﻿534 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  orthoclase 
  in 
  largest 
  part, 
  the 
  same 
  being 
  often 
  though 
  not 
  

   always 
  microperthitic. 
  Plagioclase 
  of 
  an 
  acidic 
  variety 
  is 
  not 
  

   lacking 
  but 
  it 
  is 
  far 
  inferior 
  to 
  orthoclase. 
  The 
  dark 
  silicates 
  

   are 
  emerald 
  green 
  augite, 
  hypersthene, 
  brown 
  hornblende, 
  * 
  and 
  

   considerable 
  garnet, 
  which 
  in 
  all 
  probability 
  has 
  been 
  derived 
  

   from 
  the 
  bisilicates. 
  Magnetite 
  is 
  in 
  moderate 
  amount 
  and 
  may 
  

   furnish 
  the 
  core 
  of 
  a 
  garnet 
  aggregate. 
  Apatite 
  is 
  often 
  notice- 
  

   able 
  in 
  small 
  crystals. 
  The 
  rocks 
  have 
  been 
  greatly 
  granulated 
  

   and 
  sheared 
  by 
  dynamic 
  processes 
  and 
  may 
  yield 
  excessively 
  fine 
  

   gneisses 
  with 
  thin 
  but 
  persistent 
  laminae. 
  On 
  the 
  slipping 
  sur- 
  

   faces 
  much 
  biotite 
  of 
  a 
  golden 
  brown 
  has 
  developed. 
  Quartz 
  is 
  

   variable 
  but 
  some 
  of 
  the 
  specimens 
  gathered 
  yield 
  it 
  in 
  consider- 
  

   able 
  quantity. 
  • 
  

  

  These 
  syenite-gneisses 
  of 
  the 
  Whitehall 
  type 
  make 
  up 
  the 
  east- 
  

   ern 
  front 
  of 
  Tongue 
  mountain 
  and 
  presumably 
  the 
  western 
  slope 
  

   as 
  well. 
  Our 
  specimens 
  119-22 
  inclusive 
  were 
  gathered 
  along 
  

   the 
  eastern 
  slope. 
  The 
  same 
  variety 
  was 
  also 
  collected 
  along 
  the 
  

   highways 
  leading 
  northwest 
  from 
  Bolton 
  Landing 
  to 
  Brantlake. 
  

  

  On 
  the 
  northern 
  of 
  the 
  two 
  roads 
  which 
  run 
  from 
  the 
  lower 
  

   (north) 
  end 
  of 
  Trout 
  lake 
  and 
  near 
  the 
  Schroon 
  river 
  a 
  white, 
  

   granular 
  rock 
  with 
  larger 
  quartz 
  crystals 
  through 
  its 
  mass 
  was 
  

   met 
  at 
  147. 
  In 
  thin 
  section 
  this 
  contains 
  orthoclase 
  of 
  micro- 
  

   perthitic 
  habit 
  in 
  considerable 
  abundance 
  together 
  with 
  quartz, 
  

   microcline 
  and 
  oligoclase. 
  A 
  stray 
  garnet 
  occasionally 
  appears. 
  

   The 
  rock 
  is 
  thoroughly 
  granulated 
  and 
  has 
  evidently 
  been 
  sub- 
  

   jected 
  to 
  great 
  strain 
  and 
  thorough 
  crushing. 
  

  

  At 
  148 
  however 
  on 
  the 
  western 
  slope 
  of 
  Cat 
  mountain 
  the 
  

   syenite-gneiss 
  again 
  appeared. 
  

  

  Just 
  northeast 
  of 
  Trout 
  lake 
  a 
  coarse 
  granulated 
  syenite 
  

   porphyry 
  was 
  collected, 
  which 
  exhibits 
  the 
  results 
  of 
  pressure 
  

   and 
  mashing 
  in 
  a 
  marked 
  degree. 
  It 
  has 
  a 
  coarse 
  groundmass 
  

   of 
  greenish 
  orthoclase 
  and 
  biotite, 
  with 
  a 
  little 
  plagioclase, 
  and 
  

   large 
  red 
  lenticular 
  phenocrysts 
  of 
  microcline, 
  which 
  are 
  now 
  

   chiefly 
  granular 
  aggregates. 
  This 
  recalls 
  the 
  similar 
  rocks 
  cite'd 
  

   under 
  Whitehall, 
  and 
  is 
  like 
  no. 
  128 
  from 
  a 
  quarry 
  north 
  of 
  

   Horicon 
  village. 
  

  

  