﻿688 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  with 
  some 
  detail 
  and 
  only 
  the 
  more 
  important 
  points 
  need 
  be 
  

   summarized 
  here. 
  A 
  greater 
  amount 
  of 
  variation 
  is 
  naturally 
  

   found 
  in 
  the 
  rocks, 
  as 
  the 
  examination 
  extends 
  over 
  a 
  wider 
  area. 
  

   This 
  is 
  particularly 
  true 
  of 
  the 
  gneiss, 
  of 
  which 
  several 
  varieties 
  

   occur, 
  ranging 
  from 
  a 
  medium-grained, 
  roughly-banded, 
  granitic 
  

   rock, 
  to 
  a 
  fine, 
  thinly 
  laminated 
  variety 
  on 
  the 
  one 
  hand, 
  and 
  to 
  

   a 
  coarse 
  "augen-gneiss" 
  on 
  the 
  other. 
  

  

  As 
  a 
  rule 
  the 
  gneiss 
  consists 
  of 
  quartz, 
  orthoclase, 
  plagioclase 
  

   (these 
  two 
  commonly 
  as 
  microperthite), 
  biotite 
  and 
  hornblende, 
  

   with 
  the 
  usual 
  minor 
  constituents. 
  The 
  finely 
  laminated 
  varie- 
  

   ties, 
  which 
  are 
  usually 
  in 
  close 
  proximity 
  to, 
  or 
  interbedded 
  with 
  

   limestone, 
  often 
  contain 
  sillimanite 
  and 
  garnet. 
  

  

  The 
  granite 
  also 
  shows 
  much 
  variation 
  and 
  sometimes 
  so 
  closely 
  

   resembles 
  the 
  gneiss 
  that 
  their 
  separation 
  becomes 
  a 
  matter 
  of 
  

   much 
  difficulty. 
  In 
  one 
  instance 
  a 
  large 
  area 
  of 
  granite 
  was 
  

   regarded 
  as 
  gneiss, 
  until 
  an 
  irruptive 
  contact 
  with 
  the 
  limestone 
  

   was 
  found. 
  This 
  explains 
  the 
  apparent 
  absence 
  of 
  granite 
  in 
  the 
  

   gneiss 
  areas, 
  as 
  shown 
  on 
  the 
  map. 
  While 
  granite 
  undoubtedly 
  

   often 
  occurs 
  in 
  the 
  gneiss, 
  it 
  could 
  not 
  be 
  distinguished 
  without 
  

   closer 
  study 
  than 
  was 
  possible 
  in 
  the 
  time 
  allotted 
  to 
  field 
  work. 
  

  

  The 
  normal 
  granite 
  is 
  a 
  medium-grained 
  aggregate 
  of 
  quartz, 
  

   orthoclase, 
  plagioclase 
  and 
  biotite. 
  The 
  biotite 
  is 
  often 
  absent 
  

   and 
  the 
  granite, 
  therefore, 
  of 
  a 
  very 
  acid 
  variety, 
  which 
  is 
  com- 
  

   monly 
  coarse 
  grained. 
  On 
  the 
  other 
  hand, 
  basic 
  segregations 
  

   also 
  occur, 
  in 
  which 
  biotite 
  is 
  replaced 
  by 
  abundant 
  hornblende, 
  

   and 
  orthoclase 
  by 
  plagioclase, 
  the 
  rock 
  passing 
  into 
  diorite. 
  

   Such 
  basic 
  masses 
  are 
  usually 
  not 
  extensive, 
  and 
  pass 
  gradually 
  

   into 
  the 
  ordinary 
  granite. 
  But 
  just 
  south 
  of 
  the 
  Oswegatchie 
  

   river, 
  near 
  the 
  Kossie-Gouverneur 
  town 
  line, 
  there 
  is 
  a 
  large 
  

   area 
  of 
  very 
  dark 
  and 
  coarse 
  diorite 
  which 
  shows 
  no 
  connection 
  

   with 
  any 
  granite. 
  On 
  account 
  of 
  its 
  size 
  and 
  independent 
  occur- 
  

   rence 
  it 
  is 
  indicated 
  on 
  the 
  map 
  by 
  a 
  distinct 
  pattern, 
  although, 
  

   without 
  doubt, 
  it 
  belongs 
  to 
  the 
  series 
  of 
  granite 
  intrusions. 
  

   These 
  intrusions 
  cut 
  the 
  limestone, 
  but 
  not 
  the 
  sandstone, 
  and 
  

   are, 
  therefore, 
  of 
  pre-Potsdam 
  age. 
  

  

  The 
  limestone 
  is 
  highly 
  crystalline 
  and, 
  as 
  a 
  rule, 
  quite 
  coarse. 
  

   It 
  varies 
  in 
  color 
  from 
  white 
  to 
  gray, 
  and 
  on 
  weathered 
  sur- 
  

   faces 
  is 
  nearly 
  black. 
  Mica 
  and 
  graphite 
  are 
  commonly 
  dissemi- 
  

   nated 
  through 
  it 
  in 
  scales, 
  and 
  many 
  other 
  minerals 
  occur 
  more 
  

  

  