﻿FIFTH 
  REPORT 
  OF 
  THE 
  DIRECTOR 
  I908 
  9 
  

  

  The 
  Precambric 
  rocks 
  of 
  the 
  district 
  comprise 
  old 
  sediments 
  

   of 
  Grenville 
  age 
  and 
  various 
  igneous 
  rocks 
  of 
  later 
  age 
  which 
  have 
  

   freely 
  cut 
  the 
  Grenville 
  schists. 
  The 
  latter 
  show 
  a 
  thickness 
  of 
  

   several 
  thousand 
  feet, 
  the 
  greater 
  part 
  comprised 
  in 
  a 
  series 
  of 
  

   rocks 
  of 
  varied 
  nature 
  within 
  which 
  are 
  thin 
  bands 
  of 
  white 
  lime- 
  

   stone 
  and 
  of 
  quartzite, 
  with 
  much 
  impure 
  limestone. 
  Unless 
  the 
  

   series 
  has 
  been 
  overturned 
  the 
  limestone 
  is 
  at 
  the 
  bottom 
  and 
  the 
  

   heavier 
  quartzite 
  at 
  the 
  top. 
  The 
  oldest 
  of 
  the 
  igneous 
  rocks 
  is 
  

   the 
  Laurentian 
  granite 
  gneiss, 
  two 
  considerable 
  bathylithic 
  sheets 
  

   of 
  which 
  lie 
  in 
  part 
  in 
  the 
  mapped 
  area 
  and 
  have 
  been 
  designated 
  

   the 
  Antwerp 
  and 
  the 
  Alexandria 
  bathyliths. 
  The 
  gneiss 
  is 
  full 
  

   of 
  inclusions 
  of 
  the 
  Grenville 
  rocks 
  and 
  clearly 
  shows 
  that 
  it 
  has 
  

   absorbed 
  large 
  quantities 
  of 
  the 
  Grenville, 
  with 
  the 
  production 
  of 
  

   certain 
  mixed 
  rocks. 
  

  

  The 
  Grenville 
  limestone 
  has 
  had 
  a 
  singular 
  bleaching 
  effect 
  on 
  

   the 
  red 
  granite 
  gneiss, 
  turning 
  it 
  white. 
  All 
  the 
  granite 
  dikes 
  that 
  

   cut 
  the 
  limestone 
  are 
  white 
  and 
  the 
  edges 
  of 
  the 
  larger 
  masses 
  have 
  

   the 
  same 
  color 
  in 
  the 
  vicinity 
  of 
  the 
  limestone; 
  in 
  fact 
  the 
  color 
  

   change 
  in 
  the 
  granite 
  is 
  an 
  infallible 
  indication 
  of 
  approach 
  to 
  the 
  

   limestone, 
  as 
  repeatedly 
  tested 
  and 
  proved 
  in 
  the 
  field. 
  

  

  An 
  analogous 
  change 
  is 
  observable 
  at 
  granite-quartzite 
  contacts, 
  

   the 
  granite 
  becoming 
  more 
  acid, 
  tending 
  to 
  bleach 
  and 
  showing 
  

   much 
  more 
  frequent 
  joints. 
  Over 
  the 
  area 
  mapped 
  the 
  granite 
  

   gneisses 
  seem 
  to 
  have 
  been 
  deficient 
  in 
  mineralizing 
  fluids 
  and 
  have 
  

   not 
  notably 
  altered 
  the 
  Grenville 
  rocks, 
  the 
  granite 
  showing 
  more 
  

   noticeable 
  contact 
  effects 
  than 
  the 
  sediments. 
  

  

  The 
  later 
  igneous 
  rocks 
  comprise 
  a 
  small 
  streak 
  of 
  syenite, 
  one 
  

   of 
  diorite, 
  a 
  very 
  small 
  one 
  of 
  gabbro 
  and 
  a 
  fairly 
  large 
  mass 
  of 
  

   coarse 
  red 
  granite, 
  the 
  Picton 
  granite, 
  which 
  seems 
  to 
  be 
  the 
  

   latest 
  of 
  all, 
  has 
  a 
  considerable 
  extent 
  of 
  outcrop 
  on 
  Grindstone 
  

   and 
  Welleslcy 
  islands 
  and 
  a 
  much 
  wider 
  extent 
  across 
  the 
  border 
  

   in 
  Canada, 
  though 
  on 
  the 
  New 
  York 
  side 
  it 
  makes 
  little 
  show 
  ex- 
  

   cept 
  for 
  an 
  abundance 
  of 
  dikes 
  v/hich 
  cut 
  all 
  the 
  other 
  rocks. 
  On 
  

   the 
  islands 
  the 
  granite 
  is 
  full 
  of 
  inclusions 
  of 
  the 
  other 
  rocks 
  and 
  

   on 
  Wellesley 
  they 
  are 
  remarkably 
  abundant, 
  have 
  retained 
  their 
  

   original 
  orientation, 
  their 
  strikes 
  and 
  dips 
  being 
  uniform 
  and 
  con- 
  

   cordant 
  with 
  those 
  of 
  the 
  main 
  areas 
  of 
  the 
  rocks 
  away 
  from 
  the 
  

   granite, 
  so 
  that 
  they 
  can 
  be 
  mapped 
  into 
  belts 
  of 
  quartzite, 
  amphibo- 
  

   lites 
  and 
  granite 
  gneiss 
  with 
  as 
  much 
  exactitude 
  as 
  though 
  the 
  later 
  

   granite 
  were 
  not 
  present. 
  This 
  is 
  taken 
  to 
  imply 
  that 
  here 
  the 
  very 
  

   roof 
  of 
  this 
  portion 
  of 
  the 
  bathylith 
  is 
  now 
  at 
  the 
  surface, 
  the 
  in- 
  

  

  