﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  47 
  

  

  glacial 
  Genesee 
  river 
  is 
  the 
  only 
  other 
  that 
  can 
  be 
  mentioned 
  here. 
  

   Though 
  now 
  flowing 
  northward 
  on 
  account 
  of 
  the 
  tilting 
  of 
  the 
  

   land, 
  we 
  may 
  assume 
  that 
  much 
  of 
  its 
  valley 
  was 
  carved 
  by 
  a 
  south- 
  

   ward 
  flowing 
  stream, 
  the 
  bottom 
  of 
  which, 
  as 
  shown 
  by 
  borings, 
  

   w^as 
  considerably 
  below 
  the 
  floor 
  of 
  the 
  present 
  river. 
  Whether 
  

   Irondequoit 
  bay 
  is 
  a 
  part 
  of 
  this 
  ancient 
  channel, 
  or 
  whether 
  it 
  

   marks 
  the 
  position 
  of 
  an 
  obsequent 
  stream, 
  must 
  remain 
  for 
  the 
  

   present 
  an 
  open 
  question. 
  Soundings 
  in 
  Irondequoit 
  bay 
  show 
  a 
  

   depth 
  of 
  70 
  feet, 
  though 
  the 
  rock 
  bottom 
  is 
  probably 
  much 
  deeper. 
  

  

  As 
  soon 
  as 
  the 
  consequent 
  streams 
  began 
  cutting 
  down 
  their 
  

   valleys 
  again 
  after 
  the 
  continental 
  uplift 
  which 
  followed 
  the 
  period 
  

   of 
  peneplanation, 
  the 
  lateral 
  subsequent 
  streams 
  began 
  once 
  more 
  to 
  

   open 
  out 
  broad 
  lowlands 
  in 
  the 
  weaker 
  beds 
  which 
  now 
  had 
  become 
  

   extensively 
  exposed. 
  These 
  lowlands, 
  in 
  part 
  now 
  filled 
  by 
  drift 
  

   deposits, 
  are 
  the 
  Ontario 
  and 
  Georgian 
  bay 
  valleys, 
  the 
  latter 
  con- 
  

   tinued 
  in 
  the 
  North 
  Passage, 
  all 
  carved 
  out 
  of 
  the 
  weak 
  Medina 
  and 
  

   Lorraine 
  shales; 
  the 
  Tonawanda-Chippewa 
  valley, 
  with 
  the 
  deeper 
  

   portion 
  of 
  the 
  Huron 
  valley 
  farther 
  west, 
  carved 
  out 
  of 
  the 
  soft 
  

   shales 
  of 
  the 
  Salina 
  group; 
  and 
  the 
  valley 
  of 
  Lake 
  Erie 
  cut 
  out 
  of 
  

   the 
  softer 
  middle 
  and 
  upper 
  Devonic 
  shales. 
  A 
  few 
  of 
  these 
  may 
  

   be 
  considered 
  in 
  greater 
  detail. 
  

  

  Ontario 
  valley. 
  It 
  is 
  a 
  well 
  known 
  fact 
  that 
  Lake 
  Ontario 
  is 
  deeper 
  

   in 
  its 
  eastern 
  than 
  its 
  western 
  part. 
  In 
  the 
  following 
  six 
  cross- 
  

   sections 
  (fig. 
  7), 
  constructed 
  from 
  the 
  lake 
  survey 
  charts, 
  the 
  greatest 
  

   depths 
  from 
  west 
  to 
  east 
  are 
  456, 
  528, 
  570, 
  738, 
  684 
  and 
  576 
  feet. 
  

   The 
  section 
  showing 
  the 
  greatest 
  depth 
  is 
  that 
  from 
  Pultneyville 
  

   to 
  Point 
  Peter 
  light, 
  in 
  the 
  eastern 
  third 
  of 
  the 
  lake. 
  As 
  the 
  present 
  

   level 
  of 
  Lake 
  Ontario 
  is 
  247 
  feet 
  above 
  the 
  sea, 
  the 
  deepest 
  sounding 
  

   recorded 
  in 
  these 
  sections 
  is 
  491 
  feet 
  below 
  present 
  sealevel. 
  From 
  

   this 
  point 
  of 
  greatest 
  depth, 
  the 
  floor 
  of 
  the 
  lake 
  rises 
  eastward, 
  

   at 
  first 
  at 
  the 
  rate 
  of 
  3 
  feet 
  in 
  the 
  mile, 
  and 
  later 
  at 
  an 
  average 
  rate 
  

   of 
  9 
  feet 
  a 
  mile. 
  The 
  valley 
  appears 
  to 
  be 
  continued 
  south 
  of 
  the 
  

   Adirondacks 
  in 
  New 
  York 
  along 
  the 
  present 
  course 
  of 
  the 
  Mohawk 
  

   river, 
  which 
  flows 
  at 
  present 
  several 
  hundred 
  feet 
  above 
  the 
  rocky 
  

   floor 
  of 
  the 
  valley.^ 
  This 
  floor 
  ascends 
  eastward, 
  till 
  at 
  Littlefalls 
  

  

  "Carll. 
  Pa. 
  geol. 
  sur. 
  1^:363. 
  

  

  