﻿riFTH 
  REPORT 
  OF 
  THE 
  DIRECTOR 
  I908 
  

  

  175 
  

  

  Natural 
  Bridge 
  it 
  reappears, 
  flows 
  a 
  short 
  

   distance 
  upon 
  Lowville 
  beds 
  and 
  disap- 
  

   pears 
  again 
  under 
  Black 
  River 
  limestone, 
  

   not 
  to 
  reappear 
  for 
  another 
  half 
  mile. 
  

   This 
  last 
  half 
  mile 
  is 
  the 
  most 
  important 
  

   for 
  the 
  understanding 
  of 
  the 
  process 
  which 
  

   produced 
  the 
  inlier 
  farther 
  up. 
  The 
  course 
  

   of 
  the 
  river 
  can 
  here 
  be 
  followed 
  through 
  

   the 
  woods 
  by 
  a 
  distinct 
  depression 
  that 
  is 
  

   covered 
  with 
  large, 
  variously 
  tilted 
  Black 
  

   River 
  slabs 
  and 
  partly 
  bounded 
  on 
  the 
  

   sides 
  by 
  Black 
  River 
  cHifs. 
  It 
  is 
  here 
  

   manifest 
  that 
  the 
  Black 
  River 
  strata 
  as 
  a 
  

   whole 
  have 
  been 
  sinking 
  down 
  along 
  the 
  

   river 
  as 
  in 
  a 
  graben, 
  being 
  eaten 
  away 
  

   underneath 
  by 
  the 
  dissolving 
  water. 
  

   Finally, 
  the 
  blocks 
  become 
  so 
  small 
  

   that 
  freshets 
  are 
  able 
  to 
  remove 
  them 
  

   entirely 
  and 
  the 
  river 
  again 
  flows 
  in 
  

   the 
  open 
  and 
  on 
  the 
  underlying 
  Lowville 
  

   beds. 
  While 
  it 
  is 
  quite 
  appkrent 
  that 
  this 
  

   and 
  other 
  inliers 
  of 
  the 
  same 
  kind 
  wander 
  

   upward, 
  after 
  they 
  are 
  started, 
  by 
  the 
  

   waterfall 
  at 
  the 
  upper 
  end, 
  the 
  original 
  

   cause 
  of 
  the 
  phenomenon 
  is 
  quite 
  clearly 
  

   the 
  water 
  that 
  along 
  the 
  joints, 
  which 
  are 
  

   here 
  strongly 
  developed, 
  passes 
  between 
  

   and 
  under 
  the 
  Black 
  River 
  blocks 
  until 
  it 
  

   reaches 
  the 
  harder 
  and 
  less 
  soluble 
  Low- 
  

   ville 
  beds. 
  The 
  fall 
  at 
  the 
  upper 
  end 
  is 
  

   to 
  all 
  appearances 
  a 
  secondary 
  develop- 
  

   ment. 
  

  

  It 
  is 
  obvious 
  that 
  this 
  group 
  of 
  inliers 
  

   is 
  essentially 
  a 
  Karst 
  phenomenon 
  and 
  that 
  

   these 
  inliers 
  correspond 
  to 
  the 
  '' 
  Dolinen," 
  

   so 
  v;ell 
  known 
  in 
  the 
  Karst 
  plateau 
  of 
  Aus- 
  

   tria. 
  We 
  must, 
  therefore, 
  expect 
  to 
  find 
  

   other 
  examples 
  in 
  the 
  limestone 
  regions 
  of 
  

   the 
  State. 
  The 
  Helderberg 
  plateau 
  pre- 
  

   sents 
  a 
  number 
  of 
  instances 
  of 
  depressions 
  

   or 
  sink 
  holes 
  in 
  the 
  limestones 
  through 
  

   which 
  the 
  underlying 
  rocks 
  appear. 
  Most 
  

  

  

  v^ 
  

  

  