﻿46 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  categories, 
  effects 
  produced 
  upon 
  the 
  igneous 
  rocks 
  themselves, 
  

   effects 
  of 
  the 
  igneous 
  rocks 
  upon 
  the 
  sediments 
  whereby 
  rocks 
  of 
  

   intermediate 
  composition 
  are 
  produced, 
  and 
  effects 
  produced 
  upon 
  

   the 
  sediments 
  by 
  the 
  injection 
  into 
  them 
  of 
  fluids 
  from 
  the 
  igneous 
  

   rocks, 
  fluids 
  rich 
  in 
  minerahzing 
  agents, 
  and 
  of 
  quite 
  different 
  com- 
  

   position 
  from 
  the 
  general 
  mass 
  of 
  the 
  igneous 
  rock. 
  

  

  Bleaching 
  of 
  granite 
  by 
  limestone. 
  In 
  the 
  early 
  stages 
  of 
  the 
  work 
  

   it 
  was 
  noted 
  that, 
  while 
  granite 
  dikes 
  and 
  knobs 
  of 
  all 
  sizes 
  were 
  

   of 
  frequent 
  occurrence, 
  cutting 
  the 
  Grenville 
  limestone 
  wherever 
  

   exposed, 
  in 
  all 
  cases 
  the 
  granite 
  was 
  white, 
  nearly 
  as 
  white 
  as 
  

   the 
  limestone 
  in 
  fact. 
  The 
  granite 
  of 
  the 
  bathyliths 
  is, 
  however, 
  

   uniformly 
  of 
  red 
  color, 
  as 
  are 
  also 
  the 
  dikes 
  in 
  rock 
  other 
  than 
  

   limestone. 
  This 
  led 
  to 
  search 
  for 
  limestone 
  contacts 
  along 
  the 
  mar- 
  

   gin 
  of 
  the 
  Antwerp 
  bathylith 
  and 
  of 
  the 
  smaller 
  granite 
  intrusions 
  of 
  

   the 
  Theresa 
  sheet, 
  when 
  it 
  was 
  found 
  that 
  in 
  every 
  case 
  the 
  margin 
  

   of 
  the 
  granite, 
  adjacent 
  to 
  the 
  limestone, 
  was 
  turned 
  white. 
  It 
  also 
  

   proved 
  to 
  be 
  the 
  case 
  in 
  subsequent 
  work 
  that 
  whenever, 
  in 
  passing 
  

   over 
  granite 
  counti*y, 
  a 
  whitening 
  of 
  the 
  rock 
  was 
  observable, 
  

   directly 
  beyond 
  crystalline 
  limestone 
  was 
  sure 
  to 
  be 
  found. 
  It 
  also 
  

   was 
  found 
  that 
  the 
  general 
  granite 
  of 
  the 
  Antwerp 
  bathylith 
  had 
  

   had 
  singularly 
  little 
  contact 
  effect 
  upon 
  the 
  limestone, 
  pure, 
  

   unchanged 
  limestone 
  lying 
  directly 
  in 
  contact 
  with 
  the 
  granite 
  in 
  

   most 
  cases, 
  and 
  that 
  the 
  dikes 
  also 
  had 
  had 
  no 
  contact 
  effects, 
  so 
  that 
  

   the 
  rather 
  unusual 
  condition 
  was 
  presented 
  of 
  granite-limestone 
  

   contacts 
  in 
  which 
  the 
  granite 
  was 
  the 
  rock 
  showing 
  contact 
  effects, 
  

   not 
  the 
  limestone. 
  

  

  Study 
  of 
  the 
  white 
  granite, 
  both 
  chemically 
  and 
  in 
  thin 
  section, 
  

   affords 
  no 
  explanation 
  of 
  the 
  change. 
  The 
  white 
  granite 
  is 
  in 
  

   general 
  somewhat 
  more 
  acid 
  than 
  the 
  red, 
  but 
  that 
  is 
  believed 
  to 
  be 
  

   nothing 
  more 
  than 
  an 
  expression 
  of 
  the 
  general 
  fact 
  that 
  the 
  dikes 
  

   which 
  radiate 
  out 
  from 
  the 
  bathyliths 
  are 
  more 
  acid 
  than 
  the 
  main 
  

   mass, 
  whether 
  they 
  be 
  red 
  or 
  white 
  (they 
  are 
  usually 
  red 
  in 
  all 
  rocks 
  

   except 
  the 
  limestone), 
  and 
  that 
  the 
  granite 
  also 
  is 
  apt 
  to 
  become 
  

   more 
  acid 
  near 
  the 
  margins. 
  A 
  little 
  tourmalin 
  is 
  sometimes 
  devel- 
  

   oped 
  in 
  the 
  granite 
  where 
  white, 
  but 
  it 
  also 
  developed 
  elsewhere. 
  

   The 
  change 
  seems 
  to 
  consist 
  merely 
  in 
  a 
  decoloration 
  of 
  the 
  feld- 
  

   spar, 
  changing 
  it 
  from 
  red 
  to 
  white 
  ; 
  that 
  of 
  course 
  on 
  the 
  as- 
  

   sumption 
  that 
  the 
  red 
  color 
  of 
  the 
  feldspar 
  is 
  original 
  and 
  not 
  

   a 
  later 
  coloring 
  due 
  to 
  slight 
  alteration. 
  In 
  that 
  case, 
  however, 
  

   it 
  is 
  diflicult 
  to 
  understand 
  why 
  both 
  feldspars, 
  of 
  the 
  white 
  granite 
  

   as 
  well 
  as 
  of 
  the 
  red, 
  should 
  not 
  have 
  undergone 
  the 
  alteration 
  ; 
  this 
  

   seems 
  in 
  fact 
  so 
  highly 
  improbable, 
  that 
  we 
  seem 
  justified 
  in 
  regard- 
  

  

  