﻿238 
  Lahee 
  — 
  New 
  Fossiliferous 
  Horizon 
  and 
  Underlying 
  

  

  pear 
  as 
  bent 
  and 
  twisted 
  shreds 
  of 
  colorless 
  micaceous 
  material, 
  

   associated 
  with 
  minute 
  grains 
  of 
  quartz 
  and 
  epidote. 
  

  

  Southern 
  phase. 
  — 
  The 
  southern 
  phase 
  of 
  the 
  Fitch 
  Hill 
  

   granite 
  gneiss 
  is 
  of 
  rather 
  coarse 
  grain 
  and 
  is 
  of 
  a 
  medium 
  

   grayish 
  tone, 
  with 
  light 
  pink 
  or 
  flesh-colored 
  crystals 
  of 
  feldspar. 
  

   It 
  is 
  lighter 
  in 
  color 
  and 
  coarser 
  than 
  the 
  northern 
  type. 
  Here, 
  

   too, 
  the 
  quartz 
  is 
  not 
  conspicuous. 
  Frequently 
  the 
  structure 
  

   is 
  indistinctly 
  porphyritic, 
  and 
  then 
  the 
  pink 
  feldspars 
  become 
  

   phenocrysts 
  with 
  blurred 
  edges. 
  Many 
  are 
  twinned 
  according 
  

   to 
  the 
  Carlsbad 
  law. 
  Chlorite 
  is 
  always 
  present, 
  not 
  as 
  clear- 
  

   cut 
  individual 
  flakes, 
  but 
  as 
  irregular 
  patches 
  formed 
  by 
  many 
  

   minute 
  flakes. 
  In 
  some 
  specimens 
  chlorite 
  occurs, 
  together 
  

   with 
  sericite, 
  as 
  small, 
  separate 
  flakes, 
  both 
  micas 
  being 
  meta- 
  

   morphic 
  in 
  origin 
  ; 
  and 
  in 
  such 
  cases 
  the 
  chlorite 
  is 
  more 
  

   abundant 
  the 
  greater 
  has 
  been 
  the 
  shearing. 
  No 
  hornblende 
  

   was 
  seen 
  in 
  the 
  southern 
  phase. 
  

  

  Many 
  of 
  the 
  features 
  observed 
  in 
  thin 
  sections 
  of 
  the 
  northern 
  

   phase 
  are 
  characteristic 
  of 
  the 
  southern. 
  The 
  quartz 
  shows 
  

   crushing 
  and 
  straining. 
  The 
  feldspars 
  — 
  orthoclase, 
  micro- 
  

   perthite, 
  plagioclase, 
  and 
  a 
  little 
  microcline 
  — 
  are 
  much 
  altered. 
  

   Of 
  these 
  the 
  plagioclase 
  preceded 
  the 
  others 
  in 
  time 
  of 
  develop- 
  

   ment. 
  Chlorite 
  is 
  in 
  aggregates, 
  accompanied 
  by 
  quartz, 
  

   calcite, 
  and 
  epidote. 
  Its 
  form 
  suggests 
  derivation 
  from 
  bio- 
  

   tite 
  rather 
  than 
  from 
  hornblende. 
  

  

  Variations 
  in 
  Miner 
  cd 
  composition. 
  — 
  Five 
  specimens 
  of 
  

   the 
  gneiss 
  were 
  selected 
  from 
  as 
  many 
  different 
  localities. 
  

   Specimen 
  106 
  came 
  from 
  Loc. 
  10 
  (see 
  fig. 
  2). 
  Sp. 
  302 
  came 
  

   from 
  Loc. 
  5. 
  Sp. 
  245 
  was 
  taken 
  from 
  an 
  outcrop 
  not 
  repre- 
  

   sented 
  on 
  the 
  map. 
  It 
  belongs 
  to 
  the 
  southern 
  facies. 
  Sp. 
  

   447 
  was 
  obtained 
  a 
  few 
  feet 
  south 
  of 
  Loc. 
  2 
  ; 
  and 
  sp. 
  448, 
  belong- 
  

   ing 
  to 
  the 
  northern 
  phase, 
  came 
  from 
  an 
  outcrop 
  northeast 
  of 
  

   Loc. 
  2, 
  just 
  off 
  the 
  map. 
  Thin 
  sections 
  of 
  these 
  specimens 
  

   were 
  examined 
  and 
  the 
  percentage 
  of 
  the 
  constituents 
  was 
  esti- 
  

   mated 
  by 
  thorough 
  measurements 
  according 
  to 
  the 
  Kosiwal 
  

   method. 
  

  

  To 
  be 
  sure, 
  this 
  kind 
  of 
  analysis, 
  when 
  applied 
  to 
  rocks 
  of 
  

   low 
  metamorphism, 
  and, 
  therefore, 
  of 
  incomplete 
  recrystalliza- 
  

   tion, 
  introduces 
  errors 
  which 
  are 
  large 
  compared 
  with 
  chemical 
  

   analysis 
  ; 
  but 
  it 
  does 
  bring 
  out 
  the 
  relative 
  abundance 
  of 
  the 
  

   minerals 
  clearly 
  enough 
  for 
  general 
  purposes. 
  

  

  The 
  feldspars 
  are 
  not 
  here 
  classified 
  by 
  species. 
  They 
  are 
  

   so 
  much 
  decayed 
  that 
  an 
  attempt 
  to 
  distinguish 
  them 
  specifi- 
  

   cally, 
  for 
  quantity 
  determinations, 
  would 
  be 
  fruitless. 
  

  

  The 
  results 
  of 
  the 
  analysis 
  are 
  tabulated 
  below 
  : 
  

  

  