﻿38 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  land 
  surface 
  is 
  however 
  unknown, 
  and 
  the 
  run-off 
  of 
  the 
  surface 
  

   waters 
  is 
  always 
  concentrated 
  along 
  certain 
  lowest 
  lines, 
  thus 
  con- 
  

   stituting 
  brooks, 
  streams 
  and 
  rivers. 
  While 
  there 
  may 
  be 
  numer- 
  

   ous 
  drainage 
  lines 
  of 
  this 
  type, 
  they 
  generally 
  unite 
  intO' 
  a 
  few 
  mas- 
  

   ter 
  streams, 
  the 
  direction 
  of 
  whose 
  flow 
  is 
  down 
  the 
  inclination 
  

   of 
  the 
  surface 
  of 
  the 
  land. 
  Such 
  streams 
  are 
  known 
  as 
  consequent 
  

   streams, 
  their 
  direction 
  of 
  flow 
  being 
  consequent 
  on 
  the 
  original 
  

   slope 
  of 
  the 
  surface. 
  

  

  When 
  the 
  strata 
  of 
  the 
  Niagara 
  region 
  became 
  a 
  part 
  of 
  the 
  dry 
  

   land, 
  from 
  the 
  relative 
  lowering 
  of 
  the 
  water 
  level 
  (which 
  may 
  have 
  

   been 
  due 
  to 
  rise 
  of 
  the 
  land 
  or 
  to 
  drawing 
  off 
  of 
  water 
  by 
  the 
  deepen- 
  

   ing 
  of 
  the 
  oceanic 
  basins), 
  they 
  formed 
  a 
  broad, 
  essentially 
  

   monotonous 
  belt 
  of 
  country 
  fringing 
  the 
  old-land 
  on 
  the 
  north, 
  i. 
  e. 
  

   a 
  marginal 
  coastal 
  plain. 
  The 
  strata 
  of 
  this 
  plain 
  had 
  a 
  gentle 
  

   southward 
  inclination, 
  a 
  feature 
  shared 
  by 
  the 
  surface 
  of 
  the 
  plain. 
  

   Consequent 
  streams 
  quickly 
  made 
  their 
  appearance 
  on 
  this 
  plain, 
  

   a 
  number 
  of 
  them 
  probably 
  coming 
  into 
  existence 
  almost 
  simul- 
  

   taneously 
  and 
  running 
  essentially 
  parallel 
  from 
  the 
  old-land, 
  across 
  

   the 
  new 
  coastal 
  plain 
  into 
  the 
  sea. 
  These 
  streams 
  soon 
  cut 
  down 
  

   into 
  the 
  coastal 
  plain, 
  carving 
  channels 
  for 
  themselves 
  and 
  thus 
  es- 
  

   tabhshing 
  definite 
  lines 
  of 
  drainage. 
  As 
  the 
  streams 
  at 
  first 
  con- 
  

   sisted 
  entirely 
  of 
  the 
  run-off 
  of 
  the 
  moisture 
  which 
  fell 
  on 
  the 
  plain 
  

   and 
  in 
  the 
  higher 
  old-land 
  portion, 
  it 
  is 
  evident 
  that, 
  unless 
  the 
  

   rainfall 
  was 
  continuous, 
  or 
  unless 
  extensive 
  snow 
  fields 
  were 
  present 
  

   to 
  supply 
  water, 
  these 
  young 
  streams 
  must 
  have 
  fluctuated 
  greatly 
  

   in 
  volume 
  of 
  water, 
  and 
  at 
  intervals 
  become 
  entirely 
  dry. 
  This 
  con- 
  

   dition 
  continued 
  till 
  the 
  valleys, 
  cut 
  by 
  these 
  streams 
  of 
  run-off 
  

   water, 
  had 
  become 
  sufficiently 
  deep 
  to 
  reach 
  the 
  level 
  of 
  the 
  under- 
  

   ground 
  water, 
  when 
  the 
  supply, 
  augmented 
  by 
  springs, 
  became 
  

   much 
  more 
  constant. 
  Thus 
  in 
  course 
  of 
  time 
  large 
  valleys, 
  supplied 
  

   with 
  large 
  rivers, 
  came 
  into 
  existence. 
  Meanwhile 
  the 
  sides 
  of 
  the 
  

   river 
  valleys 
  were 
  attacked 
  by 
  the 
  atmosphere, 
  and 
  degradation 
  of 
  

   the 
  cliffs 
  cut 
  by 
  the 
  stream 
  resulted. 
  

  

  As 
  long 
  as 
  a 
  river 
  is 
  narrow 
  and 
  vigorously 
  undercuts 
  its 
  banks, 
  

   the 
  latter 
  will 
  be 
  steep, 
  and 
  the 
  river 
  channel 
  will 
  have 
  the 
  character 
  

   of 
  a 
  gorge. 
  This 
  generally 
  continues 
  as 
  long 
  as 
  the 
  river 
  is 
  cutting 
  

  

  