﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  

  

  107 
  

  

  In 
  the 
  Paleozoic 
  rocks. 
  In 
  the 
  Paleozoic 
  Rocks 
  of 
  the 
  district, 
  

   Potsdam 
  to 
  Trenton, 
  the 
  joints 
  are 
  vertical, 
  or 
  nearly 
  so, 
  and 
  show 
  

   also 
  considerable 
  variabiHty 
  in 
  direction, 
  though 
  this 
  seems 
  not 
  quite 
  

   so 
  pronounced 
  as 
  is 
  the 
  case 
  in 
  the 
  Precambric. 
  Figure 
  6 
  gives 
  

   a 
  diagrammatic 
  summary 
  of 
  280 
  readings 
  on 
  these 
  joints, 
  and 
  shows 
  

   again 
  a 
  spreading 
  to 
  all 
  points 
  of 
  the 
  compass, 
  34 
  of 
  the 
  36 
  possible 
  

  

  

  \X\\MU/ 
  

  

  / 
  

  

  Fig. 
  6 
  Diagram, 
  similar 
  to 
  that 
  of 
  the 
  preceding 
  figure, 
  of 
  the 
  joints 
  of 
  the 
  Paleozoic 
  

   rocks 
  

  

  directions 
  being 
  represented. 
  The 
  great 
  number 
  of 
  readings 
  in 
  the 
  

   direction 
  n. 
  70° 
  e.-n. 
  80° 
  e. 
  constitutes 
  the 
  most 
  prominent 
  feature. 
  

   The 
  next 
  point 
  at 
  which 
  readings 
  are 
  concentrated 
  is 
  the 
  n. 
  50° 
  w. 
  

   direction, 
  but 
  readings 
  with 
  this 
  general 
  trend 
  are 
  spread 
  from 
  

   n. 
  40° 
  w. 
  to 
  n. 
  65° 
  w., 
  in 
  other 
  words 
  these 
  joints 
  are 
  somewhat 
  

   less 
  true 
  in 
  direction 
  than 
  those 
  of 
  the 
  preceding 
  set, 
  which 
  may 
  

   however 
  be 
  regarded 
  as 
  extending 
  from 
  n. 
  60° 
  e. 
  to 
  n. 
  80° 
  e. 
  A 
  

   third 
  direction 
  of 
  more 
  abundant 
  readings, 
  from 
  n. 
  20° 
  e. 
  to 
  n. 
  40° 
  e. 
  

   is 
  also 
  sihown, 
  while 
  the 
  fourth 
  direction, 
  n. 
  10° 
  w.-n. 
  30° 
  w. 
  is 
  the 
  

   least 
  prominent 
  of 
  all. 
  This 
  last, 
  however, 
  is 
  the 
  one 
  at 
  right 
  angles 
  

   to 
  the 
  first, 
  and 
  most 
  prominent, 
  set. 
  As 
  thus 
  outlined 
  there 
  are 
  

   99 
  readings 
  for 
  the 
  first 
  set, 
  81 
  for 
  the 
  second, 
  45 
  for 
  the 
  third 
  and 
  

   but 
  25 
  for 
  the 
  fourth. 
  There 
  remain 
  40 
  readings 
  which 
  lie 
  wholly 
  

   without 
  these 
  groups. 
  It 
  is 
  to 
  be 
  noted 
  that 
  the 
  mean 
  directions 
  of 
  

   the 
  four 
  groups 
  do 
  not 
  correspond 
  with 
  the 
  cardinal 
  points 
  of 
  the 
  

   compass, 
  but 
  show 
  a 
  general 
  deviation 
  of 
  20° 
  from 
  them. 
  

  

  In 
  the 
  field 
  the 
  majority 
  of 
  the 
  exposures 
  exhibit 
  but 
  two 
  good 
  

   joint 
  sets, 
  though 
  usually 
  a 
  third 
  quite 
  irregular 
  set 
  is 
  present. 
  With 
  

   two 
  good 
  sets 
  shown 
  it 
  is 
  the 
  exception 
  that 
  they 
  are 
  at 
  right 
  angles, 
  

   and 
  it 
  is 
  the 
  east-west 
  set 
  and 
  either 
  the 
  northeast 
  or 
  the 
  northwest 
  

   set 
  with 
  it, 
  that 
  usually 
  appear. 
  Often 
  all 
  three 
  of 
  these 
  sets 
  appear 
  

   with 
  lack 
  of 
  only 
  the 
  north-south 
  set, 
  and 
  with 
  the 
  east- 
  west 
  set 
  

   customarily 
  the 
  most 
  prominent 
  and 
  regular. 
  On 
  bared 
  rock 
  sur- 
  

  

  