 
  an 
  occasional 
  band 
  on 
  the 
  lower 
  slopes, 
  this 
  seems 
  

   but 
  slender 
  proof 
  of 
  a 
  gradual 
  passage 
  to 
  an 
  almost 
  pure 
  amphibo- 
  

   lite. 
  

  

  (2) 
  The 
  Serpentine 
  and 
  its 
  Relation 
  to 
  the 
  Amphibolite. 
  

  

  The 
  crags 
  on 
  the 
  grassy 
  and 
  tree-covered 
  slope 
  consist 
  mainly 
  of 
  

   serpentine 
  in 
  situ, 
  and 
  these 
  were 
  next 
  examined. 
  4 
  They 
  generally 
  

   face 
  steeply 
  towards 
  the 
  west 
  or 
  valley-side, 
  and 
  are 
  often 
  large 
  

   masses 
  extending 
  40 
  or 
  80 
  or 
  even 
  150 
  feet 
  in 
  length, 
  and 
  to 
  a 
  

   height 
  of 
  20 
  feet 
  or 
  more. 
  Among 
  them 
  examples 
  are 
  soon 
  noticed 
  

   of 
  the 
  amphibolite 
  and 
  of 
  various 
  minerals 
  associated 
  with 
  the 
  

   serpentine, 
  such 
  as 
  may 
  have 
  been 
  found 
  in 
  blocks 
  by 
  the 
  brook 
  

   and 
  roadstones 
  in 
  the 
  valley. 
  The 
  chief 
  rock 
  is 
  serpentine, 
  often 
  

   including, 
  as 
  described 
  by 
  Herr 
  Weigand, 
  a 
  peculiar 
  chlorite. 
  That 
  

   mineral 
  is 
  definitely 
  orientated, 
  the 
  rock 
  is 
  generally 
  platy, 
  and 
  its 
  

   appearance 
  on 
  transverse 
  and 
  parallel 
  surfaces 
  is 
  in 
  marked 
  contrast. 
  

   On 
  the 
  former 
  it 
  looks 
  dull, 
  of 
  a 
  rather 
  varied 
  dark 
  green 
  colour, 
  

   with 
  slightly 
  marked 
  lines 
  along 
  the 
  edges 
  of 
  the 
  planes 
  rich 
  in 
  

   chlorite. 
  If 
  these 
  are 
  exposed 
  in 
  step-like 
  fashion, 
  or 
  if 
  the 
  rock 
  be 
  

   broken 
  parallel 
  with 
  them, 
  the 
  chlorite 
  gives 
  a 
  silvery 
  glitter 
  to 
  the 
  

  

  1 
  ' 
  Diese 
  letztere 
  [Hornblende] 
  gewinnt 
  nach 
  und 
  nach 
  die 
  Oberhand 
  und 
  

   fuhrt 
  so 
  das 
  Gestein 
  durch 
  Amphibolgneiss 
  in 
  reinen 
  Hornblendef'els 
  iiber, 
  der 
  

   aber 
  die 
  Schichtung 
  des 
  Gneisses 
  beibehalt.' 
  Op. 
  cit. 
  p. 
  197. 
  

  

  2 
  The 
  road 
  has 
  been 
  made 
  somewhat 
  recently, 
  I 
  believe, 
  and 
  doubtless 
  changes 
  

   have 
  occurred 
  in 
  the 
  sections 
  exposed. 
  But 
  along 
  the 
  smaller 
  (and, 
  I 
  should 
  

   think, 
  older) 
  path 
  above 
  (marked 
  /3) 
  gneiss 
  is 
  seen, 
  in 
  small 
  outcrops 
  towards 
  

   its 
  southern 
  end, 
  and 
  in 
  bosses 
  north 
  of 
  the 
  stream, 
  and 
  these 
  are 
  of 
  the 
  same 
  

   normal 
  type. 
  . 
  

  

  3 
  This 
  would 
  be 
  rather 
  distant, 
  as 
  previously 
  stated, 
  unless 
  more 
  crags 
  occur 
  

   which 
  I 
  failed 
  to 
  see, 
  because 
  they 
  were 
  hidden 
  by 
  the 
  trees 
  on 
  the 
  lower 
  slopes 
  

   of 
  the 
  hill, 
  and 
  even 
  these 
  would 
  not 
  be 
  close 
  at 
  hand. 
  

  

  4 
  One 
  or 
  generally 
  several 
  specimens 
  were 
  taken 
  from 
  each 
  mass. 
  I 
  believe 
  

   that 
  I 
  examined 
  every 
  crag, 
  but 
  I 
  certainly 
  left 
  no 
  important 
  section 
  untouched. 
  

  

  