﻿20 
  . 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Number 
  i 
  is 
  a 
  fine 
  example 
  of 
  a 
  transition 
  rock 
  from 
  a 
  granitic 
  

   syenite 
  to 
  granite 
  as 
  seen 
  along 
  the 
  river 
  in 
  big 
  ledges 
  one-half 
  of 
  

   a 
  mile 
  south 
  of 
  The 
  Glen. 
  The 
  color 
  of 
  the 
  rock 
  is 
  pinkish 
  gray. 
  

   Especially 
  noteworthy 
  are 
  the 
  comparatively 
  low 
  quartz 
  and 
  high 
  

   hornblende 
  contents, 
  and 
  the 
  absence 
  of 
  microcline. 
  

  

  Number 
  3 
  is 
  typical 
  looking 
  pink, 
  biotite 
  granite 
  from 
  the 
  granite 
  

   ridge 
  just 
  west 
  of 
  Crane 
  mountain. 
  

  

  Number 
  6 
  is 
  a 
  very 
  quartzose, 
  hornblende, 
  biotite, 
  pink 
  granite 
  

   with 
  considerable 
  microcline 
  as 
  seen 
  in 
  excellent 
  outcrops 
  along 
  the 
  

   road 
  iy 
  2 
  miles 
  south 
  of 
  Riverside. 
  

  

  Only 
  a 
  few 
  of 
  the 
  observed 
  masses 
  of 
  Grenville 
  or 
  mixed 
  gneisses 
  

   which 
  occur 
  within 
  the 
  granite 
  are 
  large 
  enough 
  to 
  be 
  shown 
  on 
  

   the 
  geologic 
  map. 
  Small 
  inclusions 
  or 
  stringers, 
  sometimes 
  sharply 
  

   outlined 
  and 
  sometimes 
  seeming 
  to 
  grade 
  into 
  the 
  granite, 
  are 
  very 
  

   numerous. 
  Only 
  a 
  few 
  examples 
  will 
  be 
  cited. 
  Thus, 
  a 
  large, 
  

   homogeneous 
  mass 
  of 
  very 
  typical 
  granite, 
  one-quarter 
  of 
  a 
  mile 
  

   above 
  the 
  mouth 
  of 
  Glen 
  brook, 
  contains 
  a 
  number 
  of 
  clear-cut 
  

   Grenville 
  hornblende 
  gneiss 
  inclusions. 
  These 
  inclusions 
  are 
  

   mostly 
  long 
  (10 
  to 
  20 
  feet), 
  narrow 
  stringers 
  which 
  are 
  drawn 
  

   out 
  parallel 
  to 
  the 
  foliation 
  of 
  the 
  granite. 
  Similar 
  inclusions 
  are 
  

   common 
  1 
  mile 
  south 
  of 
  The 
  Glen 
  along 
  the 
  east 
  bank 
  of 
  the 
  river, 
  

   and 
  in 
  the 
  Mill 
  mountain 
  mass. 
  On 
  the 
  west 
  bank 
  of 
  the 
  Hudson 
  

   river 
  and 
  just 
  opposite 
  the 
  Ferry 
  (east 
  of 
  Heath 
  mountain) 
  a 
  

   ledge 
  of 
  coarse-grained 
  hornblende 
  granite 
  contains 
  ten 
  or 
  fifteen 
  

   fine 
  examples 
  of 
  small 
  (none 
  over 
  3 
  feet 
  long) 
  very 
  angular 
  in- 
  

   clusions 
  of 
  Grenville 
  hornblende 
  gneiss. 
  

  

  Features 
  of 
  special 
  interest 
  in 
  connection 
  with 
  the 
  granites 
  are 
  

   the 
  frequent 
  and 
  comparatively 
  sudden 
  transitions 
  from 
  the 
  gray 
  

   to 
  pink 
  varieties, 
  and 
  from 
  the 
  more 
  syenitic 
  or 
  basic 
  facies 
  to 
  the 
  

   more 
  truly 
  granitic 
  facies. 
  The 
  effect 
  is 
  to 
  give 
  wide 
  bands 
  or 
  

   layers 
  of 
  varying 
  color 
  and 
  composition 
  and 
  yet 
  all 
  clearly 
  belong- 
  

   ing 
  to 
  the 
  same 
  rock 
  mass 
  because 
  of 
  the 
  true 
  gradation 
  of 
  one 
  

   layer 
  or 
  band 
  into 
  another. 
  Among 
  many 
  places 
  where 
  such 
  

   phenomena 
  have 
  been 
  observed 
  are 
  in 
  the 
  vicinity 
  of 
  The 
  Glen, 
  

   and 
  along 
  the 
  road 
  one-half 
  of 
  a 
  mile 
  north 
  of 
  the 
  north 
  end 
  of 
  

   Loon 
  lake. 
  The 
  writer 
  has 
  already 
  described 
  similar 
  occurrences 
  

   in 
  the 
  region 
  of 
  the 
  Port 
  Leyden 
  quadrangle. 
  1 
  Professor 
  Kemp, 
  

   in 
  the 
  bulletin 
  on 
  the 
  Elizabethtown-Port 
  Henry 
  region, 
  has 
  re- 
  

   cently 
  described 
  and 
  suggested 
  an 
  explanation 
  for 
  similar 
  but 
  even 
  

   more 
  extreme 
  phenomena 
  as 
  follows 
  : 
  " 
  The 
  most 
  acidic 
  variety 
  

   will 
  quite 
  sharply 
  replace 
  it 
  [the 
  syenite] 
  ; 
  and 
  in 
  the 
  same 
  way 
  a 
  

  

  1 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  135, 
  P- 
  16-17. 
  

  

  