﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  29 
  

  

  For 
  many 
  miles 
  to 
  the 
  east 
  and 
  west 
  of 
  the 
  Niagara 
  river 
  the 
  

   plain 
  does 
  not 
  change 
  perceptibly 
  in 
  elevation. 
  Nevertheless, 
  there 
  

   is 
  a 
  gradual 
  eastward 
  descent, 
  till, 
  on 
  the 
  Genesee 
  river, 
  the 
  surface 
  

   of 
  the 
  plain, 
  where 
  not 
  modified 
  by 
  superficial 
  deposits, 
  is 
  fully 
  a 
  

   hundred 
  feet 
  lower 
  than 
  at 
  Niagara. 
  Westward 
  the 
  plain 
  rises 
  

   gradually, 
  its 
  elevation 
  near 
  Hamilton 
  averaging 
  500 
  feet 
  above 
  

   Lake 
  Ontario, 
  or 
  considerably 
  more 
  than 
  700 
  feet 
  above 
  the 
  sea. 
  

  

  Owing 
  to 
  the 
  southward 
  inclination 
  of 
  the 
  strata 
  of 
  this 
  region, 
  

   the 
  limestone 
  bed 
  which 
  forms 
  the 
  capping 
  rock 
  at 
  the 
  escarpment, 
  

   eventually 
  passes 
  below 
  the 
  level 
  of 
  the 
  plain, 
  having 
  previously 
  in- 
  

   creased 
  in 
  thickness 
  to 
  over 
  200 
  feet. 
  The 
  disappearance 
  of 
  the 
  

   limestone 
  as 
  a 
  surface 
  rock 
  occurs 
  near 
  the 
  northern 
  end 
  of 
  Grand 
  

   island, 
  as 
  shown 
  by 
  the 
  accompanying 
  geologic 
  map, 
  and 
  from 
  this 
  

   point 
  southward 
  the 
  surface 
  rock 
  is 
  formed 
  by 
  the 
  soft 
  gypsiferous 
  

   and 
  salt-bearing 
  shales 
  of 
  the 
  SaHna 
  group, 
  which 
  overlie 
  the 
  lime- 
  

   stone 
  and 
  in. 
  turn 
  pass 
  below 
  the 
  higher 
  strata 
  in 
  Bufifalo, 
  where 
  

   beds 
  of 
  limestone 
  again 
  become 
  the 
  surface 
  rock. 
  Throughout 
  the 
  

   area 
  where 
  the 
  shales 
  form 
  the 
  surface 
  rock, 
  the 
  plain 
  is 
  deeply 
  ex- 
  

   cavated 
  on 
  both 
  sides 
  of 
  the 
  Niagara 
  river, 
  a 
  longitudinal 
  east 
  and 
  

   west 
  valley, 
  now 
  largely 
  filled 
  by 
  surface 
  accumulations 
  of 
  sand 
  and 
  

   gravel, 
  being 
  revealed 
  by 
  borings. 
  Tonawanda 
  creek 
  occupies 
  this 
  

   valley 
  on 
  the 
  east, 
  though 
  flowing 
  on 
  drift, 
  considerably 
  above 
  its 
  

   floor, 
  and 
  Chippewa 
  creek 
  occupies 
  it 
  in 
  part 
  on 
  the 
  west 
  of 
  the 
  Ni- 
  

   agara 
  river. 
  This 
  valley, 
  as 
  will 
  be 
  shown 
  later, 
  can 
  be 
  traced 
  west- 
  

   ward 
  into 
  Canada 
  and 
  eastward 
  to 
  where 
  it 
  joins 
  the 
  Mohawk 
  valley, 
  

   with 
  which 
  it 
  forms 
  the 
  great 
  avenue 
  of 
  communication 
  across 
  the 
  

   state 
  of 
  New 
  York. 
  The 
  northern 
  boundary 
  of 
  the 
  Tonawanda 
  and 
  

   Chippewa 
  valleys 
  is 
  formed 
  by 
  a 
  limestone 
  clifif 
  similar 
  to, 
  though 
  

   less 
  pronounced 
  than, 
  the 
  Niagara 
  escarpment. 
  This 
  clifif, 
  gen- 
  

   erally 
  known 
  as 
  the 
  second 
  limestone 
  terrace 
  of 
  western 
  New 
  York 
  

   (the 
  Niagara 
  escarpment 
  being 
  the 
  first), 
  is 
  formed 
  by 
  the 
  upper 
  

   Siluric 
  limestones 
  (WaterHme 
  and 
  Manlius 
  limestone) 
  and 
  the 
  Onon- 
  

   daga 
  limestone 
  of 
  the 
  Devonic 
  series. 
  The 
  latter 
  is 
  a 
  very 
  durable 
  

   rock 
  and 
  hence 
  it 
  forms 
  a 
  very 
  resistant 
  capping 
  stone. 
  This 
  es- 
  

   carpment 
  is 
  scarcely 
  visible 
  at 
  Black 
  Rock, 
  where 
  it 
  is 
  crossed 
  by 
  the 
  

   Niagara 
  river, 
  for 
  here 
  it 
  is 
  low, 
  and, 
  in 
  addition, 
  extensive 
  drift 
  

  

  