﻿36 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  and 
  Rossie, 
  just 
  east 
  of 
  our 
  map, 
  has 
  been 
  noted 
  here, 
  but 
  with 
  

   that 
  exception 
  there 
  is 
  a 
  strong 
  resemblance 
  in 
  the 
  material. 
  

  

  Igneous 
  rocks. 
  Gneissic 
  granites 
  {Lauroitian) 
  . 
  There 
  are 
  two 
  

   extensive 
  (bathylithic) 
  masses 
  of 
  granite 
  gneiss 
  in 
  the 
  district, 
  

   both 
  of 
  which 
  are 
  only 
  in 
  part 
  within 
  the 
  mapped 
  area. 
  The 
  

   western 
  end 
  of 
  what 
  we 
  have 
  called 
  the 
  " 
  Antwerp 
  bathylith 
  " 
  

   is 
  exposed 
  on 
  the 
  Theresa 
  quadrangle, 
  disappearing 
  westward 
  

   under 
  a 
  Paleozoic 
  cover. 
  The 
  Alexandria 
  bathylith, 
  on 
  the 
  main- 
  

   land 
  and 
  islands 
  of 
  the 
  Alexandria 
  quadrangle, 
  seems 
  of 
  smaller 
  

   size 
  but 
  also 
  disappears 
  under 
  a 
  Paleozoic 
  cover, 
  both 
  eastward 
  

   and 
  westward, 
  and 
  passes 
  across 
  into 
  Canada 
  as 
  well. 
  There 
  are 
  

   in 
  addition 
  numerous 
  smaller 
  masses. 
  It 
  is 
  highly 
  probable 
  

   that 
  all 
  are 
  connected 
  underground, 
  and 
  represent 
  the 
  upper 
  

   portions 
  of 
  a 
  great, 
  underground 
  mass 
  of 
  granite, 
  underlying 
  all 
  

   of 
  the 
  Grenville 
  of 
  the 
  district, 
  except 
  where 
  cut 
  away 
  by 
  the 
  

   later 
  intrusions. 
  

  

  That 
  this 
  granite 
  came 
  to 
  its 
  present 
  resting 
  place 
  after 
  the 
  

   Grenville 
  was 
  deposited 
  was 
  pointed 
  out 
  by 
  Smyth 
  10 
  years 
  ago, 
  

   and 
  is 
  shown 
  clearly 
  in 
  a 
  host 
  of 
  exposures. 
  Dikes 
  without 
  

   number 
  run 
  out 
  from 
  the 
  granite 
  masses 
  into 
  the 
  Grenville 
  rocks, 
  

   the 
  granite 
  is 
  everywhere 
  full 
  of 
  included 
  fragments 
  of 
  the 
  Gren- 
  

   ville, 
  and 
  along 
  the 
  contacts 
  between 
  the 
  two 
  sets 
  of 
  rocks, 
  the 
  

   Grenville 
  rocks 
  have 
  plainly 
  been 
  modified 
  by 
  the 
  contact 
  action 
  

   of 
  the 
  intrusive. 
  

  

  The 
  general 
  rock 
  is 
  a 
  quite 
  acid, 
  red 
  granite, 
  composed 
  chiefly 
  

   of 
  feldspars 
  (microperthite, 
  microcline 
  and 
  oligoclase) 
  and 
  

   quartz, 
  with 
  small 
  amounts 
  of 
  mica 
  (both 
  biotite 
  and 
  muscovite) 
  

   and 
  magnetite, 
  and 
  wnth 
  zircon, 
  titanite 
  and 
  apatite 
  as 
  acces- 
  

   sories. 
  Such 
  rock 
  does 
  not 
  appear 
  especially 
  gneissoid, 
  though 
  

   usually 
  of 
  rather 
  fine 
  and 
  even 
  grain, 
  but 
  in 
  thin 
  section 
  it 
  

   invariably 
  shows 
  much 
  crushing, 
  and 
  a 
  considerable 
  amount 
  of 
  

   recrystallization. 
  The 
  rock 
  is 
  everywhere 
  cut 
  by 
  its 
  own 
  aplite, 
  

   pegmatite 
  and 
  quartz 
  dikes, 
  some 
  of 
  which 
  are 
  much 
  coarser 
  

   grained, 
  as 
  usual. 
  jNlany 
  of 
  the 
  granite 
  dikes 
  which 
  penetrate 
  

   the 
  Grenville, 
  especially 
  the 
  limestones, 
  are 
  coarser 
  grained, 
  and 
  

   less 
  mashed 
  than 
  the 
  general 
  rock. 
  

  

  In 
  a 
  minor 
  way 
  the 
  rock 
  of 
  the 
  bathyliths 
  is 
  quite 
  variable,, 
  

   and 
  that 
  in 
  two 
  main 
  ways, 
  one 
  apparently 
  representing 
  original 
  

   variations 
  in 
  the 
  rock, 
  and 
  one 
  owing 
  to 
  relative 
  abundance 
  of 
  

   inclusions 
  and 
  the 
  effect 
  of 
  the 
  granite 
  on 
  them. 
  The 
  rock 
  varies 
  

   from 
  one 
  which 
  is 
  almost 
  w^holly 
  constituted 
  of 
  feldspars 
  and 
  

   quartz, 
  to 
  one 
  which 
  contains 
  several 
  per 
  cent 
  of 
  mica, 
  which 
  

  

  