﻿I08 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  faces 
  therefore 
  the 
  joints 
  ordinarily 
  divide 
  the 
  exposure 
  into 
  rhom- 
  

   boidal, 
  rather 
  than 
  rectangular 
  blocks. 
  In 
  plates 
  15, 
  20 
  and 
  23 
  

   joints 
  are 
  well 
  shown. 
  

  

  The 
  limestones 
  of 
  the 
  district 
  exhibit, 
  in 
  general, 
  more 
  abundant, 
  

   more 
  regular, 
  and 
  more 
  clean 
  cut 
  joints 
  than 
  does 
  the 
  Potsdam 
  sand- 
  

   stone. 
  The 
  limestones 
  moreover 
  are 
  all 
  somewhat 
  soluble 
  in 
  rain 
  

   water 
  and 
  underground 
  water, 
  the 
  Black 
  River 
  and 
  some 
  of 
  the 
  

   Lowville 
  beds 
  being 
  preeminent 
  in 
  this 
  respect. 
  The 
  glacial 
  depos- 
  

   its 
  over 
  the 
  district 
  are 
  in 
  rather 
  scant 
  amount, 
  there 
  being 
  much 
  

   bare 
  rock 
  exposed, 
  and 
  much 
  more 
  only 
  thinly 
  coated 
  with 
  soil. 
  

   On 
  the 
  bared 
  limestone 
  surfaces 
  the 
  widening 
  of 
  the 
  joint 
  cracks 
  

   produced 
  by 
  slow 
  solvent 
  action 
  of 
  rain 
  water 
  which 
  passes 
  under- 
  

   ground 
  along 
  them, 
  is 
  magnificently 
  shown 
  [pi. 
  26, 
  27], 
  most 
  

   impressively 
  perhaps 
  in 
  the 
  Black 
  River 
  beds 
  but 
  almost 
  equally 
  

   well 
  in 
  the 
  upper 
  Lowville. 
  In 
  many 
  fields 
  which 
  might 
  other- 
  

   wise 
  be 
  available 
  for 
  pasturage, 
  the 
  cattle 
  must 
  be 
  carefully 
  ex- 
  

   cluded, 
  otherwise 
  they 
  fall 
  into, 
  and 
  become 
  tightly 
  wedged 
  in 
  these 
  

   gaping 
  fissures. 
  During 
  our 
  field 
  work 
  we 
  came 
  by 
  chance 
  upon 
  

   a 
  poor, 
  stray 
  cow 
  in 
  such 
  plight 
  in 
  the 
  vicinity 
  of 
  Limerick, 
  tightly 
  

   wedged 
  in 
  a 
  fissure 
  of 
  sufiicient 
  size 
  so 
  that 
  the 
  animal's 
  back 
  was 
  

   well 
  below 
  the 
  ground 
  surface. 
  

  

  Down 
  these 
  widened 
  joint 
  cracks 
  also 
  the 
  streams 
  go 
  underground, 
  

   so 
  that 
  surface 
  streams 
  are 
  infrequent 
  in 
  the 
  Black 
  River 
  and 
  upper 
  

   Lowville 
  districts. 
  Beneath, 
  this 
  downward 
  tendency 
  is 
  checked 
  by 
  

   the 
  less 
  soluble 
  character 
  of 
  the 
  remainder 
  of 
  the 
  Lowville, 
  on 
  the 
  

   upper 
  surface 
  of 
  which 
  these 
  waters 
  run 
  along, 
  eating 
  away 
  under- 
  

   ground 
  channels 
  of 
  considerable 
  size 
  in 
  the 
  soluble 
  layers 
  just 
  above. 
  

   In 
  their 
  early 
  stages 
  these 
  channels 
  are 
  thoroughly 
  roofed 
  over, 
  but 
  

   as 
  time 
  goes 
  on 
  the 
  roof 
  tends 
  to 
  disappear, 
  either 
  by 
  caving 
  in 
  be- 
  

   cause 
  of 
  lack 
  of 
  support 
  by 
  the 
  widened 
  channel 
  underneath, 
  or 
  by 
  

   slow 
  dissolving 
  away 
  of 
  the 
  rocks 
  above, 
  thus 
  bringing 
  daylight 
  

   down 
  to 
  the 
  upper 
  part 
  of 
  the 
  tunnel. 
  The 
  matter 
  will 
  receive 
  

   more 
  detailed 
  discussion 
  when 
  treating 
  of 
  the 
  general 
  drainage, 
  but 
  

   the 
  details 
  of 
  the 
  process 
  and 
  its 
  varying 
  stages 
  are 
  most 
  excel- 
  

   lently 
  illustrated 
  in 
  the 
  region 
  [pi. 
  35-38]. 
  While 
  it 
  is 
  in 
  many 
  

   cases 
  impossible 
  to 
  distinguish 
  . 
  between 
  preglacial 
  and 
  postglacial 
  

   solution, 
  it 
  is 
  nevertheless 
  clear 
  that 
  much 
  of 
  this 
  limestone 
  removal 
  

   is 
  postglacial. 
  

  

  Folds 
  

  

  The 
  rocks 
  of 
  the 
  district 
  exhibit 
  various 
  degrees 
  of 
  folding. 
  The 
  

   Grenville 
  sediments 
  are 
  closely 
  and 
  intricately 
  folded 
  ; 
  the 
  Paleozoic 
  

   rocks 
  show 
  slight 
  folding 
  of 
  Paleozoic 
  date; 
  and 
  the 
  same 
  rocks 
  

  

  