﻿206 
  F. 
  Leverett 
  — 
  Pleistocene 
  Fluvial 
  Planes 
  of 
  

  

  In 
  the 
  above 
  calculation 
  a 
  continuous 
  deep 
  channel 
  from 
  

   Edenburg 
  to 
  Niles 
  is 
  assumed 
  but 
  there 
  is 
  evidence 
  against 
  the 
  

   validity 
  of 
  this 
  assumption. 
  At 
  Lowellville, 
  Ohio 
  (No. 
  13), 
  the 
  

   Mahoning, 
  as 
  has 
  been 
  noted 
  by 
  Dr. 
  Newberry,* 
  has 
  a 
  rocky 
  

   bed, 
  an 
  examination 
  of 
  the 
  valley 
  at 
  this 
  village 
  for 
  the 
  pur- 
  

   pose 
  of 
  finding, 
  if 
  possible, 
  evidence 
  of 
  a 
  deep 
  channel 
  leading 
  

   through 
  it 
  convinced 
  me 
  that 
  not 
  only 
  is 
  there 
  no 
  evidence 
  of 
  

   its 
  existence 
  but 
  on 
  the 
  contrary 
  the 
  rock 
  is 
  exposed 
  at 
  fre- 
  

   quent 
  intervals 
  throughout 
  the 
  whole 
  width 
  of 
  the 
  valley, 
  the 
  

   village 
  as 
  well 
  as 
  the 
  river 
  bed 
  being 
  upon 
  rock. 
  The 
  out- 
  

   crops 
  are 
  so 
  frequent 
  that 
  there 
  appears 
  to 
  be 
  no 
  room 
  for 
  a 
  

   gorge 
  so 
  much 
  as 
  100 
  yards 
  in 
  width, 
  much 
  less 
  for 
  one 
  suffi- 
  

   cient 
  to 
  be 
  the 
  outlet 
  of 
  such 
  a 
  stream 
  as 
  must 
  have 
  been 
  dis- 
  

   charged 
  by 
  the 
  Monongahela 
  and 
  lower 
  Allegheny 
  rivers. 
  It 
  

   therefore 
  appears 
  that 
  the 
  hypothesis 
  of 
  a 
  discharge 
  northward 
  

   along 
  the 
  Mahoning 
  route 
  involves 
  a 
  hypothetical 
  uplift 
  of 
  an 
  

   improbable 
  amount, 
  wholly 
  unsustained 
  by 
  evidence, 
  and 
  

   further, 
  that 
  the 
  constriction 
  of 
  the 
  valley 
  at 
  Lowellville 
  makes 
  

   the 
  route 
  an 
  inherently 
  improbable 
  one. 
  

  

  I 
  have 
  also 
  examined 
  the 
  Shenango 
  valley 
  for 
  the 
  purpose 
  

   of 
  discovering 
  a 
  northward 
  outlet 
  for 
  the 
  deep 
  channel 
  at 
  

   Edenburg. 
  The 
  rock 
  floor 
  of 
  this 
  valley 
  is 
  struck 
  at 
  several 
  

   points 
  about 
  125 
  feet 
  below 
  the 
  present 
  stream 
  and 
  seems 
  to 
  

   slope 
  with 
  the 
  present 
  stream, 
  southward, 
  instead 
  of 
  toward 
  

   the 
  Erie 
  basin. 
  At 
  Greenville 
  several 
  borings 
  have 
  been 
  made 
  

   which 
  test 
  quite 
  well 
  the 
  valley 
  throughout 
  its 
  entire 
  width, 
  

   and 
  no 
  channel 
  of 
  greater 
  depth 
  exists 
  unless 
  it 
  be 
  a 
  narrow 
  

   gorge 
  inadequate 
  for 
  the 
  passage 
  of 
  a 
  large 
  stream. 
  The 
  level 
  

   of 
  the 
  lowest 
  part 
  of 
  the 
  valley 
  floor 
  through 
  much 
  of 
  the 
  busi- 
  

   ness 
  portion 
  of 
  the 
  city 
  is 
  about 
  815 
  feet 
  A. 
  T. 
  This 
  is 
  155 
  

   feet 
  above 
  the 
  valley 
  floor 
  at 
  Newcastle 
  and 
  at 
  least 
  160 
  feet 
  

   and 
  possibly 
  235 
  feet 
  above 
  the 
  rock 
  floor 
  at 
  Edenburg. 
  A 
  

   calculation 
  of 
  the 
  amount 
  of 
  northward 
  differential 
  uplift 
  that 
  

   must 
  be 
  assumed 
  and 
  subtracted 
  from 
  the 
  altitude 
  of 
  the 
  valley 
  

   floor 
  at 
  Greenville 
  to 
  bring 
  it 
  to 
  the 
  lower 
  of 
  the 
  levels 
  at 
  

   Edenburg 
  gives 
  8-^J- 
  feet 
  per 
  mile, 
  and 
  if 
  enough 
  uplift 
  be 
  

   assumed 
  to 
  give 
  the 
  ancient 
  stream 
  a 
  northward 
  descent 
  of 
  one 
  

   foot 
  per 
  mile 
  this 
  amount 
  will 
  be 
  increased 
  to 
  about 
  10 
  feet 
  

   per 
  mile, 
  — 
  a 
  greater 
  uplift 
  than 
  it 
  is 
  legitimate 
  to 
  assume. 
  

  

  Additional 
  evidence 
  against 
  the 
  northward 
  discharge 
  of 
  the 
  

   waters 
  from 
  the 
  great 
  drainage 
  basin 
  of 
  the 
  Monongahela 
  and 
  

   lower 
  Allegheny 
  some 
  13,000 
  square 
  miles 
  in 
  area, 
  may 
  be 
  

   found 
  in 
  the 
  narrow 
  gorge 
  of 
  the 
  Beaver 
  above 
  Beaver 
  Falls 
  ; 
  

   but 
  the 
  character 
  of 
  the 
  evidence 
  from 
  the 
  Ohio 
  valley 
  itself 
  

   appears 
  to 
  render 
  unnecessary 
  further 
  consideration 
  of 
  the 
  

   probabilities 
  of 
  northward 
  drainage. 
  This 
  valley 
  receives 
  

  

  * 
  Geology 
  of 
  Ohio, 
  vol. 
  iii, 
  p. 
  804. 
  

  

  