﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  I35 
  

  

  from 
  the 
  Leray 
  to 
  the 
  Lowville. 
  But 
  when 
  increased 
  south 
  

   dip 
  brings 
  down 
  the 
  Leray 
  again, 
  at 
  the 
  south 
  end 
  of 
  the 
  

   inlier^ 
  the 
  formation 
  appears 
  as 
  a 
  wall 
  across 
  the 
  valley, 
  and 
  the 
  

   stream 
  follows 
  the 
  Lowville 
  underground, 
  though 
  its 
  course 
  is 
  

   marked 
  by 
  a 
  depression 
  in 
  the 
  surface 
  of 
  the 
  Leray 
  above. 
  

   After 
  flowing 
  underground 
  a 
  short 
  distance 
  the 
  river 
  reappears 
  at 
  

   the 
  surface, 
  or 
  more 
  strictly 
  the 
  surface 
  comes 
  down 
  to 
  the 
  river 
  

   level, 
  owing 
  to 
  caving 
  down 
  and 
  removal 
  of 
  the 
  Leray. 
  In 
  

   plate 
  38 
  this 
  emergence 
  of 
  the 
  stream 
  is 
  shown. 
  It 
  quickly 
  passes 
  

   again 
  underground. 
  The 
  process 
  seems 
  definitely 
  the 
  enlargement 
  

   of 
  an 
  underground 
  channel 
  by 
  solution 
  until 
  the 
  roof 
  becomes 
  un- 
  

   supported, 
  sags 
  and 
  caves 
  in 
  where 
  thinnest, 
  with 
  succeeding 
  grad- 
  

   ual 
  extension 
  of 
  the 
  caving 
  in 
  process, 
  both 
  up 
  and 
  down 
  stream. 
  

   About 
  Limerick 
  the 
  Leray 
  limestone 
  forming 
  the 
  stream 
  walls 
  

   is 
  shown 
  in 
  all 
  stages 
  of 
  disturbance 
  due 
  to 
  this 
  undermining 
  pro- 
  

   cess. 
  The 
  view 
  in 
  plate 
  23 
  shows 
  the 
  process 
  in 
  an 
  early 
  stage, 
  

   and 
  that 
  in 
  plate 
  39 
  in 
  a 
  much 
  more 
  advanced 
  stage, 
  the 
  Leray 
  

   here 
  being 
  in 
  a 
  condition 
  for 
  which 
  Ruedemann's 
  term 
  of 
  

   " 
  scrambled 
  " 
  is 
  so 
  absolutely 
  applicable, 
  that 
  we 
  can 
  not 
  refrain 
  

   from 
  utilizing 
  it. 
  

  

  In 
  plate 
  40, 
  a 
  view 
  of 
  the 
  stream 
  above 
  the 
  falls 
  at 
  Limerick, 
  

   we 
  seem 
  to 
  have 
  a 
  direct 
  exposition 
  of 
  what 
  the 
  character 
  of 
  the 
  

   stream 
  is 
  when 
  underground. 
  It 
  seems 
  distinctly 
  a 
  solution, 
  not 
  a 
  

   corrasion, 
  channel 
  following 
  the 
  joints 
  in 
  beautiful, 
  zigzag 
  fashion. 
  

   The 
  chief 
  part 
  of 
  the 
  course 
  shown 
  in 
  the 
  view 
  is 
  on 
  a 
  northwest 
  

   joint, 
  but 
  in 
  the 
  foreground, 
  and 
  also 
  in 
  the 
  background, 
  it 
  is 
  

   along 
  a 
  set 
  of 
  north 
  joints. 
  It 
  seems 
  to 
  us 
  highly 
  probable 
  that 
  

   the 
  stream 
  was 
  formerly 
  underground 
  here. 
  Unquestionably 
  the 
  

   channel 
  is 
  due 
  to 
  solution 
  along, 
  and 
  guided 
  by, 
  the 
  joints. 
  The 
  

   locality 
  is 
  so 
  suggestive 
  that 
  it 
  is 
  a 
  pity 
  a 
  longer 
  portion 
  of 
  the 
  

   stream's 
  course 
  can 
  not 
  be 
  photographed. 
  A 
  contrasting 
  view, 
  that 
  

   of 
  plate 
  41, 
  shows 
  a 
  limestone 
  surface 
  (the 
  same 
  limestone) 
  cor- 
  

   raded 
  and 
  etched 
  by 
  surface 
  solution 
  and 
  wear. 
  

  

  The 
  influence 
  of 
  the 
  low 
  folds 
  in 
  the 
  Paleozoic 
  rocks 
  in 
  causing 
  

   falls 
  in 
  the 
  streams 
  which 
  more 
  or 
  less 
  directly 
  flow 
  down 
  the 
  dip, 
  

   has 
  just 
  been 
  noted 
  in 
  the 
  case 
  of 
  the 
  fall 
  at 
  Limerick. 
  The 
  course 
  

   of 
  the 
  Black 
  river 
  across 
  the 
  south 
  margin 
  of 
  the 
  map 
  furnishes 
  a 
  

   fine 
  illustration 
  of 
  a 
  stream 
  whose 
  fall 
  is 
  precisely 
  that 
  of 
  the 
  dip, 
  

   and 
  along 
  which, 
  owing 
  to 
  variations 
  in 
  the 
  amount 
  of 
  dip. 
  re- 
  

   peated 
  falls 
  occur 
  over 
  identically 
  the 
  same 
  rock 
  horizon. 
  The 
  

   river 
  here 
  has 
  cut 
  a 
  shallow 
  valley 
  in 
  rock, 
  in 
  postglacial 
  times, 
  and 
  

   the 
  chief 
  falls 
  in 
  this 
  part 
  of 
  its 
  course 
  are 
  at 
  Felts 
  Mills, 
  Black 
  

  

  