﻿COHOES 
  MASTODON. 
  105 
  

  

  of 
  water. 
  The 
  agency 
  which 
  transported 
  the 
  quartz 
  pebbles 
  

   of 
  the 
  Mohawk 
  valley, 
  was 
  doubtless 
  the 
  same 
  as 
  that 
  which 
  

   transported 
  those 
  found 
  in 
  the 
  pot-holes 
  at 
  Cohoes, 
  and 
  their 
  

   smooth 
  rounded 
  condition 
  is 
  due 
  to 
  the 
  action 
  of 
  water, 
  which 
  

   moving 
  them 
  violently 
  about 
  in 
  those 
  places, 
  not 
  only 
  produced 
  

   the 
  exceeding 
  smoothness 
  of 
  these 
  pebbles, 
  but 
  at 
  the 
  same 
  time 
  

   caused 
  the 
  depressions 
  in 
  the 
  rocky 
  surface, 
  which 
  w 
  r 
  ere 
  finally 
  

   worn 
  into 
  the 
  deep 
  pot-holes 
  which 
  we 
  now 
  find. 
  

  

  It 
  is 
  not 
  difficult 
  to 
  understand 
  how 
  fragments 
  of 
  rock 
  and 
  

   pebbles 
  may 
  be 
  transported 
  by 
  ice 
  as 
  they 
  become 
  imbedded 
  

   in 
  the 
  moving 
  glacier, 
  but 
  the 
  manner 
  in 
  which 
  these 
  fragments, 
  

   while 
  under 
  glacial 
  influence, 
  have 
  aided 
  in 
  the 
  formation 
  of 
  

   the 
  pot-holes, 
  is 
  not 
  so 
  evident, 
  and 
  for 
  the 
  explanation, 
  we 
  must 
  

   have 
  recourse 
  to 
  some 
  peculiar 
  phases 
  of 
  glacial 
  action. 
  

  

  In 
  a 
  discussion 
  of 
  this 
  question 
  before 
  the 
  National 
  Academy 
  of 
  

   Science 
  at 
  Hartford, 
  in 
  August, 
  1867, 
  Prof. 
  Agassiz 
  stated 
  in 
  regard 
  

   to 
  pot-holes 
  of 
  this 
  character, 
  that 
  they 
  are 
  never 
  formed 
  by 
  flu- 
  

   vial 
  action; 
  that 
  no 
  river, 
  however 
  large, 
  flowing 
  over 
  the 
  rocky 
  

   surface 
  could 
  produce 
  them, 
  but 
  that 
  they 
  are 
  the 
  result 
  of 
  glaciers, 
  

   or 
  rather 
  caused 
  by 
  water 
  from 
  the 
  surface 
  of 
  a 
  glacier 
  falling 
  

   into 
  crevasses 
  and 
  forming 
  cascades, 
  often 
  a 
  thousand 
  feet 
  in 
  

   height. 
  These 
  cascades 
  falling 
  upon 
  the 
  rock 
  of 
  the 
  bottom, 
  aided 
  

   by 
  fragments 
  of 
  stone 
  which 
  are 
  likewise 
  carried 
  into 
  the 
  

   crevasses, 
  or 
  moved 
  along 
  the 
  base 
  of 
  the 
  glacier, 
  produce 
  depres- 
  

   sions 
  which 
  are 
  worn 
  into 
  deep 
  holes 
  (similar 
  to 
  those 
  described), 
  

   which 
  he 
  had 
  himself 
  examined 
  by 
  being 
  let 
  down 
  to 
  the 
  bottom 
  

   of 
  the 
  crevasses 
  in 
  some 
  of 
  the 
  glaciers 
  of 
  Switzerland. 
  This 
  

   evidence, 
  therefore, 
  ousrht 
  to 
  be 
  conclusive 
  as 
  to 
  the 
  manner 
  in 
  

   which 
  similar 
  pot-holes 
  are 
  produced 
  beneath 
  existing 
  glaciers.* 
  

   We 
  are 
  at 
  least 
  driven 
  to 
  some 
  other 
  explanation 
  of 
  the 
  production 
  

   of 
  these 
  ancient 
  pot-holes 
  than 
  attributing 
  them 
  to 
  fluvial 
  action, 
  for 
  

   neither 
  along 
  the 
  Mohawk 
  or 
  any 
  river, 
  nor 
  about 
  the 
  rapids 
  or 
  

   falls 
  of 
  existing 
  streams 
  do 
  we 
  find 
  any 
  similar 
  ones, 
  though 
  in 
  

  

  * 
  Since 
  it 
  would 
  require 
  a 
  long 
  period 
  of 
  time 
  for 
  the 
  falling 
  water 
  to 
  produce 
  these 
  

   cavities 
  or 
  pot-holes, 
  it 
  is 
  not 
  easy 
  to 
  conceive 
  how, 
  with 
  the 
  constantly 
  advancing 
  motion 
  

   of 
  the 
  glacier, 
  these 
  cascades, 
  fa'ling 
  through 
  the 
  crevasses, 
  could 
  have 
  remained 
  long 
  

   enough 
  in 
  one 
  position 
  to 
  have 
  produced 
  such 
  a 
  result. 
  The 
  explanation 
  given 
  by 
  Prof. 
  

   Agassiz, 
  is 
  that 
  the 
  crevasses 
  ar<s 
  produced 
  by 
  the 
  physical 
  features 
  of 
  the 
  underlying 
  sur- 
  

   face, 
  and 
  that 
  although 
  the 
  mass 
  of 
  the 
  glacier 
  moves 
  forward 
  the 
  crevasse 
  is 
  maintained 
  

   at 
  or 
  near 
  the 
  same 
  place 
  for 
  a 
  long 
  time. 
  

  

  